TINY IRON SPHERES ARE OLDEST FOSSILIZED SPACE DUST
Japanese researchers have discovered the first micrometeorites known to land on Earth. No larger than droplets of fog, the spherical, iron-rich particles arrived 240 million years ago, 50 million years before the previous record-holding space dust.
“These are the the oldest fossil micrometeorites I’ve ever heard of, and the preservation is fantastic. They look exactly like their modern equivalents,” said geologist Susan Taylor of the U.S. Army Corps of engineers, who wasn’t involved in the work, published in Geology May 4. “If we can figure out where these things came from, they can help inform us about the history of the solar system.”
Meteorites and micrometeorites come from comets and asteroids, many as old as the Solar System itself. Although larger space rocks are more popular, they're exceedingly rare. The overwhelming majority of extraterrestrial material is dust, of which some 30,000 tons falls from space each year..
About 90 percent vaporizes while passing through the Earth’s atmosphere, producing the sparks seen during meteor showers. Of what makes it to the ground, a small fraction gets stuck in mud, clay and other sediment that becomes fossilized.