Getting the scoop on drilling

CuriosityCuriosity is continuing to work towards the delivery of samples obtained from inside a rock dubbed “John Klein” to the onboard Chemical and Mineralogy (CheMin) and Sample Analysis at Mars (SAM) suites of instruments aboard the rover itself.

As reported in my last update, Curiosity obtained its first sample from inside “John Klein” on Sol 182 – the 182nd Martian day since Curiosity arrived in Gale Crater, which equates to the period of the 8th/9th February on Earth.

A series of three images from Curiosity’s forward Hazard Avoidance cameras (Hazcam), primarily used by the rover when manoeuvring / driving, put together to create a “video” showing the drill operation in progress

The drilling operation, which cut a hole some 6.4cm (2.5 in) deep into the rock, collected around a tablespoon’s worth of material. In order to help avoid the risk of material from the surface of the rock, which has been affected by the environmental conditions on the surface of Mars, from contaminating drill samples, the actual sample gathering with the drill doesn’t commence until the bit is some 2 centimetres inside the rock. So in the case of “John Klein” the collected material comes from a depth of between two and five centimetres inside the bedrock layer.

The sample was gathered as cuttings from the drill’s boring into the rock were forced up into the drill bit shroud and delivered to one of two holding chambers (Chamber A in the diagram below) located in the head of the drill bit mechanism.

How the drill works: On the left, a view of the drill mechanism mounted on the rover's turret, with the drill bit centre bottom. On the right a cutaway showing the sample collection mechanism in the drill bit
How the drill works: On the left, a view of the drill mechanism mounted on the rover’s turret, with the drill bit centre bottom. On the right a cutaway showing the sample collection mechanism in the drill bit

Following collection, the sample was used to initiate “cleaning” operations designed to remove microscopic Earth- based contaminants left within the drill as a result of its construction to prevent them unduly affecting any later analysis of sample material by CheMin and (particularly, given its sensitivity) SAM.

The first part of this “cleaning” work actually occurred during the drilling operation itself, due to the vibrations caused by the drill’s percussive (hammer) action agitating the material in the collection chamber, causing it to scour the chamber walls. Once drilling had been completed, and the robot arm returned to its stowed configuration, cleaning resumed, this time using the mechanical vibration system which forms a part of CHIMRA – the Collection and Handling for In-Situ Martian Rock Analysis system. This vibrates the entire turret at high speed, causing the gathered deposits to “swish” around the drill’s sample chambers so that friction created between the cuttings and the chamber walls would help scour the latter clean.

Part of this work was delayed after two software bugs were reported by the rover. While these were subsequently shown to be of no significant concern, they did result in a pause in cleaning operations while the software was evaluated Earthside for potential impact on operations. However, with initial cleaning work deemed to have been completed on Sol 193 (February 20th), the sample was transferred directly to the rover’s sample gathering scoop so that it could be imaged using Curiosity’s Mastcam, and visually analysed as to its suitability for onward processing through CHIMRA.

Continue reading “Getting the scoop on drilling”

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