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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: 1, Funny) by Anonymous Coward on Wednesday June 12 2019, @07:55PM (5 children)
I'm...
an...
ent,...
you...
insensitive...
clod!...
I...
breathe...
CO2!
(Score: 2) by HiThere on Wednesday June 12 2019, @08:03PM (4 children)
The problem is that CO2 is a strong greenhouse gas, so if there's too much the seas will boil. Being an Ent wouldn't help you survive that.
But it's quite possible that microbes living in the upper atmosphere (high enough so water condenses) could over time metabolize that CO2. This has actually been proposed for Venus, but I think it's too close to the sun for a good result.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Insightful) by ElizabethGreene on Wednesday June 12 2019, @08:46PM (2 children)
My understanding is that Earth had a primarily CO2 atmosphere very early in its development, until the evolution of cyanobacteria that reduced it to Oxygen. I don't believe they could have evolved if the seas were boiling.
(Score: 3, Interesting) by HiThere on Wednesday June 12 2019, @10:18PM (1 child)
Yes, but Earth is further from the sun, and whether they could have evolved on dust floating in the atmosphere is an unanswered question.
OTOH, I'm dubious about that extreme scenario too. But high temperatures within limits aren't an obstacle for life. There are microbes that live down in rocks where the temperature is well above the boiling point of water at standard pressure...just not where they're living.
The point is, the atmosphere currently being inhospitable doesn't mean it couldn't BECOME hospitable. And life evolved on earth long before the cyanobacteria evolved. (I was under the impression that it was supposed to be largely ammonia and methane back then, though this wouldn't rule out a large CO2 component. The ammonia was supposed to be the source of the current Nitrogen. This may not be the current thinking.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Thursday June 13 2019, @02:48AM
The sun used to be dimmer. It has been slowly brightening for billions of years.
(Score: 2) by Osamabobama on Wednesday June 12 2019, @10:20PM
The point of the high CO2 concentration was to compensate for the distance from the star "at the outer edge of the conventional habitable zone". Without the high CO2 level, the seas would be frozen.
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