Beginning this bank holiday Sunday evening, NASA’s Phoenix spacecraft will hurtle through the Martian atmosphere towards the surface, where it will begin a three month mission to study the habitability potential of the Martian arctic’s ice-rich soil.
NASA’s £200 million Phoenix spacecraft is going where no spacecraft has gone before, braving the harsh arctic latitudes of the Martian north polar region. A major goal of the mission will be to examine the ice and dust in these high northern latitudes for clues about the history of water on Mars and signs for any biological activity. But first, it must execute a series of well-timed maneuvers through the Martian atmosphere in the seven scariest minutes of the mission.
It will approach Mars at a speed of over 19,000 kilometres per hour, at which point it will be subjected to a jarring deceleration, 9.2 times the force of Earth’s gravity, as its heat shield battles against the superheated friction of the atmosphere. After a few minutes, Phoenix will be swooping in at an acceptable 1,200 kilometres and the parachute can be safely deployed, slowing the lander further. When the heat shield is no longer required it will be jettisoned, and the craft’s three landing legs will be unfolded. At T-minus approximately 60 seconds from the surface, Phoenix will release its grasp from the parachute and its onboard computer will fire up 12 small rocket engines, which will guide the lander to the surface at a graceful 8 kilometres per hour. The last time this propulsion system and landing leg mechanism was used was for the Viking missions 33 years ago.
The Phoenix lander will enter the Martian atmosphere at break-neck speeds (top left) before being slowed by a parachute (top right) and guided to the surface by a rocket propulsion system (bottom left). Once safely landed on the Martian surface, its solar arrays will unfold and it will begin to dig the icy artic soil (bottom right). Images: NASA/JPL-Caltech/University of Arizona.
Throughout entry, descent and landing, data will be relayed to Earth through NASA’s Mars Odyssey spacecraft orbiting high overhead, but it will take those signals a nail biting 15.3 minutes to reach anxious flight controllers at the Jet Propulsion Laboratory. The earliest possible time mission controllers could get confirmation from Phoenix, indicating its successful landing, will be at around 23:53 GMT. The Mars Express spacecraft and the Mars Reconnaissance Orbiter will also be watching the critical entry, descent and landing phase.
Missions to Mars do not have a very high success rate – of 11 previous landing attempts only five have succeeded – but the Phoenix team are confident and all systems are go. "All systems are nominal and stable," says Ed Sedivy, Phoenix spacecraft program manager for Lockheed Martin Space Systems, which built the spacecraft. "We have plenty of propellant, the temperatures look good and the batteries are fully charged."
"The latest calculation from our navigation team shows the centre of the area where we're currently headed lies less than eight miles from the centre of our target area," adds Barry Goldstein, Phoenix project manager. "We may decide on Saturday that we don't need to use our final opportunity for fine tuning the trajectory Phoenix is on. Either way, we will continue to monitor the trajectory throughout Saturday night, on the off chance we need to execute our contingency maneuver eight hours before entry."
Mars orbiters line up above the north polar ice cap to watch Phoenix swoop in on the Martian surface. The image shows the paths of the three spacecraft currently in orbit, as well as the path by which Phoenix will approach. The + symbols show where the orbiters will be when Phoenix enters the atmosphere and the X symbols mark their location at the planned landing time. Image: NASA/JPL-Caltech/University of Arizona.
Assuming Phoenix makes it to the ground safely, it will first vent any unneeded pressurised helium from its propulsion system and then wait for 20 minutes for any dust kicked up by the descent engines to settle out. Then, two solar arrays will be unfolded, which will recharge the landers batteries. After that, Phoenix’s main camera mast will be extended, along with a boom carrying meteorology instruments. Ten days after landing, Phoenix will begin to conduct the much awaited science experiments at its landing site.
The science team is slowly adjusting to working on Mars time, in which each day lasts 24 hours and 37 minutes, in preparation for a demanding mission. "We are ready to robotically operate our science lab in the Martian arctic and dig through the layers of history to the ice-rich soil below," says Phoenix Principal Investigator Peter Smith.
The Phoenix lander with its wings spread and instruments at the ready. Image: NASA/JPL-Caltech/University of Arizona/Lockheed Martin.
The solar powered robotic lander will manipulate a 2.3 metre-long arm to scoop up samples of the ice and overlying soil, and onboard laboratory instruments will analyse the samples in a set up reminiscent to the 1977 Viking missions. Like the Viking experiments, one crucial Phoenix experiment will test for water and carbon-containing compounds that are potential building blocks for life, by heating the samples in miniature ovens and examining the resulting vapour. The Viking results were inconclusive, but technology has come along way in the last 33 years, and the cameras and microscopes on Phoenix will be able to provide information on scales spanning a factor of a hundred million.
Phoenix will also examine the composition and texture of the soil above the ice, which could give clues as to whether the ice ever melts in response to long-term climate cycles. The lander will also monitor polar-region weather on Mars from a surface perspective for the very first time.
After three months of experimenting, the mission will end with the onset of the Martian winter, and Phoenix will be buried in ice.
For mission updates over the bank holiday weekend visit http://spaceflightnow.com.The mission is also featured in this month’s issue of Astronomy Now magazine, available now from your local newsagent.
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