Phoenix Mars LanderPhoto Courtesy of NASA JPL
The Phoenix Mars Lander (The Phoenix) is set to investigate a site in the polar region of Mars and will be used to help resolve broader questions concerning water and conditions that could support life.
“Were studying the water ice on Mars, to characterize it, to see if it has ever melted. Water is an element of habitability, so if there has ever been water on this part of Mars, we can tell that it might have been a habitable zone. No mission has ever been this far north on Mars,” says Sara Hammond Public Affairs Manager of the Phoenix Mars Mission.
The Phoenix was originally designed for the Mars Surveyor mission, which was to land on the surface of Mars in tandem with it’s sister craft the Mars Surveyor Orbiter, high in orbit above the planet taking photos. The Mars Surveyor Lander was plagued by high costs and technical problems and when the Mars Polar Lander in 1999 crash-landed, it was ultimately canceled in 2001.
“A lot of the Phoenix’s hardware was stuff not used in 2001, it was placed in to sterile cold storage and is now being used for this mission,” says Guy Webster of NASA’s Jet Propulsion Laboratory.
The Phoenix is the first mission in the Mars Scout program, which is designed to send small, relatively low-cost missions to Mars. These missions are selected from a pool of proposals submitted by universities, laboratories and other interested institutes.
“NASA solicited proposals for this first Mars Scout mission that sought to use the hardware that was in storage and asked solicitors if they could it do it as part of the proposal. This brought down the costs.” Webster explains.
Lead by the University of Arizona’s Lunar and Planetary Laboratory, the Phoenix carries a complex suite of instruments that are improved variations of those that were on the lost Mars Polar Lander. Because the Phoenix mission is reusing already created technology from Mars Surveyor, the mission is expected to have a total cost of about $420 million.
The Phoenix began its mission on August 4, 2007, launching from Cape Canaveral aboard a Delta II rocket. The Delta II was chosen to carry the Phoenix, because of its ability to handle heavy payloads and because it has a long tradition of propelling crafts to Mars. The takeoff had no problems and once the third stage of the rocket separated and was well in to space, the Phoenix deployed its solar panels and phoned back to earth. It gave reassurance to the mission controllers that the launch was successful, and that it was on its way to Mars.
The trip to Mars was to take just under a year and is scheduled to arrive on May 25, 2008. The landing zone is in the icy northern polar region of the planet. Landing a craft on Mars is a gamble in which only a handful of tries have yielded results. There has never been an attempt by NASA to land a spacecraft this far north on the planet. The ill-fated Mars Polar Lander, which was to land on the planet’s southern polar area, still weighs on the thoughts of all of those who are involved in the mission.
“Certainly everyone is aware of it and any landing on Mars is difficult,” explains Webster.
Given the large chances of failure, he goes on to say that team is doing everything it can to test for possible problems. “This mission has a lot of heritage from that one that wasn’t successful [the Polar Lander], and because of the teams ability to use the recycled equipment from the Surveyor, a lot of effort over the last five years has been to bring out any potential problems that could be identified in the design of the hardware and resolve them. There’s been a lot of effort in identifying what the problems [with the Polar Lander] could have been. Because the hardware of the Phoenix was already largely built, it allowed the focus of the team and engineers efforts to be on testing and analysis and identifying what potential problems would be, instead of focusing on spacecraft development.”
But the very nature of interplanetary spaceflight will always have some chance of failure and catastrophe. “What we’re trying to do is we’re trying take a vehicle which is traveling quite quickly, slow it down, orient it and get it to land safely in an area we know very little about,” says Phoenix Project Manager Barry Goldstein.
The original target of the mission was the north pole region of the planet. Taking in to consideration the difficulties of landing a spacecraft on that part of Mars and due to the needs of the spacecraft, scientists decided to go for a lower landing zone. The target area will be the Earth equivalent just north of the Brooks Range in Northern Alaska. The landing zone was chosen based on the amount of rocks that were in the area. Rocks could prevent the Phoenix from sitting upright when it lands or prevent its solar panels from deploying correctly.
There was a decision to use thrusters to land the craft instead of airbags like the Mars Pathfinder, because the size of the craft was too large to employ the airbags safely. Weighing 772 pounds, the size of the Phoenix could have overwhelmed an airbag system and jeopardized the mission. Scientists decided that a pulse-thruster system like those used on the Viking landers in the late 1970’s would be the best way to get the Phoenix on the ground.
“It’s not an issue with the landing site. We’re too big for airbags,” says Hammond, “In a similar fashion to the Viking landers, the Phoenix will use parachutes to slow its decent until the craft’s on-board radar system tells it that the ground is approaching. The Phoenix will then shed its parachute and engage its thrusters. The thrusters will be able to adjust how much thrust is needed to slow it down also by data from the craft’s radar. If everything goes according to plan, this should slow down the craft enough to ease it on to the ground.”
Once the Phoenix arrives, it will begin taking samples of the arctic ground to look for traces of organic compounds. Scientists believe that if these compounds are present on Mars, they’ll have a better chance of finding them in the ice than anywhere else on the planet.
“It’s the first time we can take some Martian water and run it through some lab instruments,” says Webster.
The samples will be taken with a robotic arm resembling a backhoe. At almost eight feet, the robotic arm can dig up to 20 inches in to the frozen ground. Small ovens on board the Phoenix will heat the frozen soil, releasing gases that can be examined. The main goal is to see if it holds carbon compounds that are part of the building blocks of life.
A gamma ray spectrometer in orbit around Mars aboard the Mars Odyssey was also developed at the University of Arizona Lunar and Planetary Laboratory and was one of the first instruments to give details to scientists that the polar region of Mars contained vast amounts of ice.
“The designers of [the Phoenix],” according to Hammond “believed that the area could be the perfect place to study water and life on Mars. Finding these compounds would be a possible indicator that life is existing on Mars now, or had existed there at one time or another.”
When the Phoenix lands, it will be right at the start of the Martian spring season. Spring on Mars is the ideal time for the Phoenix to land, because the polar region on the planet works in a similar fashion as the polar region here on earth.
“They will be landing in late spring and conducting their science during the summer season,” Hammond says. “Just like the northern latitudes of earth, the sun doesn’t set on Mars during the summer months above the arctic circle…and because the instruments aboard the Phoenix are powered by the sun, it will provide a good supply of energy to the instruments and will help alleviate some of the strain on the heaters.”
Because the polar region of Mars operates in a similar fashion to that of Earth, the window for the Phoenix to conduct experiments once it lands is only 90 days. The already cold and harsh Mars climate will be intensified by the fact that the polar regions are colder and receive a lot less energy from the sun. A typical day in this area of Mars can see temperatures ranging from 64 degrees below zero (Fahrenheit), but once winter sets in the area can go as low as 200 degrees below zero (Fahrenheit) because the polar regions on Mars, like that of Earth, receive little to no sunlight during the winter.
Due to the lack of sunlight and the extreme temperatures during the Martian winter, there is no long-term outlook for the Phoenix.
“With no sunlight during the Martian winter,” Brewster says, “the Phoenix will have no ability to generate power using its solar panels. It will have the ability to operate using its battery for a short period of time, but once it loses its power source, it will lose the ability function.”
“It’s not expected to survive the Martian winter. It’s a low cost mission, and we’re expected to get all of our science done in 90 days. After that, it will continue to serve as a weather station and taking images of the surface of Mars. That is, until the systems lose their power.”
“The Martian atmosphere is CO2, and when the area freezes during the Martian winter, [the Phoenix] will be frozen to the surface. In the year and a half until the next spring, we don’t expect the lander to survive. Rovers have survived but we don’t expect the Phoenix to survive. It could happen, but it’s not very likely.”
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