Far out cosmology: does alien life exist? (Introduction)

by David Turell , Saturday, November 05, 2022, 18:48 (747 days ago) @ David Turell

The hunt goes on:

https://www.quantamagazine.org/alien-life-a-dream-of-discovery-finds-new-hope-20221103/

"Kaltenegger has since become perhaps the world’s leading computer modeler of potentially habitable worlds. In 2019, when another exoplanet-hunting NASA spacecraft called TESS found its own first rocky, temperate worlds, she was called on again to play the role of cosmic home inspector. Most recently, the Belgium-based SPECULOOS survey reached out for her help understanding a newfound Earth-size planet dubbed SPECULOOS-2c that’s precariously close to its star. She and her colleagues completed an analysis, uploaded as a preprint in September, showing that SPECULOOS-2c’s water could be in the process of steaming away like sauna vapor, as any seas of Venus did long ago and as Earth’s own oceans will begin to do in half a billion years. Telescope observations should be able to tell within a few years if that’s happening, which will help reveal our own planet’s future and further demarcate the knife’s-edge distinction between hostile and habitable worlds across the galaxy.

"In simulating ersatz Earths and more speculative visions of living planets, Kaltenegger leverages the bizarre life and geology found on Earth to develop a more systematic set of expectations about what might be possible elsewhere. “I’m trying to do the fundamentals,” she told me during a recent visit to Cornell University, where she leads an institute named for Carl Sagan,

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"...most astronomers believe that our best near-term chance of encountering other life in the cosmos is to detect biosignature gases — gases that could only have come from life — floating in exoplanets’ atmospheres. The sort of remote measurement necessary to make that kind of detection has strained the capabilities of even humanity’s most advanced observatories. But with the James Webb Space Telescope (JWST) now in its first few months of observations, such a discovery has become possible.

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"Without a good theoretical model for how Earth’s own spectrum has changed, Kaltenegger feared, the big planet-finding missions could easily miss a living world that didn’t match a narrow temporal template. She needed to envision Earth as an exoplanet evolving through time. To do this, she adapted one of the first global climate models, developed by the geoscientist James Kasting, which still includes references to the 1970s magnetic-tape era it originated in. Kaltenegger developed this code into a bespoke tool that can analyze not only Earth through time but also radically alien scenarios, and it remains her lab’s workhorse.

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"The first biosignatures will be tiny, ambiguous signals subjected to warring interpretations. In fact, some claims have already emerged.

"The most pertinent case study rocked the astronomy world in the fall of 2020. A team including Seager announced that they had spotted an unusual compound called phosphine in the upper atmosphere of Venus, a sweltering, acid-washed planet typically dismissed as sterile. On Earth, phosphine is commonly produced by microbes. While some abiotic processes can also make the compound under certain conditions, the team’s analysis suggested those processes weren’t likely to occur on Venus. In their view, that left tiny floating Venusian organisms as a plausible explanation. “Life on Venus?” the New York Times headline wondered.

"Outside groups formed opposing camps. Some experts, including Victoria Meadows, an exoplanet atmosphere modeler at the University of Washington who uses a similar approach to Kaltenegger’s, reanalyzed the Venus data and concluded that the phosphine signal was just a mirage: The chemical isn’t even there. Others, including Lunine at Cornell, argued that even if phosphine is present, it could, in fact, come from geologic sources.

Comment: so, no evidence so far. We live in a very specialized place. If God wanted life in any form elsewhere, it will be there.