ASTR 1210 (O'Connell): Selected Europa Images

Europa, the second Galilean satellite of Jupiter, is now regarded as one of the best candidate biospheres in the solar system because of the evidence for large amounts of liquid water beneath its icy outer crust. Here are some images of Europa from the Galileo Mission.

For general information on Jupiter and the Galilean satellites, see Study Guide 20.


Europa Hemisphere

The view of Europa combines images taken in violet, green and near-infrared filters in 1998 and 1995. The colors have been stretched to show the subtle differences in materials that cover the icy surface of Europa. Reddish linear features are some of the cracks and ridges, thousands of kilometers long, which are caused by the tides raised by the gravitational pull of Jupiter. Mottled, reddish "chaotic terrain" exists where the surface has been disrupted and ice blocks have moved around. The red material at the ridges and chaotic terrain is a non-ice contaminant and could be salts brought up from a possible ocean beneath Europa's frozen surface.

Also visible are a few circular features, which are small impact craters. Europa's surface has very few craters, indicating that recent or current geologic activity has removed the traces of older impacts. The paucity of craters, coupled with other evidence, has led scientists to surmise that there could be an ocean of liquid water beneath Europa's surface. Where there is water, there could be life. This is why Europa is a target of current interest for study of the possibility of non-Earth life. A follow-up spacecraft to Galileo will be Europa Orbiter, which should determine whether or not Europa has an ocean.

Europa cracks

Surface of Europa

The surface of Europa is covered with ice. By comparison to most terrestrial planets or satellites, it is extraordinarily smooth. Closeup images like this one show that the surface is probably a relatively thin layer of ice overlying an ocean. The blue here is ice, and the red lines are probably cracks, colored by a thin coating of darker material possibly ejected by ice volcanoes that occur along the cracks.

Closer View

A Closer View

This mosaic of a region in the northern hemisphere of Europa, displays many of the features which are typical on the satellite's icy surface. Brown, linear (double) ridges extend prominently across the scene. They could be frozen remnants of cryovolcanic activity which occurred when water or partly molten water ice erupted on the Europan surface, freezing almost instantly in the extremely low temperatures so far from our sun. Dark spots, several kilometers in diameter, are distributed over the surface. A geologically older, smoother surface, bluish in tone, underlies the ridge system. The blue surface is composed of almost pure water ice, whereas the composition of the dark, brownish spots and ridges is not certain. One possibility is that they contain evaporites such as mineral salts in a matrix of high water content.

Europa Ice Rafts

Ice Rafts on Europa

View of a small region of the thin, disrupted, ice crust in the Conamara region of Jupiter's moon Europa showing the interplay of surface color with ice structures. The white and blue colors outline areas that have been blanketed by a fine dust of ice particles ejected at the time of formation of the large (26 kilometer in diameter) crater Pwyll some 1000 kilometers to the south. A few small craters of less than 500 meters or 547 yards in diameter can be seen associated with these regions. These were probably formed, at the same time as the blanketing occured, by large, intact, blocks of ice thrown up in the impact explosion that formed Pwyll. The unblanketed surface has a reddish brown color that has been painted by mineral contaminants carried and spread by water vapor released from below the crust when it was disrupted. The original color of the icy surface was probably a deep blue color seen in large areas elsewhere on the moon. The colors in this picture have been enhanced for visibility.

North is to the top of the picture and the sun illuminates the surface from the right. The image, centered at 9 degrees north latitude and 274 degrees west longitude, covers an area approximately 70 by 30 kilometers (44 by 19 miles), and combines data taken by the Solid State Imaging (CCD) system on NASA's Galileo spacecraft during three of its orbits through the Jovian system. Low resolution color (violet, green, and infrared) data acquired in September 1996, were combined with medium resolution images from December 1996, to produce synthetic color images. These were then combined with a high resolution mosaic of images acquired on February 20th, 1997 at a resolution of 54 meters (59 yards) per picture element and at a range of 5340 kilometers (3320 miles).

Europa Cliffs

Ice Cliffs on Europa

This image, taken by the camera onboard NASA's Galileo spacecraft, is a very high resolution view of the Conamara Chaos region on Jupiter's moon Europa. It shows an area where icy plates have been broken apart and moved around laterally. The top of this image is dominated by corrugated plateaus ending in icy cliffs over a hundred meters (a few hundred feet) high. Debris piled at the base of the cliffs can be resolved down to blocks the size of a house. A fracture that runs horizontally across and just below the center of the Europa image is about the width of a freeway. North is to the top right of the image, and the sun illuminates the surface from the east. The image is centered at approximately 9 degrees north latitude and 274 degrees west longitude. The image covers an area approximately 1.7 kilometers by 4 kilometers (1 mile by 2.5 miles). The resolution is 9 meters (30 feet) per picture element. This image was taken on December 16, 1997 at a range of 900 kilometers (540 miles) by Galileo's solid state imaging system.

Cross Section

Cross Section Model of Europa

Cutaway view of the possible internal structure of Europa The surface of the satellite is a mosaic of images obtained in 1979 by NASA's Voyager spacecraft. The interior characteristics are inferred from gravity field and magnetic field measurements by NASA's Galileo spacecraft. Europa's radius is 1565 km, not too much smaller than our Moon's radius. Europa has a metallic (iron, nickel) core (shown in gray) drawn to the correct relative size. The core is surrounded by a rock shell (shown in brown). The rock layer of Europa (drawn to correct relative scale) is in turn surrounded by a shell of water in ice or liquid form (shown in blue and white and drawn to the correct relative scale). The surface layer of Europa is shown as white to indicate that it may differ from the underlying layers. Galileo images of Europa suggest that a liquid water ocean might now underlie a surface ice layer several to ten kilometers thick. However, this evidence is also consistent with the existence of a liquid water ocean in the past. It is not certain if there is a liquid water ocean on Europa at present.

Images and captions courtesy of NASA/Galileo Project and the University of Arizona.

Last modified April 2014 by rwo

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