Which chemical did NASA’s Phoenix lander detect in Martian soil in 2008?

NASA’s Phoenix lander detected perchlorate in Martian soil in 2008.

Phoenix landed in Mars’s northern plains on May 25, 2008, and used its robotic arm to dig and deliver soil samples to instruments inside the lander. The Thermal and Evolved-Gas Analyzer and the Wet Chemistry Laboratory revealed the presence of perchlorate salts, compounds containing chlorine and oxygen.

The result was scientifically important because perchlorates can influence soil chemistry and may affect the preservation or detection of organic molecules. They can also absorb water under some conditions, although the discovery did not demonstrate that liquid water currently exists at the landing site.

Perchlorate is sometimes confused with chlorate, another chlorine-oxygen compound. Phoenix’s result specifically concerned perchlorate. The lander also confirmed water ice beneath the surface, making its mission one of the most significant investigations of Martian soil and near-surface materials.