Asteroid Crisis — Kevin J. Anderson; Rebecca Moesta

From two New York Times�"bestselling authors, a group of young people go to the International Space Station on a mission to save earth from alien invasion.
 
It was supposed to be just an educational field trip to the Challenger Learning Center, but JJ Wren and her friends find themselves transported into the future, to a time when the human race is under siege from deadly alien invaders. The evil Kylarn have shifted the orbits of three asteroids, sending them tumbling toward Earth -- and a direct impact will have devastating consequences. With instructions and skills they learn from the mysterious Commander Zota, JJ and her fellow Star Challengers embark on a mission to the asteroids before it's too late, hoping to divert the giant rocks before they strike Earth. But the alien invaders aren't the only enemy -- the Star Challengers have to worry about human traitors, too!
 
Praise for The Star Challengers series:
 
“The Star Challengers with their Commander Zota ‘boldly go into the future' to bring great science fiction adventures to readers. . . . What a wonderful way to expand young imaginations.” -- Leonard Nimoy
 
“Space exploration is an adventure that benefits all mankind. The Star Challenger books inspire young readers with that sense of adventure, introducing them to a universe of exciting possibilities.” -- Buzz Aldrin
 
“The Star Challenger adventure stories could help to inspire a whole new generation of young women to value science and seek careers in high-tech, engineering and space exploration.” -- Sally Ride, astronaut