The frosty plains of Europa
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The frosty plains of Europa
As Galileo returns new images of Europa, NASA scientists
prepare to study samples from a potentially similar environment
here on Earth
Dec. 3, 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 of Europa, like this one captured by the Galileo spacecraft, and from studies of a mysterious subterranean lake here on Earth.
The picture above is a mosaic of images from Europa's 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
or partially frozen water erupts onto the Europan surface, freezing
instantly in the extremely low temperatures so far from our sun.
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 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.
The next best thing to being there....
Many scientists would love to travel to Europa to study conditions
there first-hand, but regular flights to Jupiter probably won't
begin for some time. Meanwhile, there is an environment right
here on Earth with significant similarities to Europa and Callisto,
a place called Lake Vostok.
Below: In 1993 altimetric and radar
data were used to trace this outline of Lake Vostok, located
about 1000 miles from the South Pole. Image used is copyrighted
by the Canadian Space Agency. More
Information from Caltech-JPL.
In 1974 a team of scientists conducting
airborne research passed over the Soviet research station Vostok
in Antarctica. Their sounding instruments detected an expanse
of water beneath the ice roughly the size of Lake Ontario. Although
Antarctica records some of the coldest temperatures on Earth,
Lake Vostok is buried under four kilometers of ice. The ice sheet
acts as a blanket, shielding the lake from cold temperatures
on the surface. It is also thought that geothermal heat helps
keep the water liquid. 
Earlier this year Richard Hoover of
NASA's Marshall Space Sciences Lab and Dr. S.S. Abyzov of the
Russian Academy of Sciences examined ice cores from above Lake
Vostok for evidence of microbiotic life, using an Environmental
Scanning Electron Microscope. What they found surprised them.
"We've found some really bizarre things - things that we've
never seen before," said Richard Hoover of NASA's Marshall
Space Flight Center. "There are all sorts of microorganisms
in the ice. Some are readily recognizable as cyanobacteria, bacteria,
fungi, spores, pollen grains, and diatoms, but some are not recognizable
as anything we've ever seen before," Hoover said.
Above, right: One of the more exotic forms
Hoover and Abyzov found in the deep ice. Many of these microbes
will undoubtedly fall into known categories when identifications
are made. 
Hoover
is about to begin new studies of the deep ice microorganisms
in collaboration with Academician Mikhail V. Ivanov, Director
of the Institute of Microbiology of the Russian Academy of Sciences
to search for microorganisms in very deep samples of Vostok ice.
Extremely deep ice samples from approximately 100 meters above
the surface of the lake (about 400,000 years old) were obtained
earlier this year by an international team of US, Russian, and
French scientists.
According to Richard Hoover, "These are the deepest samples
ever obtained, and the deepest that ever will be obtained until
new technology makes it possible to actually penetrate the surface
of Lake Vostok without contaminating it." Although scientists
are anxious to know what lies within the pristine waters of the
lake itself, they are contenting themselves for now with ice
from above. "Lake Vostok is an incredibly precious resource,"
Hoover continued, "and it would be a colossal mistake to
take samples before it can be done without contaminating the
waters with chemicals or surface microorganisms."
Lake Vostok is clearly a valuable new laboratory for astrobiologists,
and they intend to proceed very, very carefully.
Planetary Photojournal - image of Europa
Evidence for slush beneath the surface of Europa - from JPL and Brown University
Galileo home page at JPL, with the latest on Europa
Jet Propulsion Laboratory home page
National Science Foundation - Polar Research Program (NSF supports the Vostok Ice Core Project)
The Europa/Vostok Initiative - from CalTech-JPL
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)
Related Stories:22 Oct. 1998Callisto makes a big splash
02 Oct. 1998Galileo gets a close-up view of mysterious Europa
12 March 1998Exotic-looking microbes turn up in ancient Antarctic ice
13 March 1998Space Tether may be best way to explore Europa
05 March 1998: Clues to possible life on Europa may lie buried in Antarctic ice
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Headlinesreturn to Space Science News Home
Author: Dr.
Tony Phillips & JPL press releases
Curator: Bryan Walls
NASA Official: John M. Horack