Don't be deceived; Venus may be among the finest and most attractive things
in our night sky.
The planet next to us is utterly uninhabitable to life as we know it; it is
a poisonous, burning place where humans will never be able to walk.
Venus and Earth are not equally habitable, but they do have some remarkably
comparable characteristics. Both planets have very comparable compositions
and are roughly the same height, mass, and density. This begs the question:
Could Venus have ever supported life?
According to a recent research, if Venus once had habitable circumstances
and flowing water on its surface, it happened long ago and only existed for
a short period before the planet changed into the parched, arid place it is
today.
In order to determine the rate and mechanisms of oxygen loss, planetary
scientists Alexandra Warren and Edwin Kite of the University of Chicago
modeled the history of Venus' atmosphere. This revealed that, if the planet
ever had liquid water (which some scientists doubt), it was more than 3
billion years ago.
Here is the current state of Venus. Extremely little air is present, and it
is very arid. Its atmosphere is primarily composed of carbon dioxide (96%)
and nitrogen (3%), with traces of other gases like sulfur dioxide.
It has an atmosphere that is over 90 times as dense as Earth's, ravaged by
strong winds, and where
sulfuric acid
is constantly falling from the sky.
Furthermore, heat cannot flee due to the atmosphere's extreme density. With
a typical surface temperature of
464 degrees Celsius, Venus is the planet with the highest solar system temperature (867
degrees Fahrenheit).
Venus may have been more temperate with lakes and seas of liquid water
earlier in the Solar System's past, when the Sun was less strong.
Since Venus is so similar to Earth, with some climate models suggesting
that Venus may have had water as recently as
less than a billion years ago, planetary scientists are interested in learning how and why Venus got to
the condition it is in today. Understanding Venus' history may help us
determine how likely it is that our own planet will take the same
course.
It's a little perplexing why Venus' atmosphere doesn't contain more oxygen.
If Venus ever had a liquid ocean, it would have dissipated into the
atmosphere as the planet warmed up, splitting into hydrogen and oxygen
through a chemical process called
photodissociation
that is sparked by sunlight.
The oxygen should have stayed, but the hydrogen would have seeped out into
space.
Warren and Kite built a model modeled on a habitable Venus in order to
determine where that air might have gone. They altered variables like the
quantity of water and the time period during which it might have existed,
added mechanisms that might have led to oxygen loss, and created oceans of
water on Venus' surface.
They ran the model 94,080 times, deeming it successful if the dioxygen,
water, and carbon monoxide concentrations were within the range of those
gases' present-day top bounds in Venus' atmosphere.
Only a tiny portion of the model simulations ultimately succeeded, but they
revealed some intriguing patterns.
However, it seemed fairly unlikely that Venus' oxygen would have combined
with the carbon released by volcanoes to create carbon dioxide.
Instead, it appeared that the oxygen would either seep out into space or
end up trapped in oxidizable rock like basalt on the planet's surface.
Additionally, the last time the seas cleared up was no more than 3 billion
years ago.
But the quantity of radioactive argon still present in the planet's
atmosphere can be used to limit the scale of Venus' historical volcanic
activity. The researchers were able to calculate how much water Venus may
have had by calculating how busy its volcanism was in the past.
The reply is a meager one. The depth of Venus' seas was limited to 300
meters (984 feet). That represents less than 10% of the ocean's
3,688-meter average deep on Earth.
Thus, the findings make sense of Venus' present absence of oxygen with
possible early habitable conditions, but the researchers note that the gap
is relatively small.
When the argon data is taken into account, the gap is even smaller. When
the full range of Venus's present atmosphere was taken into consideration,
less than 0.4% of the runs were successful.
Venus' surface makeup could be measured by future probes to see if the
planet fits into this extremely small window of eligibility.
The research has been published in
Proceedings of the National Academy of Sciences.
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