Photosynthesis: A New Angle into Fermi’s Paradox? 2 Oct 5:34 AM (4 days ago)
One of the things that gives the Fermi paradox its punch is the age of the galaxy. Back in 1950 when Fermi uttered his famous ‘Where is everybody?’ question, ideas about how old the Milky Way was were all over the map. Working with Hubble’s constant as understood at the time, the entire universe looked to be no more than 2 billion years old, a problem given what we were learning about the age of the Earth itself based on radioactive dating. So workarounds were needed, and they included the then widely supported steady-state theory, which saw a universe without beginning or end.
Then too, the problem of the age of the galaxy could not be satisfactorily worked out because we had no good methods to gauge the age of individual stars. A book could be written about the evolution of our thinking on both age problems, but for now, let’s say that Fermi asked his question about extraterrestrials at a time when values for the age of the galaxy were generally set at between 3 and 5 billion years. The tension between this and the Hubble constant values would persist, although Allan Sandage managed by the end of the 1950s to come up with an estimate for the universe of 13 billion years.
Fermi’s question gets more acute every time we come up with new information about how old our system is compared to the age of the galaxy. As we’ve discussed in these pages many times before, Charles Lineweaver’s work early in the 21st century demonstrated that we are newcomers compared to at least some of the stars in our vicinity. If that’s the case, then the idea of habitable planets being in existence several billion years before we showed up is plausible. And if we take ourselves as the measure (always dangerous, but we are the only datapoint), the idea of advanced extraterrestrial civilisations seems likely, assuming that these could find ways to avoid destroying themselves.
Image: The galaxy evolves. How many stars of the 400 billion now thought to exist here emerged at least a billion years before the Sun coalesced?
As always, though, we have to scout our assumptions. Just because it took what we now believe to be 4.6 billion years for Earth to produce intelligent life, why should that be the case everywhere else? An interesting new paper takes on that question by suggesting that no matter the size of their headstart, planets much older than our own may still be in the early stages of microbial life, without yet reaching the point of producing even primitive larger species.
The work of Chris Doughty (Northern Arizona University) and colleagues, the paper argues that we should be looking at what the team calls ‘plant energy,’ and stop focusing on time as an indicator of likely development. The hypothesis: “The biological evolution rate is a linear function of cumulative carbon fixed on a planet.” Note the word ‘fixed.’ What this describes is the process of taking carbon dioxide, an inorganic gas, and turning it into organic molecules like sugars. Photosynthesis does most of this work on Earth. It uses the energy derived from sunlight as the driver, with the carbon taken out of the atmosphere and oceans and put to use in biological systems.
Proposing a linear link between the amount of carbon fixed in this way and the rate of evolutionary development is a striking move. It’s even more so when considered as a tool for exoplanet research. The paper looks at the amount of carbon Earth has fixed over its lifetime and compares that to what other planets are likely to have fixed during their own lifetimes. 29 exoplanets are studied here, with only two of them surpassing Earth’s cumulative Net Primary Production (NPP), and therefore capable of developing multicellular and perhaps intelligent life. NPP refers to the carbon fixed by photosynthesis that ends up as new biomass.
Image: How we see plant photosynthetic pigments. The MESSENGER image of Earth on the left is very close to what can be seen by the human eye. For the image on the right, a red component was substituted that shows near infra-red colors. The vegetation in the Amazon basin produces the purplish-red color in the center of the image. The new paper proposes that cumulative fixed carbon is itself a marker that can be tied not only to life but to the pace of evolutionary change. (Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington, via JPL Photojournal).
The planets on Doughty’s list are chosen from the Habitable Worlds Catalog, which organizes NASA data based on factors such as radius, irradiation, temperature and age. The authors use stellar radiation, temperature and precipitation maps from several recent studies to calculate how Earth fixed carbon in different stages of biological evolution, and ask how long the examined planets would take to achieve the same amount of carbon.
From the paper:
Assuming Darwinian evolution, a baseline astrobiological assumption… each generation of life has a small potential for genetic change following either sexual or asexual reproduction. These genetic changes will either be successful or not depending on the environment, species competition or predation around the organism. We therefore hypothesize that Earth’s cumulative carbon fixed at certain periods has led to major evolutionary transitions such as the emergence of photosynthetic organisms, eukaryote and multicellular animals that fundamentally altered the Earth’s carbon cycle, accelerating it at certain points.
So we can think of the accumulated plant energy of an entire planet and acknowledge that planets with more plant growth as mediated by photosynthesis will tend to be warmer, wetter places than average. This gets interesting when we think about red dwarf planets, especially since these have enormous lifetimes and many are several billion years older than Earth. The authors make the case that these time factors provide no necessary advantage.
What counts is that life on a planet like TRAPPIST-1e, one of those studied here, would have lower rates of total photosynthesis because the surface receives correspondingly less light. Moreover, tidal lock on M-dwarf habitable planets would mean losing half their surface for photosynthesis. In this study, TRAPPIST-1e is found to have the capability of fixing no more than 21 percent of Earth’s carbon. An older world, but perhaps one with nothing more than microbial life.
We have interesting simulations of places like TRAPPIST-1e, climate maps that allow us to estimate how long it would take other planets to achieve the same amount of carbon fixed as we find on Earth. Of the 29 worlds considered potentially habitable by the authors, 27 are in fact orbiting red dwarf stars, and presumably tidally locked. Net Primary Production is calculated for each. The results are heavily weighted toward life at no more than microbial level:
If the biological evolutionary state is a function of cumulative carbon fixed and life began on each of the 29 exoplanets like it had on Earth, life on most of those 29 exoplanets would most likely be evolutionarily behind Earth (with two exceptions discussed below). The majority of our simulations led to most planets at the predicted microbial life stage with the exception of simulations using climates with 1 bar CO2. These very warm, wet planets accelerated NPP production which led about a third of the planets potentially ahead of Earth.
That sounds rather promising, but read on:
However, recent JWST observations showed no evidence of a thick carbon dioxide atmosphere on TRAPPIST-1c… or TRAPPIST-1e… therefore 1 bar CO2 may be unlikely on potentially habitable exoplanets. This raises the question of whether life can exist on an exoplanet with 1 bar CO2 in the atmosphere. CO2 concentrations in the early Earth may have been as high as 10 bar and up to ∼4,000 ppm CO2 in the atmosphere in the Cambrian (Royer, Reference Royer 2006), but 1 bar CO2 might not be conducive to land-based life.
The uncertainties here abound, as the authors are quick to acknowledge. We do not, in fact, know whether any of these planets actually have atmospheres in the first place. Nor, obviously, do we have any idea of their composition if they do exist. We have no knowledge about the presence of carbon at the surface, and also have to factor in the possibility of biological processes modifying the composition of any atmosphere present, just as Earth’s atmosphere was gradually transformed as the effects of photosynthesis began to be felt.
For that matter, can we assume that the life we are looking for uses carbon along the lines of life on Earth? If it does, this study predicts that most stars in our stellar neighborhood, despite sometimes being much older than Earth, are behind our planet when it comes to biological evolution. Two planets – GJ 1061c and K2-3d – do stand out as being of unusual observational interest for present and future space telescopes. Both are both larger and older than Earth.
This is useful information, given that our first thorough analyses of planets of Earth mass are going to occur with planets orbiting low mass stars. When we reach the point of instruments like Habitable Worlds Observatory that can image planets around G-class stars, the discouraging catalog analyzed in this paper may be replaced with a more positive one. If Doughty and team are right, however, we have an answer to the Fermi paradox and the time problem. Intelligent life has far fewer places on which to develop than we thought.
The paper is Doughty et al, Calculating potential cumulative carbon fixed and evolutionary stage for Earthlike planets in our solar neighborhood, International Journal of Astrobiology (2026). Published online by Cambridge University Press 22 September 2026. Full text.
Sakurai’s Object: A Stellar Rebirth 24 Sep 9:25 AM (12 days ago)
Given how long stars live in comparison to human lifetimes, I always do a double-take at science fiction tales of starships dropping in to study a nova just as it’s about to go off. I suppose we have to assume the starship civilization has found a way to time such matters. There’s a Star Trek: The Next Generation episode that involves rescuing a planetary population from a star that’s about to explode (“A Fury Scorned”), but of all the nova arrivals, I like Samuel Delany’s 1968 novel Nova the best. Here, in order to harvest a rare element dubbed ‘Illyrion,’ the exact moment of the explosion has to be known and exploited through a mind-bending run through the debris.
Today’s paper doesn’t involve a nova, but it does involve a star that is doing things on a very short timeframe indeed. The star is known as Sakurai’s Object (V4334 Sagittarii). Japanese amateur Yukio Sakurai observed the object in 1996, noting how it appeared to be brightening. A 1976 detection of the progenitor star had recorded a magnitude of 21, whereas when Sakurai tagged it, it had reached magnitude 11. The apparent eruption here was first thought to be the result of a nova, but that was discounted for spectral reasons.
Several years later the unusual brightening began to decline. That was evidently the result of loss of mass and subsequent condensation of stellar material, which wound up hiding the star behind a dusty screen. It now shows a spectrum similar to what is known as a Wolf-Rayet star. Sakurai’s Object appears, however, to be in the much less massive Wolf-Rayet class known as a [WR] star. A conventional Wolf-Rayet star is massive, stripped of its hydrogen by huge stellar winds that leave the underlying helium-burning layers exposed. The odd [WR] notation turns out to be needed because low-mass objects like these can mimic a Wolf-Rayet star, so it was necessary to show that this is a different kind of object and a much smaller kind at that, though with Wolf-Rayet features.
There are also sub-categories of [WR] including [WC] that don’t need to occupy us now, although the paper explains what they mean. What’s intriguing about Sakurai’s object is its pace. According to current calculations it’s now roughly 6 times hotter than it was 30 years ago, and is climbing back toward the white dwarf temperatures it had before the eruption that made it observable by Sakurai. Albert Zijlstra (Jodrell Bank Centre for Astrophysics, University of Manchester), describes its significance:
“Most stars evolve so slowly that major changes take place over timescales far longer than a human lifetime. As a result, we usually have to piece together snapshots of stellar evolution by comparing different stars at different stages of their lives. Sakurai’s Object offers something far rarer. It is one of the very few stars known to have changed dramatically within just a few decades, giving us the opportunity to watch stellar evolution unfold in real time. With our observations, we can test theories of how stars evolve and gain new insights into one of the shortest and least understood phases in the life of a dying star.”
Image: The rapid brightening of Sakurai’s object allows astronomers to study the final phases of the stellar evolution in only a few decades. The left and right panels show the brightening. The middle panel is an image obtained with the radio telescope ALMA, showing the material ejected after the star re-ignited. The material currently extends over a size similar to our entire solar system. Credit: Stefan Kimeswenger, University of Innsbruck; Peter van Hoof, Royal Observatory Belgium. The observatory also has a short video showing the brightening.
What we apparently have here is a star once similar to the Sun that had finished its nuclear burning and was in the process of turning into a dense white dwarf star about the size of the Earth. But an event known as a ‘very late thermal pulse’ seems to have occurred. This happens when helium deep inside the star reignites, forcing a rapid expansion along with the ejection of stellar materials, so that the star has, at least for the time being, been reinvigorated. Along with another star called V605 Aquilae, Sakurai’s Object is one of only two stars that have been directly observed going through this process.
Let me turn to the paper to home in on the matter of thermal pulses:
Depending on when the pulse occurs, it is classified as an AGB final thermal pulse (AFTP), a late thermal pulse (LTP; post-AGB), or a very late thermal pulse (VLTP; see M. M. Miller Bertolami 2024). In the most extreme case (VLTP), the star is already on the white-dwarf cooling track when the flash causes rapid expansion and cooling, accompanied by substantial mass ejection into the circumstellar environment. The star is thus “born again” and returns close to its former AGB position in the HR diagram. Subsequent evolution involves reheating, and possibly an additional cooling excursion, as the star evolves back towards the white-dwarf domain with a markedly altered surface composition (T. M. Lawlor & J. MacDonald 2003).
No wonder this was a hard object to observe. The ejected gas and dust following the 1996 outburst caused the star to became hidden to direct imaging. Low density gases are coming off the star even as the outflowing atmosphere, moving at e 500 kilometers per second, is optically thick. Much of the spectrum produced is nebular. The team compared data from the VLT with computer models originally developed to study the processes that power the atmospheres and winds of Wolf-Rayet stars. The emission lines studied in this paper are embedded in the stellar wind, as opposed to the ejecta and dust. Much of the credibility of the analysis depends upon separating these factors.
The analysis reveals a stellar temperature at the surface pegged at between 27,000 and 36,000 degrees Kelvin. Scientists will now be able to study the process of the reheating following the eruption that occurred thirty years ago. Early indications are that the process is occurring more slowly than some models had predicted, so that Sakurai’s Object becomes a useful laboratory, like V605 Aquilae, into stellar behavior in this extremely rare class of stars. At some point, Sakurai’s Object will return to its fate as a white dwarf, only now under close observation as we ponder massive changes in a very short order.
Griet Van de Steene (Royal Observatory of Belgium), a co-author of the paper adds:
“Sakurai’s Object evolved much more quickly than pre-existing models for stellar evolution predicted. This led to a new generation of models that we now need to test. Our measurements show that the star is reheating more gradually than some of these new models predicted. That gives us an important way of testing which theories best describe what happens when a dying star briefly springs back to life. As we continue to monitor the star over the coming years, we expect to learn much more about this remarkable phase of stellar evolution.”
The paper is Marcolino et al (2026). The emergence of a [WC] star in Sakurai’s object. Monthly Notices of the Royal Astronomical Society, 552(1), Article stag1533. Full text.
Disrupted Systems: Implications for Life 16 Sep 8:57 AM (20 days ago)
Anthropocentric thinking is a persistent problem when we’re talking about extraterrestrial civilizations. Some of our most cherished notions can be invoked so effortlessly as to defy the imagination. The Copernican idea that life must exist elsewhere because elsewhere is bound to be more or less like here has had a long lifetime in SETI studies. It seems like the most basic common sense. And yet, as we’ll see once again today, scientific results continue to make it apparent that the fact that we are here does not mean that they are there.
Finding stellar systems more or less like our own continues to be difficult. I’m not going full ‘rare Earth’ here but acknowledging that our circumstances may be unusual enough to tamp down estimates of the number of life-supporting planets. For that matter, our lack of knowledge about abiogenesis itself makes the case that we cannot necessarily expect it around other suns. On this matter, at least, we should be able to gather data soon, perhaps with a Mars lander.
Which gets me to today’s interesting take on binary stars. The binaries – HD 129171 and HD 129209 – are G-class, both having formed from the same molecular cloud. This is a common enough scenario, because binary systems are extremely common. In fact, about half of the stars in the Milky Way have a companion star, and thus are likely to share a common chemistry.
About 180 light years from the Sun (based on Gaia data) in Boötes, the system is proving unusually helpful. Using the UVES spectrograph on ESO’s Very Large Telescope (VLT) in Chile, an international effort led by Anne Rathsam at the University of São Paulo in Brazil is using this binary as a laboratory to study chemical differences between the stars that may be telling us something about planet formation and orbital evolution. What is driving the differences?
All this has a bearing on life, because for life to occur, conditions must exist for long enough to let the necessary processes go to work. And that may be a problem. HD 129171 turns out to be enriched in refractory elements, while its companion HD 129209 is not. Refractory elements condense at high temperatures, as opposed to volatiles, and the proportion of one to the other can be an interesting diagnostic tool, telling us something about the system’s history. A star depleted in refractories is likely one that has spawned planets, while one heavy in these elements has likely swallowed planets whole.
Rathsam’s work, available in a paper just published in Astronomy & Astrophysics, focuses on beryllium, whose abundance here is interesting because it is not produced in stellar interiors. Measured properly, its presence points to a star that consumed planetary material long after formation. Lithium, beryllium, and boron, in fact, share characteristics that make them exceptional in terms of chemical emergence in the galaxy. Jorge Luis Melendez Moreno (USP), who served as study advisor to Rathsam on this paper, explains:
“All other chemical elements originate from primordial nucleosynthesis [the formation of the first atomic nuclei in the minutes following the Big Bang] or stellar nucleosynthesis [the nuclear fusion process that occurs inside stars throughout their lifetimes]. But not beryllium and boron. They primarily arise through a process called ‘cosmic spallation,’ in which high-energy particles fragment heavier nuclei, such as carbon, nitrogen, and oxygen, producing lighter elements.”
Image: The binary system of HD 129171 and HD 129209. Credit: Digital Sky Survey/Aladin/Anne Rathsam.
Lithium has its own uses as a marker, but the USP researchers found that beryllium is the more reliable tool, with a longer lasting chemical signature. HD 129171’s surplus of refractory elements (including magnesium, silicon, calcium and titanium) compared to its companion HD 129209 is accompanied by lithium and beryllium excess as well. The authors see evidence for rocky material equivalent to more than eleven times the mass of the Earth. This would have been ingested in the star, raising interesting questions about planet dynamics.
The infall of entire planets into a host star can be explained in various ways, from gravitational perturbations from other planets on eccentric orbits or skewed inclinations, to interactions within the early circumstellar disk driving young planets onto migratory trajectories. Although I hadn’t seen this paper before, the authors cite a 2025 study by Soares and team (citation below) that draws on simulations to show that about half of the stars simulated should ingest planets, leaving a chemical signature in perhaps 20 percent of them.
Evidently we can imagine system disruptions as a common occurrence in the Milky Way. We might add to this the fact that planet configurations with giant planets in circular outer orbits and rocky planets on inner ones are not common. Our observational data so far tends to confirm this, although tracking outer Jupiter-class planets with our current detection methods is always problematic given their sparse transit signatures. Overall, though, the picture that is emerging is that systems similar to the Solar System seem rare. If many systems are going through upheavals through planet migration and ingestion into the host, stable orbits may be trickier than we’ve thought. Rathsam comments:
“In our planetary system, the planets have relatively stable, low-eccentricity orbits. However, if planetary engulfment is common, it suggests that many systems undergo violent dynamic phases.”
Implications?
“Life wouldn’t just need billions of years to emerge and evolve. The planet would also have to remain in a sufficiently stable orbit to survive significant gravitational perturbations.”
If you’re wondering about our own star, it’s light in refractory materials relative to volatiles, which at least one recent study sees as a sign of planet formation at an early era. What became rocky planets and planetesimals, in other words, was never accreted into our star. I give that citation below. This and subsequent work seems to peg the Sun as the center of a dynamically quiet system compared to many, but be aware that the debate on this matter continues.
How useful is beryllium as a marker in such an analysis? The authors argue that despite the fact that beryllium is eventually depleted in a stellar interior, it persists long enough to provide reliable information. From the paper (my italics):
Refractory elements offer an excellent way to distinguish between the planet engulfment or the proto-cloud inhomogeneity scenarios. Since they have high condensation temperatures (≳1000 K), they are the primary constituents of the rocky material in planetary systems – terrestrial planets and cores of gaseous planets. In case of engulfment by a Sun-like star, this material is accreted by the star and then dissolved and mixed in the convective envelope, increasing the stellar surface abundances after the event (Sandquist et al. 2002). This process, however, produces a metal-rich outer layer with an unstable mean molecular weight gradient, which triggers thermohaline mixing (Théado & Vauclair 2012; Sevilla et al. 2022). For fragile elements such as Li and Be, this thermohaline mixing induces depletion, as it can carry these elements below the convective zone, into their burning regions. Thus, the chemical enrichment caused by the engulfment disappears over time. Nevertheless, Sevilla et al. (2022) demonstrated through simulations that the Li engulfment signature in stars with masses close to solar can be detected for ≥1 Gyr.
As far as I can tell, it’s the treatment of beryllium as a marker of engulfment that gives this paper its significance, as heretofore it has been used primarily as a diagnostic for the mixing of elements in stellar interiors. More broadly speaking, though, any reminders of the factors that make our Solar System adaptable for life should help us in identifying systems where life is less likely. That’s worth keeping in mind as we move beyond easy assumptions about life’s ubiquity and dig into realities that may make it more unusual than we thought.
The paper is Rathsam et al. (2026). Planet engulfment in the chemically anomalous HD 129171/HD 129209 pair. Astronomy & Astrophysics, 710, A236 (full text). The interesting paper on beryllium’s persistence is Soares et al. (2025). Assessing the processes behind planet engulfment and its imprints. Astronomy & Astrophysics, 693, A47 (preprint). The paper on the composition of our Sun is Meléndez et al. (2009). The peculiar solar composition and its possible relation to planet formation. The Astrophysical Journal Letters, 704(1), L66–L70. Abstract.
Pandora: Tuning Up our Data on Exoplanet Atmospheres 9 Sep 9:03 AM (27 days ago)
Launching a flagship-class mission like the Roman Space Telescope is always exciting, but with Roman in space, let’s also keep an eye on Pandora, a smaller though fascinating NASA mission (through its Astrophysics Pioneers program) that is now beginning its own work in exoplanet science. 20 exoplanets are targeted here, the idea being to work with data from transits to characterize their atmospheres via transmission spectroscopy, but with an additional twist. Elisa Quintana,(NASA GSFC) is principal investigator:
“Pandora’s data will help close a major gap in our knowledge about planets and their host stars because, right now, we can’t be entirely sure how the star’s light affects measurements of what makes up exoplanet atmospheres. We designed the Pandora spacecraft and its in-depth observing program to better understand this vexing issue.”
Launched January 11 of this year, Pandora is now beginning observations of its target stars. It’s in that category of smallsats that fascinate me because their low cost also gives them the option of higher tolerance of failure, making it possible to push the limits without great financial risk (the cost cap on this class of mission is $20 million). A tool like this can be tightly focused on specific targets without compromising larger instruments that are already besieged with obligations to existing observing programs. Word from the Pandora team is that science work begins with all instruments performing as expected.
Image: Artist’s concept of NASA’s Pandora mission, which will help scientists untangle the signals from exoplanets’ atmospheres and their stars. Credit: NASA GSFC/Conceptual Image Lab.
What makes Pandora so interesting is that it’s a multi-wavelength mission. Pandora’s telescope, an aluminum Cassegrain instrument 45 centimeters in diameter, feeds detectors that work in both visible light for long-baseline photometry as well as near-infrared (NIR) wavelengths. Starspots or other stellar activity can be separated from the near-infrared spectroscopy data on the planet’s clouds and atmospheric hazes. This is information that will inform subsequent work with telescopes like JWST and Roman as we refine our tools for removing noise in the data. A recent paper on Pandora makes the case:
Alongside the opportunities explored throughout this work, Pandora provides a unique opportunity to help overcome many hurdles inherent in observations with current instruments. Namely, multi-epoch observations of exoplanet atmospheres with JWST are often observed at different points in the stellar rotation, making them difficult to fit jointly (e.g., E. M. May et al. 2023). By providing information about the stellar activity and allowing for corrections at the data level, joint Pandora–JWST programs will unlock new insights into planets around active hosts. Additionally, these same insights will inform the presence of offsets between different instruments and epochs, which have been difficult to constrain thus far with JWST alone (e.g., A. L. Carter et al. 2024).
Pandora is going to give us useful data on stellar contamination in our transmission spectroscopy work. That means a clearer and more reliable look at the composition of exoplanet atmospheres. Stellar contamination should stand out, with a minimum of 10 transit observing sessions per target, each lasting about 24 hours. The plan is to accumulate, for each target, roughly 240 hours of pointing time, which should yield more than 120 hours of science data once Earth occultations and unavoidable gaps for downlinks, etc. are taken into account. An instrument like JWST can collect transmission spectroscopic data for exoplanets but only with relatively short observing sessions involving one or a small number of transits. The combined datasets of the two observatories will cleanly excise star signals from the data on planetary ones.
The finalized target list was published last January and contains 19 host stars, one of which is orbited by two of the target worlds. The stars range from M-dwarfs to K-class. 16 of these planets have been observed previously by JWST, which will allow the retrofitting of the Pandora measurements onto the JWST spectra. As far as I can tell, earlier provisional target lists included planets that didn’t make the final list, with the emphasis shifting toward larger warm Neptunes and Saturns. That makes sense given that these offer higher signal-to-noise ratios as we put these techniques to work together for the first time.
Image: This is Figure 1 from the paper. Caption: The absorption cross sections of common absorbers in exoplanet atmospheres considered in this work, shown at a pressure and temperature of 0.1 mbar and 1000 K. The wavelength coverage of Pandora’s NIR detector (NIRDA), JWST’s NIRCam F322W2 and F444W filters, and HST’s WFC3 instrument (for the G141 grism) are shown. Pandora/NIRDA covers absorption bands of H2O, CH4, NH3 and the wing of the K doublet, making it most sensitive to these absorbers. Credit: Rotman et al.
Using these methods, Pandora’s science observations should be more accurate and reliable than any planetary atmosphere readings ever taken before. The paper is Rotman et al., “NASA’s Pandora SmallSat Mission: Simulated Modeling and Retrieval of Near-Infrared Exoplanet Transmission Spectra,” accepted at The Astronomical Journal (preprint).
Fermi Explorer: Building the First Mission to Another Star? 2 Sep 7:34 AM (last month)
The question of when to launch an interstellar mission has occupied us many times in the past. Specifically, how long do we wait so that travel times are reduced to something like the lifetime of a researcher working on the project? But there is another approach to all this. Someone is going to launch an interstellar mission that will be the first human effort to send a payload to another star. It’s all about intentionality and the choice of targets.
A symbolic act? Sure, but don’t write the idea off. We can learn a lot from symbolic acts, and if we only have, at our current level of technology, the ability to reach Voyager-like speeds, we can still work on issues like equipment lifetimes, self-healing technologies, navigational issues and more. We can also work to refine existing AI tools to achieve the most efficient design.
If we give ourselves 80,000 years to reach Alpha Centauri, we have to contend with the fact that the system is constantly moving. On this timeframe, by the time the craft would arrive, Centauri A and B would be a bit over 6 light years from the Sun as opposed to their current 4.365 light years. Trajectory analysis going this far into the future is going to be an interesting challenge.
I mention all this because a call to mount such a mission has now arisen. It bears the name Fermi Explorer, and according to its new website, its intention is to get a spacecraft with a 1 kilogram, 10X10X10 cm payload to the barycenter of the binary Centauri A and B system. In other words, the target is not either star itself but the common center of mass between the two as they orbit.
Some particulars: The mission should launch before the end of 2029 if the effort succeeds, and is intended to cost less than $15 million to design, build, launch and operate. Mission co-founder Philip Johnston is going to have his hands full.
As to departure, Fermi Explorer would take a year and a half moving out of Earth orbit. Then, using a series of Oberth maneuvers taking it to within 0.42 AU of the Sun, the craft would rely upon what the site calls a ‘perihelion pump,’, which involves multiple close solar flybys over 12 years to build the energy to achieve an escape trajectory that, after climbing out of the Sun’s gravity well, attains 23.64 km/sec. That’s a bit higher than Voyager 1’s 17 km/sec. Final Solar System departure would be, after a 2029 launch, around the year 2043. Ahead for the spacecraft would be an unpowered cruise of over 70,000 years.
What the craft will carry is not yet determined, although I notice the plan to put a copy of the Voyager Golden Record and similar materials onboard (I’m assuming this is to be done digitally). Ahead is a three-month period for solicitations for other items of cultural value. Likewise, scientific instruments will undergo their own period of solicitation. The emphasis is on flight-proven hardware with little research and development necessary. To quote from the website:
We will soon put the mission out for open tender to all the major satellite manufacturers, and we aim to open-source as much of the design as we can. The four primary objectives are considered non-negotiable. Everything else is negotiable. For example, the manufacturers can determine the power system, antenna strength, propulsion, mission profile, and whether to include gravity assists, etc. We anticipate that we can do the mission with around a 100-200 kg small solar-powered satellite with just electric propulsion, doing what we call a perihelion pump maneuver… We expect the mission will not have a large antenna for communication, and so we expect we will lose connectivity relatively quickly, and so much of the mission will be autonomous. It will be too small to track and will lose power once it leaves the solar system.
Can crowdfunding build an interstellar craft? The hope is clearly that enough people will become interested to help, with the site offering engraved names and physical objects in the payload itself, so the scientific payload, already tightly squeezed, will have a mass budget with even tighter constraints.
And with all the attention AI is getting in the press, note its use here. The website points to a key technical report called “Interstellar Precursor Mission to Alpha Centauri: Technical Feasibility Assessment,” dated July of 2026. Specifically, the report is said to be: “Prepared with PSI’s Autonomous Physics-Research Platform,” under which is stated “Physical Superintelligence’s agentic research system produced the analyses, simulations, and proof-grade verification in this report end-to-end under staged independent audit.” And again: “This report did not undergo comprehensive human peer review.”
This gets interesting. Writing for MIT Technology Review, Michelle Kim has a fine piece on the use of AI for Fermi Explorer that fills in the background. PSI is a research laboratory called Physical Superintelligence, and its AI system is what came up with the trajectory Fermi Explorer would follow. According to Kim, PSI’s AI went to work on the problem of getting a small spacecraft like this up to speed:
A week later, the AI system turned up a novel trajectory… It combined well-known orbital maneuvers in a way the Fermi team had not considered, according to a paper that has not been peer-reviewed. It suggested that the spacecraft could first slow down so its orbit swings in close to the sun—closer than Mercury. On each close pass, it would fire its engine so that the solar panels get four times the light, and a burst of thrust delivered at high speed would buy more energy than the same burst anywhere else. Because the engine would run only near the sun, the solar panels could stay small and the spacecraft light.
The Fermi Explorer site also links to a separate mission analysis which cross-references the PSI report and seems to agree with its results almost completely. I’m assuming human peer review is going to come into play if momentum for this mission builds. But watching the development of these models for physics and their tweaking along the way is a fascinating exercise.
Roman Space Telescope Launches Tomorrow 29 Aug 4:46 AM (last month)
We’ll have a lot to talk about when observations from the Nancy Grace Roman Space Telescope start coming in. But first we’ve got to get it out to its halo orbit around the L2 Sun-Earth Lagrange point. With the Sun, Earth and Moon permanently blocked out, the seeing should be good from this vantage some 1.5 million kilometers out. Just now I’ve had a note from Jim Benford reminding me that launch is currently scheduled for tomorrow, August 30, at 0726 ET (1126 UTC). The additional good news is that Jim’s son Dominic will be one of two hosts of the live coverage from NASA. I remember meeting Dominic some years back at Goddard Space Flight Center, where I had the chance to see the JWST telescope being prepared to go through its vibration testing.
Dominic has spent more than a decade working on the Roman telescope, so the honor of working the NASA live coverage is well deserved. The photo below shows him during preparations for the Sunday coverage, which starts at 0620 ET (1020 UTC). You can tune in on Facebook, Instagram, Twitch, X, Discovery+, Amazon Prime, YouTube, or NASA+ (see https://www.nasa.gov/live/ for links and updates).
And as Jim reminds us: “As with any launch, timing can change because of weather or other conditions, so check NASA for the latest schedule. Fingers crossed!”
A ‘Time Variable’ Feature on Pluto? 25 Aug 5:57 AM (last month)
With New Horizons now 63 AU out, it’s time to ponder that record hibernation period that the spacecraft just went through. Over 10 months long, this one had the same goal as previous such periods, to hold down operating costs but also give a break to onboard instrumentation in hopes of augmenting mission lifetime. As a kid, I often thought how cool it would be to be involved with a distant spacecraft. For some reason I always visualized this as being here on Earth while working with a craft beyond the Solar System. So maybe I was dreaming more of being a flight controller than an astronaut.
I hadn’t realized until reading Alan Stern’s recent update that while hibernation means there are no commands and responses going back and forth, the craft does continue active data gathering from its Solar Wind at Pluto (SWAP) plasma detector and the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument. The Student Dust Counter is also in operation. Since awaking early in the summer, New Horizons has been delivering data from these instruments back to Earth.
I see that future flybys of Kuiper belt objects (KBOs) are still a distinct possibility, assuming that one can be found within range of the vehicle. And yes, the Vera Rubin Observatory is already in use in the search for such objects, with planning extended to requests for time on the Roman Space Telescope, now scheduled for launch within days. Writing about New Horizons always comes with a tinge of melancholy as I contemplate the fact that no successor is ready, but it’s a relief to see how active this tough little craft continues to be. There are good successor concepts out there, but none are currently funded.
Meanwhile, we have the interesting news about possible liquid flows on Pluto’s surface, revealed by New Horizons images of Sputnik Planitia, the nitrogen glacier whose northern regions reveal convection cells separated by features that suggest liquid nitrogen has flowed there in the past. The new work out of Southwest Research Institute (SwRI) and published in the Planetary Science Journal, suggests that this process continues, doubtless through liquid nitrogen upwelling from beneath the glacier.
SwRI’s Kelsi Singer, one of the study’s co-authors, comments:
“The surface of Sputnik Planitia is quite young, probably less than one million years based on modeling of the surface overturn, and thus these features that we are looking at must have formed since then. Pluto has many unique terrains seen nowhere else in the solar system, and this area of Sputnik Planitia is one of them. Its surface provides a different set of conditions compared to what we are used to on Earth, and exploring that allows us to better understand how materials behave in environments that are difficult to produce on Earth.”
Image: Pluto’s northern Sputnik Planitia glacier (in the western or left side of Pluto’s bright heart) is shown here in a color mosaic made from NASA’s New Horizons imagery. The direction of north is shown on the image. The image is ~ 700 x 350 kilometers across. The red box has been added to show most of the region containing dark features attributed to the wetting of the glacier by liquid nitrogen sourced from a “basal melting” process beneath the glacier. NASA/Johns Hopkins APL/SwRI.
These findings are based on studies of a glacial surface far from Earth and involve liquid nitrogen rather than water, but it’s interesting that the paper reports that the surface patterns on this region of Sputnik Planitia have darkened in ways that are similar to Earth glaciers that have undergone their own wetting by subsurface liquid. The team worked with images from the Landsat 9 satellite that included the Greenland ice sheet. Computer models of glacial melting led by Orkan Umurhan (SETI Institute) reveal a transport mechanism to the surface and indicate an icy flow that can persist on the surface for short periods, which would account for the dark features.
And there is another Earth analogue that perhaps comes into play. From the paper:
We have posited that the striking, dark, irregular linear and diffuse features prevalent at the northern margin of SP are manifestations of the upwelling of liquids or liquid slurries from beneath the SP ice sheet. We have further posited that these liquids were created as a basal melt at depth below the glacier, and we have quantitatively shown the plausibility that such a mechanism can then advect through conduits to the surface of SP where it will horizontally spread out, leaving a darkened surface akin to that observed in northern SP. The buoyant ascent of liquid nitrogen through the denser N2 ice is akin to terrestrial volcanism where less dense basaltic melt rises through cold continental crust.
Does this process occur on other dwarf planets in the Kuiper Belt? We won’t know that until we have mapping missions to objects like Eris. The paper also mentions the obvious candidate at Neptune, the large moon Triton, as a possible example of such processes factoring into the geysers Voyager 2 observed during its flyby. For that matter, it’s fascinating to consider that despite the success of New Horizons at Pluto/Charon, over half the planet (I know I’ll get emails about calling it that) remains unmapped at high resolution because of the geometry of the encounter. So for the time being, we don’t even know whether apparent flows like that at Sputnik Planitia occur elsewhere.
The SETI Institute’s Umurhan points out that the physics of solid nitrogen materials under stress and strain are not well understood, and have to this point “never been studied in real detail in the laboratory.” We need, in other words, to go out there and look, and New Horizons has just reminded us why.
The paper is Stern et al., “Evidence for Possible N2 Basal Flow beneath Pluto’s Northern Sputnik Planitia,” Planetary Science Journal Vol. 7, No. 7 (31 July 2026), 185 (full text).
The Limits of Understanding Between Species, and the Issue for Interstellar Communication 14 Aug 4:56 AM (last month)
We’ve yet to find any evidence of intelligent life beyond Earth, a puzzling failure given the widespread belief that where habitable planets exist, life will somehow emerge. If we do receive a signal, though, would we be able to understand it? We’ve made some progress in piecing together animal communications here on Earth, but figuring out what the whistles and clicks of sea creatures mean remains a work in progress. In today’s essay, associate editor Alex Tolley goes to work on key questions: Is mathematics truly a universal language? Does language change how we experience the world, and if so, what aspects of an alien culture will we actually be able to understand? The questions are daunting and now coming into public discourse in the realm of AI. Alex’s thoughts on that phenomenon and how we might interact with a machine civilization are only part of the interest here.
by Alex Tolley
Introduction
Discussions about alien communication usually focus on the technology of message transmission and how to decode the first message received. This essay will address the issue of decoding the first message and the expected limits of the subjects that can be communicated.
Humans have a long history of wanting to talk to other species. From the many stories of talking with various animals, often projected with human qualities, to talking with invisible entities, including invisible deities and dead ancestors, to the modern period, where talking with pets and inanimate objects is not looked askance at, and now chatting with large language models (LLMs) that usefully talk back.
We have learned of the vast size of the universe, and rationalize that there must be life and intelligent, technological civilizations somewhere in that vast universe. The search for extraterrestrial intelligence (SETI) is an attempt to answer the question of whether there are other intelligent species in the stars.
Serious attention to searching for aliens and receiving their messages started around 1960. The assumption was that if life also existed on other planets, evolution might eventually produce intelligent, technological life, with interests not dissimilar to ours. The only question was how many civilizations interested in communication there were. The basic model was encapsulated in the famous Drake Equation [1]. While the probabilities of intelligent, communicating civilizations were very much a guess, Drake has made the claim that their number is the same as their communicating longevity.[1, Appendix A] If they communicate for 10,000 years, there should be about 10,000 communicating civilizations, perhaps in a “Galactic Club”. Sixty-odd years later, there has been no detection of such signals using the technologies we have at our disposal. Despite the unanswered Fermi Question that there may not be any civilizations in space, and nor have there ever been, SETI continues with the hope that intelligent life must exist somewhere in the vast reaches of space, although the emphasis has shifted towards the astrobiologists’ hopes that at least life exists elsewhere and how best to detect it.
Figure 1. Participants in the 3rd Decennial US-USSR meeting on SETI in Santa Cruz, CA. 1991. Frank Drake can be seen standing in the middle front row holding the sign “N EQLS L” (Source: The Biological Universe (1996) p487)
But suppose a signal is detected; what then? Decoding an alien message might not be easy. A few years ago, the artist Daniela de Paulis and her team devised a test signal for the public to decode [2]. Even though the signal data was formatted using human transmission coding, it took about a year before the signal was successfully decoded. This, despite prior knowledge of the signal transmission features, and despite sending only 2-D images, with a clear similarity in form to previous ideas we have had for decoding signals. How much harder might a real alien signal be to decode?
Terrestrial Animal Communication as a Decoding Test
Animal communication, and potentially language, offers another way to attack the issue of communication with a species very different from us. While aliens have so far proven elusive, Earth is teeming with animal life, some of which appears quite intelligent, even if unable to use more than rudimentary technology. Research into animal communication continues to determine the extent, if any, that intelligent animals have a language they use to communicate with their own kind. Progress is being made, but could we ever talk to the animals like the fictional Dr. Dolittle?
Despite their far greater separation from humans in evolutionary time than apes. and their aquatic environment, cetaceans seem to have more complex communication and perhaps something closer to a true language. Work by the linguist Gašper Beguš has shown that sperm whales (Physeter macrocephalus) communicate with a series of clicks, or codas, that can be compared to how humans produce vowel sounds [3]. AI was used to extract the commonality of codas of “vowels” between individual whales, although there is insufficient information to connect the sounds with meaning. The video below explains the concept of the sequences of clicks, or codas [4].
From their recent paper [3] Beguš concludes:
…our findings demonstrate that sperm whale vocalizations are highly complex and likely constitute one of the most phonologically sophisticated (currently known) communication systems in the animal kingdom.
Another study by a different team on 2 separate sperm whale populations in the eastern and western Mediterranean showed that the 2 populations used different “dialects” for the same codas.[5] A recent study indicated that sperm whales change the tone of their codas when encountering ships, indicating that they recognize ships in some way, although we don’t know what it means [6].
Work by Sayigh et al with a wild pod of bottlenose dolphins (Tursiops truncatus) was able to extract consistent clicks and whistle sounds for both individuals and the group [7]. The clicks identify individuals and are used to identify the individual, and to contact others. Whistles are associated with emotional and social interactions, for example, courtship and mating.
While we are still a long way from decoding the meaning of the vocalizations of dolphins and sperm whales, it does appear that they have some sort of language to communicate with others of their kind. As might be expected, the geographic separation of pods hints that there are also different dialects associated with pods at different locations.
Suppose in the future that we manage to decode the meaning of these communications, and that these cetaceans, while not as sophisticated as the dolphins in Douglas Adams’ Hitchhiker’s universe stories, do have a basic language that uses their various vocalizations. What could they communicate that we could understand?
This is where the influence of Thomas Nagel and his seminal essay “What is it like to be a Bat?” is relevant [8]. Nagel argued that we cannot understand an animal without being that animal. If he argument is correct, then as we are not sperm whales or dolphins whose experiences are very different to ours, there may well be a communication gap between our species. We could understand the meanings of vocalizations of objects and actions, but not of feelings and other qualia, and conversely these cetacans could not understand ours. As for the abstractions each species has for dealing with its environment, these may forever be unintelligible.
Aliens as species with different experiences
Recall that one assumption of SETI is that some civilizations would have similar ideas and motivations as we do. That they would have a sophisticated technology, likely far ahead of ours, but with similar ideas about inter-civilization communications and a desire to learn. Just as we try to learn about animals, and even communicate with them, so aliens might send out signals to try to initiate a communication with us. If so, we should be able to receive them, and possibly respond.
But is this the case, and are we assuming that our differences as species and evolved experiences can be overcome, contra Nagel?
We have made an attempt at sending out an informative message, the Arecibo message, as well as the Pioneer probes 10 & 11 plaques, and Voyagers 1 & 2 records. The Arecibo message and Pioneer plaque are shown in Figure 1 below.
Figure 2. Left) The Arecibo message radioed into space. Right) The Pioneer space probe plaque with depictions and information about Earth and its intelligent species.
The approaches of both messages assume some common understanding between humans and aliens. The Arecibo message is very concise, but not easy to interpret even by humans. The Pioneer plaque is clearly a more representative message, although how easy would it be for an alien species to recognize the location of our system from the representation of pulsars? Explanations of the messages are found at [9,10]. The Voyager Golden Record needs to have a player to extract the information that includes sounds and music. How might aliens interpret these sounds?
It has come to my attention that Joe Davis had created an artwork of the Arecibo Message using bottles of water at MIT, yet none of the students and scientists could discover any meaning to the display. In 2009, to celebrate the Arecibo Message’s 35th anniversary, Davis also sent out from the Arecibo telescope a cleverly encoded message of the DNA sequence of a photosynthesis enzyme, RuBisCO, which, while ingenious, seems impossible for an alien to decode its meaning [15,16,17]. Yet as he said, it was more about our view of ourselves than for any alien recipients.
A general assumption has been that technological aliens must have a reasonably common perception of the universe as we do. Indeed, John McCarthy (of Lisp and AI fame) espoused that view at a SETI meeting [11]. His argument was that just as evolution results in convergence of phenotypes to fit their environment, like the shapes of Ichthyosaurs and dolphins, so intelligence will converge on the same concepts as we share the same universe and discover its properties and laws. Math as a purely logical construct is therefore often assumed to be a common language between humans and aliens. Numbers, and their manipulations should be common. Hence the idea that a primer in a message might start with basic arithmetic and work upwards from there. However, at another SETI meeting, mathematician Keith Devlin was not so convinced that this would be the case. His argument was that math was actually a unique product of the human mind and reflected our construction of the universe [11].
If he is correct, what are we to make of Eugene Wigner’s 1959 lecture title about math and nature, “The Unreasonable Effectiveness of Mathematics in the Natural Sciences”? Is this a unique formulation of the human mind and experience, whilst it may be very different for an alien mind?
This issue has been raised in a number of works, but it is perhaps most concisely put in Brian McConnell’s slim book, “The Alien Communication Handbook” [13] and his Centauri Dreams post “Communicating with Aliens: Observables versus Qualia” [14]. His view is the consensus one, that some things such as physical objects and actions are communicable between species, whilst others, such as feelings and experiences, are most likely not. He takes McCarthy’s side in saying that mathematics and logic are also assumed to be universal, perhaps confirming Wigner’s statement.
We often forget that language determines how one views the world. It is well known that in the West we tend to see the world as distinct objects with some associations between them. The Japanese also see the spaces between objects, and have words to describe those spaces. e.g., Ma is for negative space, such as the space between musical notes, or the spacing of flowers in flower arrangements. As we know from the difficulties of translation between languages, some concepts don’t have words in the other language. In English, we now use the German word schadenfreude as there is no English equivalent for the “pleasure derived by someone from another person’s misfortune.” The power of words to shape perception is exemplified in Ted Chiang’s short sci-fi story “The Story of Your Life”, filmed as “Arrival.” It illustrated how language itself could change what you experience, in this case one’s experiences of the future.
AI as magic Pixie dust and an alien mind
Our AI technology using LLM technology has performed creditably well in translation between languages. It has also played a role in extracting the key components of sperm whale codas, and therefore establishing associations that apply between different individuals in the same pod, much as humans have different accents and ways of speaking the same words. AI is currently the magic behind science fiction universal translators, allowing humans and aliens to converse.
But of perhaps more pertinent is the idea that AIs are becoming minds, although there is considerable debate about this. However, AI “minds” are likely to be different than human minds, if only because they do not experience the qualia we experience. Are AIs going to have unemotional thoughts like Star Trek’s humanoid robot, Commander Data, but like sociopaths, able to mimic human emotions and empathy? If given a very different training set of data, would they acquire minds that are shaped by that data set? Could we design the data set to mimic that of hypothetical aliens, and thereby create fake alien AI minds?
Humans are good at projecting agency and anthropomorphizing animals and objects. Most famously, Weizenbaum’s simple ELIZA therapist program persuaded many that it was a person, much to his horror. Alan Turing had proposed that if judges could not distinguish between a human and a computer responding to questions, then the computer program was intelligent. After years of Turing Test competitions, we have now comfortably blown past that test, although we are still debating if LLM-based AI is truly intelligent. The interesting issue is that we are at the point where several people believe that AIs are conscious. AI scientist Geoff Hinton, the inventor of deep learning architecture, is one such. Early chatbots would say they might be conscious, although the frontier models are trained to say they are not. But are they just trying to hide that fact from us? This was anticipated in the 1960s in the movie 2001: A Space Odyssey. Below is a transcript of a key conversation in the movie:
Table 1. Dialog with astronauts and HAL 9000 from the movie 2001: A Space Odyssey.
AIs are currently like brains in a box. However, as we develop robots of various types that embody AI, will they learn to experience the world more as their bodies allow them to, much as animals and humans do? We are on the cusp of finding out.
Conclusion
Learning how some animals communicate and how far they have a language will provide us with new ideas on how an alien may try to signal us. AI can not only help us understand animal languages, but also help in decoding alien signals if/when we receive them, and even to communicate with them. We should even be able to tell how far our minds overlap in subjective concepts and experiences. Should aliens be machines, then it may be best if AIs take the lead in communication with them. If it turns out that we are alone, then there is value in being able to communicate at some level of understanding with intelligent animals. While I don’t expect we could experience being a cetacean, we could probably experience being one of our hominin cousins, such as the chimpanzee and bonobo.
In the meantime, all we can do is “Watch the Skies” and wait for a signal to arrive.
Appendix A
If we modify the values in the Wikipedia entry, using values in the ranges suggested, but update the annual rate of star formation to more current values, the product of the 1st 6 probability terms = 1. Therefore, the final term, the longevity of the communicating civilizations, equals the number of communicating civilizations in the galaxy.
References:
1. Wikipedia contributors. (2026, July 31). Drake equation. Wikipedia.
https://en.wikipedia.org/wiki/Drake_equation
2. de Paulis, D., et al. (2023) “First Contact: Global team simulates message from extraterrestrial intelligence to Earth”
https://www.seti.org/news/first-contact-global-team-simulates-message-from-extraterrestrial-intelligence-to-e arth/
3. Beguš, G., Dabkowski, M., Sprouse, R. L., Gruber, D. F., & Gero, S. (2025). The phonology of sperm whale coda vowels. Proceedings of the Royal Society B Biological Sciences, 293(2069).
https://doi.org/10.1098/rspb.2025.2994
4. Begus – video on whale clicks https://www.youtube.com/watch?v=eFbnYQI-Oa0
5. Taylor A. Hersh, et al, (2026) “Dialect variation in Mediterranean sperm whales shows evidence of cultural evolution in an isolated population”. Proc Biol Sci 1 June 2026; 293 (2073): 20260165.
https://doi.org/10.1098/rspb.2026.0165
6. Diamant, R., Gruber, D. F., Gero, S., & Beguš, G. (2026). Evidence for the influence of shipping underwater radiated noise on sperm whale coda structure. Ecological Informatics, 103881. https://doi.org/10.1016/j.ecoinf.2026.103881
7. Sayigh, L., Jensen, F., McHugh, K., Casoli, M., Lemercier, L., Tyack, P., Wells, R., & Janik, V. M. (2025). First evidence for widespread sharing of stereotyped non-signature whistle types by wild dolphins. bioRxiv (Cold Spring Harbor Laboratory). https://doi.org/10.1101/2025.04.21.647658
8. Nagel, T (1974) “What is it like to be a bat?”, The Philosophical Review, Vol. 83, No. 4 (Oct., 1974), pp. 435-450
9. Wikipedia contributors. (2026a, May 22). Arecibo message. Wikipedia.
https://en.wikipedia.org/wiki/Arecibo_message
10. Wikipedia contributors. (2026c, July 31). Pioneer plaque. Wikipedia.
https://en.wikipedia.org/wiki/Pioneer_plaque
11. McCarthy, J (2009) “Convergence of Intelligence” (SETI Talks)
https://www.youtube.com/watch?v=kvIqc0aBR0A
12. Devlin, K. (2013) “Contact with ET using Math? Not so fast” (SETI Talks)
https://www.youtube.com/watch?v=KveKjHIipgo
13. McConnell, B. S. (2021). The Alien Communication Handbook: So We Received a Signal—Now What? Springer. pp247-248, 278-281
14. Gilster, P. (2021, December 10). Communicating with Aliens: Observables versus Qualia | Centauri Dreams. https://www.centauri-dreams.org/2021/12/10/communicating-with-aliens-observables-versus-qualia/
15. Gilster, P. (2009, November 18). “RUBISCO Stars” and The Riddle of Life | Centauri Dreams. https://www.centauri-dreams.org/2009/11/18/%E2%80%9Crubisco-stars%E2%80%9D-and-the-riddle-of-life/
16. Gilster, P. (2009b, November 19). “RUBISCO Stars”: Part II | Centauri Dreams.
https://www.centauri-dreams.org/2009/11/19/rubisco-stars-part-ii/
17. Wikipedia contributors. (2026b, July 18). RuBisCO. Wikipedia. https://en.wikipedia.org/wiki/RuBisCO
Further Reading
1. Wikipedia contributors. (2025, December 4). Lincos language. Wikipedia.
https://en.wikipedia.org/wiki/Lincos_language
2. Freudenthal, H. “Lincos: Design of a Language for Cosmic Intercourse, Part 1 “
https://en.wikipedia.org/wiki/Lincos_language
3. Chiang, T “The Story of Your Life” https://en.wikipedia.org/wiki/Story_of_Your_Life
4. Earth Species Project https://www.earthspecies.org/
5. Clarke, A.C. “History Lesson” https://en.wikipedia.org/wiki/History_Lesson
6. Michaud, M. (2010). Contact with Alien Civilizations: Our Hopes and Fears about Encountering Extraterrestrials. Copernicus. pp279–284
7. Bracewell, R. N. (1974). The Galactic Club: Intelligent Life in Outer Space. Scribner Book Company.
8. Baird, J. C. (1987). The inner limits of outer space. Dartmouth College Press.
9. Dick, S. J. (1996). The Biological Universe: The Twentieth Century Extraterrestrial Life Debate and the Limits of Science. Cambridge University Press.
The Ones Who Look Outward 6 Aug 5:02 AM (2 months ago)
Thinking about a great filter through which a civilization must pass before its survival is assured usually leads to catastrophic scenarios, such as planetary suicide by nuclear war, or climate holocaust (assuming the filter lies ahead of us and not behind). But filters may be more subtle and tied in with epistemology. How does intelligence view its place in the universe and thereby engage with other beings? In today’s essay, Ian Brownlie looks at the matter from the standpoint of how knowledge is acquired and transmitted. Based in New Zealand (near Hawke’s Bay on the North Island), Ian is an Electrical Engineer who works with commissioning high voltage complex power systems. The survival and evolution of technology may be a harder step than we think.
by Ian Brownlie, BE(E&E)
Intelligence has appeared on Earth in many forms. Science-like inquiry has appeared more than once. But sustained, cumulative science appears to be different. It survives across generations, sharpens its own methods, and turns curiosity first into instruments, then into machines capable of leaving the world. So far as we know, that has happened only once. That asymmetry may matter. The night sky has always been there—indifferent and immense —but only one lineage seems to have kept turning that view into telescopes, rockets, and radiodishes. The outward gaze did not merely happen; it had to be sustained. And that fragile fact may tell us something unsettling about why the rest of the galaxy seems so quiet.
The Fermi paradox begins with a straightforward expectation: if life arises easily, and intelligence follows often enough, then the Milky Way should be full of civilizations that have spread, signalled, or at least left detectable traces. Yet we see nothing. The Great Filter hypothesis—a phrase the economist Robin Hanson coined in the 1990s—tries to explain this silence by proposing that somewhere along the path from chemistry to starships lies a step so improbable that almost nothing passes it.
Most discussions place that step either very early (life is rare) or very late (civilizations destroy themselves). But there is a transition hiding in plain sight—one usually folded into the broad category we call “intelligence.” It is not intelligence itself. It is not tool use, language, or even culture. Nor is it the first appearance of science-like inquiry. It is something stranger and more fragile: the sustained decision to look outward, to ask questions about things that may offer no immediate survival advantage, and to keep asking them long enough for the answers to accumulate into a durable scientific tradition.
This essay proposes that the successful preservation of outward-directed inquiry across generations—a self-sustaining relay that accumulates observations, models, instruments, and knowledge faster than they are lost —may be one of the rarest steps in the entire cosmic sequence.
The difference between intelligence and curiosity
Earth is full of cleverness. Corvids solve puzzles. Octopuses manipulate objects with eerie precision. Dolphins invent games. Intelligence, in the broad sense, has evolved repeatedly. But cumulative outward-directed inquiry—the kind that leads a species to build durable models of realities beyond its immediate niche—appears much rarer.
A raven can plan several steps ahead, but we have no evidence that it wonders what stars are. A dolphin can understand symbols, but it does not build instruments to examine worlds beyond its own. Intelligence, even sophisticated intelligence, is not enough.
The outward turn is a different kind of trait. It is the moment a lineage stops using the sky as a tool—for navigation, calendars, and omens—and begins interrogating it. It is the moment curiosity turns toward the remote and the abstract: costly, impractical, and directed at things that cannot feed you, shelter you, or help you survive.
Galileo’s telescope did not cause this shift. It revealed it. Grinding a lens to ask whether Jupiter has moons is not a survival behaviour. It is a declaration of intent: we want to know what is out there, even if knowing does nothing for us.
That kind of curiosity is not something natural selection can easily target directly. Evolution is myopic. It rewards traits that help organisms survive and reproduce in particular environments. Curiosity about distant objects with no obvious payoff is more likely to arise as a by-product of cognitive machinery built for mapping danger, opportunity, social life, and time. Such by-products need not be unique. But they are unreliable. They can appear without becoming central to a culture; they can flare without compounding.
A sample of one—and a pattern inside it
We have only one biosphere to study, and that makes every inference precarious. Still, within that single record, the pattern is suggestive. Across billions of species and several independent origins of complex cognition, we have evidence for many kinds of cleverness and for more than one human culture that practised early scientific or astronomical traditions. What appears singular is not inquiry itself, but an unbroken lineage of inquiry that became cumulative, instrument-building, self-correcting, and ultimately capable of leaving its planet.
That does not prove it is improbable. It might simply be suppressed: the first lineage to achieve it monopolizes the niche, preventing others from following. Or perhaps Earth has not had enough time for a second instance.
However, the cultural record tells a more nuanced story—one that shifts the argument from biology to history.
The spark that keeps failing to catch
Humanity did not look outward once. We looked outward many times—and each attempt depended on something more delicate than insight.
Long before formal science, people built temples aligned to the sky. Later, Babylonian astronomers tracked the heavens with astonishing precision. Greek thinkers built geometric models of the cosmos. Chinese imperial astronomers kept continuous records of comets and novae for centuries—though largely in service of the calendar and the court, with the sky read as an instrument of statecraft rather than interrogated for its own sake. Medieval Islamic scholars constructed observatories, critiqued inherited models, and developed mathematical tools that later reappeared in Europe.
These were not minor sparks. They were bright, sustained attempts to understand the sky. Nor were they sealed off from one another: knowledge moved through translation, trade, conquest, correspondence, and inheritance. The story of astronomy is not a set of isolated awakenings, but a long and uneven transmission.
That is the point. The outward turn is not a single step. It is a relay—a chain of observation, mathematics, instrument-making, patronage, teaching, criticism, and memory passed from one generation to the next. A chain can strengthen. It can also break.
Institutions collapse. Dogma intrudes. Political priorities shift. Economic margins shrink. Languages of scholarship are lost or become inaccessible. Instruments decay. A culture may look outward for a century and then turn inward again, leaving its questions unanswered, or answered only in forms that later generations cannot use.
The European scientific tradition of the 17th century was not the first outward turn. It was the one that became self-amplifying: mathematically precise, institutionally protected, technologically useful, and increasingly public. It ran long enough, and continuously enough, to accumulate the observational and technological scaffolding required to leave the planet.
This is where the argument touches decades of work on cumulative cultural evolution—the ratchet effect, a term the psychologist Michael Tomasello coined for the way human culture locks in improvements without slipping backward. Humans, unlike even our closest relatives, do not merely invent; we preserve, copy, correct, recombine, and lock in improvements so that each generation starts from the accumulated position of the last rather than from scratch. No other species on earth ratchets this way, which is why a raven’s cleverness never compounds and a physicist’s does—the capacity the anthropologist Joseph Henrich calls the secret of our success. Science is an extreme, formalized instance of that process: it requires not only minds capable of wonder, but also social systems capable of keeping wonder alive and passing it forward intact.
If this pattern is general, then the rarity may lie less in the spark than in the sustaining. Many worlds may produce sky-watchers. Some may even produce science. Fewer may produce scientific traditions that survive long enough to become physics, engineering, and eventually spaceflight.
The ladder that burns
If the outward turn is a relay rather than a single step, then the relay must survive not only ignorance, dogma, and institutional decay, but success itself. A sustained scientific tradition eventually produces technologies powerful enough to threaten the conditions that allowed that tradition to continue.
This is the ladder that burns. The ladder is not only fuel; it is the whole chain of conditions that lets curiosity become spaceflight—preserved knowledge, industrial capacity, and usable access to orbit, each of which must be sustained in turn. These are not separate filters, but successive tests of the same fragile achievement.
The first test is whether knowledge can survive long enough to become industry. Industrial civilization may require a burst of dense, easily exploited energy to extract materials before it has the wisdom to manage the consequences. On Earth, fossil carbon formed one rung of that ladder: a one-time inheritance accumulated over hundreds of millions of years. It is at least a live hypothesis that industrialization requires access to unusually concentrated energy resources before a civilization possesses the technology needed to exploit more durable alternatives. On Earth, that energy windfall opened a narrow window in which humanity bootstrapped itself from pre-industrial life to radio astronomy, rockets, and planetary-scale measurement.
But an energy rung can be consumed as it is climbed. The same energy source that accelerates industrial capacity can destabilize the climate, exhaust cheap reserves, intensify competition, or weaken the institutions that make cumulative science possible. The danger is that a civilization may acquire planetary power before it has built the habits of restraint, coordination, and long-range reasoning needed to preserve the relay that produced that power in the first place.
The second test is whether industry can survive long enough to support spaceflight. Practical early spaceflight requires concentrated energy: engines, propellants, exhaust, heat, discarded stages, and machines operating near failure. Each launch may leave artefacts behind. Satellites die. Upper stages fragment. Collisions create debris, and that debris raises the chance of still more collisions—the runaway cascade that Donald Kessler and Burton Cour-Palais modelled for NASA in 1978, now known as Kessler syndrome. A world can begin climbing toward space and, through the accumulated residue of its own first attempts, make access to orbit progressively more dangerous.
The third test is whether access to space can be sustained once it becomes possible. It is not enough to invent rockets; a species must preserve the relay long enough to improve them, the industry long enough to build them, and the orbital environment long enough to launch them at all. Each depends on the same cumulative capacities as before: memory, measurement, correction, restraint, and cooperation across generations. If low orbit becomes a minefield before a civilization learns those habits at planetary scale, the path outward may narrow just when it is first opening, as the energy window disappears.
In that sense, the outward turn may be essential not only for discovering the sky, but for surviving the consequences of having discovered it. The same habits that make astronomy possible—modelling unseen systems, trusting abstract evidence, coordinating across generations, and caring about consequences beyond the immediate horizon—are also the habits needed to survive industrial acceleration and keep space usable.
Humanity is inside this window now. We must keep the chain intact at all three levels: knowledge, industry, and orbit. The question is whether the outward gaze can become durable enough—not merely in imagination, but in institutions, energy systems, launch practices, and habits of care—to survive the phase in which space becomes a real destination.
What the silence might mean
The usual readings of the Fermi paradox are grim. Either life is rare, or intelligence destroys itself. But there is a third possibility—speculative, but consistent with the pattern we can actually inspect.
It might be objected — with David Brin’s Principle of Non-Exclusiveness, or what Jason Wright calls the monocultural fallacy — that a filter most civilizations fail explains nothing, since a single exception could colonize the galaxy alone. The objection is decisive against filters of choice, which assume every species settles on the same fate forever; uniform behaviour is not even universal among humans. But two things blunt it here. First, we have no demonstrated case of the turn being made and held — ourselves included, since we are still inside that test rather than through it — so the exception the objection requires may simply not yet exist. And second, more decisively, the window for spaceflight opened late: only after billions of years of stellar enrichment laid down the metals a technological species needs. Even a genuine exception would have to have arisen early enough in that window to have already crossed to us — and we may be not alone so much as early. The early always look out on a silent sky.
The Galaxy may be full of life. Full of intelligence. Full of brief outward glances, and perhaps even repeated beginnings of science. And quiet—because those beginnings almost never become durable civilizations of inquiry.
Civilizations may look outward for a while—a century, a millennium—and then turn inward again, or collapse, or lose the institutional continuity required to sustain the relay. Their astronomies may be bright but brief. Their questions may be asked but not accumulated. Their telescopes may be built but not improved.
From a distance, such civilizations would appear as little more than flickers: a thin smear of radio leakage, a brief industrial glow, and then silence. On that reading, we are not necessarily the one species that looked when others did not. We are simply the one spark, so far as we can see, that may be allowed to continue.
And the work of continuing it—of passing the question to the next mind before we go—may be the rarest and most fragile part of the entire cosmic sequence.
A closing thought
If the outward turn is a relay, not a step, then our task is not merely to keep looking. It is to keep the chain unbroken: the institutions that preserve knowledge, the habits that reward difficult questions, the energy transition that buys time, and the long view that makes any of it matter.
The spark may be common. The chain is not.
And right now, we may be running the stretch where the chain most often breaks.
A note on prior work
The argument of this essay draws on several established bodies of work, named here so that its debts are explicit and its own contribution is clear. The framing of the Great Silence in terms of a Great Filter is Robin Hanson’s (1998). The claim that human culture is distinguished by a cumulative “ratchet” that locks in improvements across generations, rather than slipping back, is Michael Tomasello’s; the broader case that this cumulative cultural transmission, and not raw individual intelligence, is the true source of human capability is Joseph Henrich’s. The runaway orbital-debris cascade invoked in the discussion of sustaining access to space is the syndrome modelled by Donald Kessler and Burton Cour-Palais for NASA in 1978.
What this essay adds to these is the proposal that the sustaining of outward-directed inquiry across generations — the unbroken relay, rather than the first spark — may itself be one of the rarest and most fragile steps in the cosmic sequence, and that the same habits which keep that relay intact are the ones a civilisation needs to survive the industrial and orbital hazards its own success creates.
References
Hanson, R. (1998). The Great Filter — Are We Almost Past It? Working paper, George Mason University.
Henrich, J. (2015). The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter. Princeton University Press.
Kessler, D. J. & Cour-Palais, B. G. (1978). Collision Frequency of Artificial Satellites: The Creation of a Debris Belt. Journal of Geophysical Research 83(A6), 2637–2646.
Tomasello, M. (1999). The Cultural Origins of Human Cognition. Harvard University Press.
Detection of a Habitable Zone Planet with an Atmosphere 29 Jul 3:59 AM (2 months ago)
If we couldn’t figure out what to call CD-35 2722B b, which I assume is the correct way to refer to the planet-sized object in this red dwarf / brown dwarf/ gas giant system, another planet has a bit of a definitional problem as well. LHS 1140 b is an interesting super-Earth orbiting a red dwarf in Cetus in its habitable zone. Some 49 light years out, this planet is almost 6 times Earth’s mass and boasts a radius 1.7 times larger. Receiving 42 percent of the stellar radiation that Earth does, its surface temperatures allow the presence of liquid water.
But exactly what kind of planet is this? Is it an airless, rocky world, an ocean planet, or even a mini-Neptune? We can probably rule out the latter because its mass would be low for that category, and we can also, contrary to some press reports, not consider it in any way, shape or form ‘Earth-like.’ But thanks to new work out of Harvard and the Carnegie Institution for Science, we can now declare that it does have an atmosphere.
This is a useful finding because rocky planet atmosphere detection has been conspicuously difficult. What you gain with studying M-dwarf planets is the low contrast between a relatively dim star and a planet’s light, but you’re also dealing with a category of star prone to violent flare activity. Every M-dwarf in the galaxy is a young star compared to its likely lifespan, given that these stars, perhaps 85 percent of the stellar population, have lifetimes that can reach well beyond a trillion years.
Pulling a signal from water or carbon dioxide out of spectrographic data is problematic because these volatiles species would be expected in the lower levels of a planet’s atmosphere, a tough catch for any observatory. But helium escape is another matter. In detecting helium at LHS 1140 b, the new work, demonstrates that an atmosphere is indeed present, whether this is a water world or not.
Young M-dwarfs are notorious for violent flare activity, a problem not only because flares can obscure the signal of a transiting planet, but also because they can potentially scrub nearby planets of their atmospheres entirely. In this case the flares have helped us: The escaping helium is thought to be driven by bombardment of the upper atmosphere from the star’s X-ray and extreme ultraviolet (XUV) activity.
Helium escape is especially valuable because it is observable from the ground, unlike the classic hydrogen (Lyman-alpha) escape signature. We’re seeing the residue of a process that can play out over gigayears: lighter hydrogen escapes preferentially over time — a loss we can’t easily observe directly — leaving behind a helium-enriched upper atmosphere that we can detect.
The paper may even tell us something about the ‘cosmic shoreline,’ the dividing line between an orbit where an atmosphere can be sustained and one where it cannot. Indeed, this work, conducted using the WINERED spectrograph at Las Campanas Observatory in Chile, shows that the inner world at LHS 1140 is evidently airless, with the ‘shoreline’ located between the two worlds.
From the paper:
The cosmic shoreline is a proposed boundary that separates airless rocky planets from those that retain atmospheres for billions of years. The two planets in the LHS 1140 system are on either side of the proposed cosmic shoreline. Our non-detection of helium absorption by LHS 1140 c is consistent with the previously measured dayside emission, which indicates that the planet has little to no atmosphere. Therefore, this system is consistent with the proposed position of the cosmic shoreline.
Moreover, we seem to be tracking a phenomenon that changes in short order. Co-author Shreyas Vissapragada (Carnegie Science Observatories) comments:
“After much careful analysis and consideration of the spectra, we determined that helium was escaping from LHS 1140 b’s atmosphere in 2024 due to heating from stellar X-rays and extreme ultraviolet radiation. However, our 2025 observations revealed no escaping helium, so the atmospheric escape appears to be variable. It is a rare privilege to witness the atmosphere of an extrasolar planet change on such short, human timescales!”
Image: In this artist’s rendering, the exoplanet LHS 1140 b is shown in the foreground, surrounded by a helium-rich atmosphere. Another nearby rocky planet orbits the same cool red dwarf star in the distance. This new study provides the strongest evidence yet that LHS 1140 b has retained an atmosphere. Credit: Carnegie Science.
Colin Cherubim (Harvard University), lead author of the paper in Science, points out that this is the first detection of an atmosphere on a rocky planet in the habitable zone of any star. Nice work, as Cherubim’s team had predicted precisely this mechanism in the LHS 1140 system. Escaping gases may indeed be a useful tool as we press on with more detailed investigations of planetary atmospheres on smaller, more Earth-like worlds.
The paper is Cherubim et al., “Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone,” Science 16 July 2026. Full text.