[meteorite-list] Comet Siding Spring Seen Next to Mars (Hubble Space Telescope)

[Ron Baalke]

October 23, 2014
     
CLOSE ENCOUNTERS: COMET SIDING SPRING SEEN NEXT TO MARS

This composite NASA Hubble Space Telescope Image captures the positions of 
comet Siding Spring and Mars in a never-before-seen close passage of a comet 
by the Red Planet, which happened at 2:28 p.m. EDT October 19, 2014. The 
comet passed by Mars at approximately 87,000 miles (about one-third of the 
distance between Earth and the Moon). At that time, the comet and Mars were 
approximately 149 million miles from Earth.

The comet image shown here is a composite of Hubble exposures taken between 
Oct. 18, 8:06 a.m. EDT to Oct. 19, 11:17 p.m. EDT. Hubble took a separate 
photograph of Mars at 10:37 p.m. EDT on Oct. 18.

The Mars and comet images have been added together to create a single picture 
to illustrate the angular separation, or distance, between the comet and Mars 
at closest approach. The separation is approximately 1.5 arc minutes, or 
one-twentieth of the angular diameter of the full Moon. The background 
starfield in this composite image is synthesized from ground-based telescope 
data provided by the Palomar Digital Sky Survey, which has been reprocessed 
to approximate Hubble's resolution. The solid icy comet nucleus is too 
small to be resolved in the Hubble picture. The comet's bright coma, a 
diffuse cloud of dust enshrouding the nucleus, and a dusty tail, are clearly 
visible.

This is a composite image because a single exposure of the stellar 
background, comet Siding Spring, and Mars would be problematic. Mars is 
actually 10,000 times brighter than the comet, and so could not be properly 
exposed to show detail in the Red Planet. The comet and Mars were also moving 
with respect to each other and so could not be imaged simultaneously in one 
exposure without one of the objects being motion blurred. Hubble had to be 
programmed to track on the comet and Mars separately in two different 
observations.

The images were taken with Hubble's Wide Field Camera 3.

Felicia Chou
Headquarters, Washington
202-358-0257
felicia.chou at nasa.gov