Mars may get hit by a comet in 2014

March 4, 2013

(Credit: Image credit: Mars: NASA/JPL/MSSS; Comet Halley: Hale Observatory; composite: Phil Plait)

A comet called C/2013 A1 (Siding Spring) is expected to miss Mars around Oct. 19, 2014 by 37,000 km (23,000 miles), says Bad Astronomy Slate blogger Phil Plait.

Assuming it does hit, while the nucleus size is not well known, it may be as small as 15 kilometers (9 miles) or as big as 50 km (30 miles). Even using the small number means Mars would be slammed by an unimaginable impact. The comet will be moving at a speed of about 55 kilometers per second (120,000 miles per hour!) upon impact, he says.

Doing a rough calculation, Plait gets an explosive yield of roughly one billion megatons: That’s a million billion tons of TNT exploding. Or, if you prefer, an explosion about 25 million times larger than the largest nuclear weapon ever tested on Earth.

UPDATE Mar. 6, 2013 — wording improved.

Orbital diagram for the comet. The inner planets are labeled, and the comet’s path is in blue (dark blue for when it’s below the solar system’s average plane, and light blue above). This shows the comet’s position a few days before it passes Mars. (Credit: NASA/JPL_