Is Mars about to get hit? Warning over approaching comet that could cause one BILLION megaton blast

A comet hurtling into our solar system from deep space could next year score a direct and cataclysmic impact on Mars, astronomers say.

According to current calculations, comet C/2013 A1 (Siding Spring) is set for a near miss that will bring it within 23,000 miles of the surface of the Red Planet.

But the unpredictable nature of comet orbits, which can change as jet-like geysers of steam erupt from their surfaces as they near the Sun, means it could pass further away, or veer into a direct collision course.

Respected astronomer Phil Plait, author of Slate’s Bad Astronomy blog, has calculated that even if the comet is just nine miles across - a low estimate - an impact with Mars would cause a one billion megaton explosion.

That, he says, is 25million times larger than the largest nuclear weapon ever tested on Earth.