[meteorite-list] NASA Prepares its Science Fleet for Oct. 19 Mars Comet Encounter

[Ron Baalke]

October 9, 2014
     
NASA Prepares its Science Fleet for Oct. 19 Mars Comet Encounter

NASA's extensive fleet of science assets, particularly those orbiting and 
roving Mars, have front row seats to image and study a once-in-a-lifetime 
comet flyby on Sunday, Oct. 19.

Comet C/2013 A1, also known as comet Siding Spring, will pass within about 
87,000 miles (139,500 kilometers) of the Red Planet -- less than half the 
distance between Earth and our moon and less than one-tenth the distance of 
any known comet flyby of Earth.

Siding Spring's nucleus will come closest to Mars around 2:27 p.m. EDT, 
hurtling at about 126,000 mph (56 kilometers per second). This proximity will 
provide an unprecedented opportunity for researchers to gather data on both 
the comet and its effect on the Martian atmosphere.

"This is a cosmic science gift that could potentially keep on giving, and 
the agency's diverse science missions will be in full receive mode," said 
John Grunsfeld, astronaut and associate administrator for NASA's Science 
Mission Directorate in Washington. "This particular comet has never before 
entered the inner solar system, so it will provide a fresh source of clues to 
our solar system's earliest days."

Siding Spring came from the Oort Cloud, a spherical region of space 
surrounding our sun and occupying space at a distance between 5,000 and 
100,000 astronomical units. "It is a giant swarm of icy objects believed to 
be material left over from the formation of the solar system.

Siding Spring will be the first comet from the Oort Cloud to be studied up 
close by spacecraft, giving scientists an invaluable opportunity to learn 
more about the materials, including water and carbon compounds, that existed 
during the formation of the solar system 4.6 billion years ago.

Some of the best and most revealing images and science data will come from 
assets orbiting and roving the surface of Mars. In preparation for the comet 
flyby, NASA maneuvered its Mars Odyssey orbiter, Mars Reconnaissance Orbiter 
(MRO), and the newest member of the Mars fleet, Mars Atmosphere and Volatile 
EvolutioN (MAVEN), in order to reduce the risk of impact with high-velocity 
dust particles coming off the comet.

The period of greatest risk to orbiting spacecraft will start about 90 
minutes after the closest approach of the comet's nucleus and will last about 
20 minutes, when Mars will come closest to the center of the widening trail 
of dust flying from the comet's nucleus.

"The hazard is not an impact of the comet nucleus itself, but the trail of 
debris coming from it. Using constraints provided by Earth-based 
observations, the modeling results indicate that the hazard is not as great 
as first anticipated. Mars will be right at the edge of the debris cloud, so 
it might encounter some of the particles -- or it might not," said Rich 
Zurek, chief scientist for the Mars Exploration Program at NASA's Jet 
Propulsion Laboratory (JPL) in Pasadena, California.

The atmosphere of Mars, though much thinner that Earth's, will shield NASA 
Mars rovers Opportunity and Curiosity from comet dust, if any reaches the 
planet. Both rovers are scheduled to make observations of the comet.

NASA's Mars orbiters will gather information before, during and after the 
flyby about the size, rotation and activity of the comet's nucleus, the 
variability and gas composition of the coma around the nucleus, and the size 
and distribution of dust particles in the comet's tail.

Observations of the Martian atmosphere are designed to check for possible 
meteor trails, changes in distribution of neutral and charged particles, and 
effects of the comet on air temperature and clouds. MAVEN will have a 
particularly good opportunity to study the comet, and how its tenuous 
atmosphere, or coma, interacts with Mars' upper atmosphere.

Earth-based and space telescopes, including NASA's iconic Hubble Space 
Telescope, also will be in position to observe the unique celestial object. 
The agency's astrophysics space observatories -- Kepler, Swift, Spitzer, 
Chandra -- and the ground-based Infrared Telescope Facility on Mauna Kea, 
Hawaii -- also will be tracking the event.

NASA's asteroid hunter, the Near-Earth Object Wide-field Infrared Survey 
Explorer (NEOWISE), has been imaging, and will continue to image, the comet 
as part of its operations. And the agency's two Heliophysics spacecraft, 
Solar TErrestrial RElations Observatory (STEREO) and Solar and Heliophysics 
Observatory (SOHO), also will image the comet. The agency's Balloon 
Observation Platform for Planetary Science (BOPPS), a sub-orbital 
balloon-carried telescope, already has provided observations of the comet in 
the lead-up to the close encounter with Mars.

Images and updates will be posted online before and after the comet flyby. 
Several pre-flyby images of Siding Spring, as well as information about the 
comet and NASA's planned observations of the event, are available online 
at:

http://mars.nasa.gov/comets/sidingspring

-end-

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov