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NASA readies for Mars comet encounter

Jenny Winder, News Writer
Oct 11, 2014, 16:48 UTC

Sen—NASA is readying its extensive fleet of science assets to image and study a once-in-a-lifetime comet flyby of Mars on Sunday, October 19.

Comet Siding Spring (C/2013 A1) will pass within about 87,000 miles (139,500 kilometres) of the Red Planet, less than one-tenth the distance of any known comet flyby of Earth.

“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, associate administrator for NASA’s Science Mission Directorate, in a statement. “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 will be the first comet from the Oort Cloud to be studied up close by spacecraft, giving scientists an opportunity to learn more about the materials that existed during the formation of the Solar System 4.6 billion years ago.


NASA Assets Observing Comet Siding Spring. Image credit: NASA

Some of the 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 Mars Atmosphere and Volatile EvolutioN (MAVEN), in order to reduce the risk of impact with high-velocity dust particles from the comet.

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

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

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.

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


Comet Siding Spring on 16 September 2014, shown alongside spiral galaxies IC 4720 and 4721. Image credit: Sen/D. Peach

NASA's space observatories, Hubble, Kepler, Swift, Spitzer and Chandra, as well as the ground-based Infrared Telescope Facility on Mauna Kea, Hawaii, will be tracking the event.

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) and the two Heliophysics spacecraft, Solar TErrestrial RElations Observatory (STEREO) and Solar and Heliophysics Observatory (SOHO), will also image the comet. The agency’s Balloon Observation Platform for Planetary Science (BOPPS) has already provided observations of the comet in the lead-up to the close encounter with Mars.

Comet Siding Spring: A Close Encounter with Mars. Credit: NASA Jet Propulsion Laboratory