In December 1999, NASA's long-awaited Mars Polar Lander space mission came to an abrupt and disappointing end when the spacecraft apparently smashed into the surface of the planet as it attempted to touch down. It was never heard from again.
Saturday morning, however, some of the experiments that would have been performed on that mission eight years ago, plus new exploratory projects, will be launched to Mars on the Phoenix Mars Lander. The spacecraft is expected to land on the planet's surface 122 million miles away on May 25.
Phoenix is scheduled to launch from Cape Canaveral, Fla., atop a 13-story-tall Delta II launch vehicle at 5:26 a.m. EDT tomorrow.
Chris Lewicki, the Phoenix flight systems engineer for the mission, called the package of experiments on the Phoenix Lander "a kind of science chemistry lab for soil analysis." One of the main goals of the mission is to dig deeply into the Martian soil to find buried ice that will provide more information about the presence of water on the planet.
"Phoenix is actually going where the water is," on the planet's north pole, where the lander will have about 90 days to conduct experiments before the subfreezing cold of the Mars winter begins and ultimately disables the lander's power generation and heating systems, Lewicki said.
Scientists have learned through images taken using special gamma ray spectrometers from an earlier Odyssey orbiter mission that there is an abundance of frozen hydrogen -- a critical ingredient of water -- under the soil in the area where Phoenix is scheduled to land.
Those high levels of frozen hydrogen, seen in the gamma ray images, are apparently deep enough under the soil that they have not melted or evaporated, Lewicki said. Mars has no liquid water on its surface, and scientists have been debating for years whether there is frozen water on the planet.
The experiments will be conducted using a larger and more powerful robotic arm and an onboard chemistry lab equipped with several high-temperature ovens, an assortment of small beakers and other specialized equipment. The experiments are designed to help scientists learn more about how long hydrogen has been present on the planet, as well as what other trace elements and frozen gases might be trapped in it.
Soil and other materials scooped up by the robotic arm can be mixed with water and other substances, then can be heated and stirred to learn more about their makeup and conditions. An optical microscope and a special camera will be used to examine the samples more closely.
A meteorological experiment package from the Canadian Space Agency will also be on board to monitor the atmosphere, said Lewicki, who works at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"It's kind of like a weather station," he said. "This is something that we haven't done on Mars since the Viking mission" in 1977. "From our little outpost in the [Mars] Arctic, we'll be able to get a weather update on what it's like each day on Mars to help with future missions."
A key change in the lander's technology is in the software that will operate the powerful robotic arm, Lewicki said. The robotic arm, which Lewicki called "a big back hoe on our lander," will have software that uses algorithms and code that allow it to literally interpret commands from Earth on its own, rather than being told by an operator to "move to the left 5 degrees and dig down 1 inch." Using the new capabilities, the arm will be told to dig and it will know what to do without being told every step of the way, Lewicki said.
Lessons learned from the failed Polar Lander mission have helped NASA improve the odds for this flight, Lewicki said. "On Phoenix, we'll be able to do a lot of the testing that the Mars Polar Lander couldn't do," he said. Scientists have improved the mission's software to correct for the failed landing problems and many other improvements have been completed. "We've really been able to make the system much more robust," he said.
NASA has learned a lot since it launched its two Mars Rover missions -- Spirit and Opportunity -- in 2003. On those vehicles, which continue to be in use on the planet since landing in January 2004, NASA has periodically updated and patched the mission software via long-distance uploads to resolve problems with some systems. Such updates will be made to Phoenix as the mission progresses.
Clearly, preparing an unmanned spacecraft for a mission more than 100 million miles away isn't easy, Lewicki said.
"It's inherently dangerous," he said. "Landing on everything is difficult to do. With Mars being 122 million miles away, it doesn't have the ability to be directly aided by people on Earth."
By the time a radio signal leaves Earth and gets to the lander, whatever events that are scheduled have already occurred, he said. That means midcourse corrections and preventive steps can't be taken in real time, essentially leaving the lander on its own with whatever preprogrammed information it has to keep itself operating properly.
"It has to respond to everything, to wind, to the terrain. You have to be able to have the machine respond to every one of those things [without real-time help] and that's the enormous challenge," he said.
"I'm feeling very confident about the mission," Lewicki said. "I went through a similar experience designing [the] Spirit and Opportunity [Mars rovers]. I can tell you that Phoenix is much further along. It wouldn't make me too nervous if we were landing tomorrow. With the hardware and software we have, we could do the job."