The Mars Cube One, or MarCO, CubeSats have a temporary but critical objective: they will serve as real time communications liaisons between the InSight lander and the scientists at Jet Propulsion Laboratory. This task of relaying real-time information has traditionally been the job of the Mars orbiter Odyssey. However, the alignment of Odyssey doesn't sync up with InSight's landing coordinates. Instead, MarCo A and B will relay data during the lander's descent and landing. After that, the Mars Reconnaissance Orbiter will take over communications with Earth, and the CubeSats' mission will be complete.