"It checks a lot but it's not a revolution"

"For the first time, it was highlighted" a body of liquid water on Mars, welcomed Wednesday, July 25 on franceinfo Jean-Pierre Bibring, professor of physics at the University Paris- Southern and astrophysicist at the Institute of Space Astrophysics (IAS). An international team of astronomers has announced that it has discovered an "underground lake" about 20 kilometers wide. However, the head of the scientific operation Philae nuance: "It verifies many things but it is not a revolution."

franceinfo: What does this discovery mean?

Jean-Pierre Bibring : What must be remembered is that it has been a long time since we are looking for expanses of liquid water on the surface of Mars or in the Martian subsoil. For the first time, it has been highlighted, which is good. However, we have no idea of ​​the depth of what we see, it could be only a few tens of centimeters. Moreover, […] it is not the first time that we know that there is water on the surface of Mars. We know that there are two polar ice caps [de l’eau sous forme de glace] for a very long time. It was suspected that, under these ice caps, the weight of ice, the pressure increases and the water becomes stable in the liquid state at higher temperatures. So it is not very surprising that liquid water is found, simply it was never highlighted. It verifies many things but it is not a revolution, in the sense that we know that it is not there that most of the water that could have been imagined to be present on the surface of Mars is located. Most of the water, like most of the atmospheric compounds, disappeared from the planet a very long time ago. It does not look like large bodies of water that could have been imagined to be the equivalent of what is on Earth.

Does research and interest focus on the presence of water? on March because it is the essential condition for the development of life?

On both sides of the Atlantic, we do not think the same way about it. We know that on Earth, water has been important for the emergence of life. From there to say that as soon as there is water, there is life, there is an important step to overcome that we do not cross any more. We know that it is not water alone that is necessary. On Earth, it took water of a certain property, with a certain temperature and a certain acidity … None of this says that it is what is present today on the surface of Mars.

Is it better to say in the United States that where there is water, there is life?

Yes, because there is always the idea that water is necessary for life . If there is water, there may be living. Since most of the Martian missions aim to find out if life has been able to emerge elsewhere than on Earth and probably on Mars, we will instead look for it where there has been liquid water. However, what we think is that, if it emerged, it is not necessarily where we are looking today, that is to say under the poles. There are other places on the surface of Mars where we know that there may have been liquid water very early in its history – we have seen it by very specific minerals – and it is rather in these lands must be seen if there may have at a given moment a chemical evolution, organic, towards carbon compounds. This evolution has been able to move towards structures similar to what are called living structures on Earth.