NASA’s Phoenix mission discovered water ice beneath the surface of Mars in 2008.
Phoenix landed in Mars’s northern polar region on May 25, 2008. Its robotic arm dug trenches in the soil, exposing bright material that disappeared after several days. Scientists identified it as water ice, supported by observations from the lander’s instruments and later chemical analysis.
The mission was designed to study the history of water and the habitability of the Martian arctic environment. Phoenix also analyzed soil chemistry and detected perchlorate, a chlorine-bearing compound found in Martian soil.
Phoenix did not discover the first evidence that Mars once had water; orbiters and earlier landers had already found geological signs of ancient rivers and minerals. Its distinctive achievement was directly sampling shallow subsurface ice at its landing site.