This is a portion of the first 360-degree view of the martian surface taken by Spirit's panoramic camera. Part of the spacecraft can be seen in the lower part of the image. Photo
Scientsts say Mars may have once been a lusher, wetter planet similar to Earth. According to the video, one of ways Mars may have lost its atmosphere is through a process called sputtering. Sputtering occurs when high-energy photons knock away electrons from molecules. The remaining ions could have been flung back into the atmosphere, knocked into other atoms, and some of these may have "sputtered" into space. Over billions of year, this activity could have been one of the reasons Mars lost its atmosphere.