41Ca: past, present and future

Accelerator mass spectrometry measurements of 41Ca have come of age. The ability to routinely obtain currents of CaH3− of 5 μA and backgrounds of less than 10−15, and even 5×10−16 at times, makes possible measurements with a precision of 5% in an hour. Studies of 41Ca in a wide variety of extraterrestrial materials addressing several very different problems, including the temporal constancy of galactic and solar cosmic rays, the determination of terrestrial ages of meteorites, and their pre-atmospheric size are now in progress. However, the goal of employing 41Ca to date bones still remains elusive. The major experimental problem is the production of currents of sufficient intensity. But more fundamental, it seems likely that the radiocalcium dating model is seriously flawed. In this short review, we summarize the technical developments that have led to a successful technique to measure 41Ca, and discuss the more significant applications of 41Ca both on the Earth and above.