Impacts in the Earth-Moon System - What, When, and Why?
About the Speaker
Nicolle Zellner is an associate professor of physics at Albion College in Albion, MI, where she teaches introductory and advanced astronomy and physics courses. Nicolle’s research interests focus on understanding the impact history of the Earth-Moon system and how those impacts affected the conditions for life on Earth. She studies lunar impact glasses to interpret the bombardment history of the Moon (and Earth), and a second project focuses on understanding how the chemistry of simple molecules is affected by impacts.
During the 2006-2007 field season, she was a member of the ANSMET team that searched for meteorites in Antarctica. She spent two months there, and she and the team collected over 800 meteorites! Before coming to Albion College in 2005, she was a post-doctoral researcher at Lawrence Livermore National Laboratory’s Institute of Geophysics and Planetary Physics. While there, she was also a Faculty Scholar associated with the Edward Teller Education Center. Nicolle was a member of the scientific ground crew during NASA’s STS-67 Astro-2 mission in 1995.
Her PhD is from Rensselaer Polytechnic Institute (2001), where she received the school's first Multidisciplinary PhD. Her undergraduate degree, with majors in Physics and Astronomy and a certification in Environmental Studies, is from the University of Wisconsin-Madison. She was an AAUW American Fellow, as well as a two-time Zonta Amelia Earhart Fellow. Her research has been supported by the American Astronomical Society and by the National Science Foundation and is currently supported NASA.
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The Moon continues to provide scientific answers – and pose new questions – over 40 years after the last Apollo mission. While the Moon provides the most clear and complete history of impact events in the inner Solar System since its formation ~4.5 billion years (Ga) ago, the timing is not well understood and has been a topic of continued interest and persistent uncertainties. As our closest planetary neighbor, the Moon’s impact record, if properly interpreted, can be used to gain insights into how the Earth has been influenced by impacting events over billions of years.
Lunar impact glasses, pieces of melted lunar regolith created by energetic impacting events, can offer information about the Moon’s impact history. These samples possess the composition of the target material and can be dated by the 40Ar/39Ar (argon) method in order to determine their formation age. Understanding the ages of impact glasses, along with their compositions, allows us to begin to piece together information about the rate of impact events in the inner Solar System and their effects on Earth.
Important questions that can be answered include determining the form of the large-impact distribution with respect to time (e.g., smooth decline versus cataclysmic spike), whether there is periodicity in Earth-Moon cratering history, and the applicability of the lunar record to other planets. Of great interest to astrobiology and the study of the origin of life is the impact flux prior to ~3.7 Ga ago, and specifically, whether or not early life, if it existed on Earth before 4.0 Ga ago, may have been destroyed during these early impact events.
Grand Forks, ND
Zellner, Nicolle, "Impacts in the Earth-Moon System - What, When, and Why?" (2015). Space Studies Colloquium. 68.