The first fragments of the California-Nevada daylight fireball were recovered Tuesday by Robert Ward, one of the most prolific meteorite hunters in the world. Ward lives in Arizona and has been fascinated by meteorites since witnessing a fireball as a boy in 1986. In the late 1980s he found his first meteorite and today his collection of personal finds includes space rocks from almost 500 localities. You can read more about Ward in this story by fellow meteorite hunter David Gheesling.
Ward and other meteorite hunters would be looking for black stones that stand out from the native rocks. Freshly-fallen meteorites are coated in a thin layer of black, melted rock called fusion crust from heat generated by friction and pressure with the air as they fall to Earth. He may also be using a metal detector as many meteorites contain specks of iron-nickel metal.
After a preliminary assessment, it appears that the California fall is a particularly rare type of meteorite called a CM carbonaceous chondrite. I know that’s a mouthful so bear with me. CMs are rich in carbon and contain water and complex organic compounds including amino acids. Here on Earth, amino acids are used by our cells to build the proteins that make and power our bodies.
One of the most famous CM chondrites (KON-drites) fell on September 28, 1969 near the town of Murchison, Australia. Some 254 lbs. or 100 kg of specimens were recovered from the Murchison fall.
Local people who picked up the pieces right after the fall said the meteorite smelled like methanol (a form of alcohol), a sure sign that it contained organic compounds.
Bill Cooke of the Meteoroid Environments Office at NASA’s Marshall Space Flight Center in Huntsville, Ala., estimates that the meteoroid was about the size of a minivan and weighed in at around 154,300 pounds before it struck the atmosphere. At the time of disintegration it released energy equivalent to a 5-kiloton explosion.
While most meteorites trace their origins to asteroids, CM chondrites like the California fall might be fragments of a comet, which are rich in water and have similar compositions.
At the center of all comets is a several-mile-diameter, irregularly shaped “nucleus” made of ice and dust. And it’s as black as a charcoal briquette. Everything we associate with a comet – the glowing head and bright tail – are created when heat and light from the sun boil off and illuminate ice, dust and other rocky materials from the nucleus.
Comets are fragile and known to regularly break into pieces under the stress of solar heat and gravity. CM chondrites like the California fall are also nearly black inside and out. Perhaps, just perhaps, they’re pieces from a long ago shattered comet.
There’s been some talk that the meteor – especially given its possible connection to a comet – may be related to the Lyrid meteor shower that peaked this weekend. It’s not. The fireball came from the east in roughly the direction of the sun; the Lyrid radiant was high in the western sky at the time of the fall.