Diamonds in meteorites...

[Rick]

Shock compression research shows hexagonal diamond could serve as meteor impact marker

In 1967, a hexagonal form of diamond, later named lonsdaleite, was identified for the first time inside fragments of the Canyon Diablo meteorite, the asteroid that created the Barringer Crater in Arizona.

Since then, occurrences of lonsdaleite and nanometer-sized diamonds have been speculated to serve as a marker for meteorite impacts, having also been connected to the Tunguska explosion in Russia, the Ries crater in Germany, the Younger Dryas event in sites across North America and more.

It has been hypothesized that lonsdaleite forms when graphite-bearing meteors strike the Earth. The violent impact generates incredible heat and pressure, transforming the graphite into diamond while retaining the graphite's original hexagonal structure. However, despite numerous theoretical and limited experimental studies, crucial questions have remained unresolved for short-time high-pressure environments relevant to meteor impacts, particularly the structural state immediately after the shock transit, the timescales involved and the influence of crystalline orientation.

In a new paper published today by Nature Communications, a team of researchers, including scientists from Lawrence Livermore National Laboratory (LLNL), provides new insight into the process of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics of the phase change.

More from Lawrence Livermore Labs.

[Rick]

Cosmochemists find evidence of rare element in early solar system

UChicago scientists have discovered evidence in a meteorite that a rare element, curium, was present during the formation of the solar system. The finding ends a 35-year-old debate on its possible presence in the early solar system, and plays a crucial role in reassessing models of stellar evolution and synthesis of elements in stars. Details of the discovery appear in the March 4 edition of Science Advances.

"Curium is an elusive element. It is one of the heaviest-known elements, yet it does not occur naturally because all of its isotopes are radioactive and decay rapidly on a geological time scale," said the study's lead author, François Tissot, PhD'15, now a postdoctoral fellow at the Massachusetts Institute of Technology.

More from the University of Chicago

[Rick]

NASA Scientists Find Diamonds and Other Treasures in Gold Rush Meteorite (an older story on the same theme...)

Researchers digging deeper into the origins of the Sutter's Mill meteorite, which fell in California's Gold Country in 2012, found diamonds and other "treasures" that provide important new insight into the early days of our solar system. They report their results in thirteen papers in the November issue of Meteoritics & Planetary Science.

"Sutter's Mill gives us a glimpse of what future NASA spacecraft may find when they bring back samples from a primitive asteroid," said consortium lead Peter Jenniskens of the SETI Institute in Mountain View, California, at NASA's Ames Research Center in Moffett Field, California. "From what falls naturally to the ground, much does not survive the violent collision with Earth's atmosphere."

More from NASA.