19th October 2014 Sol 783

Today marks the closest approach of Comet Siding Spring to Mars.  Curiosity will be pointing MastCam and ChemCam towards it, and have been practising targeting  at stars like Spica.  Its a tough targetting  job but ChemCam might be able to get molecular information about the composition of gases in the comet’s coma from passive spectra.  One of the challenges of the targetting is that we dont really know for sure how large the comet is.

To date the most detailed information we have got about the composition of comets has been from the Stardust mission.  That brought back to Earth micron-size solid grains from the Jupiter Family Comet Wild2.   However, Siding Spring is from much further out in the farthest parts of the Solar System – the Oort Cloud, 1000’s AU away from Mars, so this is a particularly special (and very close) encounter.

Meanwhile on Mars , Curiosity is finishing analysing drill dump piles and rock and vein targets at the Confidence_Hills drillsite in Pahrump Hills.