The Red Planet’s white stuff is ice after all.
A collection of crumblike stuff the Phoenix Mars Lander photographed one day was absent from photos a few days later, hinting that the bright chunks had disappeared through a process similar to evaporation. What’s more, the ice may have come from a layer beneath the soil that extends to the horizon, scientists reported during a June 20 press briefing.
“I am proud to announce that we have found proof that this material is water ice,” said thePhoenix mission’s principal investigator Peter Smith during the briefing. “I am absolutely overjoyed that we can make this statement based on image data.”
The lander has been exploring a site in the Martian northern plains since its safe landing there May 25. It began digging beneath soil with its robotic arm earlier this month.
For the past three weeks, the Phoenix science team has speculated about what the bright, hard material found under the lander and uncovered in the trenches could be. The stuff could have been ice, salt or something else, explained Texas A&M scientist Mark Lemmon, a coinvestigator of the Stereo Surface Imager that captured those images. But “the things are gone,” they melted from the trench, he says. “Salt does not behave like that, so we believe these things are water ice.”
The lander’s robotic arm dug up the crumbs, which were about a centimeter and a half in diameter each, on June 15. Looking at images from the next day — called Sol 21 for the lander’s 21 days on Mars — scientists saw that the crumbs had shrunk in size. The June 19 images showed the crumbs were gone. The crumbs cannot be ice of carbon dioxide, based on the temperature in the region, Smith said, so “indeed we were looking at water ice.”
On Sol 24, Phoenix also worked on two trenches, dubbed Snow White 1 and Snow White 2. Digging progressed until the robotic arm struck a firm layer. After three attempts to dig through the layer, the arm went into a holding position.