Astronomers are excited about Comet Siding Spring’s very close encounter with Mars this coming Sunday. Siding Spring was spotted back in January 2013. An Oort Cloud comet, it’s said to be the size of a small mountain, with a million-year orbit. A posse of spacecraft and Mars rovers are jockeying into position right now to observe it. Here on Earth, the comet will be visible with binoculars in the Southern Hemisphere.
How close will Comet Siding Spring come to Mars? 83,000 miles–which in space distances is a hair’s breadth, about a third of the distance between here and the Moon. Last year, before they’d plotted out its trajectory, astronomers were genuinely worried that the comet might hit Mars.
Its trajectory is such that it’ll never get closer to the Earth than some 83 million miles, so no need to panic yet. Of course, passing that close to Mars, there’s a possibility that Siding Spring might upset the Red Planet’s orbit, throwing the whole solar system out of whack, in which case, well . . . Best not to think about that.
