For most organisms on Earth, rocks are objects, not food. But for one oddball microbe, desert limestone seems to have been on ...

Exposed rocks along the coastline can be broken down by the processes of weathering. Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable (allow water to pass through).

“As no known chemical or physical weathering mechanism can explain ... “we suggest that they are of biological origin.” Whatever microbes carved out the tunnels have been long dead, though ...