The first rock the new Curiosity instruments touched have presented a more varied composition than expected from previous missions. The rock also resembles some unusual rocks from Earth’s interior.
The rover team used two instruments on Curiosity to study the chemical makeup of the football-size rock called Jake Matijevic, to honor a pioneer JPL Mars rover designer.
The results support some surprising recent measurements and provide an example of why identifying rocks’ composition is such a major emphasis of the mission. Rock compositions tell stories about unseen environments and planetary processes.
“This rock is a close match in chemical composition to an unusual but well-known type of igneous rock found in many volcanic provinces on Earth,” said Edward Stolper of the California Tech who is a Curiosity co-investigator. “With only one Martian rock of this type, it is difficult to know whether the same processes were involved, but it is a reasonable place to start thinking about its origin.”
On Earth, rocks with composition like this typically come from processes in the planet’s mantle beneath the crust, from crystallization of relatively water-rich magma at elevated pressure. Jake was the first rock analyzed by the rover’s arm-mounted Alpha Particle X-Ray Spectrometer instrument and about the thirtieth rock examined by the Chemistry and Camera (ChemCam) instrument.
Two penny-size spots on Jake were analyzed Sept. 22 by this rover’s improved and faster version of earlier APXS devices on previous Mars rovers, which have examined hundreds of rocks. Thus scientists have available a comparison library of Mars rocks.
“Jake is kind of an odd Martian rock,” said APXS Principal Investigator Ralf Gellert of the University of Guelph in Ontario, Canada. “It’s high in elements consistent with the mineral feldspar, and low in magnesium and iron.”
Also, ChemCam found unique compositions at each of 14 target points on the rock, hitting different mineral grains within it. “ChemCam had been seeing compositions suggestive of feldspar since August, and we’re getting closer to confirming that now with APXS data, although there are additional tests to be done,” said ChemCam Principal Investigator Roger Wiens of Los Alamos National Lab.
Jake’s examination is the first comparison on Mars using both APXS results the ChemCam, which shoots laser pulses from the top of the rover’s mast. The wealth of information from the two instruments checking chemical elements in the same rock is just a preview. Curiosity also carries analytical laboratories inside the rover to provide other composition information about powder samples from rocks and soil. The mission is progressing toward getting the first soil sample into those analytical instruments during a “sol,” or Martian day.
Martian sand sampling progressing
Commands have sent to Curiosity instructing the rover to collect a third scoop of soil from the “Rocknest” site of windblown Martian sand and dust.
Pending evaluation of this Sol 69 (Oct. 15, 2012) scooping, a sample from the scoopful is planned as the first sample for delivery, a few days latter, to one of the rover’s internal analytical instruments, the Chemistry and Mineralogy (CheMin) instrument.
A later scoopful will become the first solid sample for delivery to the rover’s other internal analytical instrument, the Sample Analysis at Mars instrument.
The rover’s second scoopful, collected on Sol 66, was intentionally discarded on Sol 67 due to concern about particles of bright material seen in the hole dug by the scooping. Other small pieces of bright material in the Rocknest area have been assessed as debris from the spacecraft. The science team did not want to put spacecraft material into the rover’s sample-processing mechanisms.
Also, the first two scoops were used to completely scour the interior of the sample delivery mechanisms of a suspected film of material that may have been brought up from earth.
Confidence for going ahead with the third scooping was based on a new assessment that other bright particles in the area are native Martian material. One factor in that consideration is seeing some bright particles embedded in clods of Martian soil. Further investigations of the bright particles were planned, including some imaging in the Sol 69 plan. Sol 69, in Mars local mean solar time at Gale Crater, ended at 5:01 a.m. Oct. 16, PDT.