Application of radioactive sources in analytical instruments for planetary exploration

Radioactive isotopes have been used in analytical instrumentation for planetary exploration since the very beginning of the space age. An Alpha Scattering Instrument (ASI) on board the Surveyor 5, 6 and 7 spacecrafts used the isotope 242Cm to obtain the chemical composition of the lunar surface material in 1960s. The Alpha Proton X-ray Spectrometers (APXS) used on several mission to Mars (Pathfinder, Mars-96, Mars Exploration Rovers (MER) and on the Mars Science Laboratory (MSL), the next mission to Mars in 2011 and on the Rosetta mission to a comet) are improved derivatives of the original ASI, complimented with an X-ray mode and using the longer lived 244Cm isotope. 57Co, 55Fe and many other radioisotopes have been used in several missions carrying XRF and Mössbauer instruments. In addition, 238Pu isotope is exclusively being used in most of the space missions for heating and power generation.