What are Micrometeorites?
- Micrometeorites are submillimeter extraterrestrial particles
that have survived atmospheric entry
- They are fragments of asteroids, comets, Mars, and our moon.
- They range from unmelted and partially melted particles that
retain much of their original mineralogy to totally melted cosmic
spherules, some of which have lost much of their mass by vaporization.
- They are thought to contribute most of the extraterrestrial
matter accreted by the Earth on ten million-year time scales.
- Approximately 30,000 tons of cosmic dust enters Earth's atmosphere
each year
The Problem:
- Large collections of these materials are difficult to find
due to destruction of particles by weathering and highly variable
concentrating processes in terrestrial environments.
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Cross-sections of micrometeorites.
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The Approach:
- The Antarctic provides a good, "clean" source of
these particles. Micrometeorites that fell on the snow hundreds
of years ago are now frozen in ice layers under the South Pole
station.
- The South Pole water well (SPWW) is a 24-m-diameter subsurface
melt pool. As the pool melts downward, extraterrestrial particles
liberated from the ice remain on the well bottom to form a concentrated,
unbiased deposit of micrometeorites.
- CRREL researchers designed and built a robot to suction and
filter all 50- to 2,000-micrometer particles from the well bottom
without bias for density, magnetic susceptibility, or shape.
Results to Date:
- Researchers collected hundreds of thousands of cosmic spherules
(melted micrometeorites) that fell to earth between 700 to 1100
and 1100 to 1500 AD.
- Initial calculations indicate the flux of the particles onto
the earth's surface is about 2700 tons per year. Thus, about
90% of the influx of cosmic dust evaporates during atmospheric
entry.
- Ongoing work includes determining the compositional distribution
of the spherules and using this information to estimate weathering
rates for spherules collected from deep-sea sediments that are
millions of years old.
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Supported by:
National Science Foundation
Points of Contact:
Susan Taylor,
Research Physical Scientist
Environmental Sciences Branch
ERDC-CRREL, Hanover, NH 03755
(603) 646-4310
Susan.Taylor@erdc.usace.army.mil
James Lever
Mechanical and Military Engineering Branch
ERDC-CRREL, Hanover, NH 03755
(603) 646-4309
James.H.Lever@erdc.usace.army.mil
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