Curiosity discovers water in the dust that coats Mars

A series of discoveries from NASA's Curiosity rover are giving scientists a picture of Mars that looks increasingly complex, with small bits of water spread around the surface and an interior that could have been more geologically mature than experts had previously thought.


The soil that covers Mars' surface in Gale Crater, where Curiosity landed last year, seems to have two major components, according to data from the rover's laser-shooting Chemistry and Camera instrument. One is a coarse soil with millimeter-wide grains that probably came from the rocks around them; the other is very fine, with grains often a few micrometers in size, the ChemCam data show.


The researchers say they don't know where that soil comes from, whether it's created in many places or has one source that gets picked up and blown all over.

Either way, it's a handy, naturally averaged sample of the Martian surface, said Indiana University mineralogist David Bish, who led a different study.

Perhaps the most intriguing thing about this fine soil is that ChemCam's readings detected a hydrogen signal, which could explain why satellites orbiting Mars have picked up a mysterious water signal in the past, Meslin said.


But another study based on data from Curiosity's Chemistry and Mineralogy tool — part of the dirt-digesting lab in the rover's belly — found no sign of water in soil samples taken from Rocknest, a sandy dune of a pit stop on the rover's way to a region dubbed Yellowknife Bay. That's because CheMin uses X-ray diffraction to bounce high-energy light off of a mineral's crystalline structure. If the soil isn't in crystalline form, there's no way for CheMin to see it.



Bish said it was interesting that CheMin found no signs of minerals that formed in water, since looking for such clays was "one of the reasons for going to Gale Crater." Inside Gale Crater lies a 3-mile-high mountain called Mt. Sharp, whose layers could be rich in clays that hold answers to whether Mars was hospitable to life.

It's possible that this fine-grained soil is simply too young to have ever encountered liquid water, he said. If so, it would mean that many years passed between the formation of the water-rich clays locked inside of certain rocks and the dusty grains that currently cover the Martian surface.

Another of the studies focused on the rock known as Jake M, named after NASA engineer Jake Matijevic, who died shortly after the rover landed in 2012. The researchers didn't intend to study the rock — they analyzed it with Curiosity's alpha-particle X-ray spectrometer in order to help put ChemCam's measurements in context, said Caltech geologist Edward Stolper, lead author of that study.


The rock's composition also told scientists that it was clearly made of the leftovers after other minerals had crystallized out. That led them to believe that the heating and cooling and movement of magma that used to occur beneath Mars' mantle were a lot more complicated than they had thought.

"We see evidence for a more evolved planet," Grotzinger said, "so it looks like it was headed in more of a direction like Earth."

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