Top: The Phoenix spacecraft’s solar panels and robotic arm are seen in this image of Mars’s western horizon, which Phoenix took shortly after landing; bottom-left: Phoenix’s parachute slows its descent. This image, taken by the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE) camera, was the first of a spacecraft landing on Mars; bottom-center: Below: Called Dodo-Goldilocks, this trench shows chunks of white stuff, which scientists say is ice. Although ice on the Martian surface is not a new discovery (the polar ice caps have water ice, for instance), to see pieces up close—a major part of Phoenix’s mission—is cause for excitement; bottom-right: The HiRISE camera took this snapshot of the landing site after touchdown. The lander, with its solar panels open, appears as a bluish dot at the top. The black smudge on the right is the heat shield and its impact mark, and the lower part of the image shows the parachute, attached to the bottom of the capsule shell.

 

Phoenix Has Landed

On May 25, the Phoenix spacecraft landed safely in the northern polar region of Mars. The lander is now exploring the possibility that liquid water once existed on the red planet.

In 2002, the Mars Odyssey orbiter revealed evidence of water ice hidden beneath the surface of northern Mars. Phoenix’s mission, then, is to dig below that surface and analyze soil and ice samples to study the planet’s water history. Although Phoenix isn’t designed to look for signs of life, it will analyze evidence about whether the icy soil has ever been a hospitable environment for life. Liquid water, which might have existed as late as 100,000 years ago, could have given rise to microbial life; and some bacterial spores, which could remain in a dormant state for millions of years, might be lurking in the soil.

Three weeks into the mission, scientists said they’d hit pay dirt—or rather, ice. Digging into a trench 5 centimeters deep and 30 centimeters wide, Phoenix uncovered chunks of white stuff on June 15. At the time, researchers thought it could be either ice or some sort of salt. But when the white chunks disappeared four days later, the scientists knew they had to be ice. Only ice, which sublimates from solid to gaseous form, could have vanished so abruptly. In an adjacent trench, Phoenix’s robotic scoop hit a hard layer at the same depth as those ice chunks, suggesting the presence of more water ice.

Led by the University of Arizona in partnership with JPL and Lockheed Martin, who built the craft, Phoenix rose from the technological ashes of previous missions. The craft uses instruments adapted from the Mars Polar Lander, which crashed in 1999, and the Mars Surveyor lander, whose mission was cancelled just a year before its scheduled launch in 2001. Phoenix was the first spacecraft since the Viking missions in the 1970s to successfully employ rockets to land, as opposed to using the airbag system designed for Mars Pathfinder and used by Spirit and Opportunity. —MW