The sand is proof that there was water on Mars, and therefore possible life

As a child, floating on the calm surface of the sea near the shore of some beach, I spent my time looking at the ripples in the sand on the bottom, trying to guess from their shape, size and arrangement the flow of the current, and fantasizing what those tiny dunes they must have had for the little seabed creatures I had the opportunity to see not even two meters below me.

Just prior to this short essay, I had occasion to see those same delicate sandy ripples again, but in a startlingly remote setting, at the bottom of an ancient lake that was far beyond the distance I explored as a child.

On Mars, the little rover Curiosity is busy climbing a 5 km high mountain – appropriately named Mount sharp. Several times during his journey he found minerals and forms of erosion that indicate that, once upon a time, that mountain was rich in water, streams and lakes. As the rover ascends, it advances along a Martian timeline, allowing scientists to study how the red planet evolved from a planet that was more like Earth in its ancient past, with a hotter climate and abundant water, to freezing desert that it is today.

Well, now, heading towards a plateau that was believed to have never held water due to the nature of the minerals it is composed of, scientists have instead found the starkest and most incredible evidence for a shallow and relatively calm lake: that is, they have identified those same ripples in the sand that I used to follow as a child on a bottom a few decimetres from meon an ancient backdrop at a distance of more than 200 million kilometers from who writes and who reads this page.

Unfortunately, the layer of rock presenting the ripples is so hard that Curiosity has not been able to drill a sample despite several attempts, which precludes the chemical analysis of that seabed, in order to better study its nature and look for traces of ancient lives. Scientists will then look for softer rocks in the coming week. But even if we never receive a sample from this unusual seabed, there are other sites to explore.

Another feature near the ripples that has intrigued the researchers is an unusual rock structure, likely caused by some sort of regular weather or climate cycle, such as dust storms. Not far from the ripples are in fact rocks made of layers that are regular in their spacing and thickness. This type of rhythmic pattern in rock layers on Earth often results from atmospheric events that occur at periodic intervals. It is possible that the rhythmic patterns of these Martian rocks are the result of similar events, thus making it possible to study atmospheric phenomena that must have periodically occurred in ancient times on Mars.

Also, far ahead of the ripples, scientists have spotted another clue to the action of ancient water on Mars, in a valley called Gediz Vallis. The wind has sculpted the valley, but a channel running through it and starting higher up Mt sharp is thought to have been eroded by a small river. Scientists suspect liquid landslides also occurred here, sending car-sized boulders and debris to the valley floor. Because the resulting debris pile sits on top of all other valley layers, it is clearly one of the youngest structures on Mt. sharp, and is therefore of interest because it is one of the most recent evidence of the presence of liquid water identified so far.

Ripples, regularities due to atmospheric events, debris and wet landslides all tell us of a planet with a much more lively climate and weather than the current one; and perhaps the moment is not far off when, as it once happened to me looking among the ripples of the seabed a few decimeters from my nose, we will discover the first traces of a possible life that frequented the calm shallow lakes of another planet .