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30 Nov, 1998:
The large Jovian moon Europa may be hiding liquid water beneath its
frozen crust. We won't know for sure until robotic explorers one day
venture below the surface of that icy
moon in search of oceans and possibly life. For now we must
learn what we can from surface photos, like
this one captured by the Galileo spacecraft and released last week
by the Jet Propulsion Laboratory imaging team.
 The picture above is a mosaic of images from Europa's the southern hemisphere. The brown, linear ridges extending across the scene are thought to be frozen remnants of cryo-volcanic activity. "Cryo-volcanoes" (cold volcanoes) occur when liquid partially frozen water erupts onto 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.
Left: A closer view of the volcanic ridges and areas of blue that scientists believe are frozen water on Europa. |
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The colors in these images have been enhanced to bring
out the details. An astronaut orbiting this smallest of the four
Galilean satellites would see the icy surface of Europa somewhat
brighter, but with less intense colors.
The photos of Europa were captured during two separate orbits of Jupiter by the Galileo spacecraft. High resolution images from an altitude of 15,000 miles shot during the spacecraft's 15th on May 31st, 1998 were combined with lower resolution images from the spacecraft's first orbit of Jupiter on June 28th, 1996. |
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At home on Europa?Water is an important ingredient of life as we know it on Earth. If liquid water does exist beneath the icy crust of Europa, as many scientists believe, then it's possible that some form of life may exist there as well. For this reason scientists are intensely curious about cold, subterranean oceans and what kinds of life might thrive in such environments. |
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Fortunately, there may be an example of such a place right here on Earth for scientists to study.
In 1996, radio sounding and altimetry measurements confirmed the the presence of an underground lake in Antarctica near the Russian Vostok Station. Lake Vostok is overlaid by about 3,710 meters (12,169 ft) of ice and may be 500,000 to 1 million years old. Since the discovery, drilling has gone slowly while procedures are worked out to keep it pristine. No one has seen or sampled the lake - the deepest ice sample is from 100 meters (328 feet) above the liquid surface - nor is anyone sure why it is liquid, hence the scientific curiosity. Scientists are hopeful that Lake Vostok can one day serve as a terrestrial laboratory to help us understand better the oceans on the distant moons of Jupiter. |
| The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission or NASA's Office of Space Science, Washington, DC. |
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Planetary Photojournal - image of Europa Jet Propulsion Laboratory home page Callisto's moon may hide a salty ocean - JPL/Galileo press release posted Oct 21. The South Pole Web Page -- news, weather, and science from the south pole (external link) |
Galileo- Europa home page at JPL Related Stories:Exotic-looking microbes turn up in ancient Antarctic ice Space Tether may be best way to explore Europa Clues to possible life on Europa may lie buried in Antarctic ice |
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