![]() ![]() “These primitive meteorites are like time capsules, containing the most primitive materials in our solar system,” Simon said. The colors represent different mineral compositions accumulated in different environments within the protoplanetary disk from which our solar system formed. X-ray cross section of a CAI from the Allende meteorite. Carbonaceous chondrites, in particular, contain millimeter-sized chondrules and up to centimeter-sized CAIs (calcium-aluminum-rich inclusions) that were once heated to the melting point and later welded together with cold space dust. Meteorites have puzzled space scientists for more than 100 years because they contain minerals that could only form in cold environments, as well as minerals that have been altered by hot environments. Simon, now a researcher with the Astromaterials Research Office at NASA’s Johnson Space Center in Houston, Texas, along with DePaolo and colleagues at Lawrence Livermore National Laboratory (LLNL) and the University of Chicago report their findings in the March 4 issue of the journal Science. DePaolo, UC Berkeley professor of earth and planetary science and director of the Center for Isotope Geochemistry. “Justin showed not only that this dust grain moved around the solar system over quite large distances, but that it had seen the gamut of possible places it could have been in the solar system,” said Donald J. “There are a number of astrophysical models that attempt to explain the dynamics of planet formation in a protoplanetary disk, but they all have to explain the signature we find in this meteorite.” Simon, a former University of California, Berkeley, post-doctoral fellow who led the research. “This has implications for how our solar system and possibly other solar systems formed and how they evolved,” said Justin I. This odyssey is consistent with some theories about how dust grains formed in the early protoplanetary nebula, or proplyd, eventually seeding the formation of planets. The single dust grain they studied appears to have formed in the hot environment of the sun, may have been thrown out of the plane of the solar system to fall back into the asteroid belt, and eventually recirculated back to the sun. The researchers interpret these findings as evidence that dust grains traveled over large distances as the swirling protoplanetary nebula condensed into planets. Scientists have performed a micro-probe analysis of the core and outer layers of a pea-sized piece of a meteorite some 4.57 billion years old to reconstruct the history of its formation, providing the first evidence that dust particles like this one experienced wildly varying environments during the planet-forming years of our solar system. (Justin Simon/NASA) Click image for larger version It would later have followed the dashed line back toward the sun. The Allende meteorite CAI studied here had oxygen isotope signatures suggesting that it later moved outward from the sun, either kicked out of the plane (A) to fall back farther from the sun, or by migrating through the disk (B). ![]() All CAIs (calcium-aluminum-rich inclusions) are dust grains thought to have formed and grown near the protosun in the planet-forming years of the solar system some 4.5 billion years ago.
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