NASA is to send one of its two robot rovers on Mars into a gaping meteor crater – with no guarantees that it will make it out again. 

Dubbed Opportunity, the rover has been trundling around the surface of Mars for about three years, but has now been given a task that it may not return from – descending into a 70m-deep crater.
Scientists hope that the rocks at the bottom of the chasm will reveal what lies beneath the surface of Mars – and they're also hoping for hints of underground water.
The rovers, about $400-million each, were designed to operate for 90 days on the surface of Mars, so they're already gone well beyond the call of duty.
Indeed, Opportunity's sister rover, Spirit, has damaged a wheel which now drags behind it.
Opportunity will enter the crater at the so-called Duck Bay, where a slope of 15-degrees to 20-degrees among the cliffs that surround the crater.