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Not to be outdone by the feisty Opportunity Rover, the HiRISE camera on NASA’s Mars Reconnaissance Orbiter (MRO) turned in its homework this evening with a fine image of comet C/2013 Siding Spring taken during closest approach on October 19. ... To photograph a fast-moving target from orbit, engineers at Lockheed-Martin in Denver precisely pointed and slewed the spacecraft based on comet position calculations by engineers at JPL. To make sure they knew exactly where the comet was, the team photographed the comet 12 days in advance when it was barely bright enough to register above the detector’s noise level....

A comet from the outer reaches of the solar system is due to give Mars a close shave on Sunday (Oct. 19), and you can watch the flyby live online. While Comet Siding Spring (also called Comet C/2013 A1) isn't easy to spot from Earth, a couple different astronomy organizations will be tracking the comet as it flies 87,000 miles (139,500 kilometers) from Mars at 2:27 p.m. EDT (1827 GMT) on Sunday. The comet will fly three times closer to Mars than the moon is to Earth.

American Astronomical Society, DPS meeting #45, #313.18 Published in Oct 2013 The Comet 2013A1 (Siding Spring) will pass within 123,000 km of Mars on October 19, 2014 at a relative velocity of 56 km/s. The comet coma will impinge directly on the Martian upper atmosphere, causing significant perturbations.We examine the thermal effects of the encounter with a first principle model of the upper atmosphere (100-200 km) that solves for the time-dependent thermal structure. The thermal model includes solar EUV heating, radiative cooling, thermal conduction, and heating due to the impact of H2O molecules from the coma.Assuming a H2O production rate...