This
story was updated at 3:15 p.m. ET
NASA's Opportunity rover has eyed an odd-shaped, dark rock on the surface of Mars — scientists
think it could be a meteorite.
Opportunity's
handlers spotted
the rock, which measures about 2 feet (0.6 meters) across, in images sent
by the rover on July 18 in the opposite direction from which the rover was
driving. The rock, dubbed "Block Island," is unusual for its size, mission
scientists said.
"The
images came down after we had already passed," said planetary scientist
Albert Yen of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Mission managers decided the rock was worth
a closer look and had the rover then backtrack some 820 feet (250 meters).
Over the
weekend, scientists used the rover's alpha particle X-ray spectrometer to get composition
measurements and to confirm it was a meteorite.
"It's
pretty clear now that it is," Yen told SPACE.com.
The rock
has a similar composition to another
meteorite that Opportunity found in Jan. 2005. That meteorite was the first
to be found on another planet. It was lying just over half a mile from its
landing site in Mars' Meridiani Planum. Since landing on Mars in 2004, Opportunity has driven across 10.7 miles (17.2 km) of the red planet's surface.
The 1-foot
(31-cm) diameter slug of iron and nickel gained the moniker "Heat-Shield
Rock" due to the rover's discarded heat shield having come to rest only 20
feet (6 meters) from the meteorite.
There are
some differences between the two meteorites though and scientists plan to use
some of Opportunity's other instruments to learn more about Block Island.
"We're
likely to spend a good amount of time here," Yen said, at least through
the upcoming weekend.
The rover
team has also taken color and microscopic images of the meteorite. Next up are
measurements with the rover's Mössbauer spectrometer, which can tell scientists
more about the mineralogy of the rock.
Studying
the meteorite could tell scientists more about the surface conditions in place
when the meteorite fell: The pitted surface of the rock shows millimeter-sized
granules of what scientists think is hematite, which suggest the meteorite was
once buried under the Martian sand, Yen said. The meteorite could also tell the
scientists about the atmosphere at the time, since the chunk that is left is
relatively large.
Opportunity and its sister rover Spirit have
been rolling along opposite ends of the red planet for more than five years
now. While Opportunity passed the
10-mile mark, Spirit has been mired in a Martian sand trap for more than a
month. Rover engineers back on Earth are working with a test rover to come up
with ways to free the mired robot.
In its five
years on Mars, Opportunity has spent two years exploring Victoria Crater,
revealing that the whole region the crater lies in was likely shaped by water
and winds that blew up huge sand dunes. Its twin Spirit is on the other side of
Mars in a region known as Gusev Crater.
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