It's NASA's 18th annual great moon buggy race in Huntsville, Alabama.
Nearly 90 high school and college engineering student teams are competing.
The teams had to build their own version of a lunar rover and race it through an obstacle course.
The vehicles -with names like luna currus ( that's moon cariot in latin) - have to be human powered, and carry two people...and to win...have the fastest time over an obstacle course.
The competition features students from 22 states, Puerto Rico and six other nations.
NASA's original lunar vehicle made its first excursion on the moon's surface in 1971.
The competition is being held at the U.S. Space & Rocket Center. It runs through tomorrow .
Hopefully, all the machines will be put back together by that time.