It appeared out of the red, like something dropped by a Martian Homer Simpson. But now NASA has an explanation for the "jelly doughnut" object photographed by the Opportunity rover in December.
First, here's what it isn't: It is not a fungus-like Martian organism, nor is it ejecta shot into the air by a nearby (and unseen) meteor impact.
Instead, it's geologic roadkill. Basically.
"We drove over it," Opportunity's Deputy Principal Investigator Ray Arvidson said in a statement on Friday.