Jim Head says that science is about exploring the unknown. He must know. Head and his students are in the midst of a wondrous adventure, traveling incredible distances, posing new questions and overturning established ideas.
Professor Head, postdoctoral researcher Bob Pappalardo and graduate student Geoff Collins, with the assistance of other graduate students and undergraduates back at Brown, worked day and night earlier this month in California to prepare for a news conference July 10 at the Jet Propulsion Laboratory in Pasadena. On that day, Head, Pappalardo and other project scientists described for the world a series of photographs returning from NASA's Galileo spaceship, which flew by Jupiter's large icy moon, Ganymede, on June 27.
Where lower-resolution photos taken by the spacecraft Voyager in 1979 showed a smooth surface, the new images, with 20 times better resolution, revealed a land of major tectonic activity from quakes, volcanoes and other geologic shifts. Fissures, faults and pockmarks covered the surface of one of two Ganymede sites photographed by Galileo.
"The resolution and contrast of the new photos are so much better than the data from Voyager that if Brown's main green was on Ganymede's surface, we could see it," Head says.
Each day Galileo sends back even more images.
"With the first set of Galileo's photos we couldn't see University Hall if it was on Ganymede's surface," Head says. "But if the building was there, the new images we expect this week would show it."
The data about Ganymede can help scientists understand how planets form and age.
"We don't know what Earth's formative years were like," Head says. "Understanding the geologic activity of other moons and planets gives us insight into Earth and the factors that influence it over the long-term. Mars once had water. Venus is a hellish hothouse. Is Earth destined to end up somewhere in-between? From the new findings, we can learn where we are as a planet and where we are going."
Head says the latest discoveries also reflect the adage that "almost everything is not yet known."
"Static knowledge is a dead end," he says. "We think we know everything, but planetary geology, for example, is in its infancy. This shows we really don't know as much as we think. If we're not learning new things, we're dead."
If so, then Head and his students are living life to its fullest, as they continue the grueling but highly rewarding work of gathering and interpreting never-before-seen images from across the solar system.
"Everything we accept as reality today is the result of previous exploration," he says. "It's great to open our eyes to continuous learning."
Ganymede is the largest moon in the solar system. Although most moons are small, Ganymede is one-third the size of Earth. It is about half ice and half rock. About 50 percent of Ganymede's icy surface looks bright and clean, while the rest appears covered by darker ice.
Before these findings, planetary experts did not consider many of these moons to be dynamic geologic sites.
At the July 10 news conference, scientists reported another surprise: Galileo's instruments indicated Ganymede possesses the energy of a magnetic field, something never detected from an icy moon. Ganymede's weak emissions exist within the strong magnetic field generated by Jupiter, Head says.
Because magnetic fields on planets are thought to be created by the motion and convection of interiors, he says that Galileo's detection suggests that icy, frozen Ganymede may have a partially liquid interior.
"If that's so, then there must have been a huge, active ocean below Ganymede's ice in the past," Head says.