火星大气与挥发物演化任务，简称MAVEN（Mars Atmosphere and Volatile Evolution Mission）是美国国家航空航天局火星侦察兵计划的一部分，由一个轨道卫星观测火星大气，尤其是测量大气逃逸速率，进而研究火星气候历史。
The clues are adding up to give a picture of a distant Martian past, when the planet had a thick atmosphere that was warm enough for water to stream on the surface. But now the water’s gone, and the atmosphere is so thin that any water would boil away. In fact, the vestigial atmosphere is still slowly dissipating into space. Why? Well, researchers believe that solar wind and radiation is behind the theft, and they’re planning a mission to find out, called MAVEN: Mars Atmosphere and Volatile Evolution Mission The solar wind is a stream of electrically-charged particles. It continuously flows from the sun out into space. We on Earth have protection in the form of a magnetic shield. But that shield is dead on Mars, gone for billions of years. Instead, the solar wind and the sun’s UV radiation give an electric charge to atoms and particles in Mars outer atmosphere. Then electric fields generated by the solar wind sweep away the charged particles. So the atmosphere becomes even thinner. Maven is scheduled to reach the red planet in 2014. Which will allow researchers to measure how much water and atmosphere are gone with the solar wind. —Cynthia Graber
诸多线索综合起来为我们描绘出一幅画面：那是火星遥远的过去，那时的火星还有着一层厚厚的大气层，令这颗星球温热暖和，从而使水能够在火星表面流淌。但如今，地表的水消失不见，而大气层变得如此之薄，任何水分都会蒸发掉。 事实上，残余的大气层仍在缓慢地消散于太空中。为什么呢？唔，研究人员认为太阳风和辐射是“幕后黑手”，他们打算开展一项任务来找出原因何在。这项任务名为MAVEN——火星大气与挥发物演化任务（Mars Atmosphere and Volatile Evolution Mission）。 太阳风是一股带点粒子流。它由太阳不断发出，流入太空中。我们在地球上受到磁场屏蔽的保护，而火星的电磁场早在亿万年前就已经消失了。 这样，太阳风和太阳的紫外辐射赋予火星外层大气中的原子和粒子一个电荷，然后由太阳风产生的电场将带电粒子一扫而空。因此，火星的大气层变得越来越薄。 预计Maven将于2014年抵达这颗红色星球。届时，研究人员将能测出究竟有多少水和大气随太阳风而逝。