The key to understanding the geologic history of the solar system is knowing the ages of planetary rocks. So far, it is a challenging task to radioisotopically date fragments of other planetary bodies, as rock samples have to be brought to Earth.

F. Scott Anderson, Southwest Research Institute, Boulder, CO, USA, and colleagues have developed an instrument that can be used for in situ dating of rocks. The instrument uses laser ablation resonance ionization mass spectrometry for ⁸⁷Rb–⁸⁷Sr isochron dating of geological specimens. It operates with ablation laser intensity of ~0.6 GW/cm². It requires little sample preparation, is small and fast, making it appropriate for use by NASA and in field environments on Earth. The instrument can simultaneously provide geochemistry measurements and provide high-sensitivity detection of organics.

To test the device, the team has analyzed a piece of the Martian meteorite Zagami. It was formed about 180 million years ago, and fell to Earth in 1962. In each of four separate measurements the researchers obtained ⁸⁷Rb–⁸⁷Sr isochron ages for Zagami consistent with its published age, and, in both of two measurements that reached completion, they obtained better than 200 Ma precision. The instrument meets the criteria that NASA has established for in situ dating.

• Dating the Martian meteorite Zagami by the87Rb-87Sr isochron method with a prototypein situresonance ionization mass spectrometer,
  F. Scott Anderson, Jonathan Levine, Tom J. Whitaker,
  Rapid Commun. Mass Spectrom. 2015, 29, 191–204.
  DOI: 10.1002/rcm.7095