NASA astronaut Greg Chamitoff, Expedition 17 flight engineer, smiles for a photo near a chess board in the Harmony node of the International Space Station, July 19, 2008.

It's the ultimate showdown in space … at chess.

Astronaut GregoryChamitoff is taking on the world in a galactic chess match from his perchaboard the International Space Station (ISS).

Chamitoff, a NASA flight engineer, began the chess matchSept. 29, playing against the public on Earth, led by the kindergarten throughthird grade U.S. Chess Championship Team and its chess club teammates from StevensonElementary School in Bellevue, Wash. The astronaut is set to talk live to hisstudent adversaries Thursday at 2:05 p.m. ET (1805 GMT).

"I started off playing Mission Control and nowI’m playing against the school kids," Chamitoff told SPACE.comthis week. "They’re from Bellevue, Washington, and they're kind ofleading the charge here on an Earth versus space chess game, which I think isgreat."

Chamitoff and his adversaries make about one move a day onweekdays, as long as the space station schedule allows. When it's Earth's turn,the students choose up to four possible moves, and then the public votes onwhich move to send to orbit. Anyone can vote via the Web site:www.uschess.org/nasa2008.

"I think it’s a really good game for kids to playto help them learn how to think in ways that are very important for math andscience," Chamitoff said during the on-orbit interview. "It's a goodgame to stimulate kids’ thinking and it’s been a lot of fun to playwith them."

The online voting is being hosted by the U.S. ChessFederation (UCSF).

"We hope the excitement and interest this gamegenerates will inspire students to become interested in chess," said USCFexecutive director Bill Hall. "Chess is a valuable tool to lead studentsto become interested in math and to develop critical thinking skills,objectives we focus on in our work with schools nationwide."

Chamitoff launchedtoward the station aboard NASA’s space shuttle Discoveryon May 31. A lifelong chess aficionado, he brought a set up to space with him,and added Velcro to the pieces so they wouldn't float away in weightlessness.

During the four-and-a-half months he's been in Earth orbitduring the station’s Expedition 17 mission, Chamitoff has been playingchess games against space station mission control centers around the world. Sofar, he is undefeated.

As for who will win the ultimate contest between Earth andspace, time will tell.

"It's sort of still at the beginning, so it’shard at this point to tell who’s ahead, but we’ll see,"Chamitoff said this week. "Hopefully, we’ll have a conclusion herebefore it’s time for me to have to leave."

Chamitoff has spent much of his time activating the spacestation’s new Japanese laboratory Kibo, which arrived with him in Juneaboard the shuttle Discovery. He will join the station’s new Expedition18 when two new crew members launch Oct. 12 aboard a Russian Soyuzspacecraft. Chamitoff is due to return home aboard the STS-126 space shuttlemission in late November.