火卫二: 娇小的火星卫星

火卫二: 娇小的火星卫星

Small Moon Deimos
Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA

Explanation: Mars has two tiny moons, Phobos and Deimos, named for the figures in Greek mythology Fear and Panic. Detailed surface views of smaller moon Deimos are shown in both these panels. The images were taken in 2009, by the HiRISE camera on board the Mars Reconnaissance Orbiter spacecraft, NASA’s long-lived interplanetary internet satellite. The outermost of the two Martian moons, Deimos is one of the smallest known moons in the Solar System, measuring only about 15 kilometers across. Both Martian moons were discovered in 1877 by Asaph Hall, an American astronomer working at the US Naval Observatory in Washington D.C. But their existence was postulated around 1610 by Johannes Kepler, the astronomer who derived the laws of planetary motion. In this case, Kepler’s prediction was not based on scientific principles, but his writings and ideas were so influential that the two Martian moons are discussed in works of fiction such as Jonathan Swift‘s Gulliver’s Travels, written in 1726, over 150 years before their discovery.

Tomorrow’s picture: large galaxy Andromeda

火卫二: 娇小的火星卫星
影响提供与版权: HiRISE, MRO, LPL (U. Arizona), NASA

说明: 火星有2颗娇小的卫星，它们分别是以希腊神话人物“恐惧”和”恐慌”为名的火卫一（Phobos）与火卫二（Deimos）。上面这2个图板，呈现了较小的卫星火卫二的细致表面景观。这些影像，是由美国国家航空航天局长期监测火星的火星勘测轨道飞行器上的HiRISE相机摄于2009年。宽约15公里火卫二，是2颗火星卫星中最外侧的那颗，也是太阳系已知的卫星中最小的一个。这2颗火星卫星，都是由在美国华盛顿海军观测站工作的天文学家霍耳发现于1877年，但它们的存在的假设，则是由发现行星运动定律的天文学家开普勒在1610年左右提出的。开普勒的假设并无科学根据，但他的著作和想法却影响深远，以至于约翰逊‧斯威夫特所写的《格列佛游记》，就曾讨论这2颗火星卫星。这本小说写于1726年，比这2颗卫星真正的发现要超前150多年。

明日的图片: large galaxy Andromeda