NEOWISE Spies Comet C/2013 A1 Siding Spring
Date: 16 Jan 2014
NASA's NEOWISE mission captured images of comet C/2013 A1 Siding Spring, which is slated to make a close pass by Mars on 19 Oct. 2014. The infrared pictures reveal a comet that is active and very dusty even though it was about 571 million km (355 million miles) away from the sun on 16 Jan. 2014, when this picture was taken.
The infrared measurements will allow astronomers to determine the sizes and quantity of dust particles being flung off the comet. The measurements will also give engineers some indications of what orbiting spacecraft at Mars might expect when the comet gets close. Preliminary analysis of the data indicate approximately 100 kg (220 pounds) of dust are being ejected from the comet's surface each second, assuming the grains are dark and nearly the density of water-ice. The comet's activity is expected to increase as it gets closer to Mars.