NASA’s Curiosity rover finds ‘unusual rock’
13 October BBC
It was expected to be just another lump of dull basalt, but the first
rock examined up close by NASA’s Mars rover proved to be a little more
interesting. The pyramidal object, nicknamed “Jake Matijevic” after a
recently deceased mission engineer, had a composition not seen on the
planet before.Scientists have likened it to some unusual but well known
rocks on Earth.
These form from relatively water-rich magmas that have cooled slowly
at raised pressures, said Edward Stolper.”[The rock is] widespread on
Earth, on oceanic islands such as Hawaii, and St Helena, and the Azores;
and also in rift zones like the Rio Grande and so forth. So, again, it’s
not common, but it’s very well known,” the mission co-investigator from
the California Institute of Technology, Pasadena, told reporters.The
Curiosity rover examined Jake Matijevic three weeks ago. At the time,
the dark rock was not anticipated to have high science value; it was
merely an early opportunity to use the robot’s survey instruments in
unison.Jake Matijevic also had an interesting, weathered appearance that
drew attention.
The rover first zapped the rock from a distance with its ChemCam
laser, and then moved in close to study it with its X-ray spectrometer
known as APXS. The latter device is held on the end of the rover’s
robotic arm; the laser is mounted on its mast.
Jake Matijevic was found to be high in elements consistent with the
mineral feldspar, such as sodium and potassium, and low in elements such
as magnesium and iron.Prof Stolper compared the signatures with a
catalogue containing thousands of Earth rocks, and determined the
nearest match to be an igneous type, the formation of which he likened
to the production of colonial apple jack liquor.This saw barrels of
cider left outside in winter to partially freeze.
As the barrels iced up, they would concentrate the apple-flavoured
liquor. A similar process was occurring in the liquid magma several
kilometres underground that gave rise to alkalic rocks like Jake
Matijevic, said Prof Stolper.”In the case of the apple jack, you take
out water and concentrate alcohol; in this case you take out particular
minerals - olivines, pyroxenes and some feldspars - and you generate a
liquid that is very different to what you started with,” he explained.
“So, the composition of Jake Matijevic is a very close match to
highly crystallised or fractionated magmas that occur in particular
places on Earth.”Curiosity landed in Mars’ equatorial Gale Crater in
August, and has driven eastwards almost 500m since then.It is currently
stationed just short of a point called Glenelg, where satellite images
have revealed a juxtaposition of three different types of
terrain.Scientists expect this location to be a good starting point to
begin characterising the geology of Gale.
The mission is going through something of a lull presently while the
rover spends a few days preparing its sample handling system.It is
running dirt through this equipment to scrub surfaces free of any
residual contamination from Earth.This is necessary to avoid skewing the
analyses of rock and soil samples delivered to the rover’s onboard
laboratories later in the mission.Curiosity’s goal is to try to
determine if Gale ever supported environments that might have allowed
microbial life to flourish.In the short time it has been on the ground,
it has already identified rocks that were clearly deposited in fast
running water. The theory is that the rover is sitting at the head of an
ancient alluvial fan where a network of streams cut across the crater
floor billions of years ago.
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