Space Science News home |
|
November 5, 1999:
Jupiter's fiery moon Io is providing scientists a look at volcanoes
and colossal lava flows similar to those that raged on Earth
eons ago, thanks to new pictures and data gathered by NASA's
Galileo spacecraft.
"The latest flyby has shown us gigantic lava flows and lava lakes, and towering, collapsing mountains," said Dr. Alfred McEwen of the University of Arizona, Tucson, a member of the Galileo imaging team. "Io makes Dante's Inferno seem like another day in paradise." Ancient rocks on Earth and other rocky planets show evidence of immense volcanic eruptions. The last comparable lava eruption on Earth occurred 15 million years ago, and it's been over 2 billion years since lava as hot as that found on Io (reaching 2,700 degrees Fahrenheit) flowed on Earth. "No people were around to observe and document these past events," said Dr. Torrence Johnson, Galileo project scientist at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. "Io is the next best thing to traveling back in time to Earth's earlier years. It gives us an opportunity to watch, in action, phenomena long dead in the rest of the solar system."
The new data focus on three of Io's most active volcanoes -- Pele, Loki and Prometheus. The vent region of Pele has an intense high-temperature hot spot that is remarkably steady, unlike lava flows that erupt in pulses, spread out over large areas, and then cool over time. This leads scientists to hypothesize that there must be an extremely active lava lake at Pele that constantly exposes fresh lava. Galileo's camera snapped a close-up picture showing part of the volcano glowing in the dark. Hot lava, at most a few minutes old, forms a thin, curving line more than six miles (10 kilometers) long and up to 150 feet (50 meters) wide. Scientists believe this line is glowing liquid lava exposed as the solidifying crust breaks up along the caldera's walls. This is similar to the behavior of active lava lakes in Hawaii, although Pele's lava lake is a hundred times larger. Loki, the most powerful volcano in the solar system, consistently puts out more heat than all of Earth's active volcanoes combined. Two of Galileo's instruments -- the photopolarimeter radiometer and near-infrared mapping spectrometer -- have provided detailed temperature maps of Loki. "Unlike the active lava lake at Pele, Loki has an enormous caldera that is repeatedly flooded by lava, over an area larger than the state of Maryland," said Dr. Rosaly Lopes-Gautier of JPL, a member of the spectrometer team. Left: This collage of images shows the dizzying rate of geologic activity at one of the many erupting volcanoes on Jupiter's moon Io, as viewed by NASA's Galileo spacecraft during the closest-ever Io flyby on October 10, 1999. The top panel shows the best overall view of the Prometheus volcano, combining a picture at a resolution of 120 meters (400 feet) per picture element with a picture at a resolution of 1.5 kilometers (about one mile) per picture element. Inset within this panel is a smaller copy of the mosaic with a temperature map superimposed. [more] Observations of Prometheus made early in the Galileo mission showed a new lava flow and a plume erupting from a location about 60 miles (100 kilometers) west of the area where the plume was observed in 1979 by NASA's Voyager spacecraft. New Galileo data clarify where lava is erupting, advancing, and producing plumes. The most unexpected result is that the 50-mile (75 kilometer) tall plume erupts from under a lava flow, far from the main volcano. The plume is fed by vaporized sulfur dioxide-rich snow under the lava flow. Mountains on Io are much taller than Earth's largest mountains, towering up to 52,000 feet (16 kilometers) high. Paradoxically, they do not appear to be volcanoes. Scientists are not sure how the mountains form, but new Galileo images provide a fascinating picture of how they die. Concentric ridges covering the mountains and surrounding plateaus offer evidence that the mountains generate huge landslides as they collapse under the force of gravity. The ridges bear a striking resemblance to the rugged terrain surrounding giant Olympus Mons on Mars.
Additional information about the Galileo mission is available
on the Galileo home page at a new web address of http://galileo.jpl.nasa.gov.
|
Web Links |
---|
Related Stories:
Related Sites:
|
Join our growing list of subscribers - sign up for our express news delivery and you will receive a mail message every time we post a new story!!! return to Space Science News Home
|