Published online 20 June 2008 | Nature | doi:10.1038/news.2008.904

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Yes, there's ice on Mars

"Ice!" screams NASA's Phoenix lander.

Mars iceThe bright nuggets uncovered by Phoenix soon vaporized away - proving that they were ice.NASA/JPL-Caltech/University of Arizona/Texas A&M University

“Whoohoo! Was keeping my eye on some chunks of bright stuff & they disappeared! Sublimated! So it can't be salt, it's ice.” That's the triumphant verdict of the Mars lander Phoenix, which yesterday boldly declared, after 24 Martian days of scratching the planet’s surface, that yes, there is ice on Mars.

Phoenix is constantly sending back information to Earth, which is posted by the mission team using the instant messaging software Twitter (written, in touchy-feely style, in the first person as if Phoenix itself is providing its own commentary on its labours). Twitter, the 'microblogging' phenomenon, can thus claim to have brought the watery news to Earthlings' attention.

Ice, ice baby

Phoenix had uncovered some bright nuggets four days earlier, while digging in two test trenches. But the tantalizing question of whether these were ice had to wait a few days for an answer. The chunks could have been either ice or salt.

If they were ice, the newly exposed chunks would gradually sublime and disappear (ice doesn't melt in Mars's thin atmosphere — it vaporizes). If the chunks were some sort of salt deposit, they would stay put.

“These little clumps completely disappearing over the course of a few days — that is perfect evidence that it's ice,” says Peter Smith, Phoenix's principal investigator. “There had been some question whether the bright material was salt. Salt can't do that."

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Phoenix, still twittering, was emphatic. “Are you ready to celebrate? Well, get ready: We have ICE!!!!! Yes, ICE, WATER ICE on Mars! w00t!!! Best day ever!!” it yelled, in a pleasing use of web slang by NASA's usually strait-laced staff.

Collaborate and listen

Phoenix has now turned its attention to another trench, known as Snow White 2, and has hit something hard at about the same depth at which the ice was found. Phoenix's Twittering ghost-writers are eagerly awaiting details in the hope of posting more triumphant messages.

A software memory-storage problem has been fixed, and team scientists say they are well ahead of schedule for completing the three-month mission. 

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