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PASADENA, California (Reuters) - A sharp-eyed Mars orbiter snapped an image of sister probe Phoenix descending through Martian skies toward a polar landing site to search for water and assess conditions for life, mission managers said on Monday.
Phoenix touched down at 4:53 p.m. PDT (7:53 p.m. EDT/2353 GMT) on Sunday, becoming the first spacecraft to reach a polar region of Mars. Problems during descent doomed NASA's first polar lander in 1999.
The unprecedented image, taken by the Mars Reconnaissance Orbiter as a result of careful planning and good luck, shows the small probe dangling beneath its parachute.
Features of the planet's face, including polygon-shaped patterns in the frozen arctic soil, can be seen faintly in the background.
The shapes are of interest to scientists who plan to use Phoenix to dig beneath what is expected to be a thin layer of soil to sample underlying ice. They want to learn if the water was ever liquid, which is believed to be necessary for life.
So far, the Phoenix science team has had only a tantalizing glimpse of the landing site from an onboard camera that has completed only a low-resolution sliver of a planned 360-degree panoramic image.
The probe is using two satellites -- Mars Reconnaissance Orbiter and Mars Odyssey -- to communicate with controllers on Earth.
"We're particularly interested in seeing what's in our digging area," lead scientist Peter Smith told reporters at the Jet Propulsion Laboratory in Pasadena, which oversees the mission.
Cracks in the ground are a sign of changes in underlying ice, Smith said. Scientists believe the cracks are fresh because they are not covered with the fine red dust that permeates Mars' atmosphere.
Checks on Phoenix science instruments and an assessment of the landing site will continue throughout the week. Science operations, which are being overseen by the University of Arizona in Tucson, are expected to begin in June.
Phoenix completed a 10-month, 420-million-mile (676-million-km) voyage from Earth with a do-or-die plunge through the Mars atmosphere and a safe touchdown in the northern Arctic circle.
Over the next three months, scientists want to bore into the ground and study water and soil samples to determine if conditions were suitable to support life.
In addition to determining if the water was ever liquid, scientists want to find out if it holds any organic matter.
The Viking landers in the 1970s and early 1980s conducted similar tests on surface soils. Scientists later determined solar radiation, which flows virtually unimpeded by the planet's thin atmosphere, creates a sterile environment as it bombards the ground.
Subsurface conditions, however, might provide habitats for microbes and bacterial life to flourish on Mars, as they do in extreme environments on Earth.
For the past decade, NASA has been searching for signs of past water on Mars with a fleet of orbiters and a pair of rovers on the ground. The detection of subsurface frozen water in 2002 by Mars Odyssey prompted scientists to propose the Phoenix mission to investigate.
Editing by Eric Walsh