Stardust Mysteries

"You can't have life until you have a planet, so to hold a meteorite -- something that was around before there was a planet -- is totally awesome," says Harold C. Connolly Jr., one of two petrologists, or geologists who specialize in rocks, at Kingsborough Community College's Department of Physical Sciences.

Colleague Michael K. Weisberg says cradling the most primitive type of meteorite, a chondrite, "is like holding the sun, minus the gasses, and they also have organics, which are the building blocks of life."

Each meteorite tells an extraterrestrial story, and many emerged in July at the 73rd annual meeting of the Meteoritical Society in Manhattan, which Connolly and Weisberg organized under the auspices of the City University of New York and the American Museum of Natural History. The meeting drew some 500 scientists from around the world.

Presentations delved into Martian meteorites, planet formation, the origin of organic molecules on meteoroids, the structure of craters and the relation between asteroids and meteors, among other topics.

Sean Solomon of the Carnegie Institution of Washington delivered the keynote lecture. As principal investigator of Messenger, NASA's current mission to Mercury, he described how the first craft to visit the innermost planet since the 1970s whipped by Mercury three times since its launch in August 2004; it goes into orbit in March 2011. Messenger has already detected ion emissions from Mercury's atmosphere, expanded knowledge about the planet's magnetic field and proved that, at least in the past, Mercury had volcanic activity.

Connolly and Weisberg, colleagues for 30 years, work not only with meteorites found on Earth, but also with materials plucked from the cosmos.

Weisberg was on the international team that analyzed dust from NASA's Stardust Mission; launched in 1999, Stardust returned with samples of the comet Wild 2 in 2006.  "We've had particles to study in our laboratories for four years. It turns out that a lot of the particles in the comet are similar to what we find in chondrites, including the chondrules and calcium-aluminum-rich inclusions," Weisberg says.

In other words, the dust and rock formed near our sun, traveled to the deep freeze beyond Neptune, and then mated with ice to become comets. This was a stunning finding, since scientists had thought that the dust and rocks of comets came from other stars and predated our own solar system. (Stardust did retrieve some mineral grains from other stars, which were identified by their unusual isotopes.)

Also, looking beyond Earth, Connolly joined a science team that is competing with two other groups for a $650 million prize -- a NASA mission. If selected, their OSIRIS-REx probe would visit asteroid 1999 RQ36, which NASA's Goddard Space Flight Center calls "a chunk of rock and dust about 1,900 feet in diameter."  It would orbit RQ36 for a year, test ways of deflecting it from a possible impact with Earth in 2170, then extend a robotic arm and scoop up a pristine sample of its surface to return to Earth in 2022.

For extraterrestrial petrologists like Connolly and Weisberg, that's the real prize.

They flash across the sky, shooting stars that have fired the imagination ever since there were people. Meteorites, rocks that fall from the heavens -- messengers of the gods, portents of good fortune or cataclysms to come, depending on the culture. But in reality, they're so much more -- the very stuff the Solar System is made of.