Did life exist on Venus in the past?

The European Space Agency's Venus Express spacecraft has discovered traces of oceans that once covered the planet

Venus Express, the European Space Agency's space probe is helping scientists investigate whether Venus once had oceans. If so, it is possible that at the beginning of its formation, the planet was inhabited by plants similar to those found today on the Earth's surface.

As of today, Venus and Venus are completely different. Kada is full of plants, animals and oceans, while on Venus the surface of the planet is desolate, dry and too hot for habitation.

Despite this, the two planets share similar characteristics. They are almost identical in size, and now, thanks to Venus Express, scientists are discovering more similarities.

"The basic composition of Venus and Earth are very similar," says Hakan Swedham, a scientist on the Venus Express project. The degree of similarity will be a central theme at the conference on the subject that will be held this week in France. One obvious difference: Venus has little water. If we were to spread all the oceans evenly over the Earth's surface, it would create a layer 3 km deep. And if we were to condense all the water in Venus' atmosphere and spread it over the planet's surface, a layer with a depth of only 3 cm would be formed.

But billions of years ago, Venus was probably a water-saturated planet. The Venus Express probe confirmed that the planet lost large amounts of water that evaporated into space.

This happened because ultraviolet radiation from the sun bombarded the star's atmosphere and broke the water molecules into atoms: two hydrogen atoms and one oxygen atom, and these escaped into space.

Venus Express measured the escape rate of the atoms and confirmed that roughly twice the amount of hydrogen that escaped was the amount of oxygen. Therefore the scientists believe that water is the source of the escaping atoms. In addition, it can be seen that a "heavier" form of hydrogen, known as deuterium, is enriched in the higher levels of Venus' atmosphere, because it is more difficult for the heavy hydrogen to escape from the grip of the star.

"All the data indicate that the source of the hydrogen and oxygen atoms is from large amounts of water in the past of Venus," says Colin Wilson, from the University of Oxford. But this does not necessarily mean that there were oceans on the surface of the planet.

Eric Chaspierre, from the University of Paris in France developed a computer model that suggests that there used to be large amounts of water in the atmosphere, and that it existed only in the earliest history of the planet, when the surface was liquid. When the water molecules were broken up by the sun's rays and escaped into space, the dramatic drop in temperature as a result apparently caused the ground to solidify, which is why there are no oceans there today.

Although testing the theory is a difficult thing, it is a key question. If there really was water on the surface of Venus, it is possible that primitive life existed there.

Chaspeare's model does not include the possibility that comets that collided with the star brought additional water to the planet after the surface solidified, which could have created standing water sources where life could have developed.

There are many open questions. "More extensive models of the ocean-atmosphere-land system are needed, as well as models of their formation, so that we can understand the development of Venus in the initial phase of its life," says Chaspierre.

Press release