Scientists imagine Jupiter's largest moon as a much livelier place now that they've received the first interplanetary postcards from NASA's Galileo spacecraft.
The probe swung past Ganymede, a moon of Jupiter three-quarters the size of Mars, on June 26. Since then, a slow stream of photographs radioed to Earth by the probe have astonished scientists with their sharpness and detail."It's like turning on a microscope," James Head, a Brown University researcher on the Galileo project, said Wednesday as NASA released new black-and-white images of the largest moon in the solar system.
The first-ever close-ups, taken as the spacecraft passed 524 miles above Ganymede's surface, are upending geologic theories about the planet-sized moon. For the first time, the photos allow researchers to construct detailed geologic histories for parts of Ganymede.
Galileo also discovered that Ganymede has its own "baby" magnetosphere, a region of hot, ionized gases and highly charged particles that has never been found around a moon before.
Scientists now believe Ganymede's half-ice, half-rock surface was far more geologically active than fuzzier images from the Voyager spacecraft in 1979 indicated. Galileo captured more evidence than expected that frozen volcanic eruptions and quakes resurfaced the moon's stark expanses.
The photographs are mosaics made up of four shots each.
Looking at a composite view of Uruk Sulcus, filled with faults and fractures, Head said: "It looks like someone has taken a rake across the surface."