One Small Step for NASA
by Piper Wallingford
On May 25, The Phoenix Lander touched down on Mars as part of a program that depends on robotic exploration to increase knowledge and understanding of the planet closest to Earth. Failures and disasters have continuously plagued NASA's Mars Exploration Program, and the successful landing of the Phoenix is a small, but significant, step for NASA.
After the landing, Phoenix relayed a message through the Mars Odyssey, which orbits the planet, confirming that the Phoenix was intact and operational. After initial contact, the Phoenix ended transmissions, and the remaining battery power was used to open and configure the Phoenix's solar arrays, stereo camera, and weather station. Two hours after the landing, the rover reported that it had begun to generate power from its solar panels, providing a source of power for its three-month mission.
Because the Phoenix is a lander, not a rover, it will remain stationary at the arctic north of Mars. The Phoenix will test the planet's polar ice cap and determine whether frozen water is accessible. Researchers hope to learn more about the ancient Martian environment and whether it could have supported primitive life. On May 31, the lander began soil analysis and experimentation, as the robotic arm scooped up Martian soil for the first time.
The success of the Phoenix is a change from earlier attempts at landing robotic explorers. Since Viking 2 touched down in 1976, the Phoenix is the first to land without needing to employ its airbags. The descent is difficult, and timing and angle must be coordinated precisely in order to avoid incineration. In addition, mission controllers on Earth cannot immediately know if a landing was successful because it takes fifteen minutes for a signal to reach Earth from Mars. Timing of the initial launch also has to be exactly right. Because of the orbits of the Earth and Mars, launch periods occur approximately two years apart.
Because of the difficulties associated with Mars exploration, only 5 of the last 11 attempts to land on the surface have succeeded. The most recent disaster is that of the Mars Polar Lander and Deep Space 2. While approaching Mars, the Polar Lander carried Deep Space 2, which consists of two probes designed to penetrate the Martian surface. After the Polar Lander released Deep Space 2, the probes plummeted to the Martian surface and never established communication. When the Polar Lander began its descent, the sensors picked up vibration caused by entry into the atmosphere. The Polar Lander's software identified the vibration as a landing and cut off the engines. The lander, however, was still more than 40 meters (130 feet) above the surface. Sometimes, things land when they should be in orbit. Perhaps the most infamous Mars Exploration disaster is the Mars Climate Orbiter, which crashed to the ground after a mix-up between metric and imperial measurements.
Besides the Phoenix, there are two other functioning exploration robots on Mars. In January 2004, the Mars Exploration Rovers Spirit and Opportunity successfully landed on the Martian surface. The rovers performed better than expected, and in April 2004, NASA extended the rovers' missions for an additional five months. After both rovers passed criteria benchmarks, such as traveling more than 600 meters (2000 feet), they were cleared to continue past their original three-month missions. Software upgrades extended the capabilities of the rovers, and in September 2004, the rovers received another six-month mission extension. Still in operation today, the rovers have set Martian driving records, traveling more than 10 kilometers (6 miles), and have made significant contributions to knowledge about Mars.
While Spirit and Opportunity are NASA's success stories, they are still limited in their ability to explore and interpret data. The rovers travel slowly and recharge each night, and there is always a possibility that meteorites or storms could damage scientific instruments. The rovers have also experienced operating difficulties. Opportunity has limited use of its robotic arm, which can no longer be stored. Spirit now explores Mars in reverse, driving backward in order to drag a dead wheel. The Martian terrain has also proved hazardous to the rovers. In April 2005, Opportunity became stuck in a sand dune, and Martian sandstorms often threaten the ability of the rovers to recharge using their solar arrays.
A manned mission to Mars could eliminate many of the problems associated with robotic exploration. In 2004, President Bush announced that manned exploration is an eventual goal of the space program. However, a manned mission poses new difficulties to exploration of the planet. Robots can explore for greater amounts of time because they are insulated against the climate and do not require oxygen. Travel and equipment are much less expensive, meaning that robotic missions are much more cost-efficient than manned missions are.
Ultimately, an unmanned mission is also much safer. More Mars rovers have crashed than have actually landed, which does not bode well for a manned landing. While the loss of the explorers has limited the gains of new information, it is still only a loss of metal and software. While a manned landing would provide essential insight and new information about the planet, the dangers are too great to risk human life.
