Has Curiosity found Martian rock varnish?

Before and after image of a rock lasered by Curiosity. The surface of the rock has darkened around the spot hit by the laser. Credit: Los Alamos National Laboratory

Before and after image of a rock lasered by Curiosity. The surface of the rock has darkened around the spot hit by the laser. Credit: Los Alamos National Laboratory

Scientists studying data from the Curiosity rover have found another interesting puzzle, one which may easily have gone unnoticed were it not for one diligent researcher in particular, it was announced last week at the 44th Annual Lunar and Planetary Science Conference at The Woodlands, Texas.

The ChemCam’s laser is one of the most important tools Curiosity has to study the composition of Martian rocks. It vapourizes a tiny spot on a rock’s surface, and the resulting sample can then be analyzed by the spectrometer. It can zap a single spot many times over – up to 600 times in one case.

Generally, it is thought that the first five zaps are necessary to remove any dust or other material on the surface of the rock. For that reason, those initial zaps aren’t of as much interest to the scientists who want to examine the rock itself underneath. As it turns out however, there seems to be a clue to something interesting in those first five laser shots.

Nina Lanza, a postdoctoral researcher at Los Alamos National Laboratory, looked at the data from the first five shots, instead of ignoring them. She explained that those first five first shots always seemed to show the same chemical properties, regardless of what kind of rock was being studied. Is it just a coating of dust being removed by the laser? In testing done on Earth, the laser easily removes any dust present in just the first shot. If that is the case, then what is being removed by the remaining four shots?

An interesting possibility is that there is a coating on the rocks similar to desert varnish on Earth, which is commonly found on rocks in arid conditions. According to Lanza, “The thing about rock varnishes is the mechanism behind why they form is not clearly understood. Some people believe that rock varnish results from an interaction of small amounts of water from humidity in the air with the surface of rocks – a chemical reaction that forms a coating. Others think there could be a biological component to the formation of rock varnishes, such as bacteria or fungi that interact with dust on the rocks and excrete varnish components onto the surface.”

Similar-looking coatings have been seen before on Martian rocks as well, which can appear somewhat shiny. The example in the image above has that kind of appearance to it as well, suggesting it may be relatively dust-free.

It may turn out that the unidentified coating is actually just dust after all, or that it is formed by some other weathering process, but it will be interesting to see what further testing by Curiosity shows as the mission continues.

This article was first posted on Examiner.com.

One Thought on “Has Curiosity found Martian rock varnish?

  1. this is just martian lichen or cyanobacteria hidden under a thin layer of dust. stop zapping the martians!

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