Rock layers indicate that part of Mars once had water

A region called Arabia Terra, in the north of the planet Mars, may have already harbored water in a short period of time. The discovery was made by scientists at Northern Arizona and Johns Hopkins universities, who published the study (funded by NASA’s Mars Data Analysis program) in the academic journal Geology.

Slightly larger than mainland Europe, this area has craters, volcanic caldera, canyons and rocky ridges. The research team wanted to understand how these rock layers formed and find out if there ever was stable water (and for how long) and what the atmosphere and surface temperature were like.

“We were especially interested in using the surface rocks of Mars to better understand the environments of 3-4 billion years ago and whether there might have been suitable climatic conditions for surface life,” says Ari Koeppel, one of the authors of the research, in press release.

To understand the formation of rock layers, scientists began by studying thermal inertia — the ability of a material to gain or lose heat by changing its temperature. Therefore, by analyzing the surface temperature of the rocks, they were able to identify their physical properties, including evidence of erosion and which minerals were present.

The team then found that the sediments from the rocks they found were less cohesive than previously believed, which may indicate that the surface harbored water for a short period of time.

“For some people, that takes the fun out of the story, because we generally think that having more water for a longer time means there’s a greater chance there was life there at some point. But, for us, it’s very interesting, because it raises a new set of questions”, says the scientist.

“What conditions might have allowed water to exist there for a short period? Could there have been glaciers that melted quickly causing massive floods? Could there have been an underground water system that infiltrated the ground only for a short period and then sank again?”, he enumerates.

The research could only be carried out thanks to remote sensing instruments installed on satellites orbiting the planet. “Like geologists on Earth, we look to rocks to try to tell stories about past environments,” says Koeppel. “On Mars, we are a little more limited. We cannot just go to a quarry and collect samples. We are dependent on satellite data”, he comments. “There are several satellites orbiting Mars, and each one houses a collection of instruments. Each instrument has its own function to help us describe the rocks that lie on the surface.”