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|Discovered by||William Lassell|
|Mean radius||190,900 km|
|Orbital period||2.52 days|
|Mean diameter||1157.8 km|
|Surface area||4,200,000 km2|
|Mean density||1.67 g/cm3|
|Rotation period||2.52 days|
|Atmospheric pressure||0 kPa|
The name "Ariel" and the names of all four satellites of Uranus then known were suggested by John Herschel in 1852 at the request of Lassell (). Lassell had earlier endorsed Herschel's 1847 naming scheme for the seven then-known satellites of Saturn and had named his newly-discovered eighth satellite Hyperion in accordance with Herschel's naming scheme in 1848.
It is also designated Uranus I.
The first and so far only close-up observations of Ariel were made by the Voyager 2 probe during its January 1986 Uranus fly-by. Because the moon's south pole was pointed towards the Sun, only the southern hemisphere was photographed.
Ariel's composition is roughly 50% water ice, 30% silicate rock, and 20% methane ice, and it appears to have regions of fresh frost in places. Largely devoid of impact craters, Ariel appears to have undergone a period of intense geological activity that has produced a huge network of fault canyons and liquid water outflows over its surface.
Scientists recognise the following geological features on Ariel:
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