The European Space Agency’s Mars Express has finally returned with some strong evidence of Martian oceans. Using its MARSIS radar, it detected sediments reminiscent of an ocean floor, within the boundaries of previously identified shorelines.
The MARSIS radar was deployed in 2005 and has been collecting data since then. Jérémie Mouginot, from the Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), and his colleagues have been analyzing the data for more than two years. They discovered that the northern plains are covered in low-density materials.
They think that these materials are sedimentary deposits, possibly rich in ice, which is a strong indication that there was once an ocean there. Martian oceans have been suspected for years, thanks to the shorelines that were identified by various spacecraft, but it has remained a somewhat controversial issue.
One ocean might have existed around 4 billion years ago, when Mars was warmer and another one was possibly there 3 billion years ago, when the subsurface ice melted, possibly as a result of enhanced geothermal activity.
MARSIS penetrates 60 to 80 meters into the planet’s surface, and even at this depth, they see evidence of sedimentary materials and ice. The sediments hare low-density granular materials that have been carried away by water.
The later ocean would have been temporary, since within a million years or less, the water would have been either frozen or preserved underground. To find evidence of life, astrobiologists will have to look even further into Mars’ history when liquid water was around for more extended periods of time.