<b>Original Caption Released with Image</b>:  The southern hemisphere of <a href="https://en.wikipedia.org/wiki/Umbriel_(moon)" class="extiw" title="en:Umbriel (moon)">Umbriel</a> displays heavy <a href="https://en.wikipedia.org/wiki/impact_crater" class="extiw" title="en:impact crater">cratering</a> in this <a href="https://en.wikipedia.org/wiki/Voyager_2" class="extiw" title="en:Voyager 2">Voyager 2</a> image, taken Jan. 24, <a href="https://en.wikipedia.org/wiki/1986" class="extiw" title="en:1986">1986</a>, from a distance of 557,000 kilometers (346,000 miles). This frame, taken through the clear-filter of Voyager's narrow-angle camera, is the most detailed image of Umbriel, with a resolution of about 10 km (6 mi). Umbriel is the darkest of <a href="https://en.wikipedia.org/wiki/Uranus_(planet)" class="extiw" title="en:Uranus (planet)">Uranus'</a> larger moons and the one that appears to have experienced the lowest level of <a href="https://en.wikipedia.org/wiki/geology" class="extiw" title="en:geology">geological</a> activity. It has a <a href="https://en.wikipedia.org/wiki/diameter" class="extiw" title="en:diameter">diameter</a> of about 1,200 km (750 mi) and reflects only 16 percent of the light striking its surface; in the latter respect, Umbriel is similar to <a href="https://en.wikipedia.org/wiki/Moon" class="extiw" title="en:Moon">lunar</a> highland areas. Umbriel is heavily cratered but lacks the numerous bright ray craters seen on the other large Uranian satellites; this results in a relatively uniform surface albedo (reflectivity). The prominent crater on the <a href="https://en.wikipedia.org/wiki/Terminator_(solar)" class="extiw" title="en:Terminator (solar)">terminator</a> (upper right) is about 110 km (70 mi) across and has a bright central peak. The strangest feature in this image (at top) is a curious bright ring, the most reflective area seen on Umbriel. The ring is about 140 km (90 miles) in diameter and lies near the satellite's <a href="https://en.wikipedia.org/wiki/equator" class="extiw" title="en:equator">equator</a>. The nature of the ring is not known, although it might be a <a href="https://en.wikipedia.org/wiki/frost" class="extiw" title="en:frost">frost</a> deposit, perhaps associated with an impact crater. Spots against the black background are due to 'noise' in the data. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.<br><br>
The original NASA image has been modified by cropping, increasing the linear pixel density by a factor of 2.47, and converting from .TIF to .JPG format.
NASA / Jet Propulsion Lab
<a rel="nofollow" class="external free" href="http://photojournal.jpl.nasa.gov/catalog/PIA00040">http://photojournal.jpl.nasa.gov/catalog/PIA00040</a>