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Poor man's space probe reveals the Earth's past

Micrometeorites come from asteroids and comets, many as old as our solar system. By finding and comparing rare collections from Antarctica and the mid-Pacific, EU-funded researchers are now able to make guesses about the conditions that Earth experienced throughout its history.
Poor man's space probe reveals the Earth's past
Micrometeorites that have survived descent through the atmosphere provide information on the size, composition and source of cosmic dust landing on Earth. Individual particles range in size from 50 μm to 2 mm. Although they are of interest, it is the collection as a whole that provides the greatest insights.

Scientists working on the EU-funded project MICROMET (New insights on micrometeorites) focused on collections from the island of Kwajalein in the Pacific Ocean and the South Pole. State-of-the-art methods were used to study these rare collections and determine the flux of different micrometeorite types over time.

The samples from the island of Kwajalein comprised particles no larger than droplets of fog on laser-etched polycarbonate membrane filters. These had been collected from the atmosphere by a high volume air sampler. The scientists isolated sized cosmic spherules to be investigated by scanning electron microscopy.

Specifically, all particles greater than 10 μm were investigated and several ones showed surface morphology, internal texture and chemical composition consistent with cosmic spherules. These characteristics allowed scientists to identify most micrometeorites without performing trace element or isotopic analyses.

Similar particles were found in the South Pole water well collections in extremely small numbers. Thanks to a well-calibrated collection method, from this wealth of cosmic spherules, the scientists are now able to determine how the flux of micrometeorites varies over time.

About 90 % of the micrometeorites that fall from space vaporise while passing through the Earth's atmosphere, producing the sparks seen during meteor showers. Of the small portion that made it to the ground, the scientists have collected samples that may not be representative of space dust.

The problem is that the further back in time scientists go, the harder it is to find well-preserved micrometeorites. Nonetheless, the MICROMET project has offered a unique lens into cosmic history.

Related information


Micrometeorites, cosmic dust, Kwajalein, South Pole, cosmic spherules
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