Alpha particle X-ray spectrometer

[1] This method of analysing the elemental composition of a sample is most often used on space missions, which require low weight, small size, and minimal power consumption.

Alpha particles, protons, and X-rays are emitted during the radioactive decay of unstable atoms.

The Mars Exploration Rovers' Athena payload uses curium-244 with a source strength of approximately 30 millicuries (1.1 GBq).

[10] Some of the alpha particles of a defined energy are backscattered to the detector if they collide with an atomic nucleus.

This process is termed particle-induced X-ray emission and is relatively easy to detect and has its best sensitivity and resolution for the heavier elements.