ESA’s Mars Express has revealed a strong evidence of an ocean once covering the northern part of Mars.
Ancient northern ocean on Mars (ESA / C. Carreau)
Using the MARSIS radar instrument, the spacecraft detected sediments reminiscent of an ocean floor within the boundaries of previously identified ancient shorelines on Mars.
According to the European Space Agency, the radar was deployed in 2005 and has been collecting data ever since. A team of researchers, led by Dr. Jérémie Mouginot of Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) and the University of California, analyzed more than two years of data and found that the northern plains are covered in low-density material.
“We interpret these as sedimentary deposits, maybe ice-rich,” said Dr. Mouginot. “It is a strong new indication that there was once an ocean here.”
The existence of oceans on ancient Mars has been suspected before and features reminiscent of shorelines have been tentatively identified in images from various spacecrafts. Two oceans have been proposed: 4 billion years ago, when warmer conditions prevailed, and also 3 billion years ago when subsurface ice melted following a large impact, creating outflow channels that drained the water into areas of low elevation.
“MARSIS penetrates deep into the ground, revealing the first 60–80 m of the planet’s subsurface,” said Dr. Wlodek Kofman, leader of the radar team at IPAG. “Throughout all of this depth, we see the evidence for sedimentary material and ice.”
The sediments revealed by MARSIS are low-density granular materials that have been eroded away by water and carried to their final destination.
This later ocean would however have been temporary.
Dr. Mouginot estimates that within a million years or less the water would have either frozen back in place and been preserved underground again, or turned into vapor and lifted gradually into the atmosphere.
“I don’t think it could have stayed as an ocean long enough for life to form,” he concluded.
“Previous Mars Express results about water on Mars came from the study of images and mineralogical data, as well as atmospheric measurements. Now we have the view from the subsurface radar,” said Dr. Olivier Witasse, ESA’s Mars Express Project Scientist. “This adds new pieces of information to the puzzle but the question remains: where did all the water go?”
