Observations from NASA’s Curiosity rover have provided some intriguing revelations on the past climate of Mars. Based on this data, researchers believed that the Red Planet experienced dramatic fluctuations between wetter epochs and drier epochs. Mars, it appears, didn’t dry up all at once. The findings are reported in the journal Geology.
The French-US team was led by William Rapin, from the Institut de Recherche en Astrophysique et Planétologie. They looked at the different layers of sediments spotted by Curiosity on Mount Sharp (officially named Aeolis Mons). The whole exploration of Curiosity has been a look back in time. Gale Crater, where the rover is located, is an ancient lake, and the 5.5-kilometer (3.4-mile) tall Mount Sharp is made of layer after layer of deposited material that was then eroded.
But not all the layers are the same. Curiosity has spent a fair bit of time studying up close the so-called clay-bearing unit (if you like layered rocks, check this out) and it is now approaching the sulfate-bearing unit. This analysis provides the first description of this region of Mount Sharp and suggests that the different looking layers spotted by telescopic imager of the ChemCam instrument meant different climates.
The clay-rich layered deposits are expected to have been formed in a lake-bed, and on top of those, there are sediments consistent with being formed by the migrations of wind-formed dunes. This suggests that the region had dried up and the planet had lost its free-flowing water – but apparently not for the last time. Above the dry-formed sediment, there are alternating brittle and resistant beds, typical of river-floodplain deposits. So back into wet conditions. At least for a while.
The whole rocky slope is several hundred meters thick and corresponds to the Martian Hesperian age, which lasted from 3.7 to 2.9 billion years ago. So, the idea from the current observations is the climate of Mars must have fluctuated – water must have disappeared for a long while before coming back.
But where did the water go? That is actually an open question for planetary scientists. The general idea had that over time, as the planet lost its atmosphere, the water evaporated and was lost to space. But new research suggests that a large fraction of the water (if not the majority of it) might still be on Mars trapped inside rocks and minerals buried deep beneath the planet’s crust.