safe on Mars, craft seeks
signs of subsurface ice
By Ron Cowen
After a nerve-wracking but carefully choreographed seven-minute descent, NASA’s
Phoenix Mars Lander arrived on the Red
Planet at 7:38 p.m. EDT on May 25.
The first spacecraft to land on the
northern polar region of Mars, the craft’s
mission is to dig into the frigid topsoil for
evidence that the subsurface may have
offered a haven for microbial life.
After slowing down at the top of Mars’
atmosphere, Phoenix reached a temperature of 1,426˚ Celsius during its flight. The
craft then deployed its parachute, jettisoned its heat shield, deployed its three
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landing legs and activated its radar. It jettisoned its parachute and fired its thrusters
the last 18 seconds before landing.
At NASA’s Jet Propulsion Laboratory
in Pasadena, Calif., scientists cheered
after radio signals confirmed that Phoenix had safely landed about 20 kilometers
from a crater called Heimdall. The signals
were relayed by the Mars Odyssey spacecraft, which was orbiting overhead.
“We’re almost dead on,” said mission
project manager Barry Goldstein of JPL.
“I’m in shock. Not in my dreams” did the
landing go so well, he added.
The lander’s first images showed a flat
valley, devoid of rocks. “I know it looks a
little like a parking lot, but that’s a safe
place to land, by gosh,” said Phoenix project scientist Peter Smith of the University
of Arizona in Tucson. “Underneath this
surface, I guarantee you there’s ice.”
Cracks in shallow troughs suggest that
ice is still modifying the surface, buckling and creating polygonal shapes as it
expands and contracts during summer
and winter, Smith noted. By a week after
landing, the craft’s robotic arm succeeded
in making a test dig of the soil.
Early on, researchers also got a bonus
image. A camera on the Mars Reconnaissance Orbiter, passing overhead, caught
an image of Phoenix dangling from its
parachute just before touchdown. It was
the first time one spacecraft photographed
another in the act of landing on Mars.
In addition to studying the history
of water-ice in the polar region, Phoenix
has begun monitoring the weather there.
Laser pulses shot into the atmosphere
reveal the abundance of dust and clouds
up to an altitude of 20 kilometers.
The craft reached its destination
after journeying 675 million kilometers
since its August 4, 2007, launch. Designed
to last for 90 Mars days, the craft could
survive for another 60. By then, the sun,
which Phoenix relies on for power, will
have sunk below the horizon. s
The Mars Reconnaissance Orbiter captured a historic image (above left) of the
Phoenix Mars Lander as it deployed its parachute before descending to the Red
Planet’s surface. In the week after its successful May 25 landing, Phoenix captured
images of the polygonal texture in nearby soil (above right), possible ice chunks
near the lander’s leg (bottom) and a panoramic view of the arctic landing site (left).