Sky's Up Summer 2016 - Page 26

Landslides Landslides are common on Earth and have a distinctive look. However, a variety of landslides have been seen on both rocky and icy surfaces and in low and higher gravity situations around the Solar System. These images show recognizable landslides on the Moon, Saturn’s satellite Iapetus, Mars, the asteroid Vesta and Saturn’s satellite Hyperion. With ongoing monitoring, we have seen landslides in action, such as the one on Mars that is captured in the third image on the top row. The image below that shows an unusual landslide created by an impact crater on Mars. The far image of Hyperion, which has an unusual shape and a tumbling rotation shows a regional collapse that preserved the surface features inside the collapse zone. Earth 26 Iapetus Moon COURTESY OF NASA COURTESY OF US Geological Survey Mars Vesta COURTESY OF NASA COURTESY OF NASA/JPL/Space Science Institute Mars Iapetus COURTESY OF NASA COURTESY OF NASA COURTESY OF NASA/JPL-Caltech/UCLA/MPS/DLR/IDA Eruption plumes Eruption plumes are seen on a variety of objects in the Solar System, although the specific process causing the eruption plume may not always be understood. Some of the examples pictured here include: eruption plumes entering the vacuum of space from “jets” on Saturn’s Enceladus (salt wate r) and on Comet Hartley 2 (gas with dust) and Jupiter’s Io (sulfur). On Earth, geysers eject liquid water into a thick atmosphere. Triton’s plumes have colored the surface, apparently directed by the wind in a very thin atmosphere. The mechanisms that lead to the eruptions are not well understood except on Earth and Io. The results of searches for plumes above Jupiter’s Europa are disputed by planetary scientists. Mars Earth COURTESY OF NASA/JPL/Space Science Institute COURTESY OF NASA/NOAA COURTESY OF NASA/JPL-Caltech/UMD COURTESY OF NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute Triton Enceladus COURTESY OF NASA/JPL/USGS. COURTESY OF NASA/JPL-Caltech/Space Science Institute Sky’s Up COURTESY OF NASA/JPL/SSI/Gordan Ugarkovic Precipitation cycles Jupiter’s Europa and Io Comet Hartley 2 COURTESY OF US Geological Survey Hyperion Sky’s Up It is natural to wonder where the liquid comes from on other planets. In the case of Mars, the bulk of water that came during its formation is now gone, or at least well hidden. Precipitation cycle refers to the transfer of a liquid between various sources and “sinks” on a planet or satellite. Earth has a water cycle while Titan has a methane cycle. COURTESY OF U.S. Geological Survey 27