Photos courtesy of NASA/JPL/Caltech

These two images are of Jupiter’s ice-covered moon, Europa. At about 3,160 kilometers (1,950 mi) in diameter, Europa is about the size of Earth’s moon. Thanks to its smooth, glassy surface (rather than a crust pocked by craters, which is typical of most moons), Europa is the brightest moon in the solar system.

Recent findings suggest that portions of Europa’s icy surface move, which is strong evidence that liquid water lies beneath the ice. The water may be maintained in its liquid state by hydrothermal vents. Primitive bacteria inhabit vent sites on Earth. So if hydrothermal vents exist on Europa, scientists speculate, there’s a possibility that ancient microbes could live there, too.

The image on the left was taken on September 7, 1996, at a range of 677,000 kilometers (417,900 mi) by the solid-state imaging television camera onboard NASA’s Galileo spacecraft during its second orbit around Jupiter. The image was processed by Deutsche Forschungsanstalt fuer Luftund Raumfahrt e.V., Berlin, Germany.

The image on the left shows the approximate natural appearance of Europa. The image on the right is a false-color composite version combining violet, green, and infrared images to enhance color differences in Europa’s icy surface. Dark brown areas represent rocky material derived from the interior, implanted by impact, or generated from a combination of interior and exterior sources. Bright plains in the polar areas (top and bottom) are shown in tones of blue to distinguish possibly coarse-grained ice (dark blue) from fine-grained ice (light blue). Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long. The bright feature containing a central dark spot in the lower third of the image is a young impact crater some 50 kilometers (31 mi) in diameter. This crater has been provisionally named “Pwyll” for the Celtic god of the underworld.

After traveling approximately 4.6 billion miles since its launch from the Space Shuttle Atlantis in 1989, the Galileo spacecraft's 14-year odyssey came to an end on Sunday, September 21, 2003, when the spacecraft passed into Jupiter's shadow and then disintegrated in the planet's dense atmosphere at 11:57 a.m. Pacific Daylight Time. The Deep Space Network tracking station in Goldstone, California, received the last signal at 12:43:14 PDT. (The delay is due to the time it takes for the signal to travel to Earth.)

The spacecraft was deliberately destroyed to protect one of its own discoveries -- a possible ocean beneath the icy crust of the moon Europa.

NASA's Jet Propulsion Laboratory, at the California Institute of Technology in Pasadena, California, managed the Galileo mission. This image and many others are posted on the Galileo mission home page at galileo.jpl.nasa.gov. Check out additional information at www.jpl.nasa.gov/galileo/sepo.

Copyright University of Delaware.