Why is Mars barren and uninhabitable, while life has always thrived here on our relatively similar planet Earth?

There are currently several rovers searching Mars for signs of life that could have existed back in those more habitable times, millions of years ago.

Earlier this year, NASA’s Curiosity rover discovered a missing piece in this puzzle: rocks that are rich in carbonate minerals.

These “carbonates”—such as limestone on Earth—act as a sponge for carbon dioxide, pulling it in from the atmosphere and trapping it in rock.