Colliding Atmospheres: Comet C/2013 A1 Siding Spring vs Mars - Video

Incoming: NEOWise spies Comet A1 Siding Spring in early August of 2014. Credit: NASA

This week, the skies over Mars will also be graced by an unforgettable and spectacular sight: the extremely close passage of Comet C/2013 A1 Siding Spring.

The first comet discovered in 2013, A1 Siding Spring was spotted by veteran comet hunter Robert McNaught from the Siding Spring Observatory in Australia.

Dozens of comets are discovered in any given year, but this one soon gained the attention of astronomers when it was found that the comet could possibly hit Mars in October 2014.

And although further observations refined A1 Siding Spring's orbit and ruled out such an impact, the particulars of the close passage of the comet past Mars are still stunning: A1 Siding Spring will pass within 87,000 miles (139,500 kilometres) from the center of Mars on Sunday, October 19th at 18:27 Universal Time (UT) or 2:27 PM EDT.

And although we've yet to set "boots" on Mars, a fleet of spacecraft arrayed throughout the inner solar system are set to study the comet from both near and far.



NASA has taken measures to assure that spacecraft in orbit are afforded maximum protection from incoming cometary debris, and the exciting possibility exists that we'll be able to study first-hand the interaction of the comet's tail with the Martian atmosphere.

Mars-based spacecraft set to observe Comet A1 Siding Spring: a scorecard. 

Credit: NASA

The nucleus of A1 Siding Spring is thought to be 700 metres across, and the coma extends 19,300 km in diameter.

The comet's closest passage is just under six times the distance of Mars' outer moon Deimos, and at closest approach, the coma will appear almost 8 degrees in size to any would-be Martian, that's 16 times the diameter of a Full Moon as seen from the Earth, and will be crossing the skies at a staggering 1.5 degrees a minute.

You would be able to easily see the motion of the comet as it moves across the Martian sky with the unaided eye after just a few dozen seconds worth of watching!

The comet's magnitude may reach -5 as seen from Mars, though that would also be extended over its huge expanded surface area.