Mars Atmosphere and Volatile Evolution (MAVEN) is a space probe designed to study the Martian atmosphere while orbiting Mars. Mission goals include determining how the Martian atmosphere and water, presumed to have once been substantial, were lost over time.

MAVEN was successfully launched aboard an Atlas V launch vehicle at the beginning of the first launch window on November 18, 2013. Following the first engine burn of the Centaur second stage, the vehicle coasted in low-Earth orbit for 27 minutes before a second Centaur burn of five minutes to insert it into a heliocentric Mars transit orbit.

The plan is for MAVEN to be inserted into an areocentric elliptic orbit upon reaching Mars, 6,200 km (3,900 mi) by 150 km (93 mi) above the planet's surface, on September 22, 2014.The principal investigator for the spacecraft is Bruce Jakosky of the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder.

http://en.wikipedia.org/wiki/MAVEN