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Geochemical evidence for a comet shower in the late Eocene
K A Farley1, A Montanari, E M Shoemaker
1Division of Geological and Planetary Sciences, California Institute of Technology, MS 170-25, Pasadena, CA 91125, USA. farley@gps.caltech.edu
Science (New York, N.Y.)
|June 20, 1998
Summary
Earth experienced increased extraterrestrial helium-3, a dust tracer, during the late Eocene. This 2.5-million-year flux coincided with major asteroid impacts, suggesting a brief enhancement in solar system dust and Earth-crossing objects.
Area of Science:
- Geochemistry
- Planetary Science
- Paleoclimatology
Background:
- Pelagic limestones contain extraterrestrial helium-3, a tracer for interplanetary dust.
- Major impact events, like Popigai and Chesapeake Bay craters, occurred approximately 36 million years ago.
- The late Eocene epoch experienced significant geological and astronomical events.
Purpose of the Study:
- To analyze pelagic limestones for extraterrestrial helium-3 concentrations.
- To correlate helium-3 flux with major impact events in Earth's history.
- To investigate the dynamics of Earth-crossing objects and inner solar system dustiness.
Main Methods:
- Geochemical analysis of pelagic limestone samples.
- Isotopic analysis to quantify helium-3 concentrations.
- Chronological dating to establish temporal relationships between events.
Main Results:
- A 2.5-million-year (My) period of enhanced extraterrestrial helium-3 flux was identified in the late Eocene.
- The helium-3 enhancement began ~1 My before and ended ~1.5 My after the Popigai and Chesapeake Bay impact events.
- Increased helium-3 concentrations correlated with large impact events, indicating a simultaneous, brief enhancement of Earth-crossing objects and inner solar system dust.
Conclusions:
- The simultaneous correlation suggests a comet shower triggered by an Oort cloud perturbation.
- Earth-crossing objects and interplanetary dust experienced a transient increase during the late Eocene.
- This event provides evidence for dynamic processes within the solar system affecting Earth.
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