[meteorite-list] MAVEN Ultraviolet Image of Comet Siding Spring's Hydrogen Coma

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4352

MAVEN Ultraviolet Image of Comet Siding Spring's Hydrogen Coma

NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft obtained 
this ultraviolet image of hydrogen surrounding comet C/2013 A1 Siding 
Spring on Oct. 17, 2014, 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, 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 the 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 miles per hour (56 kilometers per second). This gas may have 
disturbed the Mars atmosphere


Media Contact

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster at jpl.nasa.gov 

2014-371