Enhanced versions of the Voyager 2 spacecraft's pictures reveal what look like three gigantic, ice-gushing volcanoes on Neptune's frozen moon Triton, scientists reported Friday.
If the flat, nearly circular features are volcanic, they are the fourth kind of ice volcano seen on Triton and a type never before seen in the solar system, said Pascal Lee, a Cornell University planetary scientist.The smallest circle is 175 miles wide and the largest measures 580 miles across - more than one-third of the moon's diameter - so "we think we're seeing volcanism on a global scale," although it isn't known if they are still active, Lee said Thursday by phone from Ithaca, N.Y.
Voyager 2 - operated by NASA's Jet Propulsion Laboratory in Pasadena, Calif. - flew by Neptune and its moons in August 1989.
Triton is the coldest object ever measured in the solar system, with a surface temperature of 391 degrees below zero Fahrenheit. During the flight, Voyager 2 discovered three forms of ice volcanoes on Triton:
- Geyser-like, black volcanic plumes, which were observed spewing nitrogen ice, nitrogen gas and carbon dust 5 miles skyward near Triton's south polar icecap.
- Long cracks or faults filled with oozing ice, looking somewhat like toothpaste coming out of a tube slit with a razor blade.
- Inactive, possibly extinct, crater-shaped volcanoes called calderas, which measure a couple of hundred miles wide and once emitted lakes of thick ice.