Triple-oxygen isotopes of stony micrometeorites by secondary ion mass spectrometry (SIMS): Olivine, basaltic glass and iron oxide matrix effects for sensitive high-mass resolution ion microprobe-stable isotope (SHRIMP-SI).

Rationale: Micrometeorites are extraterrestrial particles smaller than ~2 mm in diameter, most of which melted during atmospheric entry and crystallised or quenched to form 'cosmic spherules'. Their parentage among meteorite groups can be inferred from triple-oxygen isotope compositions, for example, by secondary ion mass spectrometry (SIMS). This method uses sample efficiently, preserving spherules for other investigations.

Micrometeorite collections: a review and their current status.

Micrometeorites are estimated to represent the main part of the present flux of extraterrestrial matter found on the Earth's surface and provide valuable samples to probe the interplanetary medium. Here, we describe large and representative collections of micrometeorites currently available to the scientific community. These include Antarctic collections from surface ice and snow, as well as glacial sediments from the eroded top of nunataks-summits outcropping from the icesheet-and moraines.

The Winchcombe meteorite, a unique and pristine witness from the outer solar system.

Direct links between carbonaceous chondrites and their parent bodies in the solar system are rare. The Winchcombe meteorite is the most accurately recorded carbonaceous chondrite fall. Its pre-atmospheric orbit and cosmic-ray exposure age confirm that it arrived on Earth shortly after ejection from a primitive asteroid.

The Kamil Crater in Egypt.

We report on the detection in southern Egypt of an impact crater 45 meters in diameter with a pristine rayed structure. Such pristine structures are typically observed on atmosphereless rocky or icy planetary bodies in the solar system. This feature and the association with an iron meteorite impactor and shock metamorphism provides a unique picture of small-scale hypervelocity impacts on Earth's crust.