UH Manoa Researcher Publishes Paper in the Journal of Geophysical Research (Planets)

University of Hawaiʻi
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Posted: Feb 28, 2002

Barbara Cohen, Ph.D., a researcher with the UH Manoa Hawai'i Institute of Geophysics and Planetology has co-authored a paper titled "Cataclysmic bombardment throughout the inner solar system 3.9-4.0 Ga," with David Kring, Ph.D. of the University of Arizona Lunar and Planetary Laboratory. The paper appears in today‘s edition of the Journal of Geophysical Research (Planets), a publication of the American Geophysical Union.

According to Cohen and Kring, asteroids produced a bombardment that resurfaced the Moon 3.9 billion years ago. The significance of this conclusion is that the bombardment was so severe that it destroyed older rocks on Earth as well. Which, Kring says, is the reason why the oldest rocks found are less than 3.9 billion years old.

Additionally, they argue, impact-generated hydrothermal systems would have been excellent incubators for pre-biotic chemistry and the early evolution of life, consistent with previous work that shows life originated in hot water systems around or slightly before 3.85 billion years ago.

This same bombardment according to Cohen and Kring, affected the entire inner solar system, producing thousands of impact craters on Mercury, Venus, the Moon and Mars. Most of the craters in the southern hemisphere of Mars may have been produced during this event.

On Earth, at least 22,000 impact craters with diameters greater than 20 kilometers were produced, including about 40 impact basins with diameters of about 1,000 kilometers in diameter. Several impact craters of about 5,000 kilometers were created as well-each one exceeding the dimensions ofAustralia, Europe, Antarctica or South America. The thousands of impacts occurred in a very short period of time, potentially producing globally significant environmental changes at an average rate of once per one hundred years.

Also, the event is recorded in the asteroid belt, as witnessed by the ages of meteoritic fragments that have survived to fall to Earth today.

Cohen will present this paper at the Lunar and Planetary Science Conference in Houston, Texas this March. Dr. Cohen joined the Hawaii Institute of Geophysics and Planetology in 2001 as a postdoctoral researcher. She works with the meteoritics group (http://www.higp.hawaii.edu/meteoritics.html) studying the geochemistry of meteorites and lunar samples in an effort to understand the evolution of planets. She received her Ph.D. in 2000 from the University of Arizona where she studied the ages of lunar meteorites.