Since the early 1960's, noble gas (i.e. xenon, argon, neon) anomalies in primitive carbonaceous chondrite meteorites have pointed toward the existence of materials, unhomogenized with the rest of the meteorite, containing atoms nucleosynthesized in the interior of different types of stars. In the past decade, such noble gas isotopic anomalies have been tracked to nanometer-sized diamonds, and to micron-sized silicon carbide crystals and graphite particles, in these meteorites. The graphite particles so identified appear with two morphologies, reminescent respectively of the vegetables cauliflower and onions. We focus here on the onions.
For more on this, cf. Dave Dawkin's webnote.
For more on this, cf. a slide I put together for Minh's presentation in Spring 1999.
Related Links: Invited overview presented at the 1998 AAPT meeting in New Orleans, and an Image of the Month Note on high-resolution studies of these spheres.