Alien Mineral From Comet Dust Found in Earth's Atmosphere
Astoundingly, about 40,000 tons of dust particles fall to Earth each year which originates from space "leftovers," mostly from disintegrating comets and asteroid collisions. Scientists are very interested in this dust because of its pristine nature –it is made of the original building blocks of the solar system. Some of that dust also resides in Earth's atmosphere, and for years, NASA has routinely collected cosmic and interplanetary dust from Earth's stratosphere with high-altitude research aircraft. NASA announced today that a new mineral has been found from this atmospheric research, in material that likely came from a comet.
Usually, any unique dust particles found in the atmosphere are difficult to trace as far as their origin, and whether it came from a comet or other space debris. But this new mineral, a manganese silicide which has been named "Brownleeite," was discovered within an interplanetary dust particle, or IDP, that appears to have originated from comet 26P/Grigg-Skjellerup. The comet was discovered in 1902 and reappears every 5 years. A new method of collecting IDPs was suggested by space scientist Scott Messenger, from Johnson Space Center. He predicted comet 26P/Grigg-Skjellerup was a source of dust grains that could be captured in Earth's stratosphere at a specific time of the year.
In response to his prediction, NASA performed stratospheric dust collections, using an ER-2 high-altitude aircraft flown from NASA's Dryden Flight Research Center at Edwards Air Force Base, Calif. The aircraft collected IDPs from this particular comet stream in April 2003. The new mineral was found in one of the particles. To determine the mineral's origin and examine other dust materials, a powerful new transmission electron microscope was installed in 2005 at Johnson.
"When I saw this mineral for the first time, I immediately knew this was something no one had seen before," said Keiko Nakamura-Messenger, also from Johnson Space Center. "But it took several more months to obtain conclusive data because these mineral grains were only 1/10,000 of an inch in size."
"Because of their exceedingly tiny size, we had to use state-of-the-art nano-analysis techniques in the microscope to measure the chemical composition and crystal structure of Keiko's new mineral," said Lindsay Keller, Johnson space scientist and a co-discoverer of the new mineral. "This is a highly unusual material that has not been predicted either to be a cometary component or to have formed by condensation in the solar nebula."
The mineral was surrounded by multiple layers of other minerals that also have been reported only in extraterrestrial rocks. There have been 4,324 minerals identified by the International Mineralogical Association, or IMA. This find adds one more mineral to that list.
Brownleeite, is named after Donald E. Brownlee, professor of astronomy at the University of Washington, Seattle. Brownlee founded the field of IDP research. The understanding of the early solar system established from IDP studies would not exist without his efforts. Brownlee also is the principal investigator of NASA's Stardust mission.
