Following the announcement that Curiosity had found chemical and mineral signatures pointing towards Mars – or at the very least, Gale Crater – once being wet enough to create the right conditions in which micro-organisms may have once survived, the mission team has continued to analyse data returned by the rover over the last several weeks. In doing so, they have uncovered further evidence as to role of water in area during wet periods of Mars’ past.
The most recent findings from the Mars Science Laboratory team was presented to the Lunar and Planetary Science Conference, being held in Texas, on March 18th, in which the team discussed the use of the infrared-imaging capability of the Mastcam system and the neutron-firing Dynamic Albedo of Neutrons (DAN) instrument to find further evidence of the hydration of minerals in the area.
Mastcam’s ability to capture infra-red images means it can be used as a mineral-detecting tool and as a means of observing hydration in surface rock features, where the ratio of brightness in images captured at different near-infrared wavelengths can indicate the presence of hydrated minerals. The technique was used to check rocks in the “Yellowknife Bay” area and has revealed some rock formations in the area to be crisscrossed with bright veins.
“With Mastcam, we see elevated hydration signals in the narrow veins that cut many of the rocks in this area,” said Melissa Rice of the California Institute of Technology, Pasadena. “These bright veins contain hydrated minerals that are different from the clay minerals in the surrounding rock matrix.” She went on to explain, “What Mastcam is seeing is water that is bound in the mineral structure of the rocks. This water is left over from a previous wet era and is now trapped and preserved in these hydrated minerals.”
The Russian-made DAN instrument on Curiosity detects hydrogen beneath the rover. At the rover’s very dry study area on Mars, the detected hydrogen is mainly in water molecules bound into minerals. “We definitely see signal variation along the traverse from the landing point to Yellowknife Bay,” said DAN Deputy Principal Investigator Maxim Litvak of the Space Research Institute, Moscow. “More water is detected at Yellowknife Bay than earlier on the route. Even within Yellowknife Bay, we see significant variation.”
Findings from the Canadian-made Alpha Particle X-ray Spectrometer (APXS) on Curiosity’s arm-mounted turret indicate that the wet environmental processes that produced clay at Yellowknife Bay did so without much change in the overall mix of chemical elements present, and confirmed the elemental composition of the outcrop Curiosity drilled into matches the composition of basalt, the most common rock-type on Mars. The APXS findings were initially affected by the dust layer common to most surfaces on Mars, which masked the basaltic signature of the rocks until the rover’s wire brush was used to scrub a section of rock clean of the dust.
“By removing the dust, we’ve got a better reading that pushes the classification toward basaltic composition,” Curiosity science team member Mariek Schmidt said. The sedimentary rocks at Yellowknife Bay likely formed when original basaltic rocks were broken into fragments, transported, re-deposited as sedimentary particles, and mineralogically altered by exposure to water.
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