Mars has never looked more like a planet built for hiding secrets. A cluster of eight vast, water-carved caves appears almost engineered to shield fragile chemistry, or even biology, from the brutal ...

"It's really not a question of robotic exploration or human exploration," Ehlmann said. "It is an 'and' — it's robotic and ...

Today, Mars is known as the red planet, for its rust-colored desert landscape. Once upon a time, Mars was a very different ...