Ancient Mars Looks Ever More Earthlike

Astronomers are increasingly convinced Mars once held oceans. Did it also have life?

A topographic map of Terra Sirenum, Mars. Traces of ancient rivers and lakes are dotted across the landscape. Image credit: ESA/DLR/FU Berlin (CC BY-SA 3.0 IGA)

Mars, all the evidence suggests, was once a habitable world. Oceans of liquid water may once have flooded the northern hemisphere, fed by networks of rivers and lakes stretching across the planet. The signs of this long-gone water are clear to see — but…