b'Mass spectrometry is the main technique used in radioactive dating of rocks and in tracing their originResults to date show that theto understand how and when planets formed andnew cavity ion sourcematchesseparated into core, mantle, and crust. The traditional mass spectrometer for this purpose uses a heatedor exceeds expectationsfilament for sample evaporation and ionization. Carlson and Reiminks design replaces the filament with a tube, called a cavity. Sample atoms are loadedperformance trade-offs and that can be easily fitted25into the bottom of the cavity, which is then heatedto existing mass spectrometer components. Results by high-energy electron bombardment, causing theto date show that the new cavity ion source matches sample atoms to bounce along the cavity walls untilor exceeds expectations for ionization efficiency they become ionized. Once ionized, they are extractedand transmission into the mass spectrometer for a by electric fields into the mass spectrometer.number of elements with geochemical applications. The expected improvement in isotope ratio precisions Although the cavity ion source has been used inwill reduce the uncertainty in the timing of the events nuclear science since the 1970s, it has not yet beenaccompanying Earth formation 4.5 billion years ago adapted to the geosciences. The scientists goal is tofrom tens of millions of years to under a million years. design, build, and evaluate different configurationsThis will greatly improve our ability to determine the of cavity thermal ion sources that optimize varioussequence of events that formed and modified Earth. Jesse Reimink (left) and Rick Carlson (right) are shown in the field in Canada sitting on a 3.3-billion-year-old rock. Their new instrument offers the promise of using ancient rocks like these to better understand the processes that created the first crust on Earth. Image courtesy Rick Carlson, Carnegie Institution for Science'