Nightly News | December 29, 2011
>>> finally tonight here on earth this weekend is all about new year's eve. but for a team of nasa scientists, the focus will be a quarter of a million miles away . they will be monitoring a pair of spacecraft orbiting the moon, hoping to answer some age-old questions in what's being described as the biggest moon mission since man first landed there more than 40 years ago. here's nbc's george lewis .
>> reporter: millions of years ago, earth may have had not one, but two moons. then, according to theory they collided -- an event known as the big splat. that would explain the irregularities on the present day moon. all the valleys on the side we see. all the mountains on the other side.
>> scientists have not had a good way to track that down yet. this is the going of solving that mystery.
>> zero, and liftoff of the delta ii , journey to the center of the moon.
>> reporter: in september, nasa launched two lunar probes aboard the same rocket. they'll chase each other in orbit around the moon to study it from surface to center. the mission will be run from this control room in paspasadena, california. a critical point comes this weekend when the two craft fire to get into orbit around the moon.
>> this is the big crunch time. this weekend is going to be the time when it comes together or falls apart .
>> that's one small step for man --
>> reporter: for nasa it will be the most intense focus on the moon since the days of the apollo program .
>> it's very challenging but we have done a lot of practicing and we're ready to do that.
>> reporter: former astronaut sally ride will organize thousands of middle school students to tell nasa what pictures the spacecraft should take with their on-board cameras.
>> hopefully it will encourage kids to get more involved in science and engineering.
>> reporter: so this weekend while millions are watching the new year's ball drop in times square , nasa scientists will be watching the other illuminated ball that holds so many mysteries. george lewis , nbc news, pasadena, california.