September 2000 Researchers at Washington University in St. Louis studying chemical data from the Hubble Space Telescope have determined the eruption conditions of Jupiter's volcanically active satellite, Io, and concluded that the moon has a differentiated mantle similar to that of Earth.
Differentiation is the process where various rock types are produced from a common magma.
The researchers, Mikhail Zolotov, Ph. D., senior research scientist in earth and planetary sciences, and Bruce Fegley, Jr., Ph.D., professor of earth and planetary sciences, were able to take the Hubble measurements and infer the temperature of the magma and plume pressure of Pele, one of Io's most active volcanoes. This is the first time that scientists have used chemical data obtained from a telescope to study present-day interior processes of a solar system body. Surprisingly, the magma temperature inferred from the Hubble chemical data corresponds to the temperatures deduced from infrared measurements taken by the Galileo spacecraft orbiting Jupiter. The study shows that Earth orbit observations can compete successfully with expensive planetary missions. Io, one of the four major satellites of Jupiter, is approximately the same size as our moon, but has tremendous volcanic activity occurring on its surface.