Phoenix the robotic spacecraft destined to explore the polar regions of Mars, is sitting atop a 13-story tall Delta II launch vehicle at pad 17 in Cape Canaveral, Florida. If all goes as planned, the rocket engines will roar to life at dawn on Saturday, August 4, sending the spacecraft on its long journey to the Red Planet.
The date chosen for the launch is the beginning of a three-week period when planetary positions are favorable for sending a spacecraft from Earth to Mars. The first launch opportunity will be at 2:26:34 a.m. PDT (5:26:34 a.m. EDT) on Aug. 4. A second opportunity the same day, if needed, will come at 3:02:59 a.m. PDT (6:02:59 a.m. EDT). Each of the following days will also have two launch opportunities, in case the weather doesn’t permit a launch on the first day.
Initially the Delta II launch vehicle will carry Phoenix into Earth orbit, where it will cruise for around 90 minutes. A second burn of the second stage of the rocket will then give it the push needed to send it to Mars. Phoenix will then travel 679 million kilometers (422 million miles) in an outward arc from Earth to Mars.
“We have worked for four years to get to this point, so we are all very excited,” said Barry Goldstein, Phoenix project manager at NASA’s Jet Propulsion Laboratory, Pasadena. “Our attention after launch will be focused on flying the spacecraft to our selected landing site, preparing for surface operations, and continuing our relentless examination and testing for the all-important descent and landing on May 25 of next year.”
Studies of potential landing sites by spacecraft orbiting Mars led NASA to approve a site at 68.35 degrees north latitude — the equivalent of northern Alaska — and 233.0 degrees east longitude. To minimize the risk to the spacecraft’s landing from obstacles on the ground the Phoenix team selected a level landing site where the steepest slopes do not exceed 5%. Based on images from the Mars Reconnaissance Orbiter they also determined that the region was free of large rocks or boulders, a conclusion they reached after compiling a database of 5 million rocks! According to Goldstein, the spacecraft now has a 97% chance of landing on relatively flat and rock-less ground.
By targeting the polar regions for the Phoenix mission Mars exploration is following in the footsteps of Earth exploration, explained Peter Smith of the University of Arizona, the mission’s Principal Investigator. “The North Pole, reached by Peary in 1909, and South Pole, reached by Amundsen in 1911, were the last regions of the Earth to be explored” he said. The same, he said, is true for Mars: after several generations of landers exploring the equatorial regions of Mars, it is now time to sample the far north.
According to Smith Phoenix main mission is to study whether conditions for life existed on Mars in the past, or possibly even in the present. In accordance with the guiding principle of “follow the water”, Phoenix will dig to a depth of up to 40 centimeters in an attempt to reach ice deposits believed to be present just beneath the surface. “Phoenix investigates the recent Mars Odyssey discovery of near-surface ice in the northern plains on Mars,” said Smith of the University of Arizona. “Our instruments are specially designed to find evidence for periodic melting of the ice and to assess whether this large region represents a habitable environment for Martian microbes.”
Phoenix will carry with it to 8 different instruments, comprising 15 different components to measure and study the Martian environment. Notable among them is TEGA (Thermal and Evolved-gas Analyzer) which includes eight tiny ovens for heating soil samples up to 1,000 degrees Celsius (1,800 degrees Fahrenheit). The analyzer will then study the gasses produced by the heated soil for signs of water and organic compounds. Another instrument, MECA (Microscopy, Electrochemistry and Conductivity Analyzer), will study the Martian soil by various methods, including mixing samples with water.
Unlike the Mars Exploration Rovers, explained Smith, there is no chance the Phoenix will last for years on the Red Planet. Landing at the height of summer in the northern polar regions the spacecraft will have to complete its work during a single season. When winter approaches the spacecraft will be immersed in carbon dioxide ice, bringing its robotic life to an end.
In addition to its scientific instruments the spacecraft is also carrying on board a mini-DVD contributed by The Planetary Society. Encoded on it is “Visions of Mars” – a collection of art and literature about Mars from the past century, and recorded greetings to future explorers of Mars from Society co-founder Carl Sagan, executive director Louis Friedman, and others. Also included are 250,000 names of Planetary Society members and other space enthusiasts who signed up to send their names to Mars.
The Phoenix mission was proposed in 2002 by an international team led by Smith. The spacecraft uses a lander structure built for the 2001 Mars Surveyor mission, which was scaled down before launch to an orbiter-only mission. The revival of this previously canceled mission earned the current one its name – the Phoenix.