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article imageMars rover Curiosity digs deep and finds something like Hawaii

By Robert Myles     Nov 1, 2012 in Science
NASA’s Mars rover Curiosity has continued its solitary mission to the Red Planet, this week making a start on analysing soil samples scooped up from the Martian surface. Initial results show similarities between Martian soil and soil found on Hawaii.
Initial Martian soil analysis carried out by NASA’s Mars rover Curiosity points to the mineral composition of Martian soils being similar to the weathered basaltic soils found in Hawaii. Such soils are the result of past volcanic activity, said NASA in a statement issued October 30th.
Curiosity Digs In: These 2 photos show a  bite mark  where NASA s Curiosity rover scooped up some Ma...
Curiosity Digs In: These 2 photos show a "bite mark" where NASA's Curiosity rover scooped up some Martian soil (left), and the scoop carrying soil. Scientists enhanced the color in this version to show the Martian scene as it would appear under lighting conditions on Earth.
Mars rover Curiosity used its Chemistry and Mineralogy instrument (CheMin) to analyse the initial Martian soil sample. The analysis will help scientists confirm the mineralogical composition of the fine dusts and soils which are so much a feature of the Martian landscape. Up till now, scientists could, for the most part, only theorize about how Martian soils came to be formed. The CheMin takes soil analysis a stage further.
"Our team is elated with these first results from our instrument," said David Blake, principal investigator for CheMin at NASA Ames Research Center in Moffett Field, California and CheMin’s principal developer, "They heighten our anticipation for future CheMin analyses in the months and miles ahead for Curiosity."
"We had many previous inferences and discussions about the mineralogy of Martian soil," said Blake, "Our quantitative results provide refined and in some cases new identifications of the minerals in this first X-ray diffraction analysis on Mars."
One of the principal objectives of the Curiosity Mars mission is to assess the history of the Martian environment. The CheMin is crucial to this analysis since it can return results revealing the environmental conditions under which a particular mineral came to be formed. Simple chemical analysis may identify the makeup of a particular rock but in the text book illustration quoted by NASA, graphite and diamonds have structures and properties which are poles apart yet, chemically, both are identical being forms of the element carbon.
Unlike the earlier Phoenix Mars mission of 2008 which used wet chemistry analysis on samples of Martian soil, Curiosity’s CheMin uses X-ray diffraction. X-ray diffraction is commonly used by Earth based geologists but on Earth heavy duty laboratory instruments are the norm. The method provides most accurate mineral identification to date of Martian soil and dust. Using X-ray diffraction a mineral’s internal structure is read and analysed by recording how crystals in a sample distinctively interact with X-rays.
Whilst Curiosity may be operating in the near vacuum of the Martian atmosphere, the same cannot be said of the research and development at the Ames Research Center. To make X-ray diffraction feasible on the Curiosity mission, much like electronic components had to be miniaturised for the manned Apollo missions of the 1960s and 1970s, bulky laboratory equipment had somehow to be distilled down to an X-ray diffraction instrument small enough to fit inside the Curiosity rover.
As has often been the case with space exploration, technological advances made by NASA in one field had repercussions elsewhere. CheMin technology has led to the development of portable X-ray diffraction equipment which is now deployed here on Earth in a variety of fields from oil and gas exploration to screening of counterfeit pharmaceuticals.
CheMin’s First Contact with Martian Soil
Wind-Blown Martian Sand: Two images from the Mast Camera on NASA s Curiosity rover show the upper po...
Wind-Blown Martian Sand: Two images from the Mast Camera on NASA's Curiosity rover show the upper portion of a wind-blown deposit dubbed "Rocknest." Curiosity took a scoop of soil from an area out of frame. The soil was analyzed with the Chemin instrument. The colors in the left image are unedited, showing the scene as it is on Mars.The image at right has been white-balanced to show what the same area would look like under natural light on Earth.
The first sample analysed by CheMin was scooped up from an area of dust and sand named ‘Rocknest’ by the NASA Curiosity team. As reported earlier in Digital Journal, Curiosity was scheduled to spend around three weeks in the Rocknest area.
Prior to analysis, the sample was sieved to exclude particles bigger than 0.006 inch (150 micrometers), about the width of a human hair. NASA reports that the first sample had two principal components, namely, Martian dust distributed all around the Red Planet by huge dust storms and more local fine sand originating from erosion. NASA believes the soil sample to be representative of more recent geological events on Mars, unlike the rocks which Curiosity examined a few weeks ago which were gauged to be several billion years old and showed signs of contact with running water.
"Much of Mars is covered with dust, and we had an incomplete understanding of its mineralogy," said David Bish, CheMin co-investigator with Indiana University in Bloomington. "We now know it is mineralogically similar to basaltic material, with significant amounts of feldspar, pyroxene and olivine, which was not unexpected. Roughly half the soil is non-crystalline material, such as volcanic glass or products from weathering of the glass."
"So far, the materials Curiosity has analyzed are consistent with our initial ideas of the deposits in Gale Crater recording a transition through time from a wet to dry environment. The ancient rocks, such as the conglomerates, suggest flowing water, while the minerals in the younger soil are consistent with limited interaction with water," continued Bish.
How CheMin works
Illustration of CheMin dual-cell geometry. Exploded view of dual-cell assembly showing windows  tuni...
Illustration of CheMin dual-cell geometry. Exploded view of dual-cell assembly showing windows, tuning-fork assembly, and piezodriver (left). Assembled cell, ready for testing in testbed (right).
To give it its full name, CheMin is the Chemistry and Mineralogy X-ray powder diffraction and fluorescence instrument. It was developed by David Blake and is one of four spectrometers on board the Curiosity rover. CheMin uses X-ray diffraction to identify minerals. It is the first time this technique has been deployed extra-terrestrially.
For analysis, a beam of precise X-rays is directed at fine dust or powdered soil. When the X-rays hit the soil sample, some of X-rays are absorbed by atoms in the sample and are re-emitted or fluoresced. This fluorescence is in effect a signature of the atoms present within the sample enabling NASA scientists to identify individual minerals present.
When the Curiosity rover scoops up a sample, it is delivered to one of the windowed areas of the CheMin analyser (pictured). Within CheMin, there are 16 pairs of dual-cell assemblies with each pair of cells acting like a tuning fork vibrating at approximately 2,000 times per second. The vibration causes the particles within the sample to flow like a liquid. This movement allows CheMin’s X-ray instrument to hit all the particles randomly. Each sample takes around 10 hours to analyse and once the data has been collected, it allows scientists to decipher the precise mineralogical composition.
As part of Mars rover Curiosity’s ongoing two year mission to explore Mars, a total of ten instruments will help NASA scientists get a clearer picture of whether areas in Mars’ Gale Crater were ever environmentally compatible for microbial life forms to exist.
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