14 DAY TRIAL // An international collaboration between scientists from the United States, Germany and Japan concluded its investigation recently with the discovery of a new mineral compound of manganese silicide, named Brownleeite, which probably originated from a periodical comet that passes through the inner regions of the solar system every 5 years. The 26P/Grigg-Skjellerup comet, the most likely source of the mineral, was originally discovered in 1902.
"When I saw this mineral for the first time, I immediately knew this was something no one had seen before. But it took several more months to obtain conclusive data because these mineral grains were only 1/10,000 of an inch in size", said Keiko Nakamura-Messenger from NASA's Johnson Space Center, leader of the investigation team.
Scott Messenger, also from the Johnson Space Center, had previously predicted the optimal time of the year when interplanetary dust particles (IPDs) coming from 26P/Grigg-Skejellerup could be collected from Earth's stratosphere. Following this prediction, NASA decided to initiate a dust collection expedition into the stratosphere with the help of an ER-2 high altitude aircraft from NASA's Dryden Flight Research Center at Edwards Air Force Base.
In April 2003, following the predictions of the two researchers, particles of dust coming from this specific comet were collected, some of which containing the new mineral, which was later studied with the new transmission electron microscope installed at the Johnson Space Center in 2005.
"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. 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", said Lindsay Keller, part of the research team at Johnson.
NASA had been collecting IDPs at high altitudes ever since the early 1980s, although the origin of the vast majority of samples has been relatively hard to establish. According to estimates, some 40,000 tons of interplanetary dust rains down on Earth every year, most of it coming from comets and asteroids. Because such objects are remnants of the material that created the solar system more than 4.6 billion years ago, it can be used to study the original building blocks of the planets and other objects of the system.
The International Mineralogical Association is currently holding a record of 4,324 identified minerals and decided that the newly discovered one is to be named after Donald E. Brownlee of the University of Washington, who initiated the IDP research.