Phoenix Lander

The Phoenix lander went to the Martian arctic to touch water ice directly — and it succeeded. Launched by NASA in August 2007, Phoenix landed in the far northern plains of Mars in May 2008, farther north than any previous mission. Its target was chosen based on data from Mars Odyssey, which had detected large amounts of hydrogen, and therefore likely ice, just beneath the surface at high latitudes.

Phoenix confirmed that ice directly. As its landing thrusters blew away the topsoil, they exposed a bright layer underneath, and when the lander's robotic arm dug into the ground, it uncovered white material that vanished over several days — subliming away exactly as water ice would in the thin Martian air. For the first time, a spacecraft had physically touched and confirmed water ice on Mars.

The lander's onboard chemistry laboratory also analyzed the soil, discovering perchlorates — reactive salts that have major implications for both the search for life and the challenge of growing food in Martian regolith. Phoenix even observed snow falling from Martian clouds, though it vaporized before reaching the ground. As a solar-powered lander in the arctic, its life was always going to be limited by the oncoming winter; when the sun sank and the cold deepened, Phoenix fell silent, having decisively answered the question of whether ice lay within reach beneath the surface.