Scientists believe that Mercury’s wobbly orbit could have been caused by an asteroid impact so huge that it left a basin in the planet’s surface.
Previously it was thought that the tiny planet permanently turned ‘one face’ towards the Sun – with one side scorchingly hot and the other cold.
A Mercury ‘day’ was believed to be the same as the planet’s year.
But radar scans of the planet revealed that this wasn’t the case – the planet wobbles round three times for every two circuits it makes round the sun, the Daily Mail reported.
Why the planet had escaped the ‘tidal locking’ of the Sun’s gravitational pull – the same force that makes our moon face one way towards the Earth – had been a puzzle.
Now scientists have fingered a likely culprit – a huge asteroid.
The scientists led by Alexandre Correia, speculate that the wobble could be caused by ‘large, basin-forming impact event’ and think that the planet’s odd orbit could be explained by hollows detected in its surface.
Correia and her colleagues are hopeful that NASA’s messenger spacecraft, which continues to orbit the planet, will unearth a likely crater that could explain why the planet orbits as it does.
The study has been published in the journal Nature Geoscience.