Shows‎ > ‎Moons of the Solar System‎ > ‎


News, Updates, and Resources for
Moons of the Solar System

For latest count of numbers of moons, see...

General Moons Resources:


Online Articles and Information

  • 2014-08-17.
    Cassini Saturn mission Ten Year Top Science page:
    Video about Cassini's future:
    Infographict, By The Numbers:
    Ten Year Top Images:

    Top Science of 2013:
    Top Images of 2013:
  • 2014-07-28. Cassini Spacecraft Reveals 101 Geysers and more on Icy Saturn Moon. NASA RELEASE 14-203.  Excerpt: Scientists using mission data from NASA’s Cassini spacecraft have identified 101 distinct geysers erupting on Saturn’s icy moon Enceladus.  Their analysis suggests it is possible for liquid water to reach from the moon’s underground sea all the way to its surface. ...After the first sighting of the geysers in 2005, scientists suspected repeated flexing of Enceladus by Saturn’s tides as the moon orbits the planet had something to do with their behavior.  ...Individual geysers were found to coincide with small-scale hot spots, only a few dozen feet (or tens of meters) across, which were too small to be produced by frictional heating, but the right size to be the result of condensation of vapor on the near-surface walls of the fractures. ...“Once we had these results in hand we knew right away heat was not causing the geysers, but vice versa,” said Carolyn Porco, leader of the Cassini imaging team from the Space Science Institute in Boulder, Colorado, and lead author of the first paper. “It also told us the geysers are not a near-surface phenomenon, but have much deeper roots.” Additional details, images and an animation are available at: More information about Cassini is available at: ...

  • 2014-03-18. NASA Releases First Interactive Mosaic of Lunar North Pole. NASA RELEASE 14-079. Excerpt: ...Scientists, using cameras aboard NASA's Lunar Reconnaissance Orbiter (LRO), have created the largest high resolution mosaic of our moon’s north polar region. The six-and-a-half feet (two-meters)-per-pixel images cover an area equal to more than one-quarter of the United States. ...The entire image measures 931,070 pixels square – nearly 867 billion pixels total. ...LRO entered lunar orbit in June 2009 equipped with seven instrument suites to map the surface, probe the radiation environment, investigate water and key mineral resources, and gather geological clues about the moon's evolution....
  • 2012-03-27. Is It Snowing Microbes on Enceladus? | by Dauna Coulter, NASA Science News. Excerpt: …In a series of tantalizingly close flybys to the moon, named "Enceladus," NASA's Cassini spacecraft has revealed watery jets erupting from what may be a vast underground sea. These jets, which spew through cracks in the moon's icy shell, could lead back to a habitable zone that is uniquely accessible in all the solar system. …says Carolyn Porco …"Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth's oceans." …She believes the small moon, with its sub-surface liquid sea, organics, and an energy source, may host the same type of life we find in similar environments on Earth. …But what makes Enceladus special is that its habitable zone offers itself up for easy access. "It's erupting out into space where we can sample it. It sounds crazy but it could be snowing microbes on the surface of this little world…. Read the full article:
  • 2012 March. GRAIL MoonKAM (Moon Knowledge Acquired by Middle school students), led by Dr. Sally Ride, America's first woman in space, and her team at Sally Ride Science in collaboration with undergraduate students at the University of California San Diego, enables fifth- to eighth-grade students to select target areas on the lunar surface and send requests to the GRAIL MoonKAM Mission Operations Center (MOC). Photos of the target areas are sent back by the GRAIL satellites and made available in the Images section of the MoonKAM website. Students use the images to study craters, highlands, and maria while also learning about future landing sites.
  • 2010 Dec 28. Lunar Phases Planisphere. By  Stephen Shawl. A lunar phases planisphere with which a user can answer questions about the rising and setting times of the Moon as well as questions about where the Moon will be at a given phase and time. The article contains figures that can be photocopied to make the planisphere.
  • 2010 December 14. NASA RELEASE 10-335: Cassini Spots Potential Ice Volcano On Saturn Moon. Excerpt: NASA's Cassini spacecraft has found possible ice volcanoes on Saturn's moon Titan that are similar in shape to those on Earth that spew molten rock…
    …"This is the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite," said Jeffrey Kargel, a planetary scientist at the University of Arizona, Tucson. "It's possible the mountains are tectonic in origin, but the interpretation of cryovolcano is a much simpler, more consistent explanation."...
  • 2010 December 10. Venus Has a Moon? By Mike Simonsen, Discovery News. Excerpt: ...2002 VE68 used to be a run of the mill, potential impact threat Near Earth Object (NEO). But approximately 7,000 years ago it had a close encounter with Earth that kicked it into a new orbit.
    It now occupies a place in orbit around the sun where at its closest it wanders inside the orbit of Mercury and at its furthest it reaches just outside the orbit of the Earth. It is now in a 1:1 orbital resonance with Venus…
    An orbital resonance is when two orbiting bodies exert a regular, periodic gravitational influence on each other due to their orbital periods being related by a ratio of two small numbers...
    ...In the case of Venus and 2002 VE68, they both take the same time to orbit the sun once. They are in a 1:1 orbital resonance. So by definition, 2002 VE68 is considered a quasi-satellite of Venus.
  • 2010 October 7. Titan's Atmosphere Could Produce Building Blocks of Life. By Nancy Atkinson, Universe Today. Excerpt: Saturn’s moon Titan has long been thought to be an analog of early Earth, and a recent experiment demonstrates that amino acids and nucleotide bases — which are the basic building blocks of life on Earth – could very easily be under production in Titan’s hazy atmosphere...
    ...Two recent exciting discoveries led the team to try and find out more about Titan’s atmosphere: first, the discovery of high energy oxygen ions flowing into Titan’s atmosphere, and second, that there are high heavy molecular ions in the atmosphere – neither of which were expected.
    Working with a team in France, Sarah Horst [a graduate student from the University of Arizona] and her professor Roger Yelle filled a reaction chamber with Titan-like atmosphere, (a cold plasma consisting of nitrogen, methane and carbon monoxide), and infused radio-frequency radiation as an energy source.
    ... The molecules discovered in the aerosols include the five nucleotide bases used by life on Earth (cytosine, adenine, thymine, guanine and uracil) and the two smallest amino acids, glycine and alanine.
  • 2010 October 5. Saturn’s Rings Formed from Large Moon’s Destruction. By Nancy Atkinson, Universe Today. Excerpt: The formation of Saturn‘s rings has been one of the classical if not eternal questions in astronomy...Robin Canup from the Southwest Research Institute has uncovered evidence that the rings came from a large, Titan-sized moon that was destroyed as it spiraled into a young Saturn.
    …Canup’s new alternative theory is that a Titan-sized moon with a rocky core and an icy mantle spiraled into Saturn early in solar system history. Tidal forces ripped off part of the icy mantle, distributing it into what would become the rings. But the rocky core was made of more durable material that held together until it hit Saturn’s surface. “The end result is a pure ice ring,” Canup said in an article in Nature.
    Over time the ring spreads out and its mass decreases, and icy moons are created. Due to changes in the evolving Saturn system, these “spawned” moons then spiraled outward rather than inward. In this way, ice rings and ice-enhanced inner moons originate as a primordial byproduct of the same process that produces Saturn’s regular satellite system, making the whole process simpler than if there were several events.
    Canup studies formation events with detailed computer simulations, including studying how our own Moon formed.
  • 2010. October 5. Warm ‘Perrier’ Ocean Could be Powering Enceladus’ Geysers. By Nancy Atkinson, Universe Today. Excerpt: Bottled water companies take note: an exotic form of warm, bubbly mineral water could be what feeds the mysterious jets spraying from the south polar region of Saturn‘s moon Enceladus. A new model of the sub-surface ocean explains how the small moon could be so cryo-volcanically active. The Cassini spacecraft has detected sodium and potassium salts, as well as carbonates in the water vapor plumes spewing from the moon, which indicates a liquid, bubbly subsurface ocean.
    …What we think is going on is that Enceladus has a subsurface ocean where water, heat and chemicals are stored before they erupt,” said Dennis Matson, a NASA planetary scientist from JPL. There is an ice crust, many tens of kilometers thick. The ocean is gas rich, — and previous researchers dubbed such an ocean as a ‘Perrier’ ocean -– which basically “pops the cap” of the ice crust.
    …Finding the sodium in the icy grains in the plume is huge piece of evidence pointing to a subsurface ocean. Previously, Earth-based observations did not detect salts in the plume, and so scientists didn’t think a liquid ocean was possible. But infrared observations with an instrument on Cassini found the particles in the plumes include water ice, and substantial amounts of sodium and potassium salts and carbonates, as well as organics.
  • 2010 October 6. Eris and Pluto: Two Peas in a Pod. By Nancy Atkinson, Universe Today. Excerpt: …Eris and Pluto have a lot in common. Eris appears to have a frozen surface, predominantly covered in nitrogen ice and methane, just like Pluto.
    The scientists integrated two years of work conducted in Northern Arizona University’s new ice research laboratory, in addition to astronomical observations of Eris from the Multiple Mirror Telescope Observatory from Mount Hopkins, Ariz., and of Pluto from Steward Observatory from Kitt Peak, Ariz.
    …NAU’s ice lab grew optically clear ice samples of methane, nitrogen, argon, methane-nitrogen mixtures, and methane-argon mixtures in a vacuum chamber at temperatures as low as minus 390 degrees Fahrenheit to simulate the planets’ cold surfaces. Light passed through the samples revealed the “chemical fingerprints” of molecules and atoms, which were compared to telescopic observations of sunlight reflected from the surfaces of Eris and Pluto.
    “By combining the astronomical data and laboratory data, we found about 90 percent of Eris’s icy surface is made up of nitrogen ice and about 10 percent is made up of methane ice, which is not all that different from Pluto,” said David Cornelison, coauthor and physicist at Missouri State University.
  • 2010 October 4. Titan-ic Tsunami Causing Crack in Titan's C Ring. Universe Today. Excerpt: Saturn’s rings have several gaps, most of which are caused by small moons shepherding ring debris into breaks in the rocky rings. But one gap may be caused by gravitational perturbations from Saturn’s largest moon, Titan, sending tsunami-like waves up to 3 kilometers (2 miles) high in the C ring. This causes one region of the ring to spin like a warped, uneven vinyl record on a turntable.
    …The gap in the middle of the C ring has been known since Voyager 1 flew by Saturn in the 1980, and it appeared there was a 15 km-wide gap. But when Cassini arrived in 2004 and began observations, the gap was only 2 km (1.5 miles) and sometimes it wasn’t there at all.
    …Nicholson and Cassini Deputy Project Scientist Linda Spilker said the same types of processes seen in Saturn’s rings could also explain what is seen in disks of debris around other stars, with the theory that there are gaps forming in the disks associated with the formation of planets. “Saturn provides a wonderful natural laboratory of how protoplanetary nebula may evolve,” said Spilker.
  • 2010 September 15. NASA RELEASE 10-223: NASA's Lunar Spacecraft Completes Exploration Mission Phase. Excerpt: WASHINGTON -- NASA's Lunar Reconnaissance Orbiter, or LRO, will complete the exploration phase of its mission on Sept. 16, after a number of successes that transformed our understanding of Earth's nearest neighbor.
    LRO completed a one-year exploration mission in a polar orbit approximately 31 miles above the moon's surface. It produced a comprehensive map of the lunar surface in unprecedented detail; searched for resources and safe landing sites for potential future missions to the moon; and measured lunar temperatures and radiation levels.
    The LRO team will continue to send data gathered during the last year to the Planetary Data System, which archives and distributes scientific information from NASA planetary missions, astronomical observations and laboratory measurements.
    By the time LRO achieves full mission success in March, and its data is processed and released to the scientific community, it will have sent more information to the Planetary Data System than all other previous planetary missions combined. During its new phase of discovery, LRO will continue to map the moon for two to four more years.
    ...Results from the mission include: new observations of the Apollo landing sites; indications that permanently shadowed and nearby regions may harbor water and hydrogen; observations that large areas in the permanently shadowed regions are colder than Pluto; detailed information about lunar terrain; and the first evidence of a globally distributed population of thrust faults that indicates the moon has recently contracted and may still be shrinking.
  • 2010 June 14. RELEASE: 10-144. Research Suggests Water Content of Moon Interior Underestimated. Excerpt: WASHINGTON -- NASA-funded scientists estimate from recent research that the volume of water molecules locked inside minerals in the moon's interior could exceed the amount of water in the Great Lakes here on Earth.
    …"For over 40 years we thought the moon was dry," said Francis McCubbin of Carnegie and lead author of the report published in Monday's Online Early Edition of the Proceedings of the National Academy of Sciences. "In our study we looked at hydroxyl, a compound with an oxygen atom bound with hydrogen, and apatite, a water-bearing mineral in the assemblage of minerals we examined in two Apollo samples and a lunar meteorite."
    …Previous studies found evidence of water both on the lunar surface and inside the moon by using respectively, remote sensing data from the Indian spacecraft Chandrayaan-1 and other lunar sample analysis. Carnegie researchers looked within crystalline rocks called KREEP (K for potassium; REE, for rare Earth elements; and P for phosphorus). These rocks are a component of some lunar impact melt and basaltic rocks.
    …"It is gratifying to see this proof of the hydroxyl contents in lunar apatite," said lunar scientist Bradley Jolliff of Washington University in St. Louis. "The concentrations are very low and, accordingly, they have been until recently nearly impossible to detect. We can now finally begin to consider the implications - and the origin - of water in the interior of the moon."
  • 2010 March 1. RELEASE : 10-055. NASA Radar Finds Ice Deposits at Moon's North Pole; Additional Evidence of Water Activity on Moon. Excerpt: WASHINGTON -- Using data from a NASA radar that flew aboard India's Chandrayaan-1 spacecraft, scientists have detected ice deposits near the moon's north pole. NASA's Mini-SAR instrument, a lightweight, synthetic aperture radar, found more than 40 small craters with water ice. The craters range in size from 1 to 9 miles (2 to15 km) in diameter. Although the total amount of ice depends on its thickness in each crater, it's estimated there could be at least 1.3 trillion pounds (600 million metric tons) of water ice.
    "The emerging picture from the multiple measurements and resulting data of the instruments on lunar missions indicates that water creation, migration, deposition and retention are occurring on the moon," said Paul Spudis, principal investigator of the Mini-SAR experiment at the Lunar and Planetary Institute in Houston....
    During the past year, the Mini-SAR mapped the moon's permanently-shadowed polar craters that aren't visible from Earth. The radar uses the polarization properties of reflected radio waves to characterize surface properties. Results from the mapping showed deposits having radar characteristics similar to ice.
    "After analyzing the data, our science team determined a strong indication of water ice, a finding which will give future missions a new target to further explore and exploit," said Jason Crusan, program executive for the Mini-RF Program for NASA's Space Operations Mission Directorate in Washington....
  • 2009 Nov 25. New Findings On Alan Hills Meteorite Point to Microbial Life. by Nancy Atkinson, Universe Today. Scientists caused quite a stir in 1996 when they announced a meteorite had been found in Antarctica that might contain evidence for microscopic fossils of Martian bacteria. While subsequent studies of the now famous Alan Hills Meteorite shot down theories that the Mars rock held fossilized alien life, both sides debated the issue and the meteorite is still being studied. Now, Craig Covault in reports that a new look at ALH84001 provides "evidence that supports the existence of life on the surface of Mars, or in subsurface water pools, early in the planet's history." Covault says we can expect a public announcement by NASA Headquarters within a few days.
    ...The new findings were reported in the November issue of the respected journal Geochimica et Cosmochimica Acta, the journal of the Geochemical and Meteoritic Society. The authors include Kathie Thomas-Keprta, Simon Clement, David McKay (who led the original team), Everett Gibson and Susan Wentworth, all of the Johnson Space Center.
    Covault said the new work centers on what is called magnetic bacteria that on Earth, and Mars as well, leave distinctively-shaped remnants in the rock. These features test with a high chemical purity more like a biological feature than geological.
  • 2009 Nov 13. NASA RELEASE: 09-265. NASA'S LCROSS IMPACTS CONFIRM WATER IN LUNAR CRATER. Excerpt: MOFFETT FIELD, Calif. -- Preliminary data from NASA's Lunar Crater Observation and Sensing Satellite, or LCROSS, indicates the mission successfully uncovered water in a permanently shadowed lunar crater. The LCROSS spacecraft and a companion rocket stage made twin impacts in the Cabeus crater Oct. 9 that created a plume of material from the bottom of a crater that has not seen sunlight in billions of years. ...Since the impacts, the LCROSS science team has been analyzing the huge amount of data the spacecraft collected. The team concentrated on data from the satellite's spectrometers, which provide the most definitive information about the presence of water. ..."We are ecstatic," said Anthony Colaprete, LCROSS project scientist and principal investigator at NASA's Ames Research Center in Moffett Field, Calif. "Multiple lines of evidence show water was present in both the high angle vapor plume and the ejecta curtain created by the LCROSS Centaur impact. The concentration and distribution of water and other substances requires further analysis, but it is safe to say Cabeus holds water." The team took the known near-infrared spectral signatures of water and other materials and compared them to the impact spectra the LCROSS near infrared spectrometer collected. "We were able to match the spectra from LCROSS data only when we inserted the spectra for water," Colaprete said. "No other reasonable combination of other compounds that we tried matched the observations. The possibility of contamination from the Centaur also was ruled out."
    ...For information about LCROSS, visit:
  • 2009 Sep 24. NASA RELEASE : 09-222. NASA Instruments Reveal Water Molecules on Lunar Surface. Excerpt: WASHINGTON -- NASA scientists have discovered water molecules in the polar regions of the moon. Instruments aboard three separate spacecraft revealed water molecules in amounts that are greater than predicted, but still relatively small. Hydroxyl, a molecule consisting of one oxygen atom and one hydrogen atom, also was found in the lunar soil....
    ...The confirmation of elevated water molecules and hydroxyl at these concentrations in the moon's polar regions raises new questions about its origin and effect on the mineralogy of the moon. Answers to these questions will be studied and debated for years to come.
    "Water ice on the moon has been something of a holy grail for lunar scientists for a very long time," said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. "This surprising finding has come about through the ingenuity, perseverance and international cooperation between NASA and the India Space Research Organization."...
  • 2009 Sep 21. NASA RELEASE: 09-217. CASSINI REVEALS NEW RING QUIRKS, SHADOWS DURING SATURN EQUINOX. Excerpt: NASA scientists are marveling over the extent of ruffles and dust clouds revealed in the rings of Saturn during the planet's equinox last month. Scientists once thought the rings were almost completely flat, but new images reveal the heights of some newly discovered bumps in the rings are as high as the Rocky Mountains. NASA released the images Monday. ...On Aug. 11, sunlight hit Saturn's rings exactly edge-on, performing a celestial magic trick that made them all but disappear. The spectacle occurs twice during each orbit Saturn makes around the sun, which takes approximately 10,759 Earth days, or about 29.7 Earth years. Earth experiences a similar equinox phenomenon twice a year; the autumnal equinox will occur Sept. 22, when the sun will shine directly over Earth's equator. ...The chunks of ice that make up the main rings spread out 85,000 miles from the center of Saturn, but they had been thought to be only around 30 feet thick in the main rings, known as A, B, C, and D.
    ...particles seemed to pile up in vertical formations in each of the rings. Rippling corrugations -- previously seen by Cassini to extend approximately 500 miles in the innermost D ring -- appear to undulate out to a total of 11,000 miles through the neighboring C ring to the B ring.
    The heights of some of the newly discovered bumps are comparable to the elevations of the Rocky Mountains. One ridge of icy ring particles, whipped up by the gravitational pull of Saturn's moon Daphnis as it travels through the plane of the rings, looms as high as 2.5 miles. It is the tallest vertical wall seen within the rings.
    "We thought the plane of the rings was no taller than two stories of a modern-day building and instead we've come across walls more than two miles high," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, Colo....
  • 2009 Sep 17. NASA Lunar Satellite Begins Detailed Mapping of Moon's South Pole. NASA RELEASE: 09-215. Excerpt: NASA reported Thursday that its Lunar Reconnaissance Orbiter, or LRO, has successfully completed its testing and calibration phase and entered its mapping orbit of the moon. The spacecraft already has made significant progress toward creating the most detailed atlas of the moon's south pole to date. Scientists released preliminary images and data from LRO's seven instruments. "The LRO mission already has begun to give us new data that will lead to a vastly improved atlas of the lunar south pole and advance our capability for human exploration and scientific benefit," said Richard Vondrak, LRO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. ...The south pole of the moon is of great interest to explorers because potential resources such as water ice or hydrogen may exist there. Permanently shadowed polar craters that are bitterly cold at their bottoms may hold deposits of water ice or hydrogen from comet impacts or the solar wind. The deposits may have accumulated in these "cold-trap" regions over billions of years. ...For more information about LRO and to view the new images, visit:
  • 2009 July. Newly restored video from the Apollo 11 restoration effort:
    NASA's Apollo 40th anniversary Web sites: Easy access to various agency resources and multimedia about the program and the history of human spaceflight, including a gallery of Apollo multimedia features.
  • 2009 July 16-24. Audio retrospective beginning at 6:32 a.m. CDT Thursday, 2009 July 16, two hours before the spacecraft launched. The audio continues through splashdown of the mission at 11:51 a.m. CDT Friday, July 24, and recovery of the crew shortly afterward. The Web stream features the communications between the astronauts and ground teams,and commentary from Mission Control at NASA's Johnson Space Center in Houston. To listen to the replay, visit:
    For historical information about Apollo 11, visit:
  • 2009 April. Journey to Jupiter. National Geographic video -- naked science series. Ganymede has a molten core.
  • 2009 Apr 27. Prometheus Creating Saturn Ring Streamers (APOD).
  • 2009 April 21. Electrically Charged Particles Found in Enceladus' Plumes. Written by Nancy Atkinson, Universe Today. Excerpt: A team of planetary scientists working on the Cassini-Huygens mission has discovered tiny, icy particles in the plume from Saturn's moon Enceladus that offer a tantalizing glimpse of the interior of this enigmatic world. The spectrometer on Cassini, the Cassini Plasma Spectrometer (CAPS) discovered a surprise: the ice particles are electrically charged.
    Cassini has been exploring Saturn and its moons since 2004. Enceladus is 500 kilometers (300 miles) wide and Cassini's suite of instruments has found the moon to be active, with jets near its southern pole that spew gas and water thousands of kilometers out into space. During two particularly close flybys of the moon in 2008, skimming only 52 and 25 km from the surface at around 15 km per second (54,000 km per hour), the CAPS instrument on the spacecraft was pointed to scoop up gas as it zoomed through the plume.
  • 2009 Apr 15. Jagged Shadows May Indicate Saturn Ring Particles (APOD). Also see
  • 2009 March 24. Cassini Provides Virtual Flyover of Saturn's Moon Titan. News Release from Cassini Equinox mission. Excerpt: flyover maps show, for the first time, the 3-D topography and height of the 1,200-meter (4,000-foot) mountain tops, the north polar lake country, the vast dunes more than 100 meters (300 feet) high that crisscross the moon, and the thick flows that may have oozed from possible ice volcanoes.
    The topographic maps were made from stereo pairs of radar images. They are available at and .
  • 2008 December 15. Saturn's Dynamic Moon Enceladus Shows More Signs of Activity. NASA RELEASE : 08-325. Excerpt: PASADENA, Calif. - The closer scientists look at Saturn's small moon Enceladus, the more they find evidence of an active world. The most recent flybys of Enceladus made by NASA's Cassini spacecraft have provided new signs of ongoing changes on and around the moon. The latest high-resolution images of Enceladus show signs that the south polar surface changes over time.
    Close views of the southern polar region, where jets of water vapor and icy particles spew from vents within the moon's distinctive "tiger stripe" fractures, provide surprising evidence of Earth-like tectonics. They yield new insight into what may be happening within the fractures. The latest data on the plume -- the huge cloud of vapor and particles fed by the jets that extend into space -- show it varies over time and has a far-reaching effect on Saturn's magnetosphere.
    "Of all the geologic provinces in the Saturn system that Cassini has explored, none has been more thrilling or carries greater implications than the region at the southernmost portion of Enceladus," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, Colo.
    ...Images from recent close Enceladus flybys also have bolstered an idea the Cassini imaging team has that condensation from the jets erupting from the surface may create ice plugs that close off old vents and force new vents to open. The opening and clogging of vents also corresponds with measurements indicating the plume varies from month to month and year to year.
    ...Enceladus' output of ice and vapor dramatically impacts the entire Saturnian system by supplying the ring system with fresh material and loading ionized gas from water vapor into Saturn's magnetosphere.
    ...With water vapor, organic compounds and excess heat emerging from Enceladus' south polar terrain, scientists are intrigued by the possibility of a liquid-water-rich habitable zone beneath the moon's south pole....
  • 2008 September 22. The Bone-Dry Moon Might be Damp. Written by G. Jeffrey Taylor, Hawai'i Institute of Geophysics and Planetology. Excerpt: Detailed analysis of the first lunar samples collected by Apollo 11 astronauts in 1969 revealed no evidence that lunar magmas contained even a smidgeon of water. Analysis of samples returned by subsequent missions did not contradict this important observation. It became a tenant of lunar science that the Moon is bone dry.
    ...Recent analyses of lunar volcanic glasses suggest that a smidgeon, maybe even a mega-smidgeon, of water is present. Alberto Saal and his colleagues at Brown University, the Carnegie Institution of Washington, and Case Western Reserve University have measured volatile elements in lunar volcanic glass beads, using ion microprobe capabilities not available until a few years ago. They measured OH- (hydroxyl) anions (which are fragments of the H2O) molecule). All the measurements (of OH-, sulfur, fluorine, and chlorine) had higher concentrations in the center of the 276-micrometer beads, and decreased progressively towards the surface. This is a classic diffusion profile, suggesting that these elements were present in the droplets of magma when erupted, but began to be lost to the surrounding volcanic gases. Saal and his colleagues calculated how much of these volatiles were present upon eruption. They concluded that the lunar magmas contained about 745 parts per million of water, similar to the amount in magmas produced at mid-ocean ridges on Earth. The results imply that the region of the lunar interior that melted to make the magmas contained about the same amount as in the Earth's depleted upper mantle, which is way more than a smidgeon. This may have implications for the origin of the Moon. It certainly will spark new research on lunar volatiles--and lots of arguments!
    ...The Importance of Water in the Moon
    Besides possibly overturning a long-held tenant of lunar science that proclaims that the Moon is bone dry, the discovery of water in lunar samples has implications for the conditions existing during lunar formation. It is particularly important for understanding how and when Earth obtained its water. Understanding how much water there was initially in the Moon is pertinent to understanding delivery of water to the inner Solar System and to unraveling the details of lunar formation. The amount of water in the Moon also would have affected the compositions, movement, eruption, and crystallization of lunar magmas, depending on how much water resided in the Moon.
  • 2008 August. The changing face of Titan. By Ralph D. Lorenz, Physics Today, page 34. Excerpt: ...The discovery of a significant atmosphere sets Titan apart from the other satellites in the solar system. Indeed, the atmosphere makes it more planetlike than many planets.... With our scientific appetites whetted by the prospect of surface liquids—perhaps even a global ocean—Titan was a prime target of the international Cassini–Huygens mission..... Possibly the greatest surprise from Cassini so far is how Earth-like Titan's landscape is. The pictures from the Huygens probe5 show terrain that looks familiar—hills cut by a dendritic network of river channels.... Radar and near-IR images from orbit have shown larger channels, complete with meanders like terrestrial rivers, in other locations....
    Besides Earth, Titan is the only place in the solar system today where rain falls to the surface. But in Titan's exotic environment, the balance between surface tension and aerodynamic forces on a falling drop of liquid methane allows the drops to be gigantic—about 1 cm in diameter, rather than the roughly 6-mm drops that fall on Earth. Moreover, in Titan's thick atmosphere and low gravity, those drops fall at only 1.6 m/s (compared with 10 m/s on Earth), more like fluffy snowflakes do on Earth....
    Nevertheless, seasonally changing solar heating appears to be the origin of Titan's longest-monitored change, that of the haze in the stratosphere. Even in the 1970s, it was known that Titan's overall brightness changed over the years, and by different amounts at blue and yellow wavelengths.... As Titan goes around the Sun, its two hemispheres are presented to Earth by varying amounts, and their intrinsic brightness changes, most visibly at blue wavelengths, as the seasons wax and wane.... The stratospheric haze may also be connected with a recently observed extensive cloud over the north pole, presently just emerging from winter. That cloud, perhaps largely composed of ethane, may be connected with one of Titan's most appealing landforms—lakes....
    Not all of Titan's surface is wet. Indeed, some 20% of it, all at low latitudes, is covered with giant sand dunes.... A striking feature of the dunes is that they are longitudinal in form, lining up along the mean transport direction. Such dunes form on Earth when the wind blows in two predominant nonparallel directions.... On Titan, whether the alternating wind regime is due to the gravitational tide or to seasons remains to be determined....
  • 2008 July 30. NASA RELEASE: 08-193. NASA CONFIRMS LIQUID LAKE ON SATURN MOON. Excerpt: PASADENA, Calif. -- NASA scientists have concluded that at least one of the large lakes observed on Saturn's moon Titan contains liquid hydrocarbons, and have positively identified the presence of ethane. This makes Titan the only body in our solar system beyond Earth known to have liquid on its surface. Scientists made the discovery using data from an instrument aboard the Cassini spacecraft. ...hundreds of dark lake-like features are present.
    ...Ethane and several other simple hydrocarbons have been identified in Titan's atmosphere, which consists of 95 percent nitrogen, with methane making up the other 5 percent. Ethane and other hydrocarbons are products from atmospheric chemistry caused by the breakdown of methane by sunlight.
    ...More information on the Cassini-Huygens mission.
  • 2008 April 15. NASA RELEASE: 08-098 - NASA EXTENDS CASSINI'S GRAND TOUR OF SATURN. PASADENA, Calif. -- NASA is extending the international Cassini-Huygens mission by two years. The historic spacecraft's stunning discoveries and images have revolutionized our knowledge of Saturn and its moons. Cassini's mission originally had been scheduled to end in July 2008. The newly-announced two-year extension will include 60 additional orbits of Saturn and more flybys of its exotic moons. These will include 26 flybys of Titan, seven of Enceladus, and one each of Dione, Rhea and Helene. The extension also includes studies of Saturn's rings, its complex magnetosphere, and the planet itself.
    ..."The spacecraft is performing exceptionally well and the team is highly motivated, so we're excited at the prospect of another two years," said Bob Mitchell, Cassini program manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Based on findings from Cassini, scientists think liquid water may be just beneath the surface of Saturn's moon, Enceladus. That's why the small moon, only one-tenth the size of Titan and one-seventh the size of Earth's moon, is one of the highest-priority targets for the extended mission.
    Cassini discovered geysers of water-ice jetting from the Enceladus' surface. The geysers, which shoot out at a distance three times the diameter of Enceladus, feed particles into Saturn's most expansive ring. In the extended mission, the spacecraft may come as close as 15 miles from the moon's surface.
    Cassini's observations of Saturn's largest moon, Titan, have given scientists a glimpse of what Earth might have been like before life evolved. They now believe Titan possesses many parallels to Earth, including lakes, rivers, channels, dunes, rain, snow, clouds, mountains and possibly volcanoes.
    ...Unlike Earth, Titan's lakes, rivers and rain are composed of methane and ethane, and temperatures reach a chilly minus 290 degrees Fahrenheit.
    ...More information on the Cassini-Huygens mission.
  • 2008 March 26, RELEASE: 08-089. CASSINI TASTES ORGANIC MATERIAL AT SATURN'S GEYSER MO ON. Excerpt: PASADENA, Calif. -- NASA's Cassini spacecraft tasted and sampled a surprising organic brew erupting in geyser-like fashion from Saturn's moon Enceladus during a close flyby on March 12. Scientists are amazed that this tiny moon is so active, "hot" and brimming with water vapor and organic chemicals. New heat maps of the surface show higher temperatures than previously known in the south polar region, with hot tracks running the length of giant fissures. "...A completely unexpected surprise is that the chemistry of Enceladus, what's coming out from inside, resembles that of a comet," said Hunter Waite, principal investigator for the Cassini Ion and Neutral Mass Spectrometer at the Southwest Research Institute in San Antonio. "To have primordial material coming out from inside a Saturn moon raises many questions on the formation of the Saturn system." ...Enceladus' brew is like carbonated water with an essence of natural gas," said Waite. ..."Enceladus has got warmth, water and organic chemicals, some of the essential building blocks needed for life," said Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We have quite a recipe for life on our hands, but we have yet to find the final ingredient, liquid water, but Enceladus is only whetting our appetites for more."
  • 2008 March 20. NASA RELEASE: 08-085. CASSINI SPACECRAFT FINDS OCEAN MAY EXIST BENEATH TITAN'S CRUST. Excerpt: PASADENA, Calif. - NASA's Cassini spacecraft has discovered evidence that points to the existence of an underground ocean of water and ammonia on Saturn's moon Titan.
  • 2008 Mar 20. CASSINI SPACECRAFT FINDS OCEAN MAY EXIST BENEATH TITAN'S CRUST. NASA news RELEASE : 08-085. NASA's Cassini spacecraft has discovered evidence that points to the existence of an underground ocean of water and ammonia on Saturn's moon Titan. The findings made using radar measurements of Titan's rotation will appear in the March 21 issue of the journal Science.
  • 2008 Mar 19. A BRIEF ENCELADUS SHOWER. NASA Astrobiology Magazine. NASA's Cassini spacecraft performed a daring flyby of Saturn's moon Enceladus on March 12, flying about 15 kilometers per second (32,000 mph) through icy water geyser-like jets. The spacecraft snatched up precious samples that might point to a water ocean or organics inside the little moon.
  • 2008 Mar 6. SATURN'S MOON RHEA ALSO MAY HAVE RINGS. NASA Cassini mission news. NASA's Cassini spacecraft has found evidence of material orbiting Rhea, Saturn's second largest moon. This is the first time rings may have been found around a moon.
  • 2007 Dec 13. Return to Europa: A closer look is possible. Washington University News. "We've learned a lot about Europa in the past few years," says William B. McKinnon, professor of earth and planetary sciences at Washington University in St. Louis. "Before we were almost sure that there was an ocean, but now the scientific community has come to a consensus that there most certainly is an ocean. We're ready to take the next step and explore that ocean and the ice shell that overlays it. We have a number of new discoveries and techniques that can help us do that."
  • 2007 June. Cryovolcanoes, Swiss Cheese, and the Walnut Moon. Science Fact article by Richard Lovett in Analog magazine. [Not online] Excerpt: ...One of the most useful things Cassini has done is to allow us to get a fairly precise spectrum of the particle size in each segment of the rings. That's done by observing what happens when the rings lie between the probe's radio antenna and a source of light or radio waves. [backscattering] ...ranging in size fro marbles to chunks the size of small houses. There is also a lot of dust.
    ...being watched is Pan [20 km dia], ...inhabits the 300-kilometer-wide Encke Gap in the outer portion of the A ring. ..."Pan is master of this gap," says Carolyn Porco, head of the Cassini imaging team at the Space Science Institute in Boulder, Colorado. "It is the creator of clumps and the destroyer of clumps."
    ...pairs of bright streaks shaped like two-bladed propellers...are wannabe gaps. If the moonlets creating them [only about 100 meters dia] were larger, the blades would get longer and longer until eventually they would circle all the way around the ring.
    ...Enceladus's south pole...shows a pattern of distinctive bands that reminded early observers of tiger stripes. The surrounding area is particularly's snowing...Enceladus's snow appears to be creating one of Saturn's rings. ...distinct jets...appeared to emanate from the tiger stripes. ...Enceladus is blasting out 360 kilograms of water vapor per second.... Enceladus lies in the heart of the mysterious E ring, which is so faint it wasn't discovered until 1979. The E ring is losing water at the rate of about a kilogram per second due to chemical reactions with sunlight and collisions between particles. Enceladus appears to be pumping out more than enough water to keep the ring supplied, indefinitely. ...[liquid] water pools that feed the geysers probably lie only a few dozen meters below the surface. ...One you have liquid water, you have the potential for living organisms.... Titan temperatures, ...plays a similar role to water in the Earth's atmosphere: forming clouds...and precipitating as rain or snow. Methane rain and melting methane snow should scour the landscape like flowing water, before evaporating back into the atmosphere. ...paucity of craters means that Titan's geologically young. ...Lots and lots of lakes, up to 70 kilometers in diameter. The discovery made Titan the only body in the Solar System other than Earth appearing to have bodies of liquid at it's surface.
    ...The Cassini mission carried a second probe, called Huygens, which...parachuted to the surface [of Titan] on January 14, 2005. ...With an atmosphere four times as thick as Earth's...It took the probe two-and-a-half-hours to descend.... The landing site was close enough to one of the river deltas ... covered in rounded "rocks" of to six inches in diameter. This means that by the time they reached the landing site, the floods had slowed enough to leave bigger rocks behind, but were moving fast enough to scour smaller ones away: exactly what geologists see with earthly flash floods...."The most striking find," says [Larry] Soderblom, "is that a place I expected to be alien and un-earthlike turned out to resemble a modern textbook in geomorphology....
  • 2007 April 3. Two Views of the Moon's Composition --- There is a striking dichotomy in estimates of the abundance of refractory elements in the Moon. Written by G. Jeffrey Taylor, Hawai'i Institute of Geophysics and Planetology. Estimates of the chemical composition of the bulk (entire) Moon fall into two drastically different categories. One group of estimates claims that the Moon is enriched in refractory elements (those that boil at high temperatures, such as calcium and aluminum) by about 50% compared to Earth. The other group claims that the abundances of refractory elements are the same in the Earth and Moon....
  • 2007 January 3. Another meteor shower, another bunch of lunar impacts...
    [Science@NASA] Excerpt: "On Dec. 14, 2006, we observed at least five Geminid meteors hitting the Moon," reports Bill Cooke of NASA's Meteoroid Environment Office in Huntsville, AL. Each impact caused an explosion ranging in power from 50 to 125 lbs of TNT and a flash of light as bright as a 7th-to-9th magnitude star. The explosions occurred while Earth and Moon were passing through a cloud of debris following near-Earth asteroid 3200 Phaethon. This happens every year in mid-December and gives rise to the annual Geminid meteor shower: Streaks of light fly across the sky as rocky chips of Phaethon hit Earth's atmosphere. It's a beautiful display. The same chips hit the Moon, of course, but on the Moon there is no atmosphere to intercept them. Instead, they hit the ground. "We saw about one explosion per hour," says Cooke. How does a meteoroid explode? "This isn't the kind of explosion we experience on Earth," explains Cooke. The Moon has no oxygen to support fire or combustion, but in this case no oxygen is required: Geminid meteoroids hit the ground traveling 35 km/s (78,000 mph). "At that speed, even a pebble can blast a crater several feet wide," says Cooke. "The flash of light comes from rocks and soil made so hot by impact that they suddenly glow."
  • 2007 January 3. New Evidence of Liquid Methane on Saturn's Moon. NY Times. By JOHN NOBLE WILFORD. As scientists predicted but have had a hard time proving, the surface of Titan, Saturn's largest moon, appears to be dotted with an abundance of lakes of liquid methane. The lakes are more intriguing evidence of the active phenomena at play on the only moon in the solar system that has a dense atmosphere. ...a radar survey of Titan's high northern latitudes by the Cassini spacecraft, which has been orbiting Saturn and its retinue of satellites since July 2004 ...detected more than 75 dark patches in the landscape toward Titan's northern polar region. The patches, they said, indicated smooth surfaces in an otherwise rugged topography, suggesting lake beds either partly dry or filled with liquid.
    These smooth surfaces, more or less circular and ranging in diameter from 2 to 40 miles, are associated with channels that appear to have been formed by flowing liquids, presumably tributaries to the lakes. Methane exists in Titan's atmosphere and, in the extreme cold of high latitudes, is expected to rain on the surface and be present as liquids in subsurface reservoirs. The discovery team concluded that the radar images, made on a close pass of the moon in July, "provide definitive evidence for the presence of lakes on the surface of Titan." ...Dr. Ellen R. Stofan said that the lake depressions could be volcanic craters or sinkholes....
  • 2006 Nov 9. Is the Moon Still Alive? NASA Science News. Conventional wisdom says the Moon is dead. Conventional wisdom may be wrong. Today in the journal Nature, a team of NASA-supported scientists announced evidence for fresh geologic activity on the Moon.
  • 2006 November 8. Recent Gas Escape from the Moon. By G. Jeffrey Taylor, Hawai'i Institute of Geophysics and Planetology. Excerpt: Gases may have escaped from the Moon as recently as a million years ago, implying that the lunar interior is not as lethargic as conventional wisdom dictates. The Moon is generally thought to be geologically inactive, ...The youngest returned igneous rocks are about 3 billion years old, although crater counting suggest some lava flows as young as a billion years. However, Peter Schultz (Brown University), Matthew Staid (Planetary Sciences Institute, Tucson), and Carl Pieters (Brown University) report an array of data that indicate that the Moon may be active enough inside to occasionally spew puffs of gases that blow off the fine-grained, busted up surface materials known as the regolith. The researchers studied a feature called the Ina structure, a depression containing numerous steep-sided hills, located in a mare region known as Lacus Felicitatis. ... photographs taken from orbit during the Apollo 15 mission ... Clementine spacecraft ... in 1994, returning images in several wavelengths, ...tell us ... important information about the maturity of the surface--how long the surface has been exposed to solar wind and micrometeorite bombardment, or "space weathering." ...Schultz and colleagues suggest that the regolith or pyroclastic layer was blown away by the sudden release of pressurized gases. The subdued ejecta surrounding the structure indicates that the process was not as energetic as an impact, consistent with a gas eruption. Which gases is unknown, but they must have come from deep within the Moon, and collected beneath the surface until their pressure built up enough to suddenly burp out, blowing regolith around, a rare case of wind on the airless Moon. ...Perhaps astronauts will visit Ina someday, examining its fluffy deposits and rugged underlying rock. It might not, however, be such a great place to establish a lunar base. Imagine sitting in your habitat, working on some samples you collected ..., when the habitat shakes and your view of the outside is obscured by regolith being lifted by gases spewing from the interior of the not-so-burnt-out cinder!
  • 2006 October 17. Cassini Views Dione, a Frigid Ice World (Source: Jet Propulsion Laboratory) Image: Speeding toward pale, icy Dione, Cassini's view is enriched by the tranquil gold and blue hues of Saturn in the distance. Image:
    Image info:
    See also
  • 2006 August 8. Scientists Chip Away at Mysteries of the Moon. By KENNETH CHANG, NY Times. Excerpt: The Moon is slightly squashed, as if someone had held it at the poles between thumb and forefinger and squeezed, flattening it around its equatorial midsection. That is not surprising. The Moon spins, and the outward centrifugal force should indeed have generated a bulge as the molten magma of a young moon cooled to solid rock eons ago. ...But as far back as 1799, the mathematician Pierre-Simon Laplace noticed a back-and-forth wobbling because of the Moon's deformed shape. Although the flattening was slight - the Moon's width, 2,159 miles, is about 2.5 miles greater than its pole-to-pole height - it was still greater than would be expected for its current rotation period of 27 days 7 hours 43 minutes and 11.5 seconds.
    "The puzzle had been the Moon was too flat," said Maria T. Zuber, a professor of geophysics and planetary sciences at the Massachusetts Institute of Technology. Space probes of the 1960's and 1970's found a second deformity of the Moon: it is slightly elongated along the Moon-Earth axis. That is, if the Moon were sliced in half along its equator, the cross-section would not be a circle, but more like a football, with one of the narrow ends pointing toward Earth. But no one could come up with a completely convincing explanation for the Moon's current shape. ..."Quite a lot of the darned thing is still quite mysterious," said Kimmo Innanen, a professor of astronomy at York University in Toronto. In the current issue of Science, Dr. Zuber, with Jack Wisdom and Ian Garrick-Bethell, say they have a possible answer to the problem of the Moon's shape. Actually, they say they have several. What Laplace did not know is that the Moon is moving away from Earth and slowing down. Years of bouncing laser beams off mirrors left on the lunar surface by the Apollo astronauts show that each year the Moon is another 1.5 inches farther from Earth....
  • 2006 June 9. Earth Science Picture of the Day (EPOD) shows evidence that the Moon's distance from Earth varies.
  • 2006 April 10. In Search of Water, NASA Spacecraft to Hit the Moon. NASA today announced that a small spacecraft, to be developed by a team at NASA Ames, has been selected to travel to the moon to look for precious water ice at the lunar south pole. The name of the mission is LCROSS, short for Lunar CRater Observation and Sensing Satellite. LCROSS is a secondary payload: It will hitch a ride to the moon onboard the same rocket as the Lunar Reconnaissance Orbiter (LRO) satellite due to launch from the Kennedy Space Center in October 2008. "The LCROSS mission gives the agency an excellent opportunity to answer the question about water ice on the moon," says Daniel Andrews of NASA Ames, whose team proposed LCROSS.
  • 2005 November 1. Persistent Astronomers Find Pluto Has Two More Moons. By KENNETH CHANG. NY Times. Excerpt: Astronomers using NASA's Hubble Space Telescope announced yesterday that they had spotted two small moons circling Pluto. That gives Pluto, the smallest of the nine planets, a total of three moons, or more than four of the other planets....Pluto's largest moon, Charon, was discovered in 1978. Hubble spotted the second and third moons on May 15 and May 18. For now they are known only as S/2005 P1 and S/2005 P2. S/2005 P1, estimated to orbit 40,000 miles from Pluto, is up to 100 miles wide. P2 is likely 10 to 15 percent smaller and about 30,000 miles from Pluto.... Astronomers believe that Charon formed in the aftermath of a collision between a large meteor and Pluto. ...the new moons also formed out of that collision and that there could be more. ....Another possibility is that the two moons were originally part of the Kuiper Belt, the ring of small icy bodies beyond Neptune, and were captured by Pluto's gravitational pull.
  • 31 October 2005. NASA RELEASE: 05-351. NASA's Hubble Reveals Possible New Moons Around Pluto. Using NASA's Hubble Space Telescope to view the ninth planet in our solar system, astronomers discovered Pluto may have not one, but three moons.If confirmed, the discovery of the two new moons could offer insights into the nature and evolution of the Pluto system; Kuiper Belt Objects with satellite systems; and the early Kuiper Belt. ...The team plans to make follow-up Hubble observations in February to confirm the newly discovered objects are truly Pluto's moons. Only after confirmation will the International Astronomical Union consider names for S/2005 P1 and S/2005 P2. The Hubble's Advanced Camera for Surveys observed the two new candidate moons on May 15, 2005. The candidates are roughly 5,000 times fainter than Pluto. Three days later, Hubble looked at Pluto again. The two objects were still there and appeared to be moving in orbit around Pluto.Photos at See also: background info For detailed information and images about this research on the Web, visit:
  • 30 August 2005. Cassini Finds Enceladus Tiger Stripes Are Really Cubs. The Cassini spacecraft discovered the long, cracked features dubbed "tiger stripes" on Saturn's icy moon Enceladus are very young. They are between 10 and 1,000 years old. These findings support previous results showing the moon's southern pole is active. The pole had episodes of geologic activity as recently as 10 years ago. These cracked features are approximately 80 miles long, spaced about 25 miles apart and run roughly parallel to each another. The cracks act like vents. They spew vapor and fine ice water particles that have become ice crystals. This crystallization process can help scientists pin down the age of the features.
  • 29 July 2005. NASA News Release: 05-207. CASSINI FINDS AN ACTIVE, WATERY WORLD AT SATURN'S ENCELADUS. Saturn's tiny icy moon Enceladus, which ought to be cold and dead, instead displays evidence for active ice volcanism. NASA's Cassini spacecraft has found a huge cloud of water vapor over the moon's south pole, and warm fractures where evaporating ice probably supplies the vapor cloud. Cassini has also confirmed Enceladus is the major source of Saturn's largest ring, the E-ring."Enceladus is the smallest body so far found that seems to have active volcanism," said Dr. Torrence Johnson, Cassini imaging-team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Enceladus' localized water vapor atmosphere is reminiscent of comets. 'Warm spots' in its icy and cracked surface are probably the result of heat from tidal energy like the volcanoes on Jupiter's moon Io. And its geologically young surface of water ice, softened by heat from below, resembles areas on Jupiter's moons, Europa and Ganymede," Johnson added...The fact the atmosphere persists on this low-gravity world, instead of instantly escaping into space, suggests the moon is geologically active enough to replenish the water vapor at a slow continuous rate...Images show the south pole has an even younger and more fractured appearance than the rest of Enceladus, complete with icy boulders the size of large houses and long, bluish cracks or faults dubbed "tiger stripes."
  • 29 February 2005. NASA News Release: 05-059 NASA'S CASSINI CONTINUES MAKING NEW SATURN DISCOVERIES NASA's Cassini spacecraft continues making new and exciting discoveries. The findings include wandering and rubble-pile moons; new and clumpy Saturn rings; splintering storms and a dynamic magnetosphere. "For the last seven months it has been a nonstop, science-packed mission. It has been a whirlwind, and already we have many new results," said Dr. Dennis Matson, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
  • 25 February 2005. Rainbows on Titan. NASA Science News. Saturn's moon Titan is wet, according to the ESA's Huygens probe, but Titan's "water" is not like Earth's.
    When the European Space Agency's Huygens probe visited Saturn's moon Titan last month, the probe parachuted through humid clouds. It photographed river channels and beaches and things that look like islands. Finally, descending through swirling fog, Huygens landed in mud. To make a long story short, Titan is wet.
  • 16 February 2005. Cassini's Radar Spots Giant Crater on Titan. A giant impact crater the size of Iowa was spotted on Saturn's moon Titan by NASA's Cassini radar instrument during Tuesday's Titan flyby.
  • 15 January 2005. Craft on Titan Finds Tantalizing Signs of Liquid. By JOHN NOBLE WILFORD . NY Times. DARMSTADT, Germany, Jan. 14 - A European spacecraft... Huygens... plunged through the murky atmosphere of Saturn's moon Titan on Friday and successfully came to rest on a bizarre landscape never before explored. Astronomers expressed joy at achieving the first landing on another planet's moon, particularly Titan, the only moon in the solar system with substantial atmosphere.... The first pictures from the spacecraft,, did nothing to undermine the reputation of Titan as a strange place. One showed what appeared to be deep channels leading to the shoreline of a dark, flat surface, possibly a lake of liquid methane. "Clearly there is liquid matter flowing on the surface of Titan," said Dr. Martin G. Tomasko of the University of Arizona, an imaging specialist for the mission. That possibility has tantalized scientists, who say Titan may resemble Earth early in its development and could give clues to the origin of life here.
  • 7 January 2005. NASA Press Release: 2005-005. Saturn's Moon Iapetus Shows a Bulging Waistline. Images returned by NASA's Cassini spacecraft cameras during a New Year's Eve flyby of Saturn's moon Iapetus (eye-APP-eh-tuss) show startling surface features that are fueling heated scientific discussions about their origin. One of these features is a long narrow ridge that lies almost exactly on the equator of Iapetus, bisects its entire dark hemisphere and reaches 20 kilometers high (12 miles). It extends over 1,300 kilometers (808 miles) from side to side, along its midsection. No other moon in the solar system has such a striking geological feature. In places, the ridge is comprised of mountains. In height, they rival Olympus Mons on Mars, approximately three times the height of Mt. Everest, which is surprising for such a small body as Iapetus. Mars is nearly five times the size of Iapetus. Images from the flyby are available at, and Iapetus is a two-toned moon. The leading hemisphere is as dark as a freshly-tarred street, and the white, trailing hemisphere resembles freshly-fallen snow. The flyby images, which revealed a region of Iapetus never before seen, show feathery-looking black streaks at the boundary between dark and bright hemispheres that indicate dark material has fallen onto Iapetus. Opinions differ as to whether this dark material originated from within or outside Iapetus.
  • 2 December 2004. JPL Press Release. Cassini Shows Before And After Look At Saturn's Moon Titan. Cassini's second close flyby of Titan completes a 'before' and 'after' look at the fuzzy moon and provides the first direct evidence of changing weather patterns in the skies over Titan. In images obtained less than two months ago, the Titan skies were cloud free, except for a patch of clouds observed over the moon's south pole. In images taken Monday, Dec. 13, during Cassini's second close flyby of Titan, several extensive patches of clouds have formed. Images show that Cassini has found Titan's upper atmosphere to consist of a surprising number of layers of haze.
  • 15 December 2004. New Clouds Add to Titan's Mystery. Using adaptive optics on the Gemini North and Keck II telescopes on Mauna Kea, Hawai'i, a U.S. team has discovered a new phenomenon in the atmosphere of Saturn's largest moon Titan. Unlike previous observations showing storms at the south pole, these new images reveal atmospheric disturbances at Titan's temperate mid latitudes-about halfway between the equator and the poles. Explaining the unexpected activity has proven difficult, and the team speculates that the storms could be driven by anything from short-term surface events to shifts in global wind patterns.
  • 10 December 2004. Composition of the Moon's Crust. Written by Linda M. V. Martel, Hawai'i Institute of Geophysics and Planetology. In 1997, PSRD first reported on the trailblazing efforts to map the abundance and distribution of titanium and iron on the entire lunar surface based on Clementine orbital remote sensing data [see PSRD article: Moonbeams and Elements]. Researchers calibrated the remote sensing data with the best ground-truth standards available: lunar soil and rock samples. Since the initial mapping, planetary scientists have been striving to improve the calibration of the remote sensing data to correct for over or under estimates of the global concentrations of primary elements. This work is important because it prevents us from getting erroneous ideas about the Moon's composition and origin. New calibrations to Lunar Prospector and Clementine data by Jeff Gillis (previously at Washington University in St. Louis and now at the University of Hawai'i), Brad Jolliff, and Randy Korotev (both at Washington University in St. Louis) have resulted in updated global maps for thorium (Th), potassium (K), and iron oxide (FeO) that are more consistent with the compositions of lunar samples and lunar meteorites, and allow a better understanding of the Moon's formation and evolution.
  • 5 November 2004. Radar Image Shows Titan's Surface Live and in Color. Saturn's moon Titan shows a sharp contrast between its smooth and rough edges in a new false-color radar image. Titan's surface lies beneath a thick coat of hazy clouds, but Cassini's radar instrument can peer through to show finer surface features. Scientists have added color to emphasize finer details on Titan, as shown in the image. This image can be viewed at: and
  • 31 October 2004. New Lunar Meteorite Provides its Lunar Address and Some Clues about Early Bombardment of the Moon. A newly discovered meteorite from the Moon provides a detailed record of its history, allowing scientists to make a reasonable guess about where it came from on the Moon and to test ideas for the timing of early impact bombardment.
    Full story and a PDF link at:
  • 5 July 2004. New Mineral Proves an Old Idea about Space Weathering
    --- A newly discovered vapor-deposited iron silicide in a lunar meteorite has been named hapkeite. Written by Linda M. V. Martel - Hawai'i Institute of Geophysics and Planetology. Discovered in a lunar meteorite, a new mineral named hapkeite honors the scientist, Bruce Hapke (Emeritis Professor at University of Pittsburg), who nearly 30 years ago predicted the importance of vaporization as one of the processes in space weathering. The new iron silicide mineral (Fe2Si) was announced by the research team of Mahesh Anand (formerly at the University of Tennessee, Knoxville and now at the Natural History Museum, London), Larry Taylor (University of Tennessee, Knoxville), Mikhail Nazarov (Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow), Jinfu Shu, Ho-kwang Mao, and Russell Hemley (Carnegie Institution of Washington). This mineral likely formed by impact vaporization of the lunar soil and subsequent condensation of the iron and silicon into tiny metal grains. The researchers conclude that Fe-Si phases are more common in the lunar soil than previously thought. It is nanophase-sized Fe0, these Fe-Si phases, and other space weathering products that profoundly affect the optical properties of the lunar soil at visible and near infrared wavelengths and must be taken into account when interpreting remote sensing data of the Moon.
  • 2 July 2004 Cassini Exposes Puzzles About Ingredients In Saturn's Rings -- Just two days after the Cassini spacecraft entered Saturn orbit, preliminary science results are already beginning to show a complex and fascinating planetary system. ... One early result intriguing scientists concerns Saturn's Cassini Division, the large gap between the A and B rings. While Saturn's rings are almost exclusively composed of water ice, new findings show the Cassini Division contains relatively more "dirt" than ice. Further, the particles between the rings seem remarkably similar to the dark material that scientists saw on Saturn's moon, Phoebe. These dark particles refuel the theory that the rings might be the remnants of a moon. The F ring was also found to contain more dirt.
    Like a woolly mammoth trapped in Arctic ice, Saturn's small moon Phoebe may be a frozen artifact of a bygone era, some four billion years ago. The finding is suggested by new data from the Cassini spacecraft.
  • 23 June 2004. Cassini high resolution image of Saturn's moon Phoebe
  • 19 August 2003. Mars Profiler (from Sky and Telescope Skywatchers bulletin). To compare what you see on Mars with a map, you need to know which side of the planet you're looking at. The Mars Profiler (javascript utility) tells you that and more, for any date and time.
  • 19 August 2003. Observing Mars's moons article from Sky and Telescopes. Phobos (mag 10.5 max) and Deimos (mag 11.6 max). Instructions for how to make an occulting bar on an eyepiece, as well as a "Martian Moons" javascript utility to show optimal observing times.
  • 19 August 2003. Storm Watch on Mars (from Sky and Telescope Skywatchers bulletin). If events of the past 30 years are an indication, there's a good chance that the Martian landscape may soon be cloaked by a major dust storm. Discover what to see on the red planet even if a dust storm is raging:
  • 19 August 2003. Plots showing distance and apparent size of Mars by Joe Macke [joe01@---]17 August 2003. Images and movies of Mars from ToUcam webcam taken from back yard by Howard C. Anderson [handy13@--]
  • 3 July 2003. A simply staggering image of Mars by the passing Moon. Though some image enhancements were made for clarifying the original digital file, the basic material is original.
  • 3 July 2003 Mars Express Earth-Moon image. On the night of July 3, the Mars Express spacecraft was pointed backwards to obtain a view of the Earth-Moon system from a distance of 8 million kilometres while on its way to Mars. See...Image. Also has image of spectrum of Earth, with indicators that there may be life on Earth. See also...Article.
  • 20 December 2002. Image of Uranus and 7 of it's moons in ESO press release
  • 18 December 2002. Full Moon Effect on Behavior Minimal, Studies Say
    John Roach for National Geographic News.
  • 18 December 2002, Clouds discovered on Saturn's moon Titan PASADENA, Calif.- Teams of astronomers at the California Institute of Technology (Caltech) and at the University of California, Berkeley, have discovered methane clouds near the south pole of Titan, resolving a fierce debate about whether clouds exist amid the haze of the moon's atmosphere.
  • 9 December 2002. Featherweight Jupiter Moon is Likely a Jumble of Pieces -- -- NASA's Galileo spacecraft continues to deliver surprises with the discovery that Jupiter's potato-shaped inner moon, named Amalthea, appears to have a very low density, indicating it is full of holes. "The density is unexpectedly low," said Dr. John D. Anderson, an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Amalthea is apparently a loosely packed pile of rubble."
  • 6 December 2002. Mountains on Io at Sunset -- Galileo spacecraft image of mountains on Io from February 2000. The image was taken when the Sun was low in the sky, [revealing a] low scarp, roughly 250 meters (820 feet) high, .... Mongibello Mons, the jagged ridge at the left of the image, rises 7 kilometers (23,000 feet) above the plains of Io, higher than any mountain in North America. Full article.
  • 31 October 2002 -- Galileo's Last Rendezvous -- By Monica Bobra Next September (2003) the spacecraft will plunge directly into the Jovian atmosphere. But Galileo should provide one more burst of science data before making a final orbit around Jupiter. Next week it will sweep past Amalthea (Jupiter's innermost large satellite), race through the planet's ring, and experience its most intense magnetic and radiation environment to date. It will glide 160 kilometers above Amalthea's surface on November 5th 2002 at 6:19 Universal Time.
  • 11 October 2002 DRY ICE SEEN ON SURFACE OF ARIEL -- Planetary scientists have discovered carbon dioxide ice on the surface of Ariel, one of the moons of the planet Uranus. ... The distribution of Ariel's dry ice revealed an additional curiosity. Just as Earth's Moon always shows the same face to the Earth, Ariel always shows the same face to Uranus. Each of these moons has a leading side and a trailing side as they orbit their respective planet. The leading side received more bombardment by meteors, just as a car's front windshield is struck by more insects than the rear window. Grundy and his collegues observed both leading and trailing sides of Ariel, but dry ice only appeared on the trailing side. A possible explanation for the dry ice being on the trailing hemisphere only is that the dry ice was originally distributed uniformly over the surface, but over time was buried or destroyed by the more intense bombardment of meteors on the leading hemisphere.
  • 17 April 2002 -- Hubble Hunts Down Binary Objects at the Fringe of Our Solar System -- The Hubble Space Telescope is hot on the trail of a puzzling new class of solar system object that might be called a Pluto "mini-me." Together, these objects are 5,000 times less massive than Pluto and Charon. Like Pluto and Charon, these dim and fleeting objects travel in pairs in the frigid, mysterious outer realm of the solar system called the Kuiper Belt, a long-hypothesized "junkyard" of countless icy bodies left over from the solar system's formation.
  • 12 March 2002 Once Upon a Water Planet
  • 12 February 2002 -- The Real Lord of the Rings. "After all this time we're still not sure about the origin of Saturn's rings," says Jeff Cuzzi, a planetary scientist at the NASA Ames Research Center. Astronomers once thought that Saturn's rings formed when Saturn did: 4.8 billion years ago as the Sun and planets coalesced from a swirling cloud of interstellar gas. "But lately," Cuzzi says, "there's a growing awareness that Saturn's rings can't be so old."
  • 8 February 2002 Possible Locations for Life on Europa -- A professor from the University of Arizona believes that Jupiter's moon Europa might not only sustain life, but actually foster it in various habitable "niches". Through its combination of liquid water, active tidal forces, and periodic surface exposure, the moon might encourage life faster than a cold, arid place like Mars. Microbes have been discovered on Earth which stay dormant for millions of years and then spring to life when the ice around them thaws.
  • 15 January 2002 -- FAREWELL, IO; GALILEO PAYING LAST VISIT TO A RESTLESS MOON- -- NASA's Galileo orbiter will dart past Jupiter's moon Io on Thursday in the veteran spacecraft's last and closest flyby of any of the giant planet's four major moons. Io's volcanoes have presented many surprises ... Scientists hope this week's encounter will reveal how several regions of Io have changed over the years. "Galileo's days are numbered now, so it's especially exciting to visit Io one last time," said Dr. Eilene Theilig, Galileo project manager at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif. RELEASE: 02-10
  • 10 December 2001 -- Jupiter's Io Generates Power and Noise, But No Magnetic Field -- -- As [Galileo] flew near Io's poles in August and October, the density of charged particles it was passing through suddenly increased about tenfold when the spacecraft crossed the path of a magnetic-field connection between Io and Jupiter, reported Dr. Donald Gurnett of the University of Iowa, Iowa City. The waves, indicating the density, travel in a plasma of charged particles, and would be silent to the ear, but Iowa researchers converted them to sound waves to make the patterns audible. Audio clips are available online at .
  • 5 December 2001 What makes Europa pink? Does Europa's rosy glow betray a flourishing colony of bugs? -- -- New Scientist article
  • Solar System Websites
  • 29 November 2001 -- Ocean Inside Jupiter's Moon Callisto May Have Cushioned Big Impact -- -- A recent image from NASA's Galileo spacecraft adds evidence to a theory that Callisto, the outermost of Jupiter's four large moons, may hold an underground ocean. The image shows a part of Callisto's surface directly opposite from the Valhalla basin where Callisto was punched by a major collision. The opposition point shows no effect from the impact. Points opposite major impact features on some similar-size worlds, such as Mercury and Earth's Moon, show lumpy terrain attributed to seismic shocks from the distant impacts.
  • 27 November 2001 -- New Images Catch Jupiter's Moon Io in Action JPL Press Release #2001-228
  • 8 November 2001 -- Europa's Ice Crust Is Deeper Than 3 Kilometers, UA Scientists Find -- JPL Press Release
  • 26 September 2001 -- Spacecraft at Io Sees and Sniffs Tallest Volcanic Plume -- Jupiter's moon Io has pulled a surprise on NASA's Galileo spacecraft, hurling up the tallest volcanic plume ever seen, which arose from a previously unknown volcano. ... Adding to the surprise, for the first time a Galileo instrument has caught particles freshly released from an eruption, giving scientists a direct sample of Io material to analyze. "This was totally unexpected," said the leader of that experiment, Dr. Louis Frank of the University of Iowa, Iowa City. "We've had wonderful images and other remote sensing of the volcanoes on Io before, but we've never caught the hot breath from one of them until now. Galileo smelled the volcano's strong breath and survived." JPL Press Release #2001-192
  • 16 August 2001 Moon making made easy--Mars-sized mass implicated by new model for Moon's violent birth. Nature
  • 22 August 2001 GALILEO FLYBY REVEALS CALLISTO'S BIZARRE LANDSCAPE -- A spiky landscape of bright ice and dark dust shows signs of slow but active erosion on the surface of Jupiter's moon Callisto in new images from NASA's Galileo spacecraft. RELEASE: 01-174.
  • 8 January 2001, 10 additional moons discovered around Jupiter BY JEFF FOUST SPACEFLIGHT NOW
  • 14 December 2000 Satellite Footprints Seen in Jupiter Aurora
  • 4 November 2000 Europa's lifelines -- -- The cracks in Europa's icy crust are where life is most likely to be found on the Jovian moon,.... (New Scientist)
  • 15 September 2000 Legal Loopholes Help Man Sell the Moon.
  • 25 July 2000 ( -- Companies Who Plan to Profit from the Moon--including efforts by SpaceDev, Idealab, TransOrbital and LunaCorp.
  • 24 August 2000 The slowing of Earth's period of rotation due to tidal effects of the Moon (Dome-L posting)
  • 01 June 2000 New Images Reveal Io's Fiery Nature By Josh Chamot -- WASHINGTON Æ New images of Jupiter's moon Io, taken by NASA's Galileo probes, reveal more than 100 volcanic peaks and basins -- some of which are deeper than the Grand Canyon -- with lava hotter than any found on Earth.
  • 18 May 1999 Discovery of Uranus' 18th moon -- news story from U. of Arizona
  • 16 March 1999 LUNAR DATA SUPPORT IDEA THAT COLLISION SPLIT EARTH, MOON --NASA Press Release -- Lunar Prospector
  • 21 October 1998; Jet Propulsion Laboratory, Pasadena, CA; NASA PRESS RELEASE: 98-192; JUPITER'S MOON CALLISTO MAY HIDE SALTY 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.


Magazine Articles (hard copy)

  • April, 2004. Johnson, Torrence V. A Look at the Galilean Satellites After the Galileo Mission. From volcanic eruptions hotter than those typically found on Earth to ocean sandwiches with water trapped between ice layers, the Galileo mission revealed fascinating phenomena on Jupiter's four largest moons. Physics Today. Also available online at but for AGU members only.
  • April, 2004. Canup, Robin M. Origin of Terrestrial Planets and the Earth-Moon System. Increasingly sophisticated simulations show how the four solid planets could have emerged through collisions and accretion. One late, giant collision with Earth is the likely origin of the Moon. Physics Today. Also available online at but for AGU members only.
  • May-June 2002. Jupiter's Moons and the Longitude Problem, by Robert Mentzer, Mercury Magazine, pp. 34-39.
  • May, 2001, Sky & Telescope Magazine page 41, Galileo's Closest Look at Io, by John Spencer.
  • March-April, 2001, Mercury Magazine, On the Hunt for Modern Moons Moons, by William Schomaker.
  • March-April, 2001, Mercury Magazine, The Historic Hunt for Moons, by William Sheehan.
  • 2000, February -- Raising Lunar Prospects by Robert Irion, Astronomy Magazine, p. 44. During its 19-month mission, Lunar Prospector exposed the Moon's mysteries at a bargain-basement price.
  • May 1999 Sky & Telescope magazine, page 26, Callisto's Rarefied Wisps, "...Calliso, Jupiter's second-largest moon, has a thin atmosphere of carbon dioxide... All four of Jupiter's largest moons are now known to have atmospheres--Europa and Ganymede each have thin envelopes of oxygen, while Io is surrounded by sulfur dioxide.
  • Sep 1998, Astronomy Magazine, Deconstructing the Moon, Ray Jayawardhana, p. 40. On how the Moon formed.



  • Greenberg, Richard, Unmasking Europa: The Search for Life on Jupiter's Ocean Moon. A Close Look at Europa . . . And How Big Science Gets Done . . . University of Arizona, Lunar and Planetary Laboratory, Tucson. In Unmasking Europa, Richard Greenberg tells the story of how he and his team of researchers came to believe that the surface of Europa is in fact a crust so thin that it can barely hide an ocean of liquid water below. He shows how the ocean is warmed by the friction of tidal movements in this small moon as it orbits around immense Jupiter. The implications of this interpretation-which includes the idea that there are active intermittent openings from the liquid ocean to the frozen surface-are immense. The warmth, the chemistry, and the connections from ocean to surface provide the conditions necessary for the existence of life, even at this relatively remote locale in our solar system, far beyond what's normally thought of as its 'habitable zone.' NY, Springer, 2008.
  • Kluger, Jeffery, Journey Beyond Selene, Simon & Schuster Trade pub., 1999. Historical information on the known moons of the solar system (up to 1999).
  • Montgomery, Scott L., The Moon and Western Imagination, University of Arizona Press, 1999. A collection of history, fable and reserach about the Moon.
  • Siy, Alexandria, Footprints on the Moon, Charlebridge Publishing, 2001.


About Galileo...


On tides and slowing of Earth's rotation...
Real image of the Earth-Moon system showing accurate size and distance scale

Paper Plate Moon Finder
For younger children construct moon phases out of Oreo cookies. Given the current phase of the moon, they could then tell me as what shape it would appear in the near future. For pictures, check out In upcoming weeks they will look for the moon and draw its shape. --Chuck Bueter

Explaining the moon illusion—article by Lloyd Kaufman and James H. Kaufman -


GIF Animation of phases of the Moon:

GIF animation of phases of the Moon

A series of images captured by Cassini 2008 August 30 and received on Earth 2008 August 31:

Cassini's Images of Saturn

18 October 2006
F-Ring dynamism

22 February 2006

15 December 2005
Prometheus, Pandora, and F ring

16 November 2005
Pandora color close-up

27 October 2005
Ripples in F ring

5 October 2005
Prometheus and gore in F ring

5 September 2005
Pandora and F ring

23 February 2005
Mimas + Saturn

17 February 2005
Prometheus, Epimetheus, Saturn's shadow

8 February 2005
Mimas + rings

16 December 2004