At first, the probe checked itself over, taking snapshots of its dusty feet and freshly unfurled solar arrays, ensuring all was present and correct following its 422m-mile journey and high-speed descent on to the northern plains of Mars in the early hours of yesterday.
Then the real work began. The robotic arm flexed and swivelled, bringing the camera up and around to gaze at the alien landscape. Two hours later, Nasa's mission controllers had been sent the first pictures ever to be taken within the arctic circle of the red planet.
The $420m (£212m) Phoenix mission, which settled on Mars at 00.53 BST yesterday, represents a major milestone in Nasa's exploration of the solar system and its search for evidence of life elsewhere. Not since the Viking landers touched down in 1976 has a probe landed softly on the planet, using rocket thrusters to slow its descent. More significantly, Phoenix is expected to become the first spacecraft to touch water on another planet.
At Nasa's Jet Propulsion Laboratory in California last night, the final moments before landing were tense, but at every step the Phoenix probe matched or exceeded expectations. As it hurtled into the atmosphere, engineers foresaw a communications blackout as the searing plasma around the probe's heat shield blocked their radio link. When the moment came, the probe kept in touch all the way down, settling at a near-perfect 0.25-degree angle in the Vastitas Borealis, an ancient plain near the north pole.
"In my dreams, it couldn't have gone as perfectly as it did," said Barry Goldstein, the project manager on the Phoenix mission. "I'm in shock. Never in rehearsal did it go so well."
Yesterday, Nasa engineers began analysing the first of the images, some showing the intriguing polygonal patterns that scar the Martian arctic. One of the probe's mission tasks is to dig beneath the frigid surface to collect water ice and soil, which will be analysed by the probe's onboard laboratory. Mission controllers will be looking for signs of organic compounds in the water that could indicate that the now harsh environment was once hospitable, and even habitable.
"We see the lack of rocks that we expected, we see the polygons that we saw from space, we don't see ice on the surface, but we think we will see it beneath the surface," said Peter Smith, the principal investigator on the mission at Arizona University.
The landing marks the US space agency's first return to Mars since its twin rovers, Spirit and Opportunity, touched down in January of 2004.
"This is the first chance we have had to actually collect and analyse water on the Red Planet," said Keith Mason, head of Britain's Science and Technology Facilities Council.
"If we find water ice below the Martian surface we may also be able to find evidence of past life on the planet."
Over the next eight days, the probe will continue to take measurements of the Martian atmosphere and soil before using its two-metre-long robotic arm to dig down to what lies beneath. Onboard cameras and a weather station will record information about the probe's changing environment as night turns to day and the Martian seasons turn. The mission is expected to last three months, after which the arrival of winter will see light levels fall too low to replenish the Phoenix probe's batteries.
"We're all so relieved that Phoenix has managed to land safely," said Tom Pike, head of the UK Phoenix team at Imperial College London. "The descent and landing phase of the mission is one of the most tricky and hazardous. It's great to have made it down in one piece and now we can get to work uncovering more of the Red Planet's secrets."
The London team developed tiny silicon sheets that will hold dust and soil samples for the probe to examine with high-resolution microscopes.
Another of the probe's tasks is to monitor changes in the polar weather and how it interacts with the land and atmosphere above. In the arctic summer on Mars, scientists believe water vapour is released from ice at the polar caps and into the atmosphere.
David Catling, a scientist on the team from Bristol University, said: "Our priority now is to find out if there is ice below the dirt and whether it got there recently, or it is a frozen remnant from an ancient time when liquid water may have rippled across this part of Mars."
As the name suggests, the 350kg Phoenix probe arose from the embers of previous Mars missions, themselves failed or shelved in 1999 and 2001, but useful for their spare parts, from which the spacecraft was put together.
 |  |
No comments:
Post a Comment