Mars Lander Team Prepares for "Seven Minutes of Terror"

After years of planning followed by a ten-month journey, the Mars Phoenix Lander is slated to touch down on the red planet's north pole on May 25.

If successful, the probe will be the first lander to reach a Martian pole and the first to actually touch the planet's water ice.

What's more, it could settle the debate over whether Mars was once a habitable world.

Now, as Phoenix closes in on the last 12 million miles (19 million kilometers) of its journey, NASA scientists are gearing up for the "seven minutes of terror" that could make or break the $420-million mission.

"Approximately 14 minutes before touchdown, the vehicle separates from its cruise stage," Barry Goldstein, Phoenix project manager at the Jet Propulsion Laboratory in California, said today at a press conference.

Once the craft reaches Mars's atmosphere, the next critical seven minutes make up what's known as the Entry, Descent, and Landing (EDL) phase.

Screaming down at about 12,600 miles (20,270 kilometers) an hour, the craft must open a parachute to slow itself for a three-minute glide to the surface about 70 miles (113 kilometers) below.

The craft's landing sequence then includes steps such as jettisoning its heat shield, extending its legs, and firing its landing thrusters.

"There are 14 pyrotechnic events, and each of those have to work perfectly for this to go as planned," Goldstein said. "Getting EDL communication [at touchdown]—that'll be the three seconds that I am really biting my nails over."

The tension for this mission seems especially intense, since Phoenix is not the first craft to attempt a landing at a Martian pole. In 1999 NASA lost communication with the Mars Polar Lander as it entered the atmosphere above the planet's south pole.

That lander's fate remains a mystery, but its hardware designs will be given a second chance—Phoenix is based on much of the lost craft's systems.

"We spent 15 years developing the hardware, and I really wanted some return from those," said Peter Smith, Phoenix principal investigator at the University of Arizona in Tucson, who first proposed "recycling" technology from the failed 1999 mission.

Engineers have put the so-called heritage hardware through a battery of tests, and NASA scientists say they have fixed all the known issues.

Teams using a variety of data also put serious thought into where exactly to set the lander down.

"Finding a place to land that was scientifically interesting and safe … has been a multiyear process," noted Ray Arvidson, chair of the Phoenix landing site working group at Washington University in St. Louis, Missouri.

The site, informally dubbed Green Valley, sits in a region of permafrost on Mars's northern plains that is analogous to northern Canada, JPL's Smith said.

The relatively shallow valley, which contains some of the highest concentrations of ice outside of the polar cap, is about 700 feet (213 meters) deep and stretches for 40 miles (64 kilometers).

A crater near the valley means that an impact pushed away most large rocks and spread out a soft cushion of fine particles 5 to 10 inches (13 to 25 centimeters) deep on top of the hard icy soil.

But "this is no trip to grandma's for the weekend," warned Ed Weiler, NASA's associate administrator for the Science Mission Directorate.

"Mars has been known to cause trouble, and I'll be worried until I hear the signal a few seconds after landing."

Still, NASA team members said that the scientific payoffs of a polar mission will be well worth the risks.

As opposed to the Mars rovers that have been exploring the red planet's geologic history, Phoenix will be taking samples that should reveal active processes.

Mars's northern ice cap expands and contracts with the seasons, which should allow scientists to analyze how water impacts the planet's soil chemistry.

And "we'll look at the properties of ice frozen into the surface with water vapor in the atmosphere to see if there's a communication there," Smith said.

But the biggest goal will be to look for signatures that Mars might once have been habitable. (Get full coverage of the search for water—and life—on Mars.)

"We're really doing a full geological and chemical experiment on the surface with the idea of finding if this is a habitable zone," Smith added.

The polar region offers the best hope, he said, because just like the refrigerator in a kitchen, polar ice may "preserve organic material and the history of life on this planet."

The consequence, however, is that the craft is not expected to last beyond the stated lifetime of the mission.

Unlike the Mars rovers that have roamed Mars's equatorial zone since 2004, Phoenix is touching down in a region that within months will be too cold and dark for the craft to maintain power supplies.

"Living in Hawaii would be wonderful, but we live north of the Arctic Circle," JPL's Goldstein said.

"In January [at the start of Martian winter] we'll go three to four months without any solar energy. At that point it's extraordinarily unlikely the craft will survive."

It won't actually land on the pole... it'll be at about 68 degrees north latitude, per this NASA email I got today.

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Phoenix set to land on Mars

05.13.2008

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May 13, 2008: NASA's Phoenix Mars Lander is preparing to end its long journey and begin a three-month mission to taste and sniff fistfuls of Martian soil and buried ice. The lander is scheduled to touch down on the Red Planet on Sunday, May 25th.

Phoenix will enter the top of the Martian atmosphere at almost 13,000 mph. In seven minutes, the spacecraft must complete a challenging sequence of events to slow to about 5 mph before its three legs reach the ground. Confirmation of the landing could come as early as 7:53 p.m. EDT.

Right: An artist's concept of NASA's Phoenix Mars Lander a moment before its 2008 touchdown on the arctic plains of Mars. Pulsed rocket engines control the spacecraft's speed during the final seconds of descent. [Larger image]

"This is not a trip to grandma's house. Putting a spacecraft safely on Mars is hard and risky," said Ed Weiler, associate administrator for NASA's Science Mission Directorate at NASA Headquarters in Washington. "Internationally, fewer than half of all attempts to land on Mars have succeeded."

Rocks large enough to spoil the landing or prevent opening of the solar panels present the greatest known risk. However, images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, detailed enough to show individual rocks smaller than the lander, have helped lessen that risk.

"We have blanketed nearly the entire landing area with HiRISE images," said Ray Arvidson of Washington University in St. Louis, chairman of the Phoenix landing-site working group. "This is one of the least rocky areas on all of Mars and we are confident that rocks will not detrimentally impact the ability of Phoenix to land safely."

Above: The landing site chosen for NASA's Mars Phoenix Lander, at about 68 degrees north latitude, is much farther north than the sites where previous spacecraft have landed on Mars. [more]

Earlier in 2002, NASA's Mars Odyssey orbiter discovered that plentiful water ice lies just beneath the surface throughout much of high-latitude Mars. NASA chose the Phoenix proposal over 24 other proposals to become the first endeavor in the Mars Scout program of competitively selected missions.

"Phoenix will land farther north on Mars than any previous mission," said Phoenix Project Manager Barry Goldstein of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The solar-powered robotic lander will manipulate a 7.7-foot arm to scoop up samples of soil and underground ice. Onboard laboratory instruments will analyze the samples. Cameras and a Canadian-supplied weather station will supply other information about the site's environment.

Right: An artist's concept: Months after landing, Phoenix begins to shut down operations as winter sets in. Far-northern latitudes on Mars experience no sunlight during winter, depriving the solar-powered lander of electricity. Frost covering the region as the atmosphere cools will eventually bury Phoenix in ice.

"The Phoenix mission not only studies the northern permafrost region, but also takes the next step in Mars exploration by determining whether this frosty region, which may encompass as much as 25 percent of the Martian surface, is habitable," said Peter Smith, Phoenix principal investigator at the University of Arizona, Tucson.

One research goal is to assess whether conditions at the site ever have been favorable for microbial life. The composition and texture of soil above the ice could give clues to whether the ice ever melts in response to long-term climate cycles. Another important question is whether the scooped-up samples contain carbon-based chemicals that are potential building blocks and food for life itself.

Stay tuned to Science@NASA for updates. And good luck, Phoenix!

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Editor: Dr. Tony Phillips | Credit: Science@NASA

more information

Phoenix --mission home page

Credits: The Phoenix mission is led by Smith with project management at JPL. The development partnership is with Lockheed Martin, Denver. International contributions are from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; the Max Planck Institute, Germany; and the Finnish Meteorological Institute.

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