What was the Sutter's Mill meteorite?
Sutter's Mill is a rare carbonaceous chondrite that fell in California on 22 April 2012, recovered partly thanks to weather radar, near the site of the 1848 gold discovery.
On the morning of 22 April 2012, a bright fireball crossed the skies over Nevada and California, accompanied by sonic booms. It was seen by many people and recorded by cameras.
Radar help. Weather radars detected falling fragments, pinpointing where meteorites came down. This helped searchers find the first pieces within days, near Coloma in California, close to Sutter's Mill, where gold was discovered in 1848, starting the California Gold Rush.
Recovery. About 90 pieces were recovered, totalling about 1 kilogram, many small. Some were collected quickly before rain fell, preserving their delicate minerals.
What it is. Sutter's Mill is a CM carbonaceous chondrite, a breccia containing fragments altered to different degrees and some unusual components. It contains water-bearing minerals and organic compounds. Because some pieces were collected before heavy rain, they were among the freshest CM samples available.
Orbit. Camera data allowed scientists to calculate its orbit, one of only a few known for CM chondrites. It came from the asteroid belt on an orbit reaching into the region of Jupiter-family comets.
Size. The meteoroid was estimated to be about 2 to 4 metres across and to have weighed tens of tonnes, but only a tiny fraction survived.
Importance. Sutter's Mill showed the value of rapid recovery, the use of radar and the cooperation between scientists and the public, and contributed to understanding CM chondrite parent bodies.