Cassini returns close-up images of moon's 'tiger stripes'
来源：未知 作者：樊伪讵 时间：2017-06-03 07:01:12
By Devin Powell (Image: NASA/JPL/Space Science Institute) (Image: NASA/JPL/Space Science Institute) (Image: NASA/JPL/Space Science Institute) New images from the Cassini spacecraft may help to explain the unusual geysers on Saturn’s moon Enceladus. Mission members are now checking to see if the images match the locations of known geyser vents. On Monday, Cassini flew by a region on the moon’s south pole called the “tiger stripes,” criss-crossing fractures where plumes of ice and water erupt from vents in the surface. One mission objective was to take high-resolution photos of the regions surrounding four of these vents with the spacecraft’s Imaging Science Subsystem (ISS) (scroll down for map of the targeted regions). But the probe was moving too fast and too low – it came within 50 kilometres of the surface at its closest point – to properly aim its camera system. So instead it attempted an unusual manoeuvre that NASA scientists compare to skeet shooting. The Cassini team aimed the camera like the barrel of a gun just ahead of the moon, and spun the spaceship to try to keep up as the moon raced by at 64,000 kilometres per hour. Mission members hoped that these rapid-fire photos would come out in focus, and the first data streamed back has not disappointed. The transmissions include seven crisp photos of the tiger stripe fractures, the best having a resolution of 10 metres per pixel (scroll down for images). “Damn, we do good work,” ISS team leader Carolyn Porco of the Space Science Institute in Boulder, Colorado, exclaimed in an email. The photos show icy boulders dotting the surface and several new fractures that have yet to be named. Now the team is checking to see if the regions shown in any of the photos match the locations of known geyser vents. These half-metre openings would be too small to see at the resolutions of the images, but the team hopes to find signs of their effects – such as the arrangement of nearby boulders or irregularities in the ice – on the surrounding surface geology. Cassini also took data on the moon’s surface heat using the spacecraft’s Visual and Infrared Mapping Spectrometer (VIMS). The data could help reveal whether the source of the geysers is a subsurface reservoir of liquid water or whether the water is locked up in underground ice. An initial analysis of the VIMS data may be completed by the end of the week, team members told New Scientist. Cassini: Mission to Saturn – Learn more in our continually updated special report. More on these topics: