To achieve this, the exposed sand was subjected to study by MAHLI and APXS, which obtained data on the general nature of the material and its overall cohesiveness – itself an important factor, as sand with a high level of cohesion might clog CHIMRA’s internal feeds and sieves. Data from the study confirmed the sand is suitable for the cleaning process.
“Cleaning” is required because even though all of Curiosity’s systems were assembled under the most stringent “clean” conditions, some contamination was unavoidable, which takes the form of a very thin “oily” film that adheres to surfaces exposed to the atmosphere. In order to prevent this “oil” being transferred to the SAM instruments and giving false readings (a problem which initially occurred when SAW was first used to sample the Martian atmosphere), it is essential this “oil” is removed from CHIMRA’s internal parts ahead of actual sample collection and analysis operations.
To ensure CHIMRA is properly cleaned, around three scoop operations will be completed over the course of several days. Each will pass Martian surface material through CHIMRA’s processing mechanism – the sieves designed to ensure only very fine Martian particulates are collected for transfer to SAM, the collection box itself, the interior of the scoop and the channels connecting all of these elements – before the samples are dumped back onto the Martian surface. Once a scoop of sand has been collected, CHIMRA’s vibration system will be activated for an extended period, vibrating the entire turret mechanism at up to 8G, causing the sand grains to effectively scour the internal surfaces clean of any Earth-generated residue. Each of these operations is liable to last around two days.
On the first day, the arm will be deployed with the scoop open. Once in position above the sand, the command will be given to close the scoop and gather sand. Before the scoop is fully closed, vibrations will be applied to the turret to remove excess material from the scoop and “level” the sample. The scoop will be imaged throughout this process to ensure it is operating correctly and to confirm material has been gathered.
On day two, the sample will be delivered into CHIMRA, and the vibration cleaning process will commence. This will see the turret vibrated for an extended period in order for CHIMRA’s insides to be effectively scoured. Once completed, the transfer box, which will eventually be used to deliver samples to Curiosity’s on-board sample analysis systems, will be opened to dump the used material back on the surface of Mars. The cycle will then be repeated with a fresh sample.
When cleaning operations have been completed, Curiosity will be commanded to collect samples for delivery to the on-board CheMin and SAM instruments for detailed analysis.
Once sampling work has been completed at Rocknest, the rover will resume its journey to Glenelg. Once there, the final set of commissioning tests will be undertaken. These will be for the turret-mounted drill system, and will again involve CHIMRA’s processing capabilities as well as CheMin and SAM. While at Glenelg, Curiosity will carry out a range of other activities, after which it should be “onwards to ‘Mount Sharp’!”
As well as using Twitter, the MSL team are using other social media tools to help promote Curiosity and NASA’s work. On Wednesday October 3rd, Curiosity checked-in on Mars using Foursquare, marking the first check-in on another planet, and in doing so earned itself a Newbie badge. Foursquare users can keep up with Curiosity as the rover checks-in at key locations and posts photos and tips, all while exploring the Red Planet. Commenting on the use of the social media site, David Weaver, Associate Administrator for Communications at NASA Headquarters in Washington said, “This will help to involve the public with the mission and give them a sense of the rover’s travels through Gale Crater.”
On October 5th, Curiosity tweeted an achievement in Foursquare:
Images courtesy of NASA / JPL.