12 November 2008
Successful Mars Mission Ends on Frigid Arctic Plain
Lander found ice, snow, clouds, soil filled with carbonates and clays
Washington — After more than five months of an adventure that made many new discoveries about the Red Planet, NASA’s Phoenix lander has succumbed to frigid temperatures, declining daylight and a recent dust storm on the northern plains of Mars that together have ended the spacecraft’s ability to operate.
Summer is turning to autumn on Mars, and as the project team expected, the seasonal decline in sunshine at the robot's arctic landing site is not providing enough sunlight for the solar arrays to collect the power needed to charge the batteries that run Phoenix’s instruments.
“While we’re losing a spacecraft,” Doug McCuistion, director of the Mars Exploration Program at NASA headquarters, said during a November 10 briefing, “we should celebrate what Phoenix has done, what the Phoenix team has done and where it’s going to take us in the future.”
Mission engineers last received a signal from the lander November 2. Phoenix, originally scheduled for a three-month mission, exceeded its planned operational life by more than two months to conduct and return science data.
The University of Arizona leads the Phoenix mission with project management at NASA’s Jet Propulsion Laboratory (JPL) in California and development partnership at Lockheed Martin Corp. in Colorado.
International contributions came from the Canadian Space Agency, the University of Neuchatel in Switzerland, the universities of Copenhagen and Aarhus in Denmark, the Max Planck Institute in Germany, the Finnish Meteorological Institute and the Imperial College of London.
STILL LISTENING
The team is declaring an end to mission operations but it is not giving up entirely.
“We’ve been surprised by the robustness of this vehicle,” said Barry Goldstein, Phoenix project manager at JPL, “so we’re going to continue listening.”
Every two hours, one of NASA’s orbiters — the Mars Reconnaissance Orbiter and the Mars Odyssey — flies over the Phoenix landing site.
During the flyovers, Goldstein said, “we’ll constantly turn on the radio and try to hail Phoenix to see if it’s alive. At this point, nobody on the team has an expectation of that happening, but we do hope the vehicle will surprise us once again.”
Phoenix launched August 4, 2007, and landed May 25, 2008, at a site further north than any spacecraft to land on the Martian surface. Aboard the spacecraft are a suite of science instruments representing some of the most sophisticated and advanced technology ever sent to Mars, and the lander used this technology to dig, scoop, bake, sniff and taste the planet's soil. (See “Perfect Landing Marks Start of New Mission on Mars.”)
Among early results, it verified the presence of water-ice in the Martian subsurface that NASA's Mars Odyssey first detected remotely in 2002. Phoenix's cameras also returned more than 25,000 pictures — some showing sweeping vistas, others near the atomic level with the first atomic force microscope ever used beyond Earth.
WATER AND WEATHER
Phoenix's preliminary science accomplishments advance the goal of studying whether the Martian arctic environment has ever been favorable for microbes, and its findings support the goal of learning the history of water on Mars.
“When we landed, we looked around and we saw a field of dirt and rock that was spread out to the horizon and we didn’t see ice right away,” said Peter Smith, Phoenix principal investigator at the University of Arizona – Tucson.
“It wasn’t until we looked under the spacecraft that we found out we were standing on it,” he said. “This was quite a thrill for everybody, and it’s been the study of this ice that has kept us busy for the last five months. Really, the mission is all about water, and that’s going to keep us busy for some time now as we try and understand what we’ve got.”
Water-related findings include excavating soil above the ice table, revealing at least two distinct types of ice deposits; observing snow falling from clouds; providing a mission-long weather record with data on temperature, pressure, humidity and wind; observations of haze, clouds, frost and whirlwinds; and coordinating with the Mars Reconnaissance Orbiter to perform simultaneous ground and orbital observations of Martian weather.
One of the mission’s major accomplishments, Smith said, was retrieving the weather record.
NUTRIENTS FOR LIFE
Other discoveries include documenting a mildly alkaline soil environment unlike any found by earlier Mars missions; finding small concentrations of salts that could be nutrients for life; discovering perchlorate salt, which has implications for ice and soil properties; and finding calcium carbonate, a marker of effects of liquid water.
“We noticed that the soil is alkaline and filled with carbonates and clays,” Smith said. “On Earth, we would conclude immediately that there was liquid water in the soil. For Mars, we have to be a little more careful, and we’re going to develop this story as we interpret our data. But definitely, liquid water has been a part of this soil.”
Phoenix is the first spacecraft of NASA’s Scout program, which is designed to send a series of small, low-cost, principal investigator–led missions to Mars.
The next Scout mission, McCuistion said, is the Mars Atmosphere and Volatile Evolution spacecraft, a $485 million mission scheduled for launch in late 2013. Its mission is to gather more information about Mars’ atmosphere, climate history and potential habitability.
More information about the Phoenix mission is available at the NASA Web site.
