23 August 2009

More Ariel

While I prepare the new Triton Movie for release on August 25 (the 20th anniversary of the Voyager flyby of Triton and Neptune), I will show some more of the images and data from Ariel (original data acquired January 1986). Included are a movie and the digital topography. Perspective views can be found in the original post a few days ago.

Ariel: The Movie

The Image data have a resolution of 1 kilometer. The topographic base map has a variable resolution but can resolve features taller than about 250 meters (I think). The topography is based on both stereo image analysis (stereogrammetry) and shape-from-shading (photoclinometry, PC). Stereo data were produced across most of the mapping area while PC is only available for the portion near the terminator (shadow) line. The two maps have been merged here to produce the topographic map we now see (the original data have been JPEG compressed for display.)

Image mosaic of southern hemisphere of Ariel (top). Topographic map of same region (bottom).

There are a variety of interesting features to see on Ariel. Most obvious are the 50 to 140 kilometer wide troughs along the terminator. The floors of these downdropped blocks are 3 to 5 kilometers deep and have been resurfaced by water or ammonia lavas long since frozen over. Note also the narrow ridges and troughs to the top, and the two large craters near center, which are 65 to 85 kilometers across. One of these craters is deep, the other shallow (due to relaxation or volcanic filling).

Ariel is interesting because it is even more geologically deformed and resurfaced than Miranda, which gets all the good press. Almost no ancient surface remains on Ariel, although Voyager only saw ~40% of the surface in 1986. The heat source responsible for making Ariel so volcanically active (it is likely quiet today) is unknown but is probably related to gravitational tides.

A New Global map of Ariel

This is my best current map of Ariel showing the global mapping coverage acquired by Voyager. Note that all the good stuff is south of the equator (the horizontal line in this cylindrical projection). The fuzzy area north of the equator was actually captured in Uranus-shine, and although poor in quality allows us to see another bright craters and the continuation of severa troughs. (I thank Ted Stryk for discovering that these dark-Ariel data exist.)

All Images Credit: Paul Schenk, Lunar and Planetary Institute.
Use is not restricted, but a request for use (or for a quality digital copy) should be forwarded to the author. Proper credit is always appreciated!

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