After a decade of shouting, “Follow the water!” in its exploration of Mars, NASA can finally say that one of its spacecraft has reached out, touched water ice and scooped it up.

Now, scientists will be able to tackle the main question they hope to answer: Did the ice ever melt and turn Mars into a habitable place?

In a photograph released Thursday evening of a trench that the Phoenix Mars lander has dug into the Martian soil, some white patches that were seen earlier in the week have shrunk, and eight small chunks have disappeared. Until now, scientists were not sure if the white material was ice or some kind of salt.

When exposed to air, water ice can change into water vapor, a process known as sublimation. Salt, on the other hand, is not capable of such a vanishing act.