Peter Jenniskens

Meteor astronomer, SETI Institute and nasa Ames Research Center

Mountain View, Calif.

Meteors are windows to our past and our future. When a stream of rocky material hits Earth's atmosphere and we observe what looks like shooting stars, that is called a meteor shower. The sand grains and pebbles of a meteor shower form a trail of crumbs to their body of origin: usually a comet, which is an icy leftover from the formation of our solar system. Meteor showers betray the presence of yet undiscovered comets that may one day strike us.

Only now are some of those comets being discovered in near-Earth object surveys. They periodically break, creating many of the meteor showers we see on Earth.

To map out those meteor showers, we are doing surveillance of the night sky. We use 60 video security cameras distributed over three locations. Those are at Lick Observatory, Fremont Peak Observatory and Sunnyvale, all near the San Francisco Bay Area. Instead of watching out for burglars, we look for meteors. Each meteor seen from two or three perspectives can be triangulated to measure its trajectory and speed in the atmosphere. Last year we measured 47,000. Showers are meteors arriving from the same direction. We have seen showers come into focus that I've never heard of before.

Just one was a bright fireball that penetrated deep enough in the atmosphere for something to have survived. These surviving space rocks that hit Earth are called meteorites.

My most exciting adventure hunting meteorites was in 2008. For the first time, a small asteroid was spotted in space heading right toward us. (An asteroid is like a comet but has lost its ice and some or all of its carbon compounds. It holds together better.) This object was about four meters in size. It entered over Sudan and broke into pieces. Most of them went to dust, but a few scraps survived. With students at the University of Khartoum, we searched the desert and ultimately found about 600 meteorites. To our surprise, it was a mixed bag of at least 10 different meteor types. This asteroid was a little world unto itself.

If you would like to participate in our meteor-shower surveillance, you can use a camera hooked up to your PC. You just have to find a friend who lives between 30 and 90 miles from your location so that you can triangulate the tracks. That project is online at There are meteors every night, and every night can bring you surprises, so keep your eyes open.