Origin of the oceans: what if water was on Earth from the start?

Seen from space, its color distinguishes it like no other of its neighbors in the solar system.

But where does all this water come from, which covers 70% of our Earth's surface and has earned it its beautiful nickname of "blue planet"?

A team of French researchers may have just lifted a corner of the veil.

According to the team of cosmochemist Laurette Piani (CNRS / University of Lorraine), water - or at least its fundamental ingredients - was present in very large quantities on our planet as soon as it was formed.

This defeats the dominant theory according to which it would have been brought later by asteroids and comets having bombarded an initially dry Earth.

According to this Nancy team, however, this scenario cannot be excluded.

In any case, long before the visit of these space travelers, blue gold was already present and even in abundance.

To reach this conclusion, our researchers looked at a very rare type of meteorite called “enstatite chondrites”.

Why them?

Because they have the particularity of having a chemical composition close to that of the Earth, and we can therefore assume that they are similar to the rocks that made up our planet from its formation.

By analyzing in particular their hydrogen content, the researchers concluded that these rocks had more than enough to provide the current body of water on Earth.

There was even enough there to fill "the equivalent of at least three times the oceans," argue the researchers, who have also discovered other similarities between the composition of these rocks and our oceans.

"A beginning of explanation"

“With the theory of comets, we cannot explain the enormous quantities present on the surface of our planet.

This study is perhaps the beginning of an explanation ”, comments Michel Viso, exobiologist at Cnes (national center for spatial studies).

Is this likely to upset the different scenarios existing on the very origin of life about 1 billion years ago?

“There may be a possible small effect on the chronology, it may have accelerated its appearance, but it does not change the fundamental conditions of its emergence which are first and foremost the existence of water at the liquid state, then a set of reactions allowing the birth of a chain of amino acids, such as the effect of light, heat and other external inputs ”, estimates the scientist.

Two theories

If in the debate on the origin of water, this study clearly tilts the balance on the side of the "internal" source, it does not resolve the following question, which divides the many researchers convinced that there have been water in abundance very early on on Earth.

How did this water end up on the surface?

Here again, two theories clash.

“For some, it would have come out of the earth's mantle.

A huge degassing would have followed, the condensation that would have fallen, forming the oceans, details Michel Viso.

For others, this phase of condensation is not conceivable, because within the young solar system the temperature was then much too high.

These therefore consider that the water, once raised to the surface, could only evaporate.

"

Newsletter - Most of the news

Every morning, the news seen by Le Parisien

I'm registering

Your email address is collected by Le Parisien to enable you to receive our news and commercial offers.

Learn more

How could we see more clearly?

No doubt by going to dig into the bowels of our planet.

For example by drilling 200 km deep towards its metal core in order to compare the traces of original water that remain there with that of our oceans on the surface.

But the experiment would require titanic efforts.

If it is also that the material necessary for such an operation exists one day.