[分享] 卡西尼号最新图片(2004年05月13日)

PIA05391: Bands of Clouds and Lace

As Cassini nears its rendezvous with Saturn, new detail in the banded clouds of the planet's atmosphere are becoming visible.

Cassini began the journey to the ringed world of Saturn nearly seven years ago and is now less than two months away from orbit insertion on June 30. Cassini’s narrow-angle camera took this image on April 16, 2004, when the spacecraft was 38.5 million kilometers (23.9 million miles) from Saturn.

Dark regions are generally areas free of high clouds, and bright areas are places with high, thick clouds which shield the view of the darker areas below. A dark spot is visible at the south pole, which is remarkable to scientists because it is so small and centered. The spot could be affected by Saturn's magnetic field, which is nearly aligned with the planet's rotation axis, unlike the magnetic fields of Jupiter and Earth. From south to north, other notable features are the two white spots just above the dark spot toward the right, and the large dark oblong-shaped feature that extends across the middle. The darker band beneath the oblong-shaped feature has begun to show a lacy pattern of lighter-colored, high altitude clouds, indicative of turbulent atmospheric conditions.

The cloud bands move at different speeds, and their irregularities may be due to either the different motions between them or to disturbances below the visible cloud layer. Such disturbances might be powered by the planet's internal heat; Saturn radiates more energy than it receives from the Sun.

The moon Mimas (396 kilometers, 245 miles across) is visible to the left of the south pole. Saturn currently has 31 known moons. Since launch, 13 new moons have been discovered by ground-based telescopes. Cassini will get a closer look and may discover new moons, perhaps embedded within the planet’s magnificent rings.

This image was taken using a filter sensitive to light near 727 nanometers, one of the near-infrared absorption bands of methane gas, which is one of the ingredients in Saturn's atmosphere. The image scale is approximately 231 kilometers (144 miles) per pixel. Contrast has been enhanced to aid visibility of features in the atmosphere.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information, about the Cassini-Huygens mission visit, http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

　新浪科技讯 北京时间5月17日消息，土星探测器“卡西尼”号目前在一点一点地靠近土星，预计7月1日它将进入这颗被圆环围绕着的行星的轨道。随着“卡西尼”号与土星的距离渐渐缩短，它所拍摄的土星照片现在也越来越清晰，从它拍摄的土星照片上我们几乎可以看到土星大气中云层的活动情况了。

　　日前，美国国家航空航天局(NASA)公布了“卡西尼”号探测器于5月13日拍摄的这张
 
土星照片，当时“卡西尼”号距离土星的距离约为3850万公里，该照片的清晰度为每像素约230公里。

　　在土星南极地带我们可以清楚地看到一个不大的暗斑，科学家们认为，土星磁场可能会对这颗暗斑的位置和大小造成一定的影响，事实上，土星磁场的分布方向与其自转轴应该是相吻合的。在土星南极的右上方我们还可以看到有两个较明亮的点几乎与这个暗斑排列在同一直线上，科学家们认为这可能是土星大气中云层上升形成的两个旋涡。在接近土星赤道的地方我们还能够看到一个很大的长椭圆形较暗区域，其边缘紧接着是一条比较明亮的地带，科学家们设想，这可能土星内部热量造成的大气旋涡(据科学家们提供的观测资料显示，土星自身辐射出的能量比从太阳上获取的能量还要高)。

　　从“卡西尼”号定期传回的照片上我们还将逐渐观察到土星的各颗卫星。目前科学家们已探明的土星卫星共有31颗，随着“卡西尼”号与土星的日益亲近，科学家们相信它还将发现土星的其它一些新卫星。(编译/久亮)