Perseids Dazzle, But Don't Endanger, Astronauts

August 12, 2009

Millions of people might be looking up at the Perseids tonight, but a privileged few will have a chance to look down on the meteor shower. (See Perseids pictures.)

(Also see: "Perseids: 'Last Chance' for Best Meteor Viewing Is Wednesday Night.")

The yearly light show, created when Earth passes through the rocky debris stream of the comet Swift-Tuttle, is also visible to the six astronauts currently aboard the International Space Station, said meteoroid expert Bill Cooke of NASA's Marshall Space Flight Center in Huntsville, Alabama (comet facts).

Like their earthbound counterparts, astronauts can't see the tiny Perseids until the meteoroids hit the atmosphere and burn up, Cooke said.

From space "they would like look streaks or flashes of light, depending on where the meteorites are relative to the spacecraft," he added.

Cook said he isn't sure whether the view is better from space or right here at home, though the lack of cloud interference would suggest astronauts have a better chance at clear views.

Perseids a Danger to Astronauts?

NASA keeps a close eye on the amount of meteoroids that strike Earth's atmosphere. Even so, the Perseids—each typically a fraction of an inch (about a millimeter) wide—pose no threat to the space station, which is armored with thick metal plates, Cooke said.

(Related: "Space Station Escape Options Include Shuttle, Pod.")

Meteor showers in general aren't risky for the space station, Cooke said. For example, the Perseids, which this year have an estimated peak of 80 meteors an hour, elevate Earth's meteor rate only about 5 percent over the average.

But, boasting at least a thousand meteors an hour during their peaks, meteor storms are a different, if rarer, concern.

The next predicted meteor storm should occur on October 8, 2011, during the Draconid meteor storm, Cook said.

Space Shuttle Vulnerable to Meteors

Unlike the space station, NASA's space shuttles are at risk during meteor showers.

That's because the tiny particles are moving at incredibly high speeds—Perseids, for instance, come screaming into Earth's atmosphere at about 37 miles (60 kilometers) a second.

Before every space shuttle launch, Cooke submits a meteor shower forecast to NASA's flight readiness review team.

"That is taken into account in the shuttle risk evaluation, and management decides whether the risk is acceptable or not," Cooke said.

Just in case, NASA tracks nearly all objects that might approach a shuttle. Once in space, a shuttle's only protections are relatively fragile heat tiles and astronauts' fancy maneuvering.

The worst showers are usually avoided altogether, Cooke said. "In general, shuttles do not fly during meteor storms."




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