Extraterrestrial Ice Page by Jason J Haston

In service, there is ... ice
  1. Ganymede
  2. Callisto
  3. Europa
  4. James B. Pollack
  5. Comet
  6. Moon
  7. Space
  8. Mars (Sw Mars)
    Ice Related Articles - no pics.


  • southern polar cap ice
  • Lunar Prospector
  • Clementine

    southern polar

    ice cap image.
    postulated occurrence of ice in permanently shadowed areasMoon


    Lunar Prospector

    launch on September 24, 1997.
    Lunar Prospector should directly
        A free-flier, Lunar Prospector will orbit above the Moon's surface at an altitude of approximately 63 miles during a one-year  mission.  Its five science instruments will provide detailed data  on the composition and structure of the entire lunar landscape, of  which more than 75 percent remains virtually unexplored.  A key  mission objective is to provide direct evidence of the presence or  absence of ice in the shaded lunar polar regions.
    determine the existence or absence of water ice in the Moon's
    polar regions, which has been suggested by analysis of indirect,
    radar-based data from the 


    mission. A neutron spectrometer will have the capability to locate as little as one cup of water in about a cubic yard of lunar soil (regolith). The discovery of water ice in the lunar polar regions would mean that water, necessary for life support and a potential source of both oxygen and hydrogen to produce rocket propellant, could be available for use by future lunar explorers.


  • Voyager 1
  • Polar Caps
  • Fine Details
  • Ice hills
  • soaring whistle and hissing static

    Voyager 1 Image of Ganymede

    Polar caps are composed of a light covering of water ice or frost.

    Galileo Orbiter Image of Ganymede

    Fine Details of the Icy Surface of Ganymede Ganymede

    Ice Hills.

    The bulk of the satellite is believed to be about half water-ice and half rock. Portions of its surface are relatively bright, clean ice while the other regions are covered with darker "dirty" ice. The darker areas appear to be ancient and heavily cratered, while the lighter regions display evidence of tectonic activity that may have broken up the icy crust. A thin layer of ozone has been found in Ganymede's surface by Earth (Sw Tellus/Jordan)-based astronomers.Ganymede

    Galileo Orbiter

    sounds of Ganymede
    soaring whistle and hissing static
         Jupiter's big moon Ganymede is not only the size of a
    planet -- it sounds like one too, as heard in audio
    recordings made from data returned by NASA's Galileo
    spacecraft released today.
         Characterized by a soaring whistle and hissing static,
    Ganymede's song reveals that the Solar System's largest moon
    is also the only one known to possess a planet-like, self-
    generated magnetic cocoon called a magnetosphere, which
    shields the moon from the magnetic influence of its giant
    parent body, Jupiter (Sw Jupiter).
         Using extremely precise data from tracking the
    spacecraft, investigators on Galileo's celestial mechanics
    team also have been able to confirm that Ganymede's interior
    is differentiated, probably having a three-layer structure.
    "These data show clearly that Ganymede has differentiated
    into a core and mantle, which is in turn enclosed by an ice
    shell," said JPL planetary scientist Dr. John Anderson, team
    leader on the Galileo radio science experiment.
         "At Ganymede, the magnetic field is strong enough to
    carve out a magnetosphere with clearly defined boundaries
    within Jupiter's magnetosphere, making it the only
    'magnetosphere within a magnetosphere' known in the Solar
    System," Kivelson said.
         Bright white areas seen around the circular rims of
    high-latitude impact craters on Ganymede in new Galileo
    images of that moon are likely water-ice frosts, Galileo
    scientists report.  Even though the Sun is shining from the
    south, the north-facing walls of the ridges and craters are
    brighter than the walls facing the Sun.  Images of regions
    elsewhere on Ganymede show more details of the remarkable
    juxtaposition of newer and older fractured and faulted
    terrain that characterizes so much of this big moon's
    surface.  A stereoscopic view of Ganymede has also been
    produced with two images of the Galileo Regio region (one was
    taken during the first Ganymede flyby in June and the second
    was acquired in the September flyby).  The image, which was
    computer-reconstructed by imaging scientists at JPL, shows
    new topographic information about the moon.


    frost On Callisto and Ganymede, the near-infrared mapping spectrometer found surface features indicating the presence of hydrated materials, or possibly carbon dioxide frost.


  • covered by water ice
  • ICE VOLCANOES ice volcanoes
  • subsurface ocean

    covered by

    water ice, from Galileo.
    The first midday temperature for Europa, -229 Fahrenheit has allowed the radiometer instrument team to determine that the moon has a more porous or "fluffy" ice surface than the other moons. Researchers said that such porosity indicates Europa's surface is covered with finely powdered ice grains. Scientists were surprised by the lack of small craters visible in the images. Some small craters appear to have been softened or modified by downslope movement of debris, revealing ice-rich surfaces. spacecraft makes its first close approach to Europa, the moon thought to harbor a liquid ocean beneath its icy surface. Results from that flyby will be radioed to Earth (Sw Tellus/Jordan) starting in the last half of December through early February. The Europa image received from the spacecraft earlier this week shows the cracked surface of this moon in greater detail than it has been seen before. The new image shows an area 150 miles by 140 miles that has been highly disrupted by fractures and ridges. Arizona State University planetary scientist Dr. Kelly Bender of Galileo's imaging team said that symmetric ridges in the dark bands suggest that Europa's surface crust was separated and filled with darker material, somewhat analogous to spreading centers in the ocean basins of Earth (Sw Tellus/Jordan). Although some impact craters are visible, their general absence indicates a youthful surface, she said. The youngest ridges, such as the two features that cross the center of the picture, have central fractures, aligned knobs, and irregular dark patches. These and other features could indicate cryovolcanism, or processes related to eruption of ice and gases.
    Europa Apparently


    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 on Dec. 19, were released at a news briefing today at NASA Headquarters, Washington, DC. 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, said Galileo imaging team member Dr. Ronald Greeley of Arizona State University, Tempe. "This is the first time we've seen actual ice flows on any of the moons of Jupiter," said Greeley. "These flows, as well as dark scarring on some of Europa's cracks and ridges, appear to be remnants of ice volcanoes or geysers." The new images appear to enhance Europa's prospects as one of the places in the Solar System that could have hosted the development of life, said Greeley. "There are three main criteria to consider when you are looking for the possibility of life outside the Earth (Sw Tellus/Jordan) -- the presence of water, organic compounds and adequate heat," said Greeley. "Europa obviously has substantial water ice, and organic compounds are known to be prevalent in the Solar System. The big question mark has been how much heat is generated in the interior. "These new images demonstrate that there was enough heat to drive the flows on the surface. Europa thus has a high potential to meet the criteria for exobiology," Greeley added. "This doesn't prove that there is an ocean down there under the surface of Europa, but it does demonstrate that it is a scientifically exciting place," said Galileo imaging team member Dr. Robert Sullivan, also of Arizona State University. The images also reveal a remarkable diversity in the geological age of various regions of Europa's surface. Some areas appear relatively young, with smooth, crater-free terrain, while others contain large craters and numerous pits, suggesting that they are much older. The icy crust bears the signs of having been disrupted by the motion of tectonic plates. "There appear to be signs of different styles of tectonism," said Greeley. "In many areas we see that the crust was pulled apart in a spreading similar to the processes on the sea floor on Earth (Sw Tellus/Jordan). This is different from the tectonic processes at work on, say, Jupiter's moon Ganymede. This suggests that Europa's interior may be different from Ganymede's." Galileo scientists will have a better chance to understand Europa's interior when the spacecraft gathers gravity data on another flyby next November. The gravity field is measured by tracking how the frequency of Galileo's radio signal changes as it flies past the moon. This was not possible during the recent flyby because radio conditions were degraded as Jupiter passed behind the Sun from Earth's point of view. Europa is crisscrossed by an amazingly complex network of ridges, according to Sullivan. "Ridges are visible at all resolutions," he explained. "Closely paired ridges are most common. With higher resolution, ridges seen previously as singular features are revealed to be double." Some of the ridges may have formed by tension in the icy crust: as two plates pull apart slightly, warmer material from below might push up and freeze to form a ridge. Other ridges may have been formed by compression: as two plates push together, the material where they meet might crumple to form the ridge. In addition to ice flows and tectonics, Greeley and Sullivan noted that some areas on Europa seem to have been modified by unknown processes that scientists are still debating. Greeley said that some areas, for example, seem to have been modified by "sublimation erosion" -- the evaporation of water and other volatiles such as ammonia and methane into the vacuum of space. "Something is destroying the topography," said Greeley, "and this sublimation erosion is a good candidate for what is at work." During last month's encounter, Galileo flew more than 200 times closer to Europa than the Voyager 2 spacecraft did in 1979. After a swing past Jupiter next week in what mission engineers call a "phasing orbit," Galileo's next targeted flyby will take it again past Europa as it passes within 364 miles (587 kilometers) on Feb. 20.



    subsurface ocean

    LATEST IMAGES OF ICY EUROPA AND DEBATE OVER SURFACE AGE TO BE FEATURED IN APRIL 9 GALILEO BRIEFING New images of Europa from NASA's Galileo mission and related animation supporting the theory that the icy moon of Jupiter may have a subsurface ocean will be presented at a press briefing on Wednesday, April 9, at 2 p.m. EDT. The briefing will originate from NASA's Jet Propulsion Laboratory, Pasadena, CA, and will be carried live on NASA Television. The latest images were taken during Galileo's closest flyby of Europa on Feb. 20, 1997, when the spacecraft came within 363 miles of the Jovian moon and took very high resolution images of features in regions never before studied. The tantalizing new images and data indicate Europa has a thin ice crust covering either liquid water or slush. Scientists are intrigued by the prospect that a slushy concoction of chemicals in this region could nurture life. The briefing will include outside experts raising the possibility that Europa's oceans may contain thermal vents, sea ice and other phenomena found on Earth (Sw Tellus/Jordan). The estimated age of Europa's surface also will be discussed, with controversial new information leading some scientists to conclude the surface is much younger than previously believed. As evidence of that, images will be shown of relatively smooth, crater-free areas. NASA Television is available through GE-2, Transponder 9C at 85 degrees West longitude, vertical polarization, with a frequency of 3880 Mhz, and audio of 6.8 Mhz. The new images of Europa will be released on the Galileo Internet home page at the following URL: JPL NASA Galileo Europa-end-



    NEW IMAGES HINT AT WET AND WILD HISTORY FOR EUROPA Wed Apr 9 12:22:58 1997 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 (Sw Tellus/Jordan). 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: JPL NASA Galileo

    Flooding fear after ice volcano erupts By Roger Highfield, Science Editor ICELAND remained on alert last night as a volcanic eruption under Europe's largest glacier threatened to cause widespread flooding along its south coast. The volcano sent plumes of steam and ash up to 33,000 feet while molten rock spewed from a five-mile fissure. But the main concern was the melting ice, which sent water pouring into the Grimsv=F6tn caldera, a crater-like basin underneath the glacier. The water appeared to be close to filling the caldera lake yesterday and glaciologists predicted an imminent glacier burst. Icelanders continued to reinforce barriers along the banks of the Skeidara river and prepared to dig channels through roads in the threatened region to give the torrent of water a free path, limiting potential damage to bridges, power stations and telephone lines. The glacier lies 120 miles east of Reykjavik and about the same distance south of the Arctic Circle. It is separated from the coast by a fringe of farmland. Scientists monitoring the eruption said that enough water to cover a square mile 850 yards deep had collected under the glacier, bringing the level in the lake to its highest this century. "It is now at a critical level and should start to flow out at any time," said a spokesman.


    James B. Pollack

    James B. Pollack , conceived that nearly lossless scattering by wavelength-sized particles of water ice could explain the low microwave emissivity and high radar reflectivity of Saturn's (Sw Saturnus) rings.



    1. Ganymede
    2. Components of Comets Components of Comets
    3. Violent Eruptions Violent Eruptions
    4. Mottled Nucleus Mottled Nucleus
    5. Hale Bopp Hale Bopp
    6. Hyakutake Hyakutake
    7. Halley's Comet Halley's Comet
    8. Stardust
    9. Tail

    Components of Comets

    Online Comet Page from Sky & Telescope Magazine.
    Basics of Space Flight
    working? working?

    The blue tail is composed of charged particles, while the broad whiter is composed of dust particles lit up by the sun.
         NASA's Infrared Telescope Facility (IRTF) on Mauna Kea,
    HI, will dedicate several days of observing time to study
    the release of dust and ice grains from the nucleus of the
    [Interrupt Process]are composed primarily of water.
    Spectral observations of the molecules vaporized from the
    nucleus should provide samples of molecular abundances that
    were present at the time of the formation of the Solar
    System.  The Extreme Ultraviolet Explorer spacecraft will
    make observations of neon and helium for comparison with the
    water production rates to be measured  by the IRTF.

    Violent Eruptions

    on the Comet's Surface
           During the course of long-term observations, which began in
    August 1995, astronomers unexpectedly caught the comet going
    through a sudden brief outburst, where, in little more than an
    hour, the amount of dust being spewed from the nucleus increased at
    least eight-fold.  "The surface of Hale-Bopp's nucleus must be an
    incredibly dynamic place, with 'vents' being turned on and off as
    new patches of icy material are rotated into sunlight for the first
    time," Weaver said.
    A Complex,

    Mottled Nucleus

           To their surprise, astronomers found that water ice
    sublimates (turns directly from a frozen solid into a gas) at a
    different rate than the trace ices, implying that those components
    are not contained within the water on the comet.  This conclusion
    is further supported by Hubble data showing that the rate at which
    dust left the nucleus was much different than the sublimation rate
    of water.  This result is contrary to previous models for a comet's
    nucleus, which suggest that the trace components, such as carbon
    disulfide ice, are contained inside of the most abundant ice on the
    comet, frozen water.  As water sublimates, the trace components and
    dust should be released at similar rates, but this is not what
    Hubble observed.

    Hale Bopp

    Hale Bopp
    LASCO Comet (from SOHO ) HOME PAGE


    This is a large animated GIF file showing the comet's (Hyakutake) motion over six days, April 30 - May 5, 1996 Sol w/ Hyakutake Movie - B&W Gif 1533k.
    Hyakutake and CME- Color Gif 477k bytes.
    another movie - closeup - same source
    Comet Movie (Blue filter) - Color Gif 765k bytes.

    X-Ray s Hyakutake .
    the release of dust and ice grains from the nucleus of the
    comet.  These ices are composed primarily of water.
    Spectral observations of the molecules vaporized from the
    nucleus should provide samples of molecular abundances that
    were present at the time of the formation of the Solar
    Images from IRTF and many other sources will be posted here .



    Halley's Comet

    This historic photograph shows a wide-angle view of Halley's Comet as it appeared over Flagstaff, Arizona on May 13, 1910.
    The streaks at lower left are the city lights of Flagstaff, and the large bright object below the comet is the planet Venus (Sw Venus).
    The best known of all comets, Halley orbits the Sun, and travels close enough to be seen from the Earth (Sw Tellus/Jordan) approximately once every 75 years. Its appearances have been recorded at least 30 times over the past 2000 years, and scientists have accurately predicted its return starting with its appearance in 1758.




    The fourth Discovery mission, 
    Stardust, originated from the same group of proposals and was 
    formally selected in November 1995.  Following a February 1999 
    launch, Stardust is designed to gather first-time samples of 
    interstellar dust and dust spewed from the comet Wild-2 and 
    return them to Earth (Sw Tellus/Jordan) in 2006 for detailed analysis.



    RELEASE:  97-89
    watching for a break in Comet Hale-Bopp's plasma ion tail.
    ion tail likely would be disrupted when it enters a region 
    around the Sun known as the "current sheet."
    interaction between the comet and the Sun's influence and magnetic 
    fields.  As a comet comes closer to the Sun, ices from the nucleus 
    (a porous structure of dust and ice composed of frozen gases) are 
    continually vaporized, dislodging the dust, which is formed by the 
    comet's weak gravity into a cloud, called a co