Mars Pathfinder was the first spacecraft to land on the red planet since the two Viking landers in 1976. It was launched on December 4, 1996, and reached Mars on July 4, 1997. The spacecraft entered the planet's thin atmosphere, was slowed by a parachute and then rockets, and landed by bouncing on inflated airbags. Its protective aeroshell then unfolded to provide three flat platforms, one of which held the Sojourner rover. Sojourner traveled down a ramp, studied composition with an X-ray spectrometer.