Extensive carbonate deposits reported on Mars

According to a new paper published in Nature Geoscience, large deposits of carbonates have been found buried about six kilometres (four miles) below the surface of Leighton crater (exposed by the original impact), near the huge shield volcano in the Syrtis Major region. Small deposits have been found before on the surface, including recently by the rover Spirit, but much larger amounts would be additional evidence of a warmer, wetter ancient Mars, with a thicker atmosphere of carbon dioxide. Notably, carbonates are formed in non-acidic (alkaline) liquid water. So this finding would again reinforce the idea of ancient lakes, seas or oceans on the surface. But were those waters cold or warm? What about those icebergs? It seems like every time another piece of the puzzle is found, it just raises more questions…

Ancient Martian icebergs?

Images from the Mars Reconnaissance Orbiter have provided evidence of possible icebergs in the ancient Martian past. It has long been speculated that the northern smoother plains were once the bottom of an ocean; now, clusters of boulders and chains of pits or craters have been found there which are very similar to those on Earth, in areas where icebergs have scraped the bottom of the ocean, depositing rock fragments.

Credit: HiRISE

Of course, if there were icebergs, then there must have been oceans or seas. The findings support a more recent theory, of a cold and wet early Mars. So perhaps more like the Arctic ocean rather than the tropics, but still significant in terms of possible life.

And now, the case of the disappearing methane

First, as posted a few days ago, there was the mystery of seemingly missing methane on an exoplanet. Now there’s another methane-related riddle, on Mars. First detected in 2003, the gas is being continually produced, but the origin is still unknown. It could be either geological or biological, and is concentrated in three areas in the northern hemisphere, regions of previous volcanic activity and underground water ice. The amount also varies with the seasons, increasing in the spring, more so in the summer, peaking in autumn and then rapidly decreasing in winter. That pattern could fit with either still-occurring hydrothermal activity or biology, ie. microbes, or both.

The new puzzle though is why the methane has now been observed to remain in the atmosphere for less than a Martian year. It was expected to last longer, so something is destroying it relatively quickly, faster than expected for a photochemical process (destruction by sunlight). As stated in the article, perhaps chemicals from the soil, being alofted into the atmosphere by winds.

So both the origin and demise of the Martian methane are currently unknown. Hopefully more answers can come from the upcoming Mars Science Laboratory rover (Curiosity) and the ExoMars missions, both of which are equipped to analyse the methane in more detail…

Opportunity rover now halfway to Endeavour crater

The Opportunity rover passed the halfway mark this week on its long journey from Victoria crater to the huge 22 kilometre (14 mile) diameter Endeavour crater. A fitting first post for the new blog, as it is of course in Meridiani Planum where Opportunity has been travelling since 2004… It will be interesting as we get closer, because clay minerals have been found around the rim of the crater by the Mars Reconnaissance Orbiter; clay minerals form in non-acidic (alkaline) liquid water, so this would be yet another indicator of different surface conditions in the ancient Martian past…

The halfway point to Endeavour… Credit: NASA/JPL-Caltech
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