Was There a Large Ocean on Mars?

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New data from ESA’s Mars Express reveals strong evidence that an ocean once covered the northern hemisphere of Mars. The evidence is based on signatures of ocean floor sediments in an area within the boundaries of what has thought to have been an ancient shoreline on Mars.

Deployed in 2005, the MARSIS radar has been collecting data that was recently analyzed by Jérémie Mouginot (Institut de Planétologie et d’Astrophysique de Grenoble). Mouginot’s analysis revealed that the northen plains of Mars are covered in low-density material.

“We interpret these as sedimentary deposits, maybe ice-rich,” says Mouginot. “It is a strong new indication that there was once an ocean here.”

Scientists have long suspected the presence of martian oceans in the past. One piece of evidence supporting the theory of a wetter martian past are features that closely resemble shorelines on Earth. According to some researchers, Mars may have actually had a large ocean during two seperate time periods. The first, around four billion years ago, and the second at around three billion years ago.

The first time Mars had an ocean, the planet more than likely had a thicker atmosphere and much warmer temperatures. When the second ocean appeared, it may have been due to volcanic activity that caused subsurface ice to melt and drain into lowere elevations, such as the northern plains.

“MARSIS penetrates deep into the ground, revealing the first 60–80 metres of the planet’s subsurface,” says Wlodek Kofman, (radar team lead at IPAG). “Throughout all of this depth, we see the evidence for sedimentary material and ice.”

The sediments detected by MARSIS are typically low-density materials that are carried by flowing water. In the case of the more recent ocean on Mars, it was only temporary. Mouginot estimates that within a million years or so, the ocean would have frozen, turning into subsurface ice, or evaporated into the martian atmosphere. “I don’t think it could have stayed as an ocean long enough for life to form.” adds Mouginot.

In the search for current or past life on Mars, astrobiologists have to look at Mars’ ancient past, when liquid water most likely existed. In many scientific circles, the debate continues as to exactly how wet ancient Mars really was.

“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,” says Olivier Witasse, (Mars Express Project Scientist). “This adds new pieces of information to the puzzle but the question remains: where did all the water go?”

If you’d like to learn more about ESA’s Mars Express orbiter, visit: http://www.esa.int/esaMI/Mars_Express/index.html

Source:European Space Agency

Ray Sanders is a Sci-Fi geek, astronomer and blogger. Currently researching variable stars at Arizona State University, he writes for Universe Today, The Planetary Society blog, and his own blog, Dear Astronomer

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