CAPE CANAVERAL, Florida (Reuters) - An
unmanned Atlas 5 rocket blasted off from Florida on Saturday, launching
a $2.5 billion nuclear-powered NASA rover toward Mars to look for clues
on what could sustain life on the Red Planet.
The 20-story-tall
booster built by United Launch Alliance lifted off from its seaside
launch pad at Cape Canaveral Air Force Station at 10:02 a.m. EST (3:02
p.m. GMT).
It soared through partly cloudy skies into space,
carrying NASA's Mars Science Laboratory on a 354-million mile (556
million km), nearly nine-month journey to the planet.
"I think
this mission is an important next step in NASA's overall goal to address
the issue of life in the universe," lead scientist John Grotzinger,
with the California Institute of Technology, told reporters shortly
after the launch.
The car-sized rover, nicknamed Curiosity, is
expected to touch down on August 6, 2012, to begin two years of detailed
analysis of a 96-mile (154-km) wide impact basin near the Martian
equator called Gale Crater.
The goal is to determine if Mars has
or ever had environments to support life. It is the first astrobiology
mission to Mars since the 1970s-era Viking probes.
Scientists
chose the landing site because it has a three-mile-high (4.8-km high)
mountain of what appears from orbital imagery and mineral analysis to be
layers of rock piled up like the Grand Canyon, each layer testifying to
a different period in Mars' history.
The rover has 17 cameras and
10 science instruments, including chemistry labs, to identify elements
in soil and rock samples to be dug up by the probe's drill-tipped
robotic arm.
'LONG SHOT'
The base of the crater's mountain
has clays, evidence of a prolonged wet environment, and what appears to
be minerals such as sulfates that likely were deposited as water
evaporated.
Water is considered to be a key element for life, but not the only one.
Previous Mars probes, including the rovers Spirit and Opportunity, searched for signs of past surface water.
"We
are not a life-detection mission," Grotzinger said. "We have no ability
to detect life present on the surface of Mars. It's an intermediate
mission between the search for water and future missions, which may
undertake life detection."
With Curiosity, which is twice as long
and three times heavier than its predecessors, NASA shifts its focus to
look for other ingredients for life, including possibly organic carbon,
the building block for life on Earth.
"It's a long shot, but we're going to try," Grotzinger said.
Launch is generally considered the riskiest part of a mission, but Curiosity's landing on Mars will not be without drama.
The
1,980-pound (898 kg) rover is too big for the airbag or thruster-rocket
landings used on previous Mars probes, so engineers designed a
rocket-powered "sky-crane" to gently lower Curiosity to the crater floor
via a 43-foot (13-meter) cable.
"We call it the 'six-minutes of
terror,'" said Doug McCuistion, director of NASA's Mars Exploration
Program, referring to the landing. "It is pretty scary, but my
confidence level is really high."
Curiosity is powered by heat from
the radioactive decay of plutonium. It is designed to last one Martian
year, or 687 Earth days.
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