This contains four articles on Europa. First is a NASA press release. Second, an article from Reuters. Third a NY Times article, and an article from the Discovery Channel.
I can hardly wait for us to explore this moon in more detail.
NASA RELEASE: 97-66
NEW IMAGES HINT AT WET AND WILD HISTORY FOR EUROPA
Chunky ice rafts and relatively smooth, crater-free patches on the surface of Jupiter's frozen moon Europa suggest a younger, thinner icy surface than previously believed, according to new images from Galileo's spacecraft released today.
The images were captured during Galileo's closest flyby of Europa on Feb. 20, 1997, when the spacecraft came within 363 miles of the Jovian moon. These features, which lend credence to the idea of hidden, subsurface oceans, also are stirring up controversy among scientists who disagree about the age of Europa's surface.
Dr. Ronald Greeley, an Arizona State University geologist and Galileo imaging team member, said the ice rafts reveal that Europa had, and may still have, a very thin ice crust covering either liquid water or slush.
"We're intrigued by these blocks of ice, similar to those seen on Earth's polar seas during springtime thaws," Dr. Greeley said. "The size and geometry of these features lead us to believe there was a thin icy layer covering water or slushy ice, and that some motion caused these crustal plates to break up."
"These rafts appear to be floating and may, in fact, be comparable to icebergs here on Earth," said another Galileo imaging team member, Dr. Michael Carr, a geologist with the U.S. Geological Survey. "The puzzle is what causes the rafts to rotate. The implication is that they are being churned by convection."
The new images of Europa's surface also have sparked a lively debate among scientists. Galileo imaging team member Dr. Clark Chapman is among those who believe the smoother regions with few craters indicate Europa's surface is much younger than previously believed. In essence, Chapman, a planetary scientist at Southwest Research Institute, Boulder, CO, believes the fewer the craters, the younger the region. Clark based his estimate on current knowledge about cratering rates, or the rate at which astronomical bodies are bombarded and scarred by hits from comets and asteroids.
"We're probably seeing areas a few million years old or less, which is about as young as we can measure on any planetary surface besides Earth," said Chapman. "Although we can't pinpoint exactly how many impacts occurred in a given period of time, these areas of Europa have so few craters that we have to think of its surface as young."
Chapman added, "Europa's extraordinary surface geology indicates an extreme youthfulness -- a very alive world in a state of flux."
However, Carr sees things differently. He puts Europa's surface age at closer to one billion years old.
"There are just too many unknowns," Carr said. "Europa's relatively smooth regions are most likely caused by a different cratering rate for Jupiter and Earth. For example, we believe that both Earth's moon and the Jovian moon, Ganymede, have huge craters that are 3.8 billion years old. But when we compare the number of smaller craters superimposed on these large ones, Ganymede has far fewer than Earth's moon. This means the cratering rate at Jupiter is less than the cratering rate in the Earth-moon system."
Scientists hope to find answers to some of the questions surrounding Europa and its possible oceans as the Galileo spacecraft continues its journey through the Jovian system.
"We want to look for evidence of current activity on Europa, possibly some erupting geysers," Greeley said. "We also want to know whether Europa's surface has changed since the Voyager spacecraft flyby in 1979, or even during the time of the Galileo flybys."
The craft will return for another Europa flyby on Nov. 6, 1997, the final encounter of Galileo's primary mission. However, eight more Europa flybys are planned as part of Galileo's two-year extended mission, which also will include encounters with two other Jovian moons, Callisto and Io.
The Jet Propulsion Laboratory manages the Galileo mission for NASA's Office of Space Science, Washington, DC.
Images and other data received from Galileo are posted on the Galileo mission home page on the World Wide Web at URL:
http://www.jpl.nasa.goBy Michael Miller
NOTE TO EDITORS: Stills and animation of the Galileo spacecraft are available by calling the JPL Public Information Office at 818/354-5011.
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PASADENA, Calif. (Reuter) - Space scientists said Wednesday they were confident life existed in the muddy waters of one of Jupiter's moons.
``I am sure there's life there,'' John Delaney of the University of Washington said in a reference to the Jovian moon Europa. Delaney and the other experts spoke at a news briefing detailing results of pictures from the Galileo probe.
Pictures of Europa sent back by Galileo after its closest flyby of the moon in February and released by the National Aeronautics and Space Administration Wednesday showed a red-colored sea with a crust of ice about three feet thick in which huge icebergs several miles across were floating, the scientists said. The images were taken as Galileo was 363 miles from Europa.
Talking to reporters at NASA's Jet Propulsion Laboratory, the scientists said they believed all the ingredients for creating and sustaining life forms existed in Europa's waters.
Delaney, a professor of oceanology, said he and other scientists believed the waters under the ice crust were being warmed by volcanic activity and undersea research on Earth had shown that ``volcanic activity supports life without sunlight.''
Richard Terrile of the JPL, a planetary scientist, said he believed there was organic matter in sediment at the bottom of Europa's ocean and pointed out: ``On Earth, these same ingredients in a million years gave presence to life.''
Terrile said he would like to see a ``machine exploration'' of Europa during a future unmanned probe to the moon in the hope of confirming his beliefs.
Delaney said he was ``very excited'' by Galileo's pictures. ''The bottom line is, it's about life. The discovery of life on another planet will surpass anything that has ever taken place in human history,'' he said.
He added that volcanic activity not only sustained life but encouraged it, saying when a volcano erupted under the ocean on Earth it caused bacteria to ``bloom at a massive level.''
In an effort to bolster their life-in-outer-space theory, scientists and engineers from around the world were meeting in Pasadena Wednesday and Thursday to discuss an exploration of Lake Vostok, a subglacial lake under the ice in Antarctica which they believe has conditions similar to Europa's sea.
Michael Carr of the United States Geological Survey said there was evidence of movement and rotation by the icebergs which could not be explained by wind as Europa is in a vacuum. ''The plausible cause for this motion is traction below which implies liquid below.
Dr Paul Geissler of the University of Arizona said the pictures showed the sea as a red-brown area on the surface of Europa. He speculated that the red-brown material in the waters indicated it was a ``muddy sea,'' while Max Coon, a scientist with NorthWest Research Associates, Inc., concluded after studying the pictures that, ``The ice features here (on Earth) look very, very like the ones on Europa.''
Oceanographer Clark Chapman of the Southwest Research Institute said he believed Europa was still developing and the ice crust was about one million years old, ``a mere day in geological terms.''
The scientists, who make up the Galileo imaging team and whose task it is to interpret the pictures and data sent back from the spacecraft, also said it appeared that the ice crust was slowly melting because of the warmer waters below which were being heated by volcanic activity.
Galileo was launched by the shuttle Atlantis in October, 1989 and arrived at Jupiter to begin its exploration of the planet and its moons in December of 1995.
Photos Suggest a Jupiter Moon May Hold Life
By JOHN NOBLE WILFORD
Looking at the most detailed pictures yet of Europa, a large moon of Jupiter, scientists said Wednesday that they were more confident than ever that a global ocean of liquid water or slush was lying just beneath Europa's thin crust of cracked ice. And this, they said with rising enthusiasm, might just be the place to look for extraterrestrial life.
On Europa, which is about 2,000 miles in diameter, or slightly smaller than Earth's Moon, fracture lines extend hundreds of miles across the frozen surface, curving and intersecting in spider-web patterns. Huge ice blocks stand above the crust like icebergs. Everywhere the surface is fragmented, as if chunks of ice cracked, drifted apart and then froze again in slightly different places, like pieces of a jigsaw puzzle not quite perfectly rearranged.
This was compelling evidence, scientists said, that heat from Europa's interior has turned a thick layer of Europa's ice into liquid water and that the warmth and currents of the subsurface ocean have created shattering stresses on the crustal ice.
They said they believed the heat most likely came from the radioactive decay of elements in the moon's rocky core and also from tidal forces caused by the gravitational pull of Jupiter, the solar system's largest planet, and its three other large moons, Io, Callisto and Ganymede.
"This is a very convincing set of pictures with respect to the presence of a liquid ocean," said Dr. Michael Carr, a planetary geologist with the U.S. Geological Survey.
Since water -- and the heat to keep it in a liquid state -- are essential conditions for life on Earth, the possible discovery of liquid water on another body in the solar system inevitably stirs new speculation about extraterrestrial life. Europa has no atmosphere to speak of, so for life to exist there, it would have to be in the subsurface ocean.
Oceanographers examining volcanic vents on the floors of Earth's seas have found evidence that these could be sites where terrestrial life began some 3.8 billion years ago.
The other most likely place in the solar system where life might have begun is Mars. Surface erosion shows water probably flowed on the Martian plains in the past. Last year, a meteorite from Mars was reported to contain minerals and other characteristics associated with life.
Dr. Ronald Greeley, a planetary geologist from Arizona State University in Tempe, said the widespread phenomenon of ice blocks on Europa's surface resembled pack ice on Earth's polar seas during spring thaws. "The size and geometry of these features lead us to believe there was a thin icy layer covering water or slushy ice, and that some motion caused these crustal plates to break up."
Dr. Richard Terrile, a planetary scientist at the Jet Propulsion Laboratory in Pasadena, Calif., gave an even more enthusiastic interpretation. "These are really mind-blowing pictures," he said. "How often is an ocean discovered? The last one was the Pacific by Balboa, and that was 500 years ago."
NASA made the pictures public Wednesday at a news conference at the Jet Propulsion Laboratory, where the Galileo mission is being directed. The pictures were taken Feb. 20 as the Galileo spacecraft swung within 363 miles of Europa, the closest it or any other spacecraft has ever come to the Jovian moon. Galileo is in its second year of orbiting Jupiter and taking close-up photographs of the planet's four major satellites.
For several years, planetary scientists have speculated that an ocean might lie under Europa's surface, and where there was liquid water, it followed that there could be life. They were encouraged in this line of thinking by discoveries in recent years of life at volcanic vents on Earth's sea floors.
Inspired by the new pictures and the stronger inference of subsurface seas on Europa, several scientists spoke more openly of the prospects for some kind of primitive life on Europa and what it would take to explore such a possibility. No one at the news conference struck a bolder note than Dr. John Delaney, an oceanographer at the University of Washington in Seattle, who has championed the concept of possible life on Europa.
When asked if he thought there was was life on the Jovian moon, Delaney first gave a careful response: "Science is driven by questions, by hypotheses that are then tested. NASA and oceanographers the world over will be trying very hard to prove whether there is life there. It's a challenge to all of humanity to explore this system."
Then he paused and threw caution to the winds. "But the answer is, I'm sure there's life," he said.
Dr. Torrence V. Johnson, the mission's chief scientist, noted that there was "no evidence directly bearing on life" in any water on Europa. "What we have found are the building blocks or the environment that are conducive to life," he explained. "But we don't know if those conditions necessarily lead to life."
Other scientists noted that the surface of Europa bears few marks of impacts by asteroids or comets. This suggests that liquid water from beneath the surface has risen in relatively recent times and covered parts of the surface with new layers of ice, concealing old crater scars.
Dr. Clark Chapman of the Southwest Research Institute in Boulder, Colo., said this re-surfacing has occurred more recently than expected, perhaps less than 1 million years ago. If so, it is more likely that the heat and liquid water that shaped Europa in the past are still active there.
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By Jay Ingram
Ever since the announcement last summer that there might have been life in the past on Mars, the extraterrestrial-life bandwagon has been full speed ahead. Speculation abounds but a recent case illustrates that there are limits: speculation still has to look and sound like science.
At the annual meeting of the American Association for the Advancement of Science a couple of weeks ago, scientists discussed the possibility that life might have - and might still exist on Jupiter's moon Europa.
Europa is by any measure a bizarre solar system object. Its surface appears to be a huge badly flooded skating rink at the end of a busy weekend, a vast globe of ice criss-crossed everywhere by cracks. There are very few craters, suggesting that those that once existed (almost everything in the solar system is thought to have been bombarded early on) have been smoothed out by an ever-changing surface.
Support for this idea comes from recent photos by the Galileo spacecraft showing what look like knew ice floes covering over old cracks. Also some of the cracks seem wider and darker than others.
This visual evidence, together with theoretical estimates of the heat-generating tidal pull on Europa by nearby Jupiter have prompted speculation that under that crust of ice (possibly very far under) there is a vast singular ocean of liquid water.
The dark cracks might be Europa's counterpart of shifting ice pans in the dark Arctic, which sometimes break apart to reveal narrow channels of darker water between.
At the AAAS meeting, scientists were building on the idea of the moon-girdling ocean to suggest that undersea volcanoes on Europa, powered by Jovian tidal forces, once (or still) spewed forth organic matter into this ocean, just as happens at the hot vents under our oceans.
On Earth, these upwellings contain micro-organisms. On Europa, who knows? Maybe this unlikely moon is a reservoir of undersea life.
Or then again, maybe it isn't. The Europa discussion at the AAAS was partially prompted by yet another close approach that might confirm or deny some of these ideas.
But there is a more interesting background to the idea. Speculation about Europa is by no means new. In late 1979, a science writer in the United States named Richard Hoagland first broached the idea that there might be life under the ice there. The images that sparked his imagination had arrived at Earth from the Voyager spacecraft, the one that gave us our first views of Jupiter, Saturn and their moons.
Hoagland put his ideas on paper in a verbose article in a magazine called Star and Sky in 1980. It's intriguing to read the article now, partly because he so clearly anticipates the thinking today and partly because no one today seems to be acknowledging his priority.
Some of the details are dated (Hoagland leans heavily on electricity in the early Europan atmosphere to generate the life-forming organic molecules, while today, as I mentioned above, scientists rely on undersea volcanoes). But in most respects the two arguments are absolutely consistent.
So where is Hoagland today and why aren't the Europa theorists talking about him. Is it perhaps because in the intervening years he took on a much more notorious cause, the face on Mars? Yes, it is the same Richard who is the prime mover behind the idea that a Viking spacecraft photo of a flat-topped mesa on the surface of Mars is a huge carved face.
Where Hoagland sees physiognomy, scientists see a chance juxtaposition of geology and shadow. But that hasn't stopped him. Last time I checked, he'd identified a complex of temples and pyramids nearby.
So when it comes to Europa, why don't we hear about Richard Hoagland? I think it's because it's perfectly okay to speculate about extraterrestrial life; it's even okay to dream about it swimming under the Europan ice; but it's just not respectable to think about somebody carving a big face on Mars.
Jay Ingram hosts the tv program '@discovery.ca' on the Discovery Channel in Canada.