© –Archival image of Venus made by NASA based on data from the Magellan and Pioneer probes.
A recent scientific study, whose organizers used a sophisticated climate model, concluded that Venus has never formed an ocean-incubating environment, with results that weaken the hypothesis that Earth’s “twin” planet may have harbored life.
“We may have underestimated the difficulty needed to make oceans appear on planets like Earth, Venus or even exoplanets,” astrophysicist and climatologist Martin Turbet of the University of Geneva Astronomical Observatory told AFP.
It became known, for example, thanks to probes and exploration missions, that Mars had large bodies of water. But the surface of Venus, which is hidden by thick clouds of sulfuric acid droplets, remains largely a mystery.
The enormous pressure that prevails there, which is more than 90 times higher compared to Earth, and the enormous temperatures of more than 470 degrees Celsius, quickly came to resist the rare probes that managed to land there.
However, a 2016 study questioned whether Venus constituted a habitable environment, assuming that special cloud cover has long served as protection for hypothetical bodies of water.
However, the study, the results of which were recently published in the journal “Nature” and signed by Martin Turbet with a team of scientists from his university, the astrophysics laboratories in Bordeaux and the French laboratory “Latmos” specializing in the atmosphere, raises doubts about this scenario.
– greenhouse effect –
The scientist says, “Before we ask how any ocean could be stable on the surface of Venus, we must ask how it could have formed.”
So we must study how we moved a few billion years ago, from a “young and very hot” planet, where all available water “in the atmosphere was in the form of vapor”, to a planet where the vapor could form oceans through condensation by cooling.
Turbet’s team used a complex climate model, taking into account cloud formation and atmospheric circulation. The conclusions were decisive.
The sun has heated water vapor in Venus’s atmosphere to a very high temperature to allow clouds to form through condensation. Clouds, by protecting the planet’s sunny side, may have allowed its atmosphere to cool enough to cause water vapor to condense and thus oceans to form.
Also, the air masses heated by the sun, on the “day” side, moved to the night side of the planet. There they formed clouds at high altitudes, which caused the greenhouse effect and prevented the cooling of Venus’s atmosphere.
– solar radiation –
But why did the Earth, a planet of the same size, escape this fate? Because “when the sun was younger, four billion years ago, it was 25 to 30 percent less luminous than today,” according to Turbet.
And the temperature at which the Sun bathed our planet was low enough to allow water vapor to condense and oceans to form. Venus, which is closest to the Sun, at that time received levels of exposure to sunlight nearly twice as high, a level too high to allow for such a phenomenon.
Turbet notes that the results of this study bear a “small surprise”: with much higher solar radiation today, “if we vaporize Earth’s oceans, this will be a stable state.” In other words, we would be swimming in oceans of water vapor, where no condensation is likely. A few billion years ago, levels of slightly higher warmth in the sun would have prevented the oceans from forming, which would undoubtedly prevent the emergence of life forms.
The climate model adopted in this study will be used to study exoplanets belonging to other solar systems. But he is waiting to complicate the hypothesis of the emergence of life on Venus.
بسل / جك / اا