What's in Jake?
The graph shows the abundances of elements in the Martian rock "Jake Matijevic" (black line) and a calibration target (red line) as detected by the Alpha Particle X-ray Spectrometer (APXS) instrument on NASA's Curiosity rover. Compared to previously found rocks on Mars, the Jake rock is low in magnesium and iron, high in elements like sodium, aluminum, silicon and potassium, which often are in feldspar minerals. It has very low nickel and zinc. The salt-forming elements sulfur, chlorine and bromine are likely in soil or dust grains visible on the surface of the rock. These results point to an igneous or volcanic origin for this rock.
The Jake rock was targeted on Sept. 22, 2012, which was the 46th sol, or Martian day, of operations. The calibration target was targeted on Sept. 9, 2012, which was sol 34. APXS obtained its data by aiming alpha particles and X-rays at the rock and observing the energies of the X-rays that are emitted by the sample rock. These data are also known as spectra. The spectra on the rock and calibration target were taken for an hour at night, where the X-ray detector delivers its very best resolution, which means that the elemental peaks are the sharpest. Scales of the two different spectra were adjusted to make comparisons easier because each was measured at a slightly different distance.
The calibration target was a rock slab brought from Earth with a well-determined composition so that scientists can extract the composition of newly targeted Martian rocks very precisely.
All other Mars rovers -- Spirit, Opportunity and Sojourner -- were equipped with earlier versions of the APXS, which allows scientists to make detailed comparisons among rocks on different parts of Mars.
Image credit: NASA/JPL-Caltech/University of Guelph/CSA