Oct 1, 1998

Galileo takes a close look at icy Europa





The spacecraft flew within 2300 miles of the mysterious satellite last weekend
2 October, 1998: NASA's Jet Propulsion Laboratory reports that the Galileo spacecraft completed a close-up flyby of Europa on schedule and on target. On Friday, Sept. 25, at 8:54 p.m. PDT, Galileo skimmed over the icy moon at an altitude of only 2,226 miles.

The flyby was performed in cruise mode without Galileo's gyroscopes, because the gyros activated a fault protection program last Thursday, Sept. 24. The on board star scanner was used instead as the primary reference for determining the spacecraft's orientation in space. Nevertheless, the flyby was considered a success.




This color image of Jupiter's moon Europa was produced by combining low resolution color data with higher resolution mosaics recorded during three separate flybys by Galileo. The image covers an area a little less than 120 by 150 miles. More Information
Europa is one of the most intriguing bodies in the solar system because scientists are increasingly confident that it harbors a deep, underground ocean of liquid water. Europa's icy surface has intrigued scientists ever since the Voyager spacecraft missions flew through the Jupiter system in 1979. At -260° F, the moon's surface temperature could deep-freeze an ocean over several million years, but it's possible that warmth from a tidal tug of war with Jupiter and neighboring moons could be keeping large parts of Europa's ocean liquid. Tidal friction from Jupiter is also thought to be responsible for volcanic activity on Europa's neighbor Io.



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Images of Europa from the Galileo spacecraft reveal a complicated terrain of grooved linear ridges and crustal plates which seem to have broken apart and rafted into new positions. That could indicate subsurface water or slush. In the image above, blue tints represent relatively old ice surfaces while reddish regions may contain material from more recent internal geological activity. White splotches are bright material blasted from the young impact crater Pwyll located about 600 miles south (to the right) of this area.

Life under the ice?


The mounting evidence for an ocean beneath Europa's frozen surface raising the exciting possibility of life on that distant world. In recent years scientists have discovered a new class of micro-organisms here on Earth that can live or, at least remain viable, under very extreme conditions -- from volcanic vents deep in ocean trenches, to ice more than 400,000 years old, to Siberian permafrost more than 5 million years old. These microbes called archaeabacteria, or simply "archaea", constitute a third branch of life on Earth, along with prokaryotes (normal bacteria) and eukaryotes (plants and animals). Like prokaryotes, the genetic material of archaeabacteria float freely throughout the cell -- they are not contained within the cell nucleus like eukaryotic organisms. However, the DNA of archaeabacteria more closely resemble that of plants and animals than normal bacteria. They are truly in a class by themselves, and if life is discovered elsewhere in the solar system it may be similar to the archaeabacteria of Earth.


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Mickey Mouse, Klingon, porpoise, sphere, and leftover turkey are nicknames given to objects found in ancient Antarctic ice from as deep as 1,249 meters beneath Vostok Station.


The strongest clues to life on Europa may lie right here at home. In 1996, seismic and other tools revealed 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 distant Europa.

Hitting the Beach on Europa

NASA scientists have several projects in the planning stages to explore Europa. One is the Europa Orbiter. It would use a radar sounder to study Europa's icy surface and attempt to determine the thickness of the ice and whether liquid water exists below the ice. Other instruments to study the surface and interior would include an imaging device with multiple filters to map the surface at a resolution of 100 meters and an altimeter to measure the topography and characterize the tidal response of the surface. The mission could launch in 2003 and would serve as a precursor to spacecraft that would actually send undersea explorers into the Europan oceans.




Artists's conception of a JPL proposal to send undersea explorers to Europa. The hydro-craft would map the undersea terrain and look for life near volcanic vents.


Web Links


Galileo- Europa home page at JPL

Jet Propulsion Laboratory home page

The South Pole Web Page -- news, weather, and science from the south pole

More NASA Science News

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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Author: Dr. Tony Phillips
Production Editor: Dr. Tony Phillips
Curator: Bryan Walls
Responsible NASA official: John M. Horack