Prometheus 土卫十六(中英)

Prometheus is the third of Saturn¹'s known satellites:

　　orbit:    139,350 km from Saturn

　　diameter: 91 km (145 x 85 x 62)

　　mass:     2.7e17 kg

　　Prometheus was a Titan who stole fire from Olympus and gave it to humankind, for which Zeus punished him horribly; son of Iapetus; brother of Atlas² and Epimetheus. "Prometheus" is Greek for "foresight³".

　　Discovered by S. Collins and others in 1980 from Voyager photos.

　　Prometheus is the inner shepherd satellite of the F ring.

　　Prometheus has a number of ridges⁴ and valleys and several craters⁵ about 20 km in diameter but appears to be less cratered⁶ than the neighboring moons Pandora, Janus and Epimetheus.

　　From their very low densities⁷ and relatively⁸ high albedos, it seems likely that Prometheus, Pandora, Janus and Epimetheus are very porous⁹ icy bodies. (Note, however, that there is a lot of uncertainty¹⁰ in these values.)

　　The 1995/6 Saturn Ring Plane Crossing observations found that Prometheus was lagging by 20 degrees from where it should have been based on Voyager 1981 data. This is much more than can be explained by observational error. It is possible that Prometheus's orbit was changed by a recent encounter with the F ring, or it may have a small companion moon sharing its orbit.

　　Prometheus 是距土星第三近卫星：

　　公转轨道：距土星 139,350 千米

　　卫星直径：91 千米（145×85×62）

　　质量：2.7e17 千克

　　Prometheus（普罗米修斯）是一位从奥林匹斯山偷走火种并把它带到人间的巨人。就因为这，宙斯用残忍的手段来惩罚他；他是Iapetus的儿子，Atlas和Epimetheus的兄弟。它在希腊语中意为“深思远虑”

　　它是被S. Collins和其他一些人于1980年从旅行者号传回的照片中发现的。

　　土卫十六是F光环中的一颗牧羊卫星。

　　土卫十六有许多山脉和山谷和一些直径为20千米左右的陨石坑。但是看上去它的陨石坑比周围邻近的卫星（土卫十七，土卫十和土卫十一）少。

　　从它们很低的密度和相对较高的反照率来看，土卫十六，土卫十七，土卫十和土卫十一可能是多孔的冰质天体。（注解：对于这些数值还有很多不能确定。）

　　根据1995年6月的土星光环平面交叉线观察发现，土卫十六比从旅行者号1981年数据算出的所在位置落后了20度，这是不足以用观察误差所能解释的。可能土卫十六的轨道最近与F环遭遇而发生改变或者他可能有一个小伴星与它一起分享这个轨道。