Ice in a crater of the Vastitas Borealis region of Mars

© VUZE/NASA/Alamy

Ice in a crater of the Vastitas Borealis region of Mars

There’s water on Mars, and the European Space Agency’s satellite Mars Express has the photos to prove it. Up in the northern parts of the red planet, the water stays frozen all year. But in winter a layer of frozen carbon dioxide—dry ice—forms on top of the frozen water. The Mars Express has taken enough photos of the planet’s surface to create one of the most complete topographical maps of Mars we have.