Rare, fast meteorite took roundabout path

UC DAVIS (US) — The minivan-size meteorite that exploded over California in April was among the fastest, rarest meteorites known to have hit the Earth.

Researchers say the meteorite is the rarest type known to have hit the Earth—a carbonaceous chondrite composed of cosmic dust and presolar materials that helped form the planets of the solar system.

The meteorite, which fell over Northern California on April 22, formed about 4.5 billion years ago and was knocked off its parent body, which may have been an asteroid or a Jupiter-family comet, roughly 50,000 years ago. That began its journey to Sutter’s Mill, the gold discovery site that sparked the California Gold Rush.


Lucy is a piece of the Sutter’s Mill Meteorite, which fell over El Dorado County in Northern California on April 22, 2012. (Credit: UC Davis)


As it flew toward Earth, it traveled an odd course through the solar system, flying from an orbit close to Jupiter toward the sun, passing by Mercury and Venus, and then flying out to hit Earth.

The high-speed, minivan-sized meteorite entered the atmosphere at about 64,000 miles per hour—the fastest, “most energetic” reported meteorite that’s fallen since 2008, when an asteroid fell over Sudan.

“If this were a much bigger object, it could have been a disaster,” says co-author Qing-zhu Yin, professor of geology at University of California, Davis. “This is a happy story in this case.”

Before entering Earth’s atmosphere, the meteorite is estimated to have weighed roughly 100,000 pounds. Most of that mass burned away when the meteorite exploded.

Scientists and private collectors have recovered about 2 pounds remaining. Pieces of the meteorite were found on residents’ driveways and in local forests and parks in the El Dorado county towns of Coloma and Lotus.

When the meteorite fell, Yin searched for and collected pieces of the fallen meteorite with students and volunteers and also led a 35-member subgroup of international researchers to study and share information about the meteorite’s mineralogy, internal textures, chemical and isotopic compositions, and magnetic properties.

Meteorites like Sutter’s Mill are thought to have delivered oceans of water to the Earth early in its history. Using neutron-computed tomography, researchers helped identify where hydrogen, and therefore water-rich fragments, resides in the meteorite without breaking it open.

For the first time, the Doppler weather radar network helped track the falling carbonaceous chondrite meteorite pieces, aiding scientists in the quick recovery of them. Yin expects that the weather radar data in the public domain could greatly enhance and benefit future meteorite recoveries on land.

“For me, the fun of this scientific gold rush is really just beginning,” says Yin. “This first report based on the initial findings provides a platform to propel us into more detailed research.

“Scientists are still finding new and exciting things in Murchison, a similar type of meteorite to Sutter’s Mill, which fell in Victoria, Australia, in 1969, the same year Apollo astronauts Neil Armstrong and Buzz Aldrin returned the first lunar samples to the Earth. We will learn a lot more with Sutter’s Mill.”

The team presents these and other findings in a study published Friday, December 21, in the journal Science. The 70-member team includes researchers from UC Davis, along with scientists from the SETI Institute, NASA, and other institutions.

Source: UC Davis