Joshua Sokol writes:
One of the many times Lisa Kaltenegger’s dream jolted a little closer toward reality was on a cold April morning a decade ago at an astronomy conference. She was clutching what she recalls was a terrible, just awful cup of coffee, not because she was going to drink any more of it but because she had waited in line and it was warm in her hands. Then Bill Borucki veered in her direction.
She readied herself to tell him to avoid the coffee. But Borucki, head of NASA’s Kepler mission, a space telescope designed to hunt for planets orbiting other stars (or “exoplanets”), had something else to discuss. Kepler had glimpsed its first two Earth-size exoplanets with a decent chance of having liquid water on their surfaces. These were the sort of strange new worlds that everyone at the conference — and possibly most of the human race — had imagined at least once. Would Kaltenegger confirm that the planets might be habitable?
Kaltenegger, at the time an astrophysicist at the Max Planck Institute for Astronomy in Heidelberg, Germany, started running new climate models before the conference was over, incorporating basic facts like the planets’ diameters and the lukewarm glow of their star. Her ultimate answer: a qualified yes. The planets might be suitable for life, or at least for liquid water; they could even be water worlds, encased in endless oceans without a single rocky outcrop poking above the waves. The caveat was that she would need more advanced observations to be sure.
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, another charismatic Ithaca-based astronomer with big ideas about ending humanity’s lonely sojourn in the cosmos.
Full article at Quanta Magazine.
This very extensive article provides some informative insights into possible bio-signatures that astronomers would hope to see from an exoplanet that might indicate the presence of life.