Could Upcoming Comet Flybys Damage Mars Spacecraft?

Two comets will buzz Mars over the course of the next year, prompting excitement as well as some concern that cometary particles could hit the spacecraft orbiting the Red Planet and exploring its surface.
Three operational spacecraft currently circle Mars: NASA’s Odyssey and Mars Reconnaissance Orbiter (MRO), as well as Europe’s Mars Express. NASA also has two functioning rovers, Curiosity and Opportunity, on the ground on Mars.
All of these spacecraft will have ringside seats as Comet ISON cruises by Mars this year, followed by Comet 2013 A1 (Siding Spring) in 2014.