As Comet C/2013 A1 Siding Spring hurtles toward Mars, NASA is taking steps to protect its Martian orbiters. The plan? Use the planet itself as a shield between the spacecraft and the comet’s potentially dangerous debris.
As part of its long-term Mars Exploration Program, NASA currently has two spacecraft orbiting the Red Planet, Mars Reconnaissance Orbiter (MRO) and Mars Odyssey, with Mars Atmosphere and Volatile Evolution (MAVEN) set to arrive in late September. Teams of scientists at the University of Maryland, the Planetary Science Institute, and NASA’s Jet Propulsion Lab (JPL) have used data from both Earth-based and space telescopes to model Siding Spring’s journey through the inner solar system, and determined that there is no risk of the comet colliding with Mars. However, at its closest approach to Mars on October 19, 2014, Siding Spring will come within 82,000 miles of the Red Planet, which is about a third of the distance from Earth to the Moon. The closest comets ever to whiz by Earth have been at least ten times more distant.