In Nick Lane's Oxygen: The Molecule that Made the World, he talks about the importance of both methane and carbon dioxide and how they exist at the extremes of a complex metabolic oxidation-reduction cycle. Methane stores a lot of chemical energy in its C-H bonds which can be burned directly, or metabolized through repeat oxidation events to ultimately form CO2, which plants utilize with the help of the sun to form more CH bonds before ultimately breaking down into methane again. Hence, an exoplanet with both molecules in its atmosphere is a promising candidate in the search for life.
What an unintuitive and sketchy-looking Bayesian model. They only have 11 chemicals in the database they're matching that messy IR spectrum against: 6 reasonable ones, and 5 bullshit ones that are only there because theory papers suggested that they'd be biomarkers of alien life. And, fit to just those 11 chemicals, the best-fit includes one of the bullshit ones (dimethyl sulfide, (CH₃)₂S).<p><a href="https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf" rel="nofollow noreferrer">https://stsci-opo.org/STScI-01HA2G716KS9YGAGVY1WBVFJ8Y.pdf</a><p>Is this approach, like, sane? I'm not a Bayesian statistics expert.
On this topic, I just finished reading "A Very Short Introduction to Planetary Systems"[0] by Raymond T. Pierrehumbert. He devotes a good portion of the book to exoplanet atmospheres. It is one of the best science books I've read. Pierrehumbert really has a knack for explaining complex material clearly and concisely. I really recommend it.<p>[0] <a href="https://global.oup.com/academic/product/planetary-systems-a-very-short-introduction-9780198841128?cc=us&lang=en&" rel="nofollow noreferrer">https://global.oup.com/academic/product/planetary-systems-a-...</a>
That spectrum is so noisy. How can they infer the blue fit from the (noisy) white points? The data look almost consistent with flat (no detection). And even if there is a detection, it looks like many other models could potentially fit the data...
Gosh - imagine that place!<p>I wonder how old this world is, and how stable its enviroment is/has been. Complex animal life took 3.5 bn years to emerge on Earth, of course that's a meaningless data point by itself but intuitively for this place to have an ecosystem or complex life it needs to be old.<p>Still, even without this what a wonderful and weird environment.
It's mind-bendingly cool that people can figure out the composition of an atmosphere without actually being close to that atmosphere.<p>Had not heard of dimethyl sulfide before. That's a good keyword to know.
> These initial Webb observations also provided a possible detection of a molecule called dimethyl sulfide (DMS). On Earth, this is only produced by life. The bulk of the DMS in Earth’s atmosphere is emitted from phytoplankton in marine environments.<p>Given a sufficient quantity of reactants/reagents, could DMS be produced via a natural process, or is this a sufficiently unfavorable reaction that it's unlikely?
Seems to be down. This page seems to work: <a href="https://webbtelescope.org/contents/news-releases/2023/news-2023-139" rel="nofollow noreferrer">https://webbtelescope.org/contents/news-releases/2023/news-2...</a>
I picked up a random book in the science section of the city library today and opening it to a random page I started reading about an exciting "goldilocks" exoplanet discovery from 2015. Apparently this was the first exo-planet which had a positive spectroscopic identification of water in the atmosphere. It was a rocky world, 2 billion years old, 8 times Earth's size (mass?), on a 33 day orbit around a red dwarf. K-something-or-other. The book said the really exciting discoveries will happen when Webb comes online in 2021. The link is down, but someone mentions this planet is 8 x Earth size down thread. I wonder if it's the same planet?
> "Our ultimate goal is the identification of life on a habitable exoplanet, which would transform our understanding of our place in the universe," concluded Madhusudhan.<p>What sort of observation or measurement would allow us to identify life on an exoplanet?
Paywalled paper: <a href="https://www.nature.com/articles/s41550-019-0878-9" rel="nofollow noreferrer">https://www.nature.com/articles/s41550-019-0878-9</a><p>Preprint: <a href="https://arxiv.org/abs/1909.05218" rel="nofollow noreferrer">https://arxiv.org/abs/1909.05218</a><p>Figure 2 pp. 14 of the preprint shows much more plausible error bounds on the curve fit. That press release "best fit" curve is merely an artist's conception.