Venus probably never had oceans

Did our neighbor Venus ever shelter oceans? The planet might never have had them, according to a new climate model. These results, theoretical for the moment, would also help to better understand the past evolution of the Earth.

« The water never condensed and […], therefore, oceans never formed on the surface of Venus. “Here is the conclusion reached on October 13, 2021 by scientists in the journal Nature. According to their climate model, the “twin” planet of Earth could never have had oceans, which would mean that it would not have had oceans. probably not been habitable. This announcement contradicts a previous hypothesis, according to which the star could have sheltered oceans.

Venus is one of the four terrestrial planets in the solar system, along with Mercury, Earth, and Mars. One of the mysteries about her is whether she may have owned oceans in the past. ” Earth has had oceans for almost four billion years, and Mars had lakes and rivers 3.5 to 3.8 billion years ago. However, it is still unclear whether the water has condensed on the surface of Venus because the planet – now completely dry – has undergone global resurfacing events that obscure much of its history. », Underline the authors.

What is their hypothesis?

If the authors of this new study are correct, then that could mean that the surface of Venus has always been so hellish. The model of these researchers allowed them to establish the following scenario:

  1. When Venus formed, it was covered in magma.
  2. For oceans to form, Venus would have had to experience, like the Earth, a decrease in the temperature of its atmosphere. This would have resulted in rains for several thousand years.
  3. However, when Venus formed 4.5 billion years ago, the Sun was only 30% less bright – too small a drop for Venus’s temperature to drop to form oceans.

As for the clouds of Venus, they could not help reduce the temperature of the planet – one could say that they would have protected the surface of the star from solar radiation. The scientists’ climate model shows that these clouds were mostly on the night side of Venus (the side not illuminated by the Sun). These clouds would have even contributed to maintain high temperatures, by trapping heat under the atmosphere. Result: the rain could not have fallen under these conditions.

The white point is Venus, seen through a telescope during a transit. // Source: Flickr / CC / Barney Moss (cropped image)

It should be borne in mind that these are theoretical results, which remain to be confirmed by future space missions on the surface of Venus. However, these conclusions could already have interesting consequences: “ These results have important consequences for our understanding of the comparative evolution of the atmosphere of Earth and Venus, as well as of rocky exoplanets. The scientists write.

If the Sun had shone brighter, the Earth could have looked like Venus

They estimate, based on their finding, that this means that the Earth’s oceans needed less luminosity, compared to that of the Sun today. For them, the weaker brightness of the Sun 4 billion years ago ” played a key role in allowing water to condense on Earth in the first place […] and to form the oceans, and therefore for the emergence and development of life on Earth “. If the Sun had been a little brighter then (92% of its current brightness), perhaps the Earth’s atmosphere would never have condensed and the Earth would have looked more like Venus.

They conclude that ” the younger, weaker-glow Sun, which has long been problematic in explaining the longevity of liquid water oceans on Earth, may in fact have been a necessary opportunity for life to appear on Earth ».

Look at the world from space

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