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Paper Roundup July 2025: 3I/ATLAS "fanfiction," arsenic life retraction, and K2-18b

Elise Cutts

Elise Cutts

— 19 min read
Paper Roundup July 2025: 3I/ATLAS "fanfiction," arsenic life retraction, and K2-18b
Magpies famously "collect" things.

Every month, I collect interesting, fun, rage-inducing, or otherwise noteworthy papers in complexity, astrobiology, and origins. Inclusion is not endorsement. Weird suggestions, glaring omissions, and typos are 100% human error and 0% AI hallucination. Think something should be included in next month's newsletter? Shoot me an email at elise@reviewertoo.com.

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Highlights

Astrobiology: "Comet fanfiction about aliens"

Is the Interstellar Object 3I/ATLAS Alien Technology? (July 22, arXiv preprint) by Adam Hibberd, Adam Crowl, and Abraham Loeb

For the third time, astronomers have spotted a visitor from beyond the solar system: interstellar comet 3I/ATLAS. Avi Loeb, a Harvard astrophysicist- turned-alien-hunter who thinks we should be devoting more energy and funding to searching for intelligent life than exoplanet biosignatures. Loeb has a bad reputation for making sensational claims and behaving unprofessionally with colleagues who disagree with him; he's effectively been ostracized from the astro community at this point. He also has a history of thinking objects like this might be interstellar alien spacecraft. So the jokes started flying basically as soon as 3I/ATLAS was announced, and only intensified after Loeb did indeed suggest that the interstellar interloper could be a spaceship in comments for a predictably sensational story in the British tabloid Daily Mail.

As of tonight's Arxiv I don't believe my colleague on the 2nd floor has yet published a claim that it's a spaceship.

— Jonathan McDowell (@planet4589.bsky.social) July 3, 2025 at 3:19 AM

Not long afterwards, Loeb and some colleagues posted a preprint about 3I/ATLAS maybe being a spaceship, which presents itself as a pedagogical exercise rather than a serious claim. Even so, local and national news stations and magazines picked up the story and ran with it, interviewing Loeb for TV and quoting him in articles. Joe Rogan straight up presented 3I/ATLAS as an ongoing alien invasion based on the preprint published on "arr-ex-I-vee, whatever that is" to his podcast audience of tens of millions. And then, to top it all off, the Daily Mail ran a story in response with the honestly hilarious headline: "Joe Rogan predicts 'the end of the Earth' as unidentified space object sets course for home planet."

Captain Picard from Star Trek: The Next Generation does a facepalm
Make it not so.

Bluesky was not amused — or maybe actually very amused, because being angry is fun.

An excellent list of questions, although does not address why Avi Loeb always writes a comet fan-fiction about aliens.

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— Elizabeth Tasker (@elizabethtasker.bsky.social) July 18, 2025 at 2:02 PM

Journalists really need to stop asking Avi Loeb for his opinions, on any subject. Because astronomers should not have to spend even more time debunking him.

— Michael Busch (@michael-w-busch.bsky.social) July 3, 2025 at 6:48 PM

My ears are almost bleeding due to the tonal dissonance between Loeb's writings, which are more cautious than you might expect, and his public appearances which are absolutely not cautious. It's not exactly Loeb's fault that tabloids and Joe Rogan-types blow anything and everything to do with aliens out of proportion. But he does nothing to correct them, so it's hard not to shake the feeling that he's carelessly leaving a mess for other astronomers to clean up.

Scientists understandably get upset about this. And beyond frustration, they worry about cooky claims like this eroding public trust in science. On that front, I think they can probably mostly relax. Astrobiology is not epidemiology, and I'm skeptical that bombastic alien claims are as bad for public trust in science as astrobiologists seem to think they are; Bill Clinton went on TV to tell the world we'd probably found aliens in a Mars rock in 1996, and it was basically fine. NASA's science wing even got a funding boost while the rest of the agency was slimmed down.

Unpopular opinion incoming. I think there's arguably a place in science for people who make bombastic, almost-certainly-wrong claims that bedazzle the press and piss off colleagues — namely, on the outer fringes of fields like astrobiology in which the costs of failure are low and the rewards of discovery are potentially enormous. Setting Loeb himself aside, his core argument — that searching for signs of intelligent life could be a more productive way to find aliens in our lifetime than looking for gases in exoplanet atmospheres — is one I'm sympathetic to. That said, there certainly is a line between earnest nuttiness and snake oil salesmanship. But that's a topic for another day.

Doubts Grow About the Biosignature Approach to Alien-Hunting | Quanta Magazine
Recent controversies bode ill for the effort to detect life on other planets by analyzing the gases in their atmospheres.
Quanta MagazineElise Cutts

The Brain: Sleep is the price of breathing

Mitochondrial origins of the pressure to sleep (July 16, Nature) by Raffaele Sarnataro, Cecilia D. Velasco, Nicholas Monaco, Anissa Kempf and Gero Miesenböck

We spend a third of our lives unconscious — why? Sleep seems like something science should have explained by now. But while researchers know in pretty gruesome detail what happens if you don't sleep, they don't actually know why we need to do it. It's a big outstanding question, and this study may have finally helped resolve it. Based on gene expression experiments, Sarnataro and colleagues makes the case that animals made an evolutionary devil's bargain to evolve complex, energy-hungry nervous systems: breathing oxygen could provide the needed power, but in doing so an organism would slowly poison itself. Its mitochondria, eventually, would need to rest and repair themselves.

... sleep pressure and hunger both have mitochondrial origins, and that electrons flow through the respiratory chains of the respective feedback controllers like sand in the hourglass that determines when balance must be restored.

Evolving a brain capable of consciousness meant accepting the temporary death of that consciousness every night — something that gets a bit more horrifying the more you think about it, as neuroscientist Erik Hoel recently explored in a short science fiction story that might make it a bit harder to go to sleep tonight.

“They Die Every Day”
An information hazard
The Intrinsic PerspectiveErik Hoel

Astrobiology: "Prebiotic" was always a bad name for interesting carbon chemistry, and now this opinion is citable

Rethinking "Prebiotic Chemistry" (July 11, Perspectives of Earth and Space Scientists) by Michael L. Wong, Madeline Christensen, and Stuart Bartlett

As of this writing, determining the factors that contribute to the emergence of life remains one of the greatest enduring scientific mysteries (Cleaves, 2012). In other words, we actually do not know what prebiotic chemistry is, nor what is important for it, since there is no fully fleshed-out pathway or theory behind life's emergence (Bartlett & Wong, 2023).

Wong and Bartlett are great at coining new terms that draw important distinctions astrobiologists, in general, are very bad at drawing. Genesity, lyfe, and now protobiotic processes are all very helpful terms that would cut through a lot of confusion if adopted more broadly. People should use them.

Cosmology: Is time emergent?

Kinematic Flow and the Emergence of Time (July 18, Physical Review Letters) by Nima Arkani-Hamed, Daniel Baumann, Aaron Hillman, Austin Joyce, Hayden Lee, and Guilherme L. Pimentel

The idea that time could be emergent isn't new; you can find hints of it going back to Ludwig Boltzmann's work on the 2nd law of thermodynamics, and Ilya Prigogine had quite a lot to say about this in his book The End of Certainty. Here, the authors present a toy model of cosmological evolution that doesn't have time baked in, but nonetheless manifests something that they argue could be reasonably interpret as time evolution.

I can't pretend I understood this paper on a short skim, but hopefully some of you got it better and can help clear things up in the comments.

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Origins of Life: "Arsenic life" paper retracted after 15 years

Retraction (July 24, Science) by H. Holden Thorp

The infamous "arsenic life" paper claiming the discovery of a microbe that can grow on arsenic instead of phosphorus has been retracted by Science. This paper is a classic controversy in astrobiology — it came up in just about every geobiology or astrobiology course I took back in the 2010s. The context for this retraction is unusual, to say the least. Usually, papers retracted for reasons other than misconduct (i.e., for being wrong) are retracted with the permission of at least some of the authors. That didn't happen here. In fact, the authors dispute the retraction and all but 1 of the living authors co-penned a response to the retraction.

Whatever you think about the arsenic life paper, this case clearly raises some interesting questions about what should warrant retraction. Is an idea being wrong enough? Does it need to be both wrong and famous, like the arsenic life paper? I don't pretend to have an intelligent answer. Bluesky's reactions seem like an even split between gleeful Schadenfreude, cautious approval, and concern. I found the most interesting contribution to be this thread by former Science Editor in Chief Jeremy Berg explaining why he didn't retract the paper when he was in charge years ago despite having concerns about it:

Why I didn't retract this paper when I was Editor-in-Chief at Science (THREAD 🧵)

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— Jeremy Berg (@jeremymberg.bsky.social) July 27, 2025 at 1:48 PM

Artificial Life: A SFI paper on scaling laws in cells

Scaling in Cells (July 10, Preprints.org preprint) by Jose Ignacio Arroyo, Jordan Okie, Daniel Muratore, Christopher Kempes, and Geoffrey West

A little review of scaling laws in cells and a call for general theories in cell biology based on first principles out of the SFI, seemingly aimed at the artificial life community. The last author, Geoffrey West, is famous for having contributed to metabolic scaling theory, which ironically I'm not sure would count as a theory under the definition put forth in this article. I enjoyed his book Scale, which shoes just how deep the rabbit hole can go when you start asking why things are the size (or duration, or whatever other magnitude) they are.

Emergence: The "Mother of All Processes"

Way More Than the Sum of Their Parts: From Statistical to Structural Mixtures (July 10, arXiv preprint) by James P. Crutchfield

I didn't have time to read this closely, but I wanted to highlight it because Crutchfield's concept of an "epsilon machine" has been picked up by other researchers interested in developing theories of emergence. Notably it was important for Fernando Rosas et al.'s "Software in the Natural World" idea, which was covered for Quanta by Philip Ball.

The New Math of How Large-Scale Order Emerges | Quanta Magazine
The puzzle of emergence asks how regularities emerge on macro scales out of uncountable constituent parts. A new framework has researchers hopeful that a solution is near.
Quanta MagazinePhilip Ball

Astrobiology: Last episode on the K2-18b show...

A spectroscopist’s view of the evolving story of exoplanet K2-18 b (July 17, Nature Reviews Physics) by Jonathan Tennyson and Sergei N. Yurchenko

K2-18b is a sub-Neptune exoplanet in the habitable zone of a dim red star, and it's the star of a raging biosignature detection claim drama. For several years now, Nikku Madhusahan, an astronomer at Cambridge has been building up the idea that certain sub-Neptune planets could be hospitable water worlds — what he calls Hycean planets — instead of dead balls of gas. He thinks K2-18b is such a planet. Basically every exoplanet astronomer or astrobiologist I've ever spoken to about this disagrees on that point. They disagree even more vehemently with Madhusahan's more recent claim of a strong detection of dimethyl sulfide — a gas that's considered a biosignature even though, as I reported for Science, is present on dead comets. For context, usually I have to email about three times as many scientists as I need to speak to for a magazine article because people don't respond; for an article on the K2-18b biosignature for National Geographic, all 10 scientists I contacted responded within 1 day. Because they had thoughts.

Is there really alien life on this exoplanet? We asked 10 experts.
A team of astronomers claims to have sniffed out a “biosignature” in the atmosphere of a distant planet called K2-18b. But not everyone agrees that it signals life.
Science

The authors of this short, sweet analysis succinctly summarize the state of the K2-18b controversy. But they do more. They astutely point out that the ongoing controversy highlights a serious and often unspoken limitation baked into the way that astronomers analyze and report the compositions of exoplanet atmospheres: statistical significance means nothing outside the context of your causal model. We can only find what we're looking for, and we're looking for pretty simple explanations for pretty complicated objects.

The original detection of water in K2-18 b, which we now know is not there, was reported with a significance of 3.6σ (ref. 1) and 3.93σ (ref. 2). In medical research it is no longer acceptable to ascribe significance to a statistical correlation without some underlying causal relationship. Similarly for exoplanets, chemical models should be linked to assumptions used to interpret observations

Free Will: Objections to the Luck Objection

Chance, Choice, and Control: Free Will in an Indeterministic Universe (July 25, philarchive preprint) by Henry D. Potter and Kevin Mitchell.

Kevin Mitchell and his colleagues have been publishing some interesting things about free will that almost have me convinced that I am not, in fact, a meat robot. This is a philosophy-focused companion paper to a previous, more physics-focused preprint that argues the future is undetermined and open to being changed by our choices in the present. I'm interested in what physicists make of the argument.

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The Rest

Exoplanet Astrobiology

Search for Life and SETI

Origins and Artificial Life

Physics and Foundations of Complexity

Biological Complexity and Self-Organization

Networks and Graphs

The Brain

Neural Networks, Collective Computing, and AI

Just for Fun

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