July 31, 2008: Using an on-board soil analysis tool, the Phoenix Lander finally confirmed what scientists had long suspected: there is water-based ice on Mars.NASA.gov: NASA Spacecraft Confirms Martian Water, Mission Extended (July 31, 2008) The revelation followed a June 20 report of photographic evidence suggesting ice.

"It must be ice. These little clumps completely disappearing over the course of a few days, that is perfect evidence that it's ice. There had been some question whether the bright material was salt. Salt can't do that."—Peter Smith, Phoenix Principal InvestigatorPhoenix Mars Mission: Bright Chunks At Phoenix Lander's Mars Site Must Have Been Ice (June 19, 2008)

"We have water. We've seen evidence for this water ice before in observations by the Mars Odyssey orbiter and in disappearing chunks observed by Phoenix last month, but this is the first time Martian water has been touched and tasted."—William Boynton, lead scientist for the Phoenix Lander's Thermal and Evolved-Gas AnalyzerNASA.gov: NASA Spacecraft Confirms Martian Water, Mission Extended (July 31, 2008)

On June 20, 2008, it was reported that scientists examining a set of photographs taken over a period of four days had observed the disappearance of a white substance. The Phoenix Lander team considered this to be evidence that the substance was ice and not salt, which would not have evaporated.Phoenix Mars Mission: Bright Chunks At Phoenix Lander's Mars Site Must Have Been Ice (June 19, 2008)

The soil analysis reported July 31, 2008 was done using an on-board tool called the Thermal and Evolved-Gas Analyzer, or TEGA. The mechanism found proof of water ice by heating a soil sample and analyzing its vapors.NASA.gov: NASA Spacecraft Confirms Martian Water, Mission Extended (July 31, 2008)