Mars is the most explored planet in the solar system other than Earth. With all of our robotic visitors there, we’ve discovered that it is a world far too dry, cold and irradiated to support the scheming humanoids or tentacled invaders once imagined by science fiction.This summer, NASA will launch its latest rover, Perseverance, on a seventh-month journey to Mars. Like its predecessor, Curiosity, Perseverance will touch down in the remains of an ancient Martian lake bed. What it finds there — along with missions launched by China and the United Arab Emirates — could help us Earthlings understand what Mars was like as a young planet some four billion years ago, and whether life ever blossomed on its surface....