Rocks/Rocky objects/Ariel

The complex terrain of Ariel is viewed in this image, the best Voyager 2 color picture of the Uranian moon. Credit: NASA/JPL.

"The complex terrain of Ariel is viewed in [the image at right], the best Voyager 2 color picture of the Uranian moon. The individual photos used to construct this composite were taken Jan. 24, 1986, from a distance of 170,000 kilometers (105,000 miles. Voyager captured this view of Ariel's southern hemisphere through the green, blue and violet filters of the narrow-angle camera; the resolution is about 3 km (2 mi). Most of the visible surface consists of relatively intensely cratered terrain transected by fault scarps and fault-bounded valleys (graben). Some of the largest valleys, which can be seen near the terminator (at right), are partly filled with younger deposits that are less heavily cratered. Bright spots near the limb and toward the left are chiefly the rims of small craters. Most of the brightly rimmed craters are too small to be resolved here, although one about 30 km (20 mi) in diameter can be easily distinguished near the center. These bright-rim craters, though the youngest features on Ariel, probably have formed over a long span of geological time. Although Ariel has a diameter of only about 1,200 km (750 mi), it has clearly experienced a great deal of geological activity in the past."

Opticals

Main articles: Radiation astronomy/Opticals and Optical astronomy

This image of Ariel is a a composite of four clear filter images taken by the Voyager 2 spacecraft on January 24, 1986, from a distance of 130,000 kilometers (80,000 miles). Two of these images that covered the terminator on the right were smeared because of the longer exposure times. The color is based upon lower resolution color images. Much of Ariel's surface is densely pitted with craters 5 to 1O kilometers (3 to 6 mi) across. These craters are close to the threshold of detection in this picture. Numerous valleys and fault scarps crisscross the highly pitted terrain. Voyager scientists believe the valleys have formed over down-dropped fault blocks (graben); apparently, extensive faulting has occurred as a result of expansion and stretching of Ariel's crust. The largest fault valleys, near the terminator at right, as well as a smooth region near the center of this image, have been partly filled with deposits that are younger and less heavily cratered than the pitted terrain. Narrow, somewhat sinuous scarps and valleys have been formed, in turn, in these young deposits. It is not clear whether these sinuous features have been formed by faulting or by the flow of fluids.

Visuals

Main articles: Radiation astronomy/Visuals and Visual astronomy

Distinct bright patches are visible on Ariel. Credit: Voyager 2 / NASA / Jet Propulsion Laboratory.{{free media}}

Distinct bright patches are visible on Ariel, the brightest of Uranus' five largest satellites. Voyager 2 obtained this image Jan. 22, 1986, from a distance of 2.52 million kilometers (1.56 million miles). The clear-filter image, obtained with the narrow-angle camera, shows a resolution of 47 km (29 miles). Ariel is about 1,300 km (800 mi) in diameter. This image shows several distinct bright areas that reflect nearly 45 percent of the incident sunlight; on average, the satellite displays a reflectivity of about 25-30 percent. The bright areas are probably fresh water ice, perhaps excavated by impacts. The south pole of Ariel is slightly off center of the disk in this view. Voyager 2 will obtain its best views of the satellite on Jan. 24, at a closest-approach distance of 127,000 km (79,000 mi).

Infrareds

Main articles: Radiation astronomy/Infrareds and Infrared astronomy

This Hubble Space Telescope image shows Uranus in the near-infrared. Credit: NASA, ESA, L. Sromovsky (University of Wisconsin, Madison), H. Hammel (Space Science Institute), and K. Rages (SETI).

At right is an infrared image of Uranus "showing Ariel in transit across Uranus, taken on July 26, 2006. Due to the planet's extreme axial tilt--carried through in the tilt of its satellites's orbits--transits are only possible near the equinoxes. Taken in the near-infrared, atmospheric banding and the planet's oblateness are readily apparent."

See also

• Uranus

References

External links