Drilling means learning

The Curiosity rover has collected and started the analysis of her second sample of Martian rock that seems to have formed in a lake environment more acidic than the previous site. Because of the fragility of the rock, has been used a technique of drilling hammer with less energetic.


Credit: NASA/JPL-Caltech/MSSS

If the first bite of Martian dust from Curiosity tasted a few months ago had a strong aftertaste of hematite, the second tasting of fine dust of Mount Sharp left at NASA rovers a bit of acid in the mouth. Curiosity has reached the base of Mount Sharp five months ago after long pilgrimage, taking a sample of soil from a site called “Confidence Hills”. Last week the drill of the big robot Martian came back in operation, on a layered rock called “Mojave 2”. A first analysis on minerals that make up the sample, carried out with the instrument CheMin within Curiosity, shows a significant amount of jarosite, a mineral containing oxidized iron and sulfur which forms in acidic environments.


Credit: NASA/JPL-Caltech/MSSS

“Our initial assessment indicates that the latter sample contains much more than the jarosite sample Confidence Hills,” said David Vaniman, the Planetary Science Institute in Tucson, Arizona, deputy head of the instrument CheMin. In other words, the minerals Mojave 2 were formed in the presence of water more acidic than Confidence Hills. Scientists cannot tell if they were still waters that permeated the environment in which they are deposited sediments from which the pad is made, or a fluid that has soaked the site later.
Both sites sampled by Curiosity found in an outcrop called “Pahrump Hills”, a fragment of the exposed formation Murray, the geological unit base of Mount Sharp. The team’s mission Curiosity has already proposed the hypothesis that the genesis of this mountain is due to sediments deposited in a repeated series of fills and drying processes of lake basins.


Credit: NASA/JPL-Caltech/MSSS

The team chose a target called “Mojave”, mainly because of the abundance of grains, slightly smaller than grains of rice, which are visible on the surface of the rock. The researchers sought to determine whether these grains are salt crystals of some mineral, such as those that might result from evaporation or drying of a lake, or if they have some other composition.
The real star of this sampling is the drill of Curiosity, rather the software that governs it, which is worth a few words. The drill, which is essentially a chisel, has six level settings percussion, ranging from “gently tap” to “beat vigorously”, all at 30 times per second.


Credit: NASA/JPL-Caltech/Univ. of Arizona

The drill is capable of controlling the speed at which is penetrating into the rock, and adjusts accordingly, in an autonomous way, its level of percussion. While previous drilling began at 4 and has used an algorithm which tended to remain at that level, the breaking of the rock on the first attempt in the Mojave site has required a software upgrade drilling. The new cautious algorithm starts at level one, and then moves to the next level only if progress in drilling are too slow. The rock Mojave 2 is so soft that the drill has reached its full depth to 6.5 cm in 10 minutes using only the levels one and two of the energy of percussion.
While the Martian terrain He performed all these maneuvers, kept an eye on him from above the winged brother, the NASA probe Mars Reconnaissance Orbiter. Here’s how it looks from orbit Curiosity at work among the arid hills of Pahrump.

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