The asteroids that orbit close to Earth are packed with clues on, among other things, the origins of life. But few of those details are actually known.

That's where a team of scientists based at Northern Arizona University comes in.

David Trilling, an assistant professor of physics and astronomy at NAU, and his associates are using asteroid data gathered from the Spitzer Space Telescope to answer the simple question, "What's out there?"

They're finding that the near-Earth asteroids are actually a diverse bunch, and that's key.

Trilling is the lead author of a paper in the September issue of Astronomical Journal covering the first 100 sets of details, culled from the asteroids using infrared technology. The observations reveal brightness, size -- the ones he's studying are about the size of the Skydome, Trilling said -- how much light they reflect and their compositional profiles.

Some are just rocks. But some contain metal, or water, or organic molecules. And if and when those asteroids hit Earth, what's on board can significantly alter the environment for better or for worse.

The near-Earth asteroids a relatively small group -- most of the asteroids in the solar system are far-Earth, beyond the orbit of Mars -- but important because of the potential consequences of their proximity.

"You move to Flagstaff (and) the first people you meet are the people who live to your left and to your right, not the people who live across town," Trilling said.

MOST KNOWLEDGE WILL COME FROM NAU

There are about 7,000 known near-Earth asteroids, but before the NAU project, the physical properties of only 70 had been measured. The rest were known essentially as points of light.

The NAU-led team has recorded the properties of about 300 by now and hopes to have studied 700 by next summer, making much of the known data a product of NAU research.

Near-Earth asteroids are what they sound like: bodies close to Earth, sometimes close enough to buzz or crash into the planet. They're closer than Venus or Mars, Earth's planetary neighbors, and sometimes even closer than the Moon.

Cristina Thomas, an NAU post-doctoral scholar of physics and astronomy working with Trilling, is one of the five NAU-based researchers on the project. About 15 more are scattered throughout Europe and the United States.

Thomas said these asteroids didn't start in near-Earth space. They moved there over long periods of time from locations all over the solar system.

"Unfortunately they don't come with a postmark, so a lot of research goes into determining which objects come from which parts of the solar system. If we can trace them back to where they started, we can put together the distribution of materials and temperatures in our solar system now and throughout its history," she said. "Knowing the history of the solar system isn't just an academic exercise. (It) helps us understand the Earth's past, present and future."

Trilling said small asteroids land unnoticed all the time and don't cause much damage -- they land as a pile of rocks or burn up in the atmosphere. Medium-sized ones like the one that created Meteor Crater would have immediate consequences -- if it hit now, Winslow would be seriously affected, but people in Flagstaff wouldn't die and people in Phoenix might not even feel the bump, he said. The big ones, though rare, can be catastrophic, in a kill-off-the-dinosaurs way.

The impact is also different depending on what the asteroid contains. If it's rich in metal -- like the solid-iron meteorite that made Meteor Crater -- it makes a much bigger bang. If it's rich with water or organic molecules, it'd still leave a mark, but it would also deposit the building blocks of life.

"I think it's a really neat sort of karmic arc that these rocks can both contribute to the origin of life but can also contribute to the eradication of life," Trilling said.

WHAT, THEN WHY

In addition to explaining the evolution of the solar system, origins of life and predicting the results of impact, the makeup of asteroids is also important knowledge for space travelers.

Now Trilling wants to know why these asteroids are so diverse.

His team began collecting data last summer and has one year left on the study before asking for an extension.

"We've learned a lot, and of course when you learn things then you learn new questions to ask, so I hope we'll be able to continue this," he said.

Hillary Davis can be reached at hdavis@azdailysun.com or 556-2261.

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