A Perfect Landing

AFTER A FLAWLESS LANDING on flat terrain near Mars's north pole on May 25, the Phoenix Mars Lander spacecraft is gearing up to perform the first-ever wet chemistry experiments on another planet, according to mission scientists.

Mission engineers have spent the past week assessing Phoenix' desolate, pebbly surroundings and commanding the craft to begin testing its robotic arm. This week, they hope, Phoenix will start digging into the martian soil, which is believed to contain water ice just below the surface. "We're not going to rush anything," says Barry Goldstein, Phoenix mission project manager at NASA's Jet Propulsion Laboratory.

Using Mars-worthy beakers that contain premeasured reagents, Phoenix will examine soil samples for the presence of ions such as nitrate and chloride or metals such as lead and copper. From this most tangible exploration yet, scientists hope to supplement their ideas about the history of water on Mars and whether life could have possibly existed there.

Researchers recently calculated the salinity of water in various ancient martian environments, based on information gleaned from spacecraft and rovers, and concluded that those areas were likely too salty to support life (Science 2008, 320, 1204). "The Phoenix mission will add more data to that story," says Nicholas J. Tosca, coauthor of the study and postdoctoral researcher in the organismic and evolutionary biology department at Harvard University.

NASA's Mars Reconnaissance Orbiter , which has been circling the planet for the past two years, captured images of Phoenix with its parachute deployed as it plunged toward the surface and at rest on the martian surface with its solar panels extended.

The northern surface of Mars, where the craft landed, resembles Arctic regions on Earth, marked by polygonal ground features about 15 feet across. "I know it looks a little like a parking lot, but that's a safe place to land," says Peter H. Smith of the University of Arizona, the principal investigator for the $460 million mission.

The Phoenix mission is the first in NASA's planned series of relatively low-cost exploratory Mars Scout missions as the agency makes plans for eventual human exploration of the planet.