Study warns of ‘oxygen false positives’ in search for signs of life on other planets

Study warns of 'oxygen false positives' in search for signs of life on other planets
By various the preliminary stock of risky parts in a mannequin of the geochemical evolution of rocky planets, researchers obtained a variety of outcomes, together with a number of situations by which a dull rocky planet round a sun-like star might evolve to have oxygen in its ambiance. Credit score: J. Krissansen-Totton

Within the seek for life on different planets, the presence of oxygen in a planet’s ambiance is one potential signal of organic exercise that is perhaps detected by future telescopes. A brand new research, nevertheless, describes a number of situations by which a dull rocky planet round a sun-like star might evolve to have oxygen in its ambiance.


The brand new findings, revealed April 13 in AGU Advances, spotlight the necessity for next-generation telescopes which might be able to characterizing planetary environments and trying to find a number of strains of proof for all times along with detecting oxygen.

“That is helpful as a result of it exhibits there are methods to get oxygen within the ambiance with out life, however there are different observations you may make to assist distinguish these false positives from the true deal,” stated first writer Joshua Krissansen-Totton, a Sagan Fellow within the Division of Astronomy and Astrophysics at UC Santa Cruz. “For every state of affairs, we attempt to say what your telescope would want to have the ability to do to tell apart this from organic oxygen.”

Within the a long time, maybe by the late 2030s, astronomers hope to have a telescope able to taking photos and spectra of doubtless Earth-like planets round sun-like stars. Coauthor Jonathan Fortney, professor of astronomy and astrophysics and director of UCSC’s Different Worlds Laboratory, stated the concept can be to focus on planets related sufficient to Earth that life might need emerged on them and characterize their atmospheres.

“There has a been loads of dialogue about whether or not of oxygen is ‘sufficient’ of an indication of life,” he stated. “This work actually argues for needing to know the context of your detection. What different molecules are discovered along with oxygen, or not discovered, and what does that let you know concerning the planet’s evolution?”

This implies astronomers will desire a telescope that’s delicate to a broad vary of wavelengths in an effort to detect several types of molecules in a planet’s ambiance.

The researchers primarily based their findings on an in depth, end-to-end computational mannequin of the evolution of rocky planets, ranging from their molten origins and increasing by way of billions of years of cooling and geochemical biking. By various the preliminary stock of risky parts of their mannequin planets, the researchers obtained a surprisingly big selection of outcomes.

Oxygen can begin to construct up in a planet’s ambiance when high-energy ultraviolet gentle splits water molecules within the higher ambiance into hydrogen and oxygen. The -weight hydrogen preferentially escapes into house, leaving the oxygen behind. Different processes can take away oxygen from the ambiance. Carbon monoxide and hydrogen launched by outgassing from molten rock, for instance, will react with oxygen, and weathering of rock additionally mops up oxygen. These are only a few of the processes the researchers included into their mannequin of the geochemical evolution of a rocky planet.

“In case you run the mannequin for Earth, with what we predict was the preliminary stock of volatiles, you reliably get the identical final result each time—with out life you do not get oxygen within the ambiance,” Krissansen-Totton stated. “However we additionally discovered a number of situations the place you will get oxygen with out life.”

For instance, a planet that’s in any other case like Earth however begins off with extra water will find yourself with very deep oceans, placing immense strain on the crust. This successfully shuts down geological exercise, together with the entire processes akin to melting or weathering of rocks that might take away oxygen from the ambiance.

Within the reverse case, the place the planet begins off with a comparatively small quantity of water, the magma floor of the initially molten planet can freeze rapidly whereas the water stays within the ambiance. This “steam ambiance” places sufficient water within the higher ambiance to permit accumulation of oxygen because the water breaks up and hydrogen escapes.

“The everyday sequence is that the magma floor solidifies concurrently with water condensing out into oceans on the floor,” Krissansen-Totton stated. “On Earth, as soon as water condensed on the floor, escape charges have been low. However in the event you retain a steam ambiance after the molten floor has solidified, there is a window of about 1,000,000 years when oxygen can construct up as a result of there are excessive water concentrations within the higher ambiance and no molten floor to eat the oxygen produced by hydrogen escape.”

A 3rd state of affairs that may result in oxygen within the ambiance includes a planet that’s in any other case like Earth however begins off with a better ratio of carbon dioxide to water. This results in a runaway greenhouse impact, making it too sizzling for water to ever condense out of the ambiance onto the floor of the planet.

“On this Venus-like state of affairs, all of the volatiles begin off within the ambiance and few are left behind within the mantle to be outgassed and mop up oxygen,” Krissansen-Totton stated.

He famous that earlier research have targeted on atmospheric processes, whereas the mannequin used on this research explores the geochemical and thermal evolution of the planet’s mantle and crust, in addition to the interactions between the crust and ambiance.

“It isn’t computationally intensive, however there are loads of shifting elements and interconnected processes,” he stated.


Ancient Earth had a thick, toxic atmosphere like Venus—until it cooled off and became liveable


Extra info:
Joshua Krissansen‐Totton et al. Oxygen False Positives on Liveable Zone Planets Round Solar‐Like Stars. AGU Advances. First revealed: 13 April 2021 doi.org/10.1029/2020AV000294

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College of California – Santa Cruz

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Research warns of ‘oxygen false positives’ in seek for indicators of life on different planets (2021, April 13)
retrieved 13 April 2021
from https://phys.org/information/2021-04-oxygen-false-positives-life-planets.html

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