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Space Topics: Uranus
Voyager 2 color view of Ariel
Voyager 2 captured this view of Ariel on January 24, 1986. It has been specially processed by Ted Stryk to reveal details on Ariel's night side, faintly lit by reflected light from Uranus.
Credit: NASA / JPL / Ted Stryk
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Uranus' Moon Ariel
Diameter: 1,162.2 x 1,155.8 x 1,155.4 kilometers
Orbital distance: 190,900 kilometers from Uranus
Orbital period: 2.52 days
Discovery: 1851 by William Lassell
Ariel has the youngest, as well as the brightest, surface of Uranus’ five
major moons. Large areas of the moon are seamed
with a weird network of broad, flat-floored valleys. These valleys form
a sharp contrast to an adjacent smooth hemisphere, pocked with small craters. No
enormous craters were seen by Voyager 2, only small ones, indicating Ariel’s
youth.
The Voyager 2 Ariel image catalog
To create this montage, Ted Stryk stacked the best images of Ariel taken during each of Voyager 2's observations to increase their sharpness. The 13 observations center on the south pole during Voyager 2's approach, then shift over the pole toward Ariel's leading hemisphere. The largest image is shown at reduced resolution. The image immediately before that one was cut off at one limb (at the top of the view); Stryk used data from a lower-resolution earlier observation to fill in the missing portion of the disk.
Credit: NASA / JPL / Ted Stryk
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Some selected recent research on Ariel includes the following:
- Will Grundy and Leslie and Eliot Young reported the results of infrared
observations using the SpeX instrument at the 3-meter Infrared Telescope
Facility (IRTF) on Mauna Kea close to the Uranian system's equinox, the only
time of Ariel's year when its rotation causes it to show completely different
faces to Earth. They found that Ariel, like the moons of Jupiter and Saturn,
has a leading-trailing dichotomy (that is, the side that faces forward along
its orbit has different characteristics from the side that faces backward).
They found evidence for carbon dioxide on the trailing but not leading hemispheres.
(Abstract presented to the AAS DPS meeting in 2002: "Discovery
of leading-trailing asymmetry and CO2 ice on Ariel," followed by a 2006
paper in Icarus with three other coauthors, "Distributions
of H2O and CO2 ices on Ariel, Umbriel, Titania, and Oberon from IRTF/SpeX
observations.")
- Olga Prieto and Jeff Kargel mapped the blocks of crust that shifted as
a result of the faulting on Ariel, and examined their margins. They found
that some scarps were four kilometers high, and that the walls of some scarps
appeared to expose brighter material than the stuff on the surface -- probably
nearly pure water ice, whereas the surface is dirty. (Abstract presented
to the LPSC in 1997: "The
interior structure and paleogeography of Ariel.")
- Guy Consolmagno, Dan Davis, and Paul Nyffenegger mapped the orientations
of the flat-floored faults on Ariel and state that the orientation "is far
from random, and these cracks probably arose from stresses due to the flexing
of a tidal bulge and the despin of the planet. A statistical analysis of
the cracks suggests that the location of the tidal bulge at the time of their
emplacementmay have been 60 degrees east of the current sub-planetary point."
(Abstract presented to the LPSC in 1994: "Has
the tidal bulge on Ariel shifted in longitude?)
Voyager 2's Ariel image catalog
This montage represents the entire catalog of images captured by Voyager
2 that resolve any features on the moon's surface. Voyager 2 passed relatively
close to Ariel on its January 24, 1986 flyby, acquiring a high-resolution,
four-image mosaic that suffers from some motion blur. The image at the top
of this page was created from those four photos. Credit: NASA / JPL / PDS
Rings Node / montage by Emily Lakdawalla
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Ariel in color
This color view was assembled from the four-image set taken just prior to
the highest-resolution mosaic.
Credit: NASA / JPL / Ted Stryk
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Ariel transits Uranus
The Hubble Space Telescope pointed toward Uranus on July 26, 2006 at about
15:30 UTC to take the images used to assemble this color view of Ariel, the
fourth largest of Uranus' moons, transiting the planet's disk. The rings are
also faintly visible, as is Miranda, just below the rings to the left of the
disk. Another spot to the left of Uranus is a background star. Credit: NASA
/ STScI / Larry Sromovsky / processing by Ted Stryk
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