Kees Welten got his PhD from the Department of Physics and Astronomy, Utrecht University, Netherlands. From 1995-1997, he was an NRC postdoctoral fellow at NASA Johnson Space Center, Houston. Since 1997, he has worked in the Cosmochemistry group at the Space Sciences Lab analyzing cosmic-ray produced (cosmogenic) radionuclides in meteorites, lunar samples, terrestrial rocks and ice cores. The measurements of cosmogenic nuclides in extraterrestrial samples, which are mostly done by accelerator mass spectrometry (AMS), are used to study dynamical processes in the asteroid belt, and on the lunar surface. Since 2008, Welten has also been a member of the West Antarctic Ice Sheet (WAIS) Divide ice core project that employs high-resolution measurements on a 3400 m deep ice core to obtain detailed information on rapid climate change in the past 68,000 years. The high-resolution 10Be measurements in this ice core carried out by Welten – in collaboration with colleagues at Purdue University – provide information on temporal variations in the cosmic-ray flux due to changes in geomagnetic field strength, solar activity, and the occurrence of large solar proton events.