Venus may have been a temperate planet for 2-3 billion years, with liquid water on it until a dramatic transformation over 80 million years ago reappeared about 80% of the planet. A study presented today by Michael Way of the Goddard Institute for Space Science at EPSC DPS in 201
Forty years ago, NASA's Pioneer Venus mission found tantalizing evidence that the planet's & # 39; twisted sister & # 39; Earth once had the water of a shallow ocean. To find out if Venus has ever had a stable climate that could support liquid water, Dr. Way and his colleague Anthony Del Genio created a series of five simulations that assumed different water coverages.
In All Five Scenarios They found that Venus was able to maintain stable temperatures of no more than about 50 degrees Celsius and at least about 20 degrees Celsius for about three billion years. A temperate climate might even have been sustained today on Venus if there had not been a series of events that would have led to a release or "outgassing" of carbon dioxide in the rocks of the planet some 700 to 750 million years ago.
"Our hypothesis is that Venus has had a stable climate for billions of years, and it's possible that the near-global event of surface renewal is responsible for transforming an Earth-like climate into a hellish hot house that we see today "he said Way.
Three of the five scenarios studied by Way and Del Genio took on today's topography of Venus, viewing a deep ocean averaging 310 meters, a shallow water layer averaging 10 meters, and a small amount of trapped water in the earth. For comparison, they also included a scenario with the topography of the Earth and a 310 meter high ocean, and finally a world completely covered by a 158 meter deep ocean.
To simulate the environmental conditions 4.2 billion years ago, it was 715 million years ago and today researchers have adapted a general 3-D circulation model to the increase in solar radiation during the warming of our sun and the change in atmospheric To consider composition.
Although many researchers believe that this is Venus The new study suggests that this could be the case beyond the inner boundary of our solar system's residential zone and too close to the sun to promote liquid water.
"Venus currently has nearly twice the solar radiation we have in Earth, but in all of the scenarios we modeled, we found that Venus can still tolerate surface temperatures suitable for liquid water," said Way.
4.2 billion years ago, shortly after its creation, Venus had a period of rapid cooling and its atmosphere was dominated by carbon dioxide. If the planet had developed earth-like over the next 3 billion years, the carbon dioxide would have been extracted from silicate rocks and trapped on the surface. In the second epoch, modeled 715 million years ago, the atmosphere would probably have been dominated by nitrogen with traces of carbon dioxide and methane, similar to Earth today, and these conditions may have remained stable to this day.
The cause of the outgassing that led to the dramatic transformation of Venus is a mystery, although it is probably related to the volcanic activity of the planet. One possibility is that large amounts of magma bubble into the air and release carbon dioxide from molten rock into the atmosphere. The magma froze before it reached the surface and a barrier formed which meant that the gas could no longer be absorbed. The presence of large amounts of carbon dioxide triggered a runaway greenhouse effect that led to the current average temperatures of 462 degrees Celsius on Venus. Do not allow the rocks to absorb them again. On Earth, there are some examples of large-scale outgassing, such as the emergence of Siberian traps 500 million years ago, which are associated with mass extinctions, but nothing to that extent transformed Venus, "said Way.
There are two more important ones Unknowns that need to be addressed before the question of whether Venus could have been habitable can be fully answered.The first is how fast Venus initially cooled, and whether it was able to condense liquid water on its surface at all Unknown is whether the global emergence event is a single event or simply the latest event in a series of events spanning billions of years in the history of Venus.
History and Evolution, "Way said. "However, our models show that there is a real possibility that Venus could be livable and radically different from the Venus that we see today, which opens up all possible implications for exoplanets living in the so-called 'Venus' Zone & # 39; may indeed host liquid water and moderate climate. "
New research sheds light on the possibility of an earlier life on Venus
The Europlanet Society
Could Venus have been habitable? (2019, 22nd September)
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