When a strange, jelly doughnut-shaped rock suddenly appeared in front of the venerable Mars rover Opportunity a few weeks ago, many people demanded Nasa investigate.
And while it looked like the kind of story which means more to armchair alien speculators that serious scientists, Nasa said it was looking into it with interest.
Since then, however, we've not heard much about what the weird rock is, why it appeared or which particular species of green-skinned lifeform put it there for us to find.
Now even William Shatner - frequent Nasa cheerleader and generally interested third party - is joining the clamour.
Above: the rock before and after
He asked Nasa to explain the situation during a Twitter press conference, Space.com reported.
"We've got another question from Twitter, this one from William Shatner," Nasa spokesman Guy Webster said. "He'd like to know if you've ruled out the Martian rock throwers in the case of the jelly doughnut."
Mars rover lead scientist Steve Squyres of Cornell University was happy to reply - but said alas that Martians remained an unlikely cause.
"I think Martian rock throwers are unlikely, though we'll keep our eyes open for those," Squyres said. "We did actually have another scenario which we're still thinking about. It's the 'smoking hole in the ground hypothesis' as I've called it. We cannot yet rule out the possibility with certainty that there wasn't a freshly formed impact crater nearby, and that this is a piece of stuff that was thrown out by a small impact."
Alas, so far it looks like the rock was probably just thrown up when the rover bobbled over a rough bit of land. Still it's still interesting, mainly because the side of the upturned rock facing the rover hasn't seen the surface for perhaps billions of years.
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