Sensor head on the Mars-bound APXS instrument

The Alpha Particle X-ray Spectrometer instrument on Curiosity will measure the chemical components in Martian rocks and soil, NASA says.

The instrument bombards targeted samples of rock and soil with alpha particles, or helium nuclei, and X-rays; NASA says it then reads the resulting signature alpha particle and radiation that is given off and revealing which elements and how much of each are in the rock and soil samples.