The discovery of tiny carbon-rich balls and tunnels inside a Martian meteorite has once again raised the possibility that the Red Planet was teeming with primitive life millions of years ago.

The meteorite, which fell to Earth during the Stone Age, contains microscopic burrows and spheres that resemble the marks microorganisms leave when they eat through rocks on Earth, scientists report in the journal Astrobiology this month. What’s more, these features seem to have been pressed into the Mars rock before it was hurled off the Red Planet by an impact event, the researchers add.

via Mars Meteorite’s Strange ‘Tunnels’ & ‘Spheres’ Revive Debate Over Martian Life | Space.com.