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New Study Dramatically Narrows the Search for Advanced Life in the Universe:
In a new study, a UC Riverside–led team discovered that a buildup of toxic gases in the atmospheres of most planets makes them unfit for complex life as we know it.
Traditionally, much of the search for extraterrestrial life has focused on what scientists call the "habitable zone," defined as the range of distances from a star warm enough that liquid water could exist on a planet's surface. That description works for basic, single-celled microbes—but not for complex creatures like animals, which include everything from simple sponges to humans.
The team's work, published today in The Astrophysical Journal, shows that accounting for predicted levels of certain toxic gases narrows the safe zone for complex life by at least half—and in some instances eliminates it altogether.
"This is the first time the physiological limits of life on Earth have been considered to predict the distribution of complex life elsewhere in the universe," said Timothy Lyons, one of the study's co-authors, a distinguished professor of biogeochemistry in UCR's Department of Earth and Planetary Sciences, and director of the Alternative Earths Astrobiology Center, which sponsored the project.
"Imagine a 'habitable zone for complex life' defined as a safe zone where it would be plausible to support rich ecosystems like we find on Earth today," Lyons explained. "Our results indicate that complex ecosystems like ours cannot exist in most regions of the habitable zone as traditionally defined."
[...] "To sustain liquid water at the outer edge of the conventional habitable zone, a planet would need tens of thousands of times more carbon dioxide than Earth has today," said Edward Schwieterman, the study's lead author and a NASA Postdoctoral Program fellow working with Lyons. "That's far beyond the levels known to be toxic to human and animal life on Earth."
Similar difficulties occur with respect to ultraviolet light which leads to excess carbon monoxide; even small amounts preferentially bind to hemoglobin leading to "death of body cells due to lack of oxygen."
More information: Edward W. Schwieterman et al. A Limited Habitable Zone for Complex Life, The Astrophysical Journal (2019). DOI: 10.3847/1538-4357/ab1d52
No word on what parameters would apply to the planet Vulcan.
(Score: 3, Insightful) by Hartree on Thursday June 13 2019, @03:29AM
Heck, we can't even give all that great a definition for "life". We've got some general rules in biology classes but it only really fits for the kinds of life we've seen.
It's a bit like that old saw about pornography: "I can't define it but I know it when I see it."
On the other hand, I'm not at all convinced that we would immediately know some kinds of life if we saw it. How about a rocklike being not based on the usual earth chemistry that has a childhood lasting half a million years? We'd have sawed it up and made jewelry out of it without knowing unless we figured it out from the fossil record and even that would be pretty subtle to pick out of normal geology.