NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft obtained this ultraviolet image of hydrogen surrounding comet Siding Spring on Friday, Oct. 17, two days before the comet’s closest approach to Mars. The Imaging Ultraviolet Spectrograph (IUVS) instrument imaged the comet at a distance of 5.3 million miles (8.5 million kilometers). The image shows sunlight that has been scattered by atomic hydrogen, and is shown as blue in this false-color representation. Comets are surrounded by a huge cloud of atomic hydrogen because water (H2O) vaporizes from the icy nucleus, and solar ultraviolet light breaks it apart into hydrogen and oxygen. Hydrogen atoms scatter solar ultraviolet light, and it was this light that was imaged by the IUVS. Two observations were combined to create this image, after removing the foreground signal that results from sunlight being scattered from hydrogen surrounding Mars. The bulk of the scattered sunlight shows a cloud that was about a half degree across on the “sky” background, comparable in size to Earth’s moon as seen from Earth. Hydrogen was detected to as far as 93,000 miles (150,000 kilometers) away from the comet’s nucleus. The distance is comparable to the distance of the comet from Mars at its closest approach. Gas from the comet is likely to have hit Mars, and would have done so at a speed of 125,000 mph (56 kilometers/second. This gas may have disturbed the Mars atmosphere. Credit: Laboratory for Atmospheric and Space Physics, University of Colorado; NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
“Rock Comet” 3200 Phaethon has sprouted a tail, proving that the mysterious object is the source of the annual Geminid meteor shower.
NASA NEOWISE mission captured images of Comet C/2013 A1 Siding Spring. The infrared pictures reveal a comet that is active and very dusty.
This first image of comet 103P/Hartley 2 was taken from NASA Deep Impact spacecraft 60 days prior to the spacecraft flyby of the comet.
The Compact Reconnaissance Imaging Spectrometer for Mars CRISM aboard NASA Mars Reconnaissance Orbiter obtained this spectrum for comet C/2013 A1 Siding Spring during the comet close approach to Mars.
This image from an animiation of comet C/2013 A1 Siding Spring were taken by the Mast Camera Mastcam on NASA Curiosity Mars rover as the comet passed near the red planet on Oct. 19, 2014.
This image was taken during the close approach phase of NASA Stardust Jan 2, 2004 flyby of comet Wild 2. It is a distant side view of the roughly spherical comet nucleus.
This artist depiction shows the close encounter between comet Siding Sprng and Mars in 2014. The comet powerful magnetic field temporarily merged with, and overwhelmed, the planet weak magnetic field.
These images were taken of comet C/2013 A1 Siding Spring by NASA Mars Reconnaissance Orbiter on Oct. 19, 2014, during the comet close flyby of Mars and the spacecraft.
This composite image was taken by NASA Stardust navigation camera 42 hours before its encounter with comet Tempel 1. The spacecraft is due to encounter the comet in the evening hours of Feb. 14, 2011.