Science. 1987 Oct 2;238(4823):55-8. doi: 10.1126/science.238.4823.55.
The satellites of Jupiter eclipsed each other in 1985, and these events allowed an unusual measurement of the sodium in Io's extended atmosphere. Europa was used as a mirror to look back through the Io atmosphere at the sun. The measured column abundances suggest that the atmosphere is collisionally thin above 700 kilometers and may be collisionally thin to the surface. The sodium radial profile above 700 kilometers resembles a 1500 kelvin exosphere with a surface density near 2 x 10(4) sodium atoms per cubic centimeter, but a complete explanation of the dynamics requires a more complex nonthermal model: the calculated loss rates suggest that the atmosphere is being replaced on a time scale of hours.
木星的卫星在 1985 年相互掩食，这些事件使得对木卫一延伸大气中的钠进行了一次不寻常的测量。木卫二被用作镜子，通过木卫一的大气回望太阳。测量到的柱状丰度表明，在 700 公里以上的大气层是因碰撞而稀薄的，并且可能一直稀薄到表面。在 700 公里以上的钠径向分布类似于 1500 开尔文的日冕，表面密度接近每立方厘米 2 x 10(4)个钠原子，但对动力学的完整解释需要更复杂的非热模型：计算出的损失率表明，大气正在以数小时的时间尺度被替换。
