The Red Planet is set to get a close encounter of the cometary kind according to estimates of the latest trajectory of comet 2013 A1 (Siding Spring) by NASA’s NEO Program Office, which suggests that the comet will pass within 31,000 miles of the Martian surface in October 2014.
The comet, which is thought to have swung in from the Oort cloud – a spherical cloud of icy planetesimals almost a light year away from the Sun – was first spotted in January of this year by Scottish-Australian astronomer Robert McNaught of the Australian National University, using the Siding Spring Observatory. However, it was subsequently realised that images of comet Siding Spring had been made as far back as October 2012, providing enough data to make an estimate of its trajectory.
Building the dirty snowball’s path from old archives, scientists at the Near-Earth Object Program Office, who are behind the Near-Earth Object Observations program, also called ‘Spaceguard’, realised that the Red Planet, is right in the range of possible paths that the comet could take. However, experts predict that with further and further refinement of the data, an impact into Mars will become less and less likely. Currently there is a one in six hundred chance of the icy body crashing down into Martian soil after its journey, which is thought to have lasted more than a million years.
However, scientists are currently hedging their bets on the comet passing within at least 186,000 miles and possibly closer – to within 31,000 miles – around two and a half times that of the orbit of the outermost martian moon, Deimos. Spaceguard, which uses an arsenal of both ground- and space-based telescopes, tracks and characterises asteroids and comets passing close to Earth, plotting their orbits to determine if they could pose a threat to our planet.
Unfortunately Earth’s comet watchers could be disappointed as the short-period comet will only be putting on a spectacular show for Mars. Hitting a total visual magnitude of zero or brighter in the Martian skies, which is equivalent to the fifth brightest star in the night sky – Vega in the constellation of Lyra or Saturn at its maximum – us Earthlings will find it more difficult to be able to see the comet.
In order to catch comet 2013 A1 at its closest approach towards the end of next year, observers are not only going to need to be in the southern hemisphere, but they will also need binoculars or a small telescope as this distant traveller is only expected to reach a dim magnitude of 8 – the same brightness as the 8th planet from the Sun, Neptune, at its best.
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Images courtesy of NASA/Chris Smith (top) and NASA/JPL-Caltech (bottom)