Ice has been found on Mars!
Or at least some kind of "whitish matter" found by the Mars Phoenix Lander:
The proof came in a series of pictures sent back by Phoenix of a trench it dug with its robotic arm at the arctic circle of Mars, showing dice-sized chunks of white material that are seen to melt away over the course of several days.
Phoenix Lander's robotic arm was used to dig a trench named Dodo-Goldilocks which exposed the white matter to sunlight which later melted.
The ice is important because it indicates Mars has water, and with water is the potential for life.