Steve Desch, Arizona State University
Meteorites record evidence of the one-time presence in the solar system of many radionuclides with half-lives on the order of one million years. Their importance in meteoritics cannot be overstated: aluminum 26 was a potent heat source and is what melted asteroids, and measurements of the decay products of these radionuclides allow formation times of meteorites and their inclusions to be dated, if their abundances were uniform throughout the early solar system. That would be the case if the solar system inherited these radionuclides from the molecular cloud, but not if they were injected into the Sun's disk by a nearby supernova or created by nuclear reactions due to irradiation by solar energetic particles. In this talk I will review how we acquire data about short-lived radionuclides, and the evidence that argues that the radionuclides were well mixed throughout the solar nebula and inherited from the Sun's molecular cloud. The abundances of short-lived radionuclides strongly suggest the Sun formed (like most stars) in a spiral arm of the Galaxy.
About the presenter
Steve Desch is a professor of astrophysics in the School of Earth and Space Exploration at ASU. His research focuses on developing models of star and planet formation, using data from meteoritics and planetary science. He especially studies the origins of chondrules and meteorites. He also works in the fields of exoplanets and astrobiology and is Principal Investigator (PI) of the NASA-funded NExSS grant to study geochemical cycles on exoplanets to aid searches for signs of life on other planets. He has modelled small icy bodies to explore the likelihood of subsurface water on Pluto and its moon, Charon, the asteroid Ceres, and others. He has recently advocated the concept of Arctic Ice Management, to study how to increase sea ice in the Arctic in response to climate change. Asteroid 9926 Desch is named after him.