With a sample delivered to the observation tray and then to CheMin on Sol 71, sample gathering resumed on Sol 74 (October 24th) with a fourth scoop of the sand-like material being gathered and examined via camera in preparation for it being delivered into the CHIMRA processing system for further cleaning operations.
The sample was transferred into CHIMRA, which is mounted on the robot arm of the rover (the sample scoop itself forming a part of the overall CHIMRA mechanism) on Sol 75 (October 21st). Further cleaning of the CHIMRA sieves and filters is required to ready them for the delivery of samples to the highly sensitive SAM (Sample Analysis at Mars) system aboard the rover itself. Because SAM is so very sensitive, it was determined to go ahead with further planned cleaning cycles despite visual examination of the scoop and the visible part of the CHIMRA inlet revealing them to be well coated in Martian material.
At the same time as sample gathering was underway, Curiosity continued to monitor its environment with the Radiation Assessment Detector (RAD), Rover Environmental Monitoring Station (REMS – the rover’s weather station) and Dynamic Albedo of Neutrons (DAN) instruments of its science payload.
The laser system on ChemCam was also used to zap the soil around the rover for analysis by ChemCam’s own spectrometer. One target in particular, dubbed “Crestaurum”, was struck 30 times by the laser on Sol 74, resulting in a dark pit some 3 mm (roughly an eighth of an inch) across being created in the target location, 2.7 metres (8 feet) away from the laser at the top of the rover’s mast. The shots themselves brought the total number of laser firings in the mission so far to a staggering 10,000.
Zapping the surface in this way vaporizes the material hit by the laser, allowing the ChemCam telescope system to images of the resultant plasma which can be fed via fibre-optics to ChemCam’s own spectrometer. Working in tandem with both the Chemistry and Minerology (CheMin) and SAM systems, which analyse surface samples directly, ChemCam provides a far broader range of data on soil composition, etc., for return to Earth than has previously been possible with rover missions.
Rather than discarding the fourth scoop sample following cleaning operations within CHIMRA, the sample was used for two further activities.
In the first, on Sol 77, around 20 grams of the material was delivered to CheMin for analysis, making it the second sample of surface material delivered to that system.
In the second, on Sol 78 and after CheMin had completed initial analysis of its new sample, a further measure of the material was delivered to Curiosity’s on-board observation tray for visual analysis.
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