Challenges for Determining Exoplanet Atmospheres

Attempting to determine the precise compositions of exoplanets has a number of significant challenges. Even some of the more recent works utilizing the James Webb Space Telescope are not quite at the necessary noise resolution limits to obtain the precise spectra of nearby sub-Neptunes and terrestrial exoplanets.

One of the more recent methodologies to extract the spectral signal from the noise has been to use Bayesian modeling techniques. This statistical method utilizes the inferences of difference chemical species to attempt to rule out competing molecular spectral overlaps and end up with a highly probable answer of what produced the spectral absorption line. The problem is that Bayesian inference requires prior distributions to produce posterior probabilities. Key point: we don't have prior exoplanet data to utilize.

In a recent paper by Welbanks, et al. (2026) they note that some of the earlier claims of molecular detection on exoplanet K2-18b may be erroneous since they were able to show "numerous alternatives providing equally good or better fits." In the graph below they show that multiple hydrocarbons can produce significant overlaps.

This critique won't last long, however. Improvements in instrumentation along with the Nancy Grace and Pandora space telescopes will start clarifying the data. Clearly a Level 1 approach.

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New White House UAP Council

Avi Loeb, the Harvard astronomer who has publicly pushed the envelope on extraterrestrial life has been approached by the Trump White House to run a new UAP council that will study and advise on Unidentified Aerial Phenomena.

Loeb has served in government functions before such as Trump’s Council of Advisors on Science and Technology. The council will be made up of a number of other Harvard staff, some astrobiologists and some miscellaneous members. The intention is to coordinate UAP investigations and help with the “timely coordination of declassification of UAP-related information.” It will be interesting to see if much can come of this!!

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SKA Could Detect Earth's Cell Phone Network within 5 Lightyears

As the Square Kilometer Array (SKA) radio telescope arrays continue to build out in Australia and South Africa, the potential resolution of this massive radio astronomy project is enormous - enhancing the possibility of discovering extraterrestrial signals. Some current estimates propose that leakage radiation from something like Earth’s cellphone network could be detected within a radius of 5 light years.

You can see the SKA overall projected sensitivity (min detectable reference signal at 100 light years) in the graph below (solid green line - Trenblay et al., 2026).

Read more here: Searching for Extraterrestrial Intelligence with the SKA

Ability of world-wide radio telescopes to detect transmissions by frequency

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SETI Institute Kickstarter for Scanning the Sky

What if we could create a network of independent sky scanning systems that could coordinate the observations of anomalous astronomical events that might hint at extraterrestrial activity? As they note - “A potential discovery must be carefully authenticated by independent organizations and different instruments before it is announced as credible evidence of extraterrestrial intelligence.”

Well, it seems the SETI institute has partnered with SkyMapper - a Kickstarter funded device that links to a global network of independent, separated instruments - each running on a rooftop anywhere in the world. 

You can find out more here: https://www.seti.org/news/disclosure-needs-data/

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Science Fairs and Exoastronomy

Last month I had the honor again to be a judge at the regional high school science fair comprised of students from the full metro area of the Twin Cities. There were over 200 projects across all disciplines from over 50 high schools (so great to see). Nevertheless, each year I'm usually disappointed (not in the projects) due to the fact that there is typically only one astronomical project in the program.

However, this year was an exception with 6 projects having astronomical ties including 2 that were specifically about exoplanet research. For me personally it was exciting to be able to interview the students on their approach and research. In the exoastronomy realm, one of the two projects focused on improving Apodized Pupil Lyot Coronagraphs (APLC) for direct exoplanet imaging and the other on comparisons of the K2-18b exoplanet's DMS spectra with other known spectral signatures in the HITRAN database.

Just amazing to see the creativity and good science coming out of our high schools!

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What is the Closest Earth-like Exoplanet?

Artist View of M dwarf Exoplanet Sun

Recently I was asked this question by a friend which made me stop and ponder it for a minute. Of course, my mind jumped to my older posts on what an 'Earth-like' planet is along with the definition of a "habitable" planet (the key differentiator being Earth-like doesn't necessarily mean habitable or terrestrial).

This isn't an easy question to answer since we don't fully understand what habitable or terrestrial might look like for different exoplanet stellar systems. For example, if we're going to limit the question to exoplanets around F, G, K and M dwarf stars due to stellar lifespan (for example, bright A5V stars only have a lifespan of about 750 million years), then one current estimate is there are 65 billion terrestrial planets around these 4 classes of stars in the Milky Way galaxy. However, since cool, low mass M dwarf stars comprise 76% of the total, terrestrial exoplanets are going to be in tight, short orbits, most likely tidally locked with low UV stellar radiation. That doesn't rule out Earth-like habitable exoplanets, but that's a large unknown at this point (something we'll talk about in a future post). 

So, to get back to the question, let's pick F, G and K main sequence stars first. Using that criteria, 82 Eridani in Eridanus (visible from the southern hemisphere) is going to be the best answer for those stellar candidates. At about 20 light years away, the two planets, 82 Eridani e and f orbit a G6V star (very similar to the Sun) with a periods of 147 and 647 days potentially within the star's habitable zone. As of this writing, both fall on the edges of that habitability zone with e on in the inner edge and f on the outer edge. Also, the detected exoplanets masses are at least 4x that of Earth's. Given that, this is probably the best case for now. 

In the northern hemisphere, if you look in the constellation of Cassiopeia, the orange star Gliese 892 (stellar type K3V - cooler than the Sun) may be the closest at 21 light years. However, the main problem is the candidate exoplanet's mass at over 10x Earth's. Also, that particular exoplanet hasn't been confirmed.

Honestly, there's not much beyond this since we're dealing with more distant, brighter stars (see my mention of the Malmquist bias in my previous post). If we go back to lower mass, cooler M dwarf stars then my favorite pick is Gliese 667 in the constellation of Scorpius at 23 light years away. It is a triple star system with the third star, Gliese 667 C, having detected exoplanets. Planet e with an orbit of about 62 days and mass of about 3x that of Earth's is within the star's habitable zone. There are many other M dwarf star systems with detected exoplanets. If you're interested, you can browse the Habitable Worlds Catalog or NASA's Exoplanet Catalog to see what potential exoplanets could be candidates.

Given how difficult this question is, there just isn't a good answer yet. There are still so many assumptions along with unanswered questions as to just what extraterrestrial life is, how it may evolve and what types of stellar systems would support it. All we can do is continue to gather more data and assume life on Earth as the initial standard to measure against.

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The New SETI Protocols for Discovery of Alien Life

Imagining the SETI Announcement

If you were a scientist who just happened to discover and verify the existence of extraterrestrial life, how would you proceed to announce it? What would be your proper course of action? This was the question asked by SETI scientists in the 1980s when they began to ponder how a discovery like this might unfold. By 1989 they had drafted what was called Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence, or, the First SETI Protocol (you can read it here). It was revised and renamed in 2010. 

So, now, in 2026 another revision is on the docket to be voted on by the members of the Permanent SETI Committee which is much more robust than previous versions. With the advent of social media along with more public mistrust in information, the authors have hinted at their reasons for the change: 

 

to prepare an updated version of the 2010 Declaration of Principles Concerning the Conduct of the Search for Extraterrestrial Intelligence, with the aim of preserving the enduring values of earlier documents while making them relevant to the realities of twenty-first century science, media, and public engagement. 

Having worked in industry for many years, I understand the need for protocols and processes. However, I’m not convinced that discoveries of extraterrestrials be it from SETI scientists or aliens announcing themselves publicly is going to follow the declaration’s standards. It seems that extraterrestrials and first contact may be a messy social event no matter what kinds of best practices we as humans develop. Take this statement for example:



 

SETI practitioners shall adhere to the highest ethical standards, ensuring cooperation, honesty, and integrity in all aspects of their work. They will collaborate with international legal authorities to establish clear frameworks for managing the dissemination of information about potential extraterrestrial detections and comply with relevant laws and regulations.

When dealing with an event of worldwide importance, adhering to the standards outlined are hard to imagine for something that could be this messy and chaotic. Nevertheless, it’s good to have a set of principles to drive awareness in the scientific community.

You can find the new revision in the proposal paper here.

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The Eschatian End to an Extraterrestrial Civilization

If you’re familiar with Dr David Kipping of Columbia University you may have seen his appearances on various YouTube channels or his Cool Worlds channel talking about extraterrestrial life. Kipping recently published a very short paper hypothesizing how we might first detect an extraterrestrial civilization based on observational bias. But, before we get into that let’s first pronounce the new word derived by Kipping - eschatian (es-ska-ti-un) derived from the word eschatology (es-ska-ta-le-gee)^[1] meaning the final events in the world or history. Typically eschatological discussions are reserved for Christian theology but the word does serve some purpose to what some may coin “end times”.

So how does that definition tie to extraterrestrials? Kipping hypothesizes that our first detection of signals may be very similar to other types of large and loud events in then universe (think supernovae explosions, gamma-ray bursts, etc) or objects that emits large amounts of energy that can be detected. Add to that astronomers are burdened with something called the Malmquist bias meaning we detect the brightest, most energetic objects first and lower energy objects are hidden until more sensitive technology is developed.

Given those conditions our first detections of any extraterrestrial civilization may very well be its end - the “loud” burst of energy from a nuclear war or some other catastrophic event. As Kipping notes 

 

rare examples of loud civilizations will truly be more likely to be detected, against the backdrop of what is (presumably) a more abundant quiescent population.

 

He goes on to create a simple toy mathematical model based on the fraction of loud and quiet civilizations and their possible time windows of extreme energy output from an event. In his discussion, the suggestion is some wide field observations may be able to detect such transient events.

This is an interesting hypothesis that touches Level 2 of the exoastronomy categorization. Granted, this is highly speculative without actual values to use for the model. However, these are the types of scientific speculations we need to see more of. His paper can be found here. (I may do a deeper dive on the model in a later post)

1. Note that I'm not using standard dictionary pronunciation guides here↩

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Mars Atmospheric Pressure affecting Ingenuity

Seasonal pressure variation on Mars

A very interesting update on the Mars 2020 mission appeared recently - specifically the Ingenuity helicopter's ability to fly in relationship to Mars' atmospheric pressure. The atmospheric density of Jezero crater is dropping. 

Seasonally, the atmospheric pressure on Mars varies approximates 25-30% peak-to-peak (Smith 2008) due to the exchange of CO2 with the polar ice cap. Ingenuity was designed for flights in atmospheric densities of 1.2-1.5% of Earth's. However, the density may drop to 1.0% requiring some extra spin-up of the blades to stop any aerodynamic stalling.

This does imply some considerations on how atmospheric variability might affect habitability when deeper exoplanet data is analyzed (Linsenmeier et al. 2015 have a good overview)

You can read more about the Ingenuity issues here.

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Avi Loeb Continues to Push the Science of ET

Oumuamua - Credit ESO M. Kornmesser

It's great to see a respected Harvard scientist push the envelope on extraterrestrial life. Avi Loeb was chastised for his speculation on Oumuamua but has bounced back with backing for his Galileo Project - "the search for extraterrestrial technological signatures of Extraterrestrial Technological Civilizations (ETCs) from accidental or anecdotal observations".

 

Loeb published an interesting op ed in Scientific American yesterday outlining his opinions on AI-enabled self-replicating technologies exploring the galaxy and how we might be able to detect these extraterrestrial objects. It's a short read but demonstrates the core idea of his project.

 

Loeb is no lightweight here and has published a number of scientific papers (one example Lingam & Loeb 2019) working through the problems of alien panspermia, probabilities of encounters and implications of the galactic environments on extraterrestrial life.

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Astronomers, UFOs and the Null Hypothesis

In a recent article, Ethan Siegel a Senior Contributor on Astronomy in Forbes magazine, provides a very good overview as to why scientists seems to remain mostly mute on the topic of UFOs. Clearly, part of the problem is that UFOs as a general topic doesn't specifically apply to one scientific discipline such as astronomy - it applies to many different areas of science, sociology, biology, engineering, philosophy, etc. Astronomers tend to get the brunt of the questions - especially due to SETI and astrobiology (or, just because they keep their eyes on the sky).

Many people complain that science isn't doing enough to study the UFO evidence. But, is it really a scientific problem? If aliens revealed themselves wouldn't it fall directly into a social/political problem space? Yes, scientists and engineers would be happy to start extending our knowledge based on what we might learn at that point but currently the types of science we need falls more into statistical work and observational evidence since much of the measures are not repeatable. This is more in line with investigators, sociologists and other disciplines (like the military, of course).

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Significant UFO Disclosures on the Rise

Interesting to see the amount of press interest in UFOs / UAPs recently. It's really quite unusual to see the mainstream media start to report these sightings and stories without some silly, campy quips or side stories to save face (in 'My Blog List' in the right column of the home page, the reporter Billy Cox, aka Devoid, was quite serious on the topic but was shut down recently).

I will be writing much more on this in the future, but to hear a former President of the United States admit there are unknown craft in the sky and that's reported in mainstream media might just raise the extraterrestrial problem more into the scientific realm (even though the discussion was still part of a comedy program).

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Buried Lakes on Mars

Mars south polar region
Fenton & Hayward (2010)

Utilizing the ESA's Mars Express Orbiter, Lauro et al. 2020 reported in Nature Astronomy the potential discovery of additional large water ponds or lakes under the Martian surface. The deposits were identified near the south polar region of Ultimi Scopuli (circled in red on the photo) using the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument. This extends the 2018 work by Orosei et al. 2018 on radar evidence of subglacial liquid water near the south polar region.

Operating between 1.8 and 5mhz, MARSIS reflects 10W radio waves off the surface at a repetition frequency of 127.7 hz. Water has a unique higher reflection property than the surface. With multiple passes by the orbiter, the surface area of interest can get scanned at slightly different regions revealing a region that indicates the potential of a pond or lake. The researchers used data gathered from 2010 to 2019 from MARSIS to strengthen the overall evidence.

Described as lakes and ponds, the water is most likely a slush-like, high saline solution that is pooled about 1 mile under the surface with a temperature of about -90F.

Though it is still too early to fully confirm the discovery of subglacial lakes, this is mounting evidence that should help drive more missions that can eventually use water to fuel hydrogen for Martian bases and/or missions.

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Mars 2020 ExoScience

With less than a year away for the next Mars rover mission of Mars 2020, it seems that a quick overview of one of the science payloads is worth mentioning.  Mars 2020 is expected to launch next July with a landing on Mars in Feb of 2021. Some of the most exciting scientific experiments relate directly to exoastronomy. For the mission, the search for biosignatures is Science Goal #1.

Attempting to detect both past and present biosignatures is no easy feat considering how difficult it is to measure and not contaminate the samples. For the 2020 science team, "a biosignature (a 'definitive biosignature' or DBS) is an object, substance and/or pattern whose origin specifically requires a biological agent. Examples of DBS are complex organic molecules and/or structures whose formation  and abundances relative to other compounds are virtually unachievable in the absence of life." (Mustard et al. 2013). But, how to achieve a DBS is the problem.

We've seen some false positives/tentative results decades before through the Viking Mars missions--such as the metabolic reaction in the Labeled-Release experiment (still controversial) and failure of the gas chromatograph mass spectrometer (GCMS) to detect organics. But, both the Mars Global Surveyor and Mars Exploration Rovers demonstrated Mars was wet in the past hinting at the strong possibility of life during a warmer, wetter period.

For Mars 2020, the primary biosignature instrument will be SHERLOC or the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals. Raman spectroscopy utilizes a laser to interact with the vibrational and rotational states of molecules which shift the scattered photon frequency. For SHERLOC this is a 248.6 nm UV laser which provides both fluorescence and resonant Raman scattering at a wavelength suited to condensed carbon and aromatic organics. The good news is that the power level of the UV laser can be low enough to reduce concern on heating and/or destroying the organic samples.

It's important to note that a detection of a DBS does not complete the 'life on Mars' journey. There is still a second stage to secure a sample, seal it in containers and make it available for return to Earth in future missions thus allowing for more definitive analysis. Small steps but important ones.

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Mission to Europa

This is great news! The Europa Clipper is set to launch in 2025.

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Breakthrough Listen Optical

Breakthrough Listen is one of the most recent SETI efforts by to scan for signals across the optical, radio and near-infrared spectra. It is the largest program in history to search for extraterrestrial civilizations among 1 million of the closest stars (see Gajjar et al. 2019 for an excellent overview and Isaacson et al. 2017 for some suggested candidates). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) at the Fred Lawrence Whipple Observatory in Amado, Arizona has just announced the search for optical signals using 4 12-meter optical telescopes.

Optical SETI is difficult due to multiple factors of distance, ISM and atmospheric absorption, parent starlight, etc. It is a bit of a needle in a haystack to find just the right amount of energy, pulse duration and optical frequency which calls for very high sensitivity in detection. I'll write more about this but 20 years ago Howard et al. (2000) wrote some good preliminary work.

Note: I'm all in support of more funding for SETI-like efforts but not overly pleased that Facebook is on the board.

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Extraterrestrial Cognitive Dissonance?

Quartz had a recent interesting article that talks to the popularity of the science of searching for extraterrestrial life. Their initial example of the media sensation regarding Oumaumau, the unusual object that was observed within the Solar System, is revealing on how scientific information along with speculation can be distorted. Sutter and Siegel calling Bialy and Loeb's paper (2018) insulting and/or sensationalist was too extreme in my opinion (deGrasse Tyson as well). The authors were clearly speculating which warrants more investigation rather than anger. The paper is well structured, scientific and worth a look.

The more significant problem is that scientific speculation gets mixed with popular extraterrestrial theories and UFOs by those with what the article calls 'cognitive dissonance'. This mix can be easily remedied by clear, logical scientific defense of evidential speculation. Academic institutions are going to have to give in sooner or later to this as younger scientists enter the mainstream.

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