At 02:24 UTC today NASA's MAVEN spacecraft reached planet Mars and entered its orbit. MAVEN (Mars Atmosphere and Volatile Evolution) is the first spacecraft dedicated to exploring the tenuous upper atmosphere of Mars. It is expected to begin its primary mission in about six weeks.
MAVEN launched November 18, 2013, from Cape Canaveral Air Force Station in Florida, carrying three instrument packages which will characterize the solar wind and the ionosphere of the planet, identify characteristics present throughout the upper atmosphere and ionosphere and measure the composition and isotopes of atomic particles.
Following orbit insertion, MAVEN will begin a six-week commissioning phase that includes maneuvering into its final science orbit and testing the instruments and science-mapping commands.
But as MAVEN prepares for its primary mission there will be one more, relatively big, obstacle to pass. On October 19, 2014, Comet C/2013-A1 (Siding-Spring) will fly historically close to Mars, just 132 000 km (82 000 miles) away from its surface.
Animation courtesy of the Near-Earth Object (NEO) office at NASA's JPL
While the comet will not impact Mars its coma may very well envelop entire Planet and its man-made satellites. The encounter could spark Martian auroras, a meteor shower, and other unpredictable effects.
It's nucleus will be shedding material hurtling at about 56 kilometers (35 miles) per second, relative to Mars and Mars-orbiting spacecraft. At that velocity, even the smallest particle - estimated to be about half a millimeter (one-fiftieth of an inch) across - could cause significant damage to a spacecraft.
Comet C/2013 A1 Siding Spring simulation of encounter with Mars. Image courtesy of Paul Wiegert - the University of Western Ontario
According to document prepared by Dr. Althea Moorhead (Geocent, LLC/Jacobs ESSSA Group) and Dr. Bill Cooke (Meteoroid Environments Oce/EV44, Marshall Space Flight Center) the meteor shower that will accompany Siding Spring will have Zenithal hourly rate (ZHr) of 40 000 at Mars. It will lasts a few hours, and may be observable from Opportunity.
The hazard is not an impact of the comet nucleus, 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. - Rich Zurek, chief scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory in Pasadena, California.
There will be 5 spacecraft orbiting Mars, operated by NASA, ESA and ISRO (India), when Siding Spring arrives. They will be positioned on the opposite side of the Red Planet when the comet is most likely to pass by.
Featured image: NASA