Mars was habitable longer, more recently than thought
Warmer, wetter conditions lasted until 3.5 billion years ago

WETTER ONCE Curiosity’s Mast Camera surveyed Mars’ Yellowknife Bay formation, a region that could have supported liquid water for millions of years. The foothills of Mount Sharp, Curiosity’s primary destination, are at upper left.
JPL-Caltech/NASA, MSSS