The Search Is ON!

• Ongoing new discoveries from the Galileo Orbiter

• Is there liquid water under Europa's ice?

• Wedges

• Chaos Terrain

• Crater evidence of liquid subsurface

• Volcanism? Upwelling through fissures and other linear features. Tectonic processes

• Tidal Heating

• Radioactive decay in the core? Hot spots

• The Mystery of the Red Coloration

• Magnetic Field

• Protection from Radiation

• Future Missions, Proposed Europa Orbiter

• Links

Nasa is preparing plans for a possible mission to Europa that would put a lander on the surface. It has even been suggested that a mission could be devised that would drill through the ice layer and release a probe into the liquid underment. This is the "hydrobot" concept.

Water or ice? Liquid or slushy or frozen solid? Ever since the Voyager spacecraft missions flew through the Jupiter system in 1979, planetary scientists have wondered about the layer of ice surrounding the second moon of Jupiter.

Europa's ice surface makes it one of the brightest, and smoothest, objects in our solar system.

Recent Galileo spacecraft images have provided evidence that Europa had a liquid ocean underneath the frozen crust sometime in its history, but it is not clear if this ocean still exists. Of the various explanations proposed by scientists, most scenarios of Europa's evolution have the water layer freezing solid earlier in its history. The moon's surface is -260° F, which could freeze an ocean over several million years. But scientists think that the warming caused by a tidal tug of war with Jupiter and neighboring moons could be keeping large parts of the ocean liquid.

from Detailed Images From Europa Point To Slush Below Surface
-- Jet Propulsion Laboratory

The Latest Scoop: A Second Moon with Ocean?
Jupiter's second largest moon, Callisto, may have a liquid ocean tucked under its icy, cratered crust, according to scientists studying data gathered by NASA's Galileo spacecraft.

The Galileo findings, to be published in the Oct. 22 issue of the journal Nature, reveal similarities between Callisto and another of Jupiter's moons, Europa, which has already displayed strong evidence of a subsurface ocean.

Jupiter's Moon Callisto May Hide Salty Ocean
- -Jet Propulsion Laboratory, 10/22/98

"These ... data lend support to the hypothesis that Europa is warm and active today and potentially characterized by a global subsurface water layer or ocean. Europa, like Mars and the Saturn moon Titan, is a laboratory for the study of conditions that might have led to the formation and evolution of life.

The combination of interior heat, liquid water, and infall of organic material from comets and meteorites means that Europa has the key ingredients for life, and it represents an exciting environment that is worthy of further detailed exploration."

-- James Head, Brown University professor of geological sciences.

On arrival, a probe was shot into Jupiter and returned nearly an hour's worth of data on Jupiter's atmosphere. The main spacecraft then performed a tremendous "burn" to shed velocity and achieve system orbit.

Each orbit consists of an "encounter phase" of one of the Galilean moons, lasting about one week, followed by a "cruise phase". Data from the remote sensing instruments is compressed by the computer and logged onto the tape recorder during encounter and played back during the cruise phase for beaming to Earth.

But consider the hard-workin' fellow roaming the reaches of the Jupiter system.

The Little Robot that Could

	Galileo is arguably the greatest engineering achievement of the 20th Century, a Modern Wonder of the World, a science Colossus. Considering that Galileo is sporting technology that is twenty-years old (e.g. 8-bit computer with 64K - that's 'K' - memory), that it has survived catastrophes that could have scuttled the mission, that it's been in space for over eight years - it's a marvel indeed.
	See the sidebar for Galileo-specific links On post for the last two and a half years, continuing the daunting journey that led half a billion miles from Earth launch to Jupiter orbit, Galileo accomplished its primary mission in December of '97 and is now doing research in the extended mission, GEM (Galileo-Europa Mission). See the sidebar for the GEM Itinerary graphic.

As of this writing (10/22/98), Galileo is in process of sending data gathered during the 9/26 Europa flyby (E17). There are two more Europa flyby's that will take us into 1999, then a series of Jupiter-specific studies, and for the last act of the Millenium, a pair of Io flyby's. The Jovian inner system has been "off-bounds" for Galileo up to this point, because of the highly-energetic charged particle and radiation environment there. Galileo is already starting to show signs of integrated circuit failure in its electronics from radiation and the Io flyby has all the makings of a last, "kamikaze" mission. Mission controllers have saved this for the last - it is not thought that Galileo's circuitry will survive.

Hardly a week goes by that there isn't new information posted on the JPL main site. While researchers are concentrating on Europa, data is also still being gathered on the other Galilean moons and on Jupiter and the energetic environment of the system.

JPL runs a "listserv" which is an automatic email. This gets you news hot off the press: the same news item will have been posted at the JPL site too. Here's how to get it:

• E-mail JPLNews@jpl.nasa.gov
• Leave the subject field blank
• Type subscribe galileo in the body of the message.

Recent Galileo News

Jupiter's Moon Callisto May Hide Salty Ocean, 10/22/98

Galileo Scientists Release New Images, Findings about Jupiter's White Ovals, 10/14/98

Galileo Releases New Images of Jupiter's Lightning, Io's Aurora, Callisto and Europa, 10/13/98

from Galileo Webchat 4/10/97

Surface Features
There are two types of terrains on Europa's icy crust. One type of terrain is mottled, brown or gray in color and consisting of mainly small hills. The other type of terrain consists of large smooth plains criss-crossed with a large number of cracks, some curved and some straight. Some of these cracks extends for thousands of kilometers. The cracked surface appears remarkably similar to that of the Arctic Ocean on Earth. The crust may be no thicker than 150 km

from A Summary of Facts about Europa
-- Jet Propulsion Laboratory, 6/96

Evidence for Liquid Water
"Together, the craters, chaos and wedges support the hypothesis that in Europa's most recent history, liquid or at least partially liquid water existed at shallow depths below the surface of Europa in several different places," says James Head, Brown University professor of geological sciences.

Data like this have pushed forward the GEM agenda which aims to make the best possible use of the Orbiter's remaining life to focus on the question of the possibility that there exists today, perhaps several kilometers deep beneath the ice crust, a liquid sub-ocean.

Terrestrial Sea Ice Analogs
The surface of Europa is crossed by bands and ridges of a variety of specific morphologies [1,2,3]. Reconstruction of gray and wedge-shaped bands indicates that they formed through opening and separation of lithospheric blocks atop a liquid or ductile substratum [4,5], perhaps broadly analogous to processes that operate in terrestrial sea ice [4,5,6]. Furthermore, theoretical models of thermal balance suggest that a liquid water ocean may underlie the icy surface of Europa [7,8]. We have begun investigation of whether the landforms of Europa can be explained through analogy to terrestrial sea ice processes. We propose a sequence in which cyclical tensional and compressional stresses (predicted from nonsynchronous rotation [9,10]) open and close lithospheric scale ice plates to produce dark bands, triple bands, and ridges.

A Sea Ice Analog for the surface of Europa
-- Department of Geological Sciences, Brown University, 1996

-----------

Other images are helping unravel more mysteries. Pieces of the moon's glaringly white crust are separated by wedged-shaped pieces of darker, newer crust, welling up from below, freezing and cracking. The separated pieces of white crust would fit back together like a jig-saw puzzle, suggesting that plate tectonic-like activity might be occurring on Europa to form the wedges. Composed of a set of narrow linear ridges and parallel grooves, the dark wedge has many similarities to new crust formed at mid-ocean ridges on the Earth's sea floor, says Brown graduate student Louise Prockter, who has studied high- resolution sonar images of the Mid-Atlantic Ridge and has visited the Pacific Ocean floor in the research submersible vehicle Alvin. Like Earth, new crust seems to be welling up, separating, and replacing older crust. On Europa, the molten material solidifying on the surface was likely slushy ice or liquid water.

from Detailed Images From Europa Point To Slush Below Surface
-- Jet Propulsion Laboratory

According to mission scientists, this motion can not be accounted for by wind or slope but could be caused only by the traction of currents in a liquid medium. The plausible cause for this motion is traction below which implies liquid below. The tilted bergs show just how thin is the surface here--perhaps only 1- or 2-km thick. Apparently, convection in solid ice (suspected on Ganymede) could not account for all the observed movement. And the lack of any feature higher or deeper than a few hundred meters would be consistent with a 1- or 2-km layer of floating ice [remember, icebergs are 90 percent below the surface].

JK (SSI Imaging Team): . . . . Thu, Apr 10, 5:26PM PDT (-0700 GMT)
Petrus - What was shown in the press conference yesterday were images of giant ice rafts that appear to have at one time floated through a liquid slush on Europa's surface. This strongly supports the presence of liquid oceans beneath this icy shell. We haven't found any life, of course, just an environment that may be well suited for it.

Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 5:29PM PDT (-0700 GMT)
Petrus: you need three things for life as we know it: water, an energy source, and organic material. Europa has an energy source from tidal heating by Jupiter. It could gather organic material from comets hitting its surface (we've seen comets hit Jupiter lately). The big question was, did/does Europa have liquid water under its surface? And now we see ice "rafts": icebergs that have been tilted and displaced. Wind didn't do that. They didn't slide down a slope (Europa is remarkably flat, overall). Only remaining possiblity is water underneath.

from Galileo Webchat 4/10/97

The new images from Galileo help answer some questions about other areas of Europa that are littered with fractured and rotated blocks of crust the size of several city blocks (dubbed chaos terrain). These fractured ice chunks appeared to be either sliding on soft glacier-like ice below the surface or floating like icebergs in a more fluid material. The new images show that the material between the cracked and separated plates of crust is rough and swirly, says Robert Papp alardo, a postdoctoral research scientist at Brown. The pieces are immersed in what appears to be a slush that is now frozen solid. The very low temperatures at the surface of Europa (-260° F) mean that any water exposed at the surface would freeze immediately and might create this kind of texture. The rough chaos terrain, as well as the movement and rotation of the blocks, suggest that the crust was at least partially liquid at shallow depths.

from Detailed Images From Europa Point To Slush Below Surface
-- Jet Propulsion Laboratory

Macula craters
This image of Europa, an icy satellite of Jupiter about the size of the Earth's Moon, was obtained from a range of 7415 miles (11933 kilometers) by the Galileo spacecraft during its fourth orbit around Jupiter and its first close pass of Europa. The image spans 30 miles by 57 miles (48 km by 91 km) and shows features as small as 800 feet (240 meters) across. The large circular feature centered in the upper middle of the image is called a macula, and could be the scar of a large meteorite impact. The surface of Europa is composed mostly of water ice, so large impact craters on Europa could look different from large bowl-shaped depressions formed by impact into rock, such as on the Moon. On Europa's icy surface, the original impact crater has been modified into a central zone of rugged topography surrounded by circular fractures which reflect adjustments to stress in the surrounding icy crust.

from Detailed Images From Europa Point To Slush Below Surface
-- Jet Propulsion Laboratory

Crater Morphology
Unlike Mars or Jupiter's other moons, the crust of Europa is remarkably free of impact craters -- the result of a collision with an asteroid or comet -- indicating that it has been resurfaced within the past 1 million years. ... Such recent activity makes it more likely that Europa currently has enough inner warmth to keep water liquid.

Furthermore, the few craters that do exist are smooth and shallow, lacking the raised rims and central peaks of craters on a rigid surface like the Earth or our moon ... this implies that Europa has an icy crust 6 to 10 miles thick, floating on top of a fluid ocean.

from NASA data support theory of life on moon of Jupiter
-- The Record Online, 10/16/98

Although the images do not show currently active ice volcanoes or geysers, they do reveal flows of material on the surface that probably originated from them.

"This is the first time we've seen actual ice flows on any of the moons of Jupiter. These flows, as well as dark scarring on some of Europa's cracks and ridges, appear to be remnants of ice volcanoes or geysers."

from Ice Volcanoes Reshape Europa's Chaotic Surface
-- Jet Propulsion Laboratory, 1/7/97

Curiosity Question
Considering the icy surface "seals" the planet, is it possible that many of the dissolved "Volatile" compounds that would normally outgass on a low gravity world may actually remain trapped within the ocean on europa? I would imagine any "Breaks" in the ice seal over rather quickly, so outgassing would be a time-limited event. The reason I ask is that if dissolved gasses exist trapped inthe oceans of Europa, I would imagine it might be more hospitable to life.

Jim Lukash
this was exactly one of the points made at the press conference yesterday: it's certainly possible that there is an enrichment of organic material under Europa's crust.

from Galileo Webchat 4/10/97

Fissure Eruptions
The major moons of Jupiter that are composed of ice are Callisto, Ganymede, and Europa. Callisto has a ``classic'' small-body surface -- it is covered with craters of various sizes, at least at first glance. At a closer look, however, an observer can find numerous faults and ridges on that battered world. Ganymede is cratered as well, but it shows much evidence of internal activity -- the large, light colored upwellings that cover the moon. Europa is perhaps one of the few worlds without craters; instead, its molten (read fluid H20) interior erases evidence of cratering by periodic fissure eruptions from the numerous linear features.

Triton: A New Version of Ice Geology
A broad overview of "ice geology" of all the Icy Moons of the Outer Planets
-- Quanta, an online scifi magazine

Another interesting possibility arises from the "tidal flexing" of Europa. Some scientists that heat generated by have suggested the creating lakes or oceans expansion and contraction may be enough to melt the icy crust at depth, below the surface. The possibility naturally leads to the question of whether life of liquid water just below Europa's surface could have evolved there. The communities on Earth that thrive in the deep ocean near hydrothermal vents discovery of marine provides us with a model for how similar organisms might survive on Europa. While the existence of liquid water beneath the surface would add one oflife's key ingredients, we know that many other factors, including organic material and a continuous energy source, need to be present. Even if there is no ocean currently on Europa, however, one may have existed in the past, possibly leaving fossilized remains to be found by a future mission.

from Why Europa?
-- Jet Propulsion Laboratory

In 1979, however, when the first pictures of Io were beamed to Earth ... were the unmistakable plumes of up to 10 erupting volcanoes. Ordinarily, a body the size of Io should have cooled off long ago, making volcanoes impossible. But for every pass the moon makes around Jupiter, it makes several passes by its large, slower-orbiting sister moons: Europa, Ganymede and Callisto. Every time Io does that, the gravitational tug of these nearby satellites gives it a twang. On Earth, the gravity of just one moon is sufficient to cause the oceans to rise and fall in great crashing tides. On Io, the gravitational influence of three nearby moons is enough to distort the shape of the world itself, causing it to pulse with a heartbeat-like lub-dub. This rhythmic motion churns up internal heat, which in turn stirs up moonwide volcanoes.

On Europa ... tidal heating may have produced something truly remarkable. The formations Galileo spotted last week are definitely icebergs ... small, rising just 300 to 600 ft. above the surrounding ice. Since only 10% of an iceberg shows above the water, that means these measure a mile or so from top to bottom--and so, therefore, does the planet-wide ice crust from which they came. On the scale of a 2,000-mile-wide moon, that's not much of a crust at all. No matter how thick the ice is, the waters beneath it must still be liquid, thanks to tidal heating.

from Life in a Deep Freeze?
-- Time, 4/21/97

anonymous: . . . . Thu, Apr 10, 3:46PM PDT (-0700 GMT)
What is tidal heating?

Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 3:50PM PDT (-0700 GMT)
anonymous, tidal heating is when tidal forces (in this case, tidal forces caused by Jupiter acting on Europa) heat something by friction. The tidal force tugs on the interior back and forth (for Io, these tidal forces are fairly dramatic, even for solid material), which causes heating. You can model this by bending a paper clip back and forth, and then feeling how the metal near the bend heats up.

Duane Bindschadler, Magnetometer & Dust Detector, Planetary Scientist: . . . . Thu, Apr 10, 3:51PM PDT (-0700 GMT)
anonymous: Tidal heating is caused by gravitational forces acting on (in this case) the moons of Jupiter. If the orbit of a satellite is anything other than a perfect circle, the changes in gravitational force actually stretch the body. When you flex solid material that way, it causes frictional heating. (that's the$.05 explanation, anyway)

Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 3:55PM PDT (-0700 GMT)
Hi anonymous, tidal heating is caused by friction as Europa is squeezed in and out each Europan "day" (3.6 Earth days). Because it isn't in a circular orbit aroud Jupiter, it is sometimes closer to Jupiter and sometimes farther away. As it gets closer, the tidal bulges grow (by an amount that depends on how deep the subsurface ocean is) and as it gets farther away, they subside. Friction during this process heats the interior. The extreme example is Io, where tidal heating produces the most geologically active body in the solar system.

from Galileo Webchat 4/10/97

Radioactive decay in the core? Hot spots...

Scattered about the surface are raised domes that may have been created when the ice over a "hot spot" thinned and water broke through. "It looks as though a reddish liquid soaked through or bubbled up from below" ...

from NASA data support theory of life on moon of Jupiter
-- The Record Online, 10/16/98

In other places on the surface, 7 to 15 kilometer diameter pits, spots, and domes disrupt the cross-cutting ridges, suggesting that in places the lower pa rt of the ice layer is upwelling in blobs (like those rising in a lava lamp) that push up and deform the surface.

Galilean Satellites of Jupiter
-- American Geophysical Union, 12/4/97

The Mystery of the Red Coloration

In contrast, the brownish mottled regions on the right side of the image may be covered by hydrated salts and an unknown red component. The yellowish mottled terrain on the left side of the image is caused by some other unknown component.

Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long.

from Europa Global Views in Natural and Enhanced Colors
-- Nasa's Planetary Photojournal, 5/8/98

Tim: . . . . Thu, Apr 10, 3:14PM PDT (-0700 GMT)
Is it possible that the redish-brown substance around the water geysers on europa is organic?

James Granahan, Planetary Geologist, Galileo SSI & NIMS: . . . . Thu, Apr 10, 3:18PM PDT (-0700 GMT)
It is possible that the brown "gunk" on Europa might be organic. Us spectral folks are working on interpreting some of the brown linea. We are attempting to make spectral models to remove the water ice components to see what the spectral signature of the non water ice stuff is.

Leslie, Galileo Outreach: . . . . Thu, Apr 10, 5:33PM PDT (-0700 GMT)
Messier, we believe under Europa's surface is or has been liquid water. It won't be PURE water, as it has some of the dark surface contaniments in it. These are likely from the meteorites which have bombarded Europa overtime, and do contain the building blocks for life.

from Galileo Webchat 4-10-97

Galileo's instruments have shown us that the physical properties of water ice vary from place to place on the surface, but we still know very little about the source and composition of the reddish-brown material that covers much of the landscape. It may have been brought to the surface through the many cracks in the ice, or could be material derived from objects that have impacted the surface. It may even contain organic compounds. Some scientists have suggested sending a lander or rover to collect and analyze samples directly on the surface using an instrument such as a mass spectrometer.

from The Future of Europa Exploration
-- Jet Propulsion Laboratory

Could the brownish-red substance be "tholins"?

The organics were detected by Galileo instruments that capture solar radiation reflected off the surface of the moons. The wavelength of the reflection is unique for each molecule, giving an electromagnetic "signature" of the surface chemistry ...the findings included various combinations of oxygen, carbon, sulfur, hydrogen and nitrogen that can make up several types of organic compounds.

One signature suggested the presence of tholins, an organic "gunk" that laboratory experiments have linked to the evolution of life, he said.

from Researchers: Jupiter moon has 'ingredients' for life
-- Associated Press, 10/10/97

  Magnetic Field

from Galileo Returns New Insights Into Callisto and Europa
-- 5/23/97

Variable Magnetic Field
Galileo data indicates that electrical currents flowing near Europa's surface cause changes in Europa's magnetic field. Other data supports the idea that beneath Europa's icy crust, a liquid ocean might be serving as a conductor of electricity.

Galileo data has shown that these electrical currents flow in opposite directions at different times. Scientists hypothesize that this is a key signature consistent with the idea of a salty ocean because it shows that Europa's response is synchronized with the effects of Jupiter's rotation.

from Jupiter's Moon Callisto May Hide Salty Ocean
-- 10/21/98

Electromagnetic Induction
The scientists hypothesized the existence of underground seas from data collected by the Galileo spacecraft. Galileo measured strong disturbances to Jupiter's magnetic field as the spacecraft zipped past Europa and Callisto. However, the moons lack strong magnetic fields of their own that could exert such a force. The scientists concluded that Jupiter's magnetism must be giving rise to secondary fields within some powerful electrical conductor on each moon -- a phenomenon known as electromagnetic induction, which is at work on Earth in generators and electromagnets.

The researchers could imagine only one sufficiently strong conductor that is plausible on those moons: huge bodies of salt water. They would be within about 60 miles of the frozen surface, kept from icing over by heat within the interior of the moons.

Assuming they are as salty as Earth's oceans, they would be about 6 miles deep.

from Jupiter's moon Callisto may hide underground sea
-- CNN.com, 10/23/98

Possible Sources for Magnetic Fields (re: Ganymede)
There are several possible sources for an internal magnetic field. (1) A self-generating dynamo in an iron core (this is how we think Earth's magnetic field is created). (2) A similar dynamo in a highly saline water layer deep in Ganymede (this is how some scientists think the magnetic fields of Uranus and Neptune are created). (3) Remnant magnetism "frozen in" to rocks inside Ganymede. I think that the last of these is very unlikely because Ganymede's magnetic field is so strong (at least 5 or 6 times as strong at Ganymede's surface as Jupiter's field at the same point). It's very hard to get such large mag. field strengths when Ganymede is mostly made up of non-magnetic material. The group at UCLA working on this data (they have a paper that will come out in the journal Nature very soon -- look for reports in your local newspapers) believes that an iron core is the most likely source.

from Galileo Webchat 10/30/96

Protection from Radiation

Jo Pitesky, Galileo Outreach: . . . . Thu, Apr 10, 4:55PM PDT (-0700 GMT)
Tim, Jupiter's magnetic field bends somewhat when there's a powerful flare, but the flare itself will not penetrate.

Paul Geissler, Galileo SSI: . . . . Thu, Apr 10, 5:00PM PDT (-0700 GMT)
Hi Tim, Both Jupiter's magnetic field and Europa's ice would prevent charged particles from reaching down into Europa's interior... as has already been pointed out, this makes Europa's subsurface a potentially cozy environment in which to nurture life (we always assumed that a magnetic field or thick atmosphere would be needed to shield the surface of a planet capable of supporting life...).

from Galileo Webchat 4/10/97

Future Missions, Proposed Europa Orbiter

Galileo was designed more than 20 years ago, before Voyager provided the first clues to Europa's surface, and the instruments on board Galileo are not really appropriate for searching for subsurface water. That is why NASA is currently investigating how future missions might be designed for the next step in the exploration of Europa. One instrument that could be used in this way is a microwave sounder, or radar system. Placed on an orbiting spacecraft around Europa, it could send signals through the ice to a depth of a kilometer or more to search for liquid water. In addition, precise mapping of the global shape of Europa would allow for determining how distorted the moon might be in response to tidal forces. If subsurface liquid water is found, either globally or locally, plans for future exploration call for landed spacecraft with the ability to drill or melt through the ice to sample and explore the potential water world.

from The Partially Watery World of Europa
-- American Geophysical Union, 12/4/97

Links

Pictures support theory of water on Europa
"Newly released images of Jupiter's moon Europa -- the most detailed ever taken -- show more evidence that there is slush, and perhaps even water, beneath Europa's icy surface."
-- CNN.com, 3/2/98

Galileo takes a close look at icy Europa
" ... 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."
-- Jet Propulsion Laboratory, 10/2/98

Reports Finding "Ingredients for Life" on Jupiter's Moons
"The Galileo mapping spectrometer instrument detected combinations of oxygen, carbon, sulfur, hydrogen and nitrogen on the surfaces of Callisto and Ganymede, two of Jupiter's moons. This makes it highly likely, McCord says, that similar compounds existed on Europa, but it is the only one of four Jupiter moons that is also believed to have liquid water."
-- Planetary Science, University Hawaii, 10/24/97

Application of Terrestrial Sea Ice Mechanics to the Icy Surface of Europa
"Reconstruction of gray and wedge-shaped bands on Europa suggests that their formation is analogous to the creation of leads in terrestrial sea ice, involving separation of ice plates, but on a large scale."
--Planetary Geosciences Group of the Department of Geological Sciences, Brown University

Hubble Finds Oxygen Atmosphere on Europa
"Astronomers using NASA's Hubble Space Telescope (HST) have identified the presence of an extremely tenuous atmosphere of molecular oxygen around Jupiter's second moon, Europa. The planets Mars and Venus are the only two other solar system objects beyond Earth known to have traces of molecular oxygen in their atmospheres."
-- NASA, JPL

Europa -- orbiting incubator?
"Since we already know that this moon is coated with frozen water and is not dense enough to be pure rock, the photos support the notion that Europa also contains water inside."
-- The Why Files, 3/26/98

NASA gives a new angle on jovian moon's water
"Pwyll Crater on Jupiter's moon Europa shows some of the best evidence yet for water or warm slush underlying the moon's crust of hard ice.
-- Nature, 3/5/98 (requires free registration)

Water World
"When Galileo Galilei aimed a telescope at Jupiter one dark night in 1610, he spied four large,
bright satellites, lost to the naked eye in the glare of the gassy giant planet. He could hardly
have guessed that one of those moons--Europa, second closest to Jupiter--might one day shine
light on the origin of life on Earth."
-- Discover Magazine,

Jupiter's Europa Harbors Possible "Warm Ice" or Liquid Water
"Tantalizing new images of Jupiter's moon Europa from NASA's Galileo spacecraft indicate that "warm ice" or even liquid watermay have existed, and perhaps still exists today beneath Europa's cracked icy crust."
-- NASA, Project Galileo, 8/13/96

Possibility of Life on Europa
"What makes Europa such an attractive place to look for life is the possibility that it has liquid water and volcanic activity. Liquid water is essential for life on earth and is the most probable solvent for life elsewhere. Volcanic activity provides some of the heat necessary to keep the water on Europa from freezing and could provide important dissolved chemicals needed by living organisms."
-- Milwaukee School of Engineering.

Ice Volcanoes Reshape Europa's Chaotic Surface
"Ice-spewing volcanoes and the grinding and tearing of tectonic plates have reshaped the chaotic surface of Jupiter's frozen moon Europa, images from NASA's Galileo spacecraft reveal ... The images, captured when Galileo flew within just 430 miles (692 kilometers) of Europa ... Although the images do not show currently active ice volcanoes or geysers, they do reveal flows of material on the surface that probably originated from them "
-- Views of the Solar System

Jupiter system
"Jupiter exerts a special fascination through its sheer size: it is the largest planet, more massive than all the others lumped together, and its four giant Galilean satellites are entire worlds in themselves "
-- Scientific American, 3/3/97

Europa Update
"The latest pictures beamed from the Galileo spacecraft provide further suggestions that there is ample slushy water on Jupiter's moon Europa (pictured). Meanwhile, American and Russian astrobiologists are looking closer to home, Antarctica, for hints on what life-forms might inhabit such conditions. "
-- Access Excellence (Genentech, Inc., sole sponsor), national educational program for biology, 3/5/98

Organic Molecules on Jovian Moons
"Having previously discovered water on the Jovian moon Europa, the Galileo spacecraft now reports the presence of organic molecules on two other moons, Ganymede and Callisto. Because Europa shares common characteristics with the other Galilean moons, researchers believe it is reasonable to expect that organic molecules will also be found on Europa. Europa, with water and heat energy provided by the moon's core, is now considered the leading contender for a second source of life in the solar system. "
-- Access Excellence (Genentech, Inc., sole sponsor), national educational program for biology, 10/10/97

Life on Europa?
"Stunning new photos transmitted by the Galileo spacecraft have revealed what may be a huge ocean of water, leading some scientists to predict that finding life there is all but inevitable ... the ice rafts reveal that Europa had, and may still have, a very thin ice crust covering either liquid water or slush. "
-- Access Excellence (Genentech, Inc., sole sponsor), national educational program for biology, 4/9/97

Water on Europa?
" Close on the heels of the discovery of bacterial fossils from Mars comes another compelling suggestion of life in the solar system, the discovery that water may have existed, or might even still exist on Jupiter's moon Europa. "
-- Access Excellence (Genentech, Inc., sole sponsor), national educational program for biology, 8/21/96

What do most scientists believe about the possibility of life in Europa's oceans?
FAQ
-- NASA, Galileo Project, 12/31/97

Tidal flexing
"Another interesting possibility arises from the "tidal flexing" of Europa. Some scientists have suggested that heat generated by the expansion and contraction may be enough to melt the icy crust at depth, creating lakes or oceans below the surface. The possibility of liquid water just below Europa's surface naturally leads to the question of whether life could have evolved there. The discovery of marine communities on Earth that thrive in the deep ocean near hydrothermal vents provides us with a model for how similar organisms might survive on Europa. "
-- NASA, Galileo Project, 1/26/98

NASA has grand exploration plans
"It's an ice-cold fact: Europa is a bizarre, frozen land awash in deadly radiation from its giant parent, Jupiter. Such a forbidding place demands fantastic plans for exploration... "
-- FLORIDA TODAY Space Online, 2/10/98

The Greening of Europa
"The heightened interest in Europa comes at a time when scientists are increasingly considering the possibility that satellites, not just planets, might support conditions suitable for life. Within the past two years, astronomers have discovered possible planets circling eight sunlike stars. These giant worlds probably offer poor prospects for terrestrial-type biologies. But in a recent paper ... suggested that possible large moons orbiting two of the planets might fall into the 'habitable zone' where life can arise. "
-- Scientific American, 4/97

Life under the ice? (radio broadcast transcript)
"So if life can exist undetected for millenia on Earth's ocean floor, might the same be true on another body in our solar system - one that might have an ocean? If a growing number of oceanographers and planetary scientists are
-- Federation of American Scientists

Did Earth Spawn Life On Europa
"... life may have hitchhiked across the solar system. The proof may be found at the ends of the Earth. This week, American and Russian scientists are examining deep ice from the Antarctic and hoping to find clues that fungi, bacteria, and even diatoms could survive conditions in icy solar system bodies ... ancient impacts of asteroids on the Earth could have ejected soil, rocks, and seawater containing terrestrial microorganisms into space, and that they may have made it to other places in the solar system ..."
-- Spacer.com

Exploring Ice Worlds
links
-- Astrobiology Web

Future Missions to Europa

Outer Planets/Solar Probe Project:Europa Orbiter
"... preliminary development has begun on a mission to send a spacecraft to Europa to measure the thickness of the surface ice and to detect an underlying liquid ocean if it exists. Using an instrument called a radar sounder to bounce radio waves through the ice, the Europa Orbiter sciencecraft would be able to detect an ice-water interface... "
-- NASA/JPL Outer Planets/Solar Probe Project

Europa Ice Clipper: A Proposed Discovery Mission
"The Europa Ice Clipper is a flyby mission. To obtain samples of the surface of Europa we will use an impact sampling method. As we approach Europa a 10 kg hollow copper sphere is released on a impact trajectory. The spacecraft then diverts to fly through the plume of surface material that is created by the impact. The ability to create a plume, predict its properties, and sample the particles in the plume while protecting the spacecraft are the basis for this mission design. "
-- Astrobiology Web

High wire act may be best way to explore Europa
"As NASA works to make space missions cheaper, it is looking at the possibility of using a long wire to power spacecraft exploring space around Jupiter where Galileo is gathering more hints that icebound Europa may have the right conditions for life."
-- NASA, Space Science Laboratory, 3/13/98

Design a Spacecraft to test for Life on Europa (student activity)
"Activity Overview: This activity challenges students to design a spacecraft that will travel to Europa, one of Jupiter's moons, and test for the presence of life. Students should take into account various factors affecting the design of a spacecraft travelling to the outer solar system as well as develop tests to determine if life is present on Europa."
-- NASA Quest Project

Europa Ocean Explorer project
"... a main bus spacecraft, or "mothership", which would either flyby or orbit the moon and drop a number of small probes onto this world. Some of these landers would explore the surface, while others would find their way beneath the ice into the Europan waters and reveal their long-held mysteries."
-- MIT

Aquarium test helps scientists look for life in extreme environments
"NASA's search for life elsewhere in the solar system is bringing space scientists to the giant kelp forest exhibit at the Monterey Bay Aquarium to test a new scientific probe that might one day look for life in oceans that may exist on Jupiter's icy moon Europa."
-- JPL, 8/20/98

Europa Geology Jigsaw Puzzle
"Written for middle school teachers - This module includes several activities designed to introduce students to concepts related to properties of matter, styles of deformation, and the nature of Europa's icy crust. In addition, similarities are drawn between geological processes on Europa and Earth, as well as the possibility that a subsurface ocean existed on Europa in the past (and perhaps still exists today)."
-- Galileo Solid State IMAGING (SSI) Team, Education and Public Outreach

Europa: Ingredients for Life?
"Grade Level: Elementary and Middle School - Objective: Students will learn about the ingredients necessary for life (as we know it) to exist, the sources of these ingredients, the role of large impact events in shaping life, and the potential difficulty of producing life even when these ingredients are present."
-- Galileo Solid State IMAGING (SSI) Team, Education and Public Outreach