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EYEPIECE
Journal of the Amateur Astronomers Association of New York June 2009 Volume 57, Number 6, ISSN 0146-7662

How `Stuff ' Provides Clues to Origin of Solar System
By Terrell Kent Holmes
I study stuff," Denton Ebel said proudly. "Stuff is what I'm interested in." Ebel, associate curator and associate professor of earth and planetary sciences at the AMNH, def ined "stuff " and its signif icance in the May 1 AAA lecture, "Stardust Findings and Meteorites: New Constraints on Solar System Formation Models". He discussed how some of this stuff f igures in the origins of the solar system, and described anomalies that make tracing those origins problematic. Stardust was the f irst space mission to return samples of extraterrestrial solid material since the Apollo era. Before this, information about chondrites, meteorites and such was provided through gathering of interplanetary dust particles captured by silicon plates applied to the wings of high-flying aircraft. Stardust, launched in 2001, captured ions from the solar wind, one component of Ebel's beloved stuff. The data were sent to Earth via a canister supported by a parachute. The parachute didn't open up, though, and the craft crash landed in Utah. What was salvageable was taken to UCLA and analyzed via an instrument known as a "Mega SIMS," SIMS standing for Secondar y Ion Mass Spectrometer. The sample was bombarded with cesium atoms. Secondary ions of oxygen arose from this bombardment, then accelerated and were sent into a spectrometer, where they were analyzed. "One of the most important elements in the solar system, of course, is oxygen," Ebel said. There are three stable isotopes of oxygen--O16, O17 and O18. "The actual amount of oxygen in a thing can be characterized by the total amount of O16. And then we look at the ratios of O17 to O16, and O18 to O16. So we're not looking at the abundance of oxygen in a rock, but we're looking at the isotope ratios in a rock. When we look at rocks that we know come from Mars, they're not quite on the same line. They have a different composition and ratio of isotopes. And that's the easiest way for us to identify Mars rocks, to look at their oxygen isotopes. When we look at rocks we think come from Vesta, they're not on the same line as Earth's either, so these bodies, which were homogenized at one time, had separate ratios of O16, O17 and O18 relative to each other when they formed." Ebel discussed the components of chondrites and their role in determining planetary formation. "We look at these chondrites in vivisection and see chondrules, little blobs of stuff that were molten in space and collected together to make the rocks we call chondrites. When I take the oxygenisotope composition using a laser instrument, I look at different grains [and] f ind I get points near the end of the same data f ield I would get in O17 and O18 space for the whole chondrule. That's consistent with what I see. But if I look at some of these grains in the center of the chondrule, I f ind they go way down [in the f ield of data]. That's not consistent with chemistry that happens on Earth. There's a signature there of some other stuff, and we don't know what that is, and we want to know what it is. " Material captured by Stardust from the solar wind was off the beaten path of the line where terrestrial-related chondrites lay. "So we're all anomalous," Ebel said. "We don't belong in the solar system. We have oxygen-isotope compositions that are not the same as the bulk of the solar system, which is the Sun, by def inition." Ebel thought this was fascinating. "These little pieces that are leftovers of the most primitive stuff somehow capture the same oxygen isotopecomposition that the Sun has, yet that's not what's seen in Mars, Vesta, the Moon and the meteorites we have access to in bulk." A c c o rd i n g t o E b e l , t h e m a i n i d e a c o m i n g f r o m Stardust data is that stuff formed by the hot Sun that was then ejected or thrown by solar wind out to the Kuiper Belt. Other proposals include shocks. "In the [Milky Way] galaxy we have these spiral arms that are formed by gravitation. These can create shock waves if they're in a disc the size of our solar system. There's also the shock that happens when things are accreted to the solar system. These discs form from large cloud cores in planet-forming regions and starStuff continued on page 2


What's Up
By Tony Hoffman
The Sky for June 2009
June's Constellations. The nights around the Summer Solstice are brief, but f illed with some of the most splendid nights of our sky. We see our own galaxy at its best, with the galactic center, the Sagittarius, Ophiuchus, and Scorpius region, at its highest in the south in the early evening. From there the summer Milky Way stretches up across the eastern sky through Scutum and Aquil, to Cygnus, then down into the northeast through Cepheus to Cassiopeia. The area around the galactic center is rich with star clusters (open and globular) and nebulae, but they're also found elsewhere in the summer sky, such as the globular clusters M13 and M92 in Hercules, which is high in the east, and M3 in Canes Venatici. Lyra, with its brilliant star Vega, stands high in the east, above Cygnus, while equally bright Arcturus, in Bootes, stands near the zenith. Meanwhile, the Big Dipper tilts towards the northwest, and Virgo stands in the southwest. Cancer with Jupiter sinks westward, trailed by Leo, while Castor and Pollux stand side-by-side above the twilight, preparing to depart. A small world with an identity crisis comes to opposition in northern Sagittarius this month, though 14th-magnitude Pluto may be hard to identify in this star-rich region of the sky. Jupiter blazes in Capricornus at magnitude -2.6, rising shortly after midnight. June 5 Venus at greatest elongation from Sun in morning sky. June 6 Moon occults Antares. June 7 Full Moon at 2:12 p.m. June 13 Mercury at greatest elongation from Sun in morning sky; Moon lies near Jupiter. June 15 Last-quarter Moon at 6:15 p.m. June 19 Moon lies near Venus and Mars in morning sky. June 20 Moon lies near Pleiades in morning sky. June 21 Summer Solstice is at 1:46 a.m.; Moon lies near Mercury. June 22 New Moon at 3:35 p.m.; Mercury lies near Aldebaran. June 23 Pluto at opposition; Moon at perigee. June 26 Moon lies near Regulus. June 27 Moon lies near Saturn. June 29 First-quarter Moon at 7:28 a.m. g

April Flowers Bring May Showers
By Joseph A. Fedrick
A dry late winter season and early spring provided clear skies for viewing after the February and March meetings of the Observers' Group, but by late April the sky became cloudy so that Mercury and Saturn were obscured by clouds and the crescent Moon was only intermittently visible between the clouds on April 28, the night of the April meeting. Rain followed during early May so I couldn't get a good view of Saturn until May 10. Even then, the sky was partly cloudy. Saturn appeared as a markedly oblate, almost eggshaped, paletan-yellow disk with faint brownish cloud belts in my 6-inch Newtonianreflector at 150x. The rings were tilted at about 4 degrees, the maximum tilt for this year. They appeared dull and brownish as comparedto the brilliant white when they were tilted near their maximum in earlier years. The inner crepe ring wasn't readily visible and the outer B ring was barely perceptible. The Cassini division between the darker outer A ring and inner brighter B was perhaps at the threshold of visibility. The ring shadow on Saturn's disk was visible crossing near theequator, and the north and south equatorial belts were visible onSaturn's disk on either side of the rings. The preceding edges of the rings were darker and browner than the following edges on the other side of the planet, which were slightly bluish and a bit brighter. The A and B rings, and Cassini division, were less diff icult to discern. Saturn appeared nearly as spectacular in Michael O'Gara's 76-mmapochromatic refractor at 120x on March 31 even with a smaller aperture (3 inches vs. 6 inches). The apochromatic refractor had the advantage of producing sharp contrasting images due to the lack of a central obstruction and lack of chromatic aberration. g Stuff continued from page 2 forming regions. There's an accretion shock when stuff comes in [at high speeds] and slams into the disc. So maybe everything's getting homogenized and heated and condensed way out there," he said, gesturing to the boundary beyond the solar system. "That's why we need a global disc model. We need to have a model for modeling this disc the same way they do global climate models that predict climate over long periods of time." Stardust is now on its way to Comet Tempel I to gather more data. "That's why these missions are so important, because they provide the constraints, things we have to answer." But for now, Ebel and others will just have to settle for providing the age-old answer: We're not sure. g

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A Message from AAA President Richard Rosenberg
Hello members: I thank the members of the club for re-electing me to the board of directors and to the board for re-electing me as president. More details on the annual meeting can be found in Dan Harrison's article below. The AAA will have deep-sky observing sessions at North-South Lake in the Catskills this summer. We'll be limited to four cars at each session. The location, about 125 miles from the city, is exceptionally dark. It is about a two-and-a-half-hour trip each way from the city. Besides the campground and other nearby places to lodge, there is a possibility of staying at a member's summer place nearby. We'll have a list of observing dates shortly. Irv Robbins, director of the observatory at the College of Staten Island and a former board member of the AAA, is looking for amateurs to help discover asteroids. The college now controls robot observatories in Arizona and Australia and may get involved with Hawaii. I'm not sure if the work will involve making images, looking at images or both Volunteers will be trained. The Brooklyn Bridge Park Conservancy, which hosted the free "Movies with a View" last summer, is having a money-raising event on Thursday, June 4. Four Dobsonian telescopes will be available. We need one more person to operate the fourth. Free refreshments will be available (and we don't have to pay admission).

Rosenberg Re-elected AAA President for Fourth Term
By Dan Harrison
Richard Rosenberg was elected to a fourth one-year term as AAA president by the AAA board of directors following the May 20 annual meeting. Other off icers were re-elected: vice president Rik Davis, treasurer Thomas Haeberle, f inancial secretary Alice Barner, recording secretary Edward J. Fox and corresponding secretary Ron McCullough. At the annual meeting, members re-elected four members to three-year terms on the board of directors: Rosenberg, McCullough, Eyepiece editor Dan Harrison, and Amateur Astronomers Medal recipient and Eyepiece columnist Tony Hoffman. Two new members were elected, Joe Delfausse and Jocelyn Wilkes. John Delaney and Richard Tihany didn't stand for re-election. Outlining the state of the club, Rosenberg said the big news of the past year was the move of the AAA to its new headquarters at 120 Warren Street in downtown Manhattan. This provides better visual capability and Internet connection. "We can make use of planetarium programs regarding what's up and coming up." In addition, the seminar on recent advances in astronomy met at New York University, though in the summer it will move to headquarters. "We've saved considerable money on rent while at the same time upgrading our presentations. With Internet access and computer software, our seminar has available up-to-date news on space missions, scientif ic discoveries and new comets. At the Observers Group we can illustrate upcoming celestial events with a planetarium program." The club plans an online version of Eyepiece shortly, he continued. "This will enable the club to save considerable expense in postage and printing costs, and effort in monthly mailings. In return, those receiving Eyepiece online will be able to receive not only the articles but images and star charts." The club continues to expand its observing sites. It's arranged for dark-sky observing at North-South Lake in the Catskills. "Thanks to the efforts of Jason Kendall," Rosenberg noted, "we're back in Inwood Hill Park with multiple observing sessions each month. We've begun astronomy talks followed by observing at the Salt Marsh Nature Center in south Brooklyn." Rosenberg noted that the club has established a relationship with the Brooklyn Bridge Park Conservancy. AAA members staffed telescopes at the park's "Movies with a View" series last summer and will do so again this year. The scopes will be out again at a Conservancy money-raiser on Thursday, June 4 at Pier 5 in Brooklyn Heights. "We hope to develop similar relationships with the Audubon Society at Prospect Park and the Intrepid Museum." Rosenberg continued on page 4

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Galileo's Telescope in Philadelphia and on PBS Show
By Luis Marcelo Cabrera
Last month I visited "Galileo, the Medici, and the Age of Astronomy" at the Franklin Institute in Philadelphia. The exhibition, which runs through Sept. 7, is actually two exhibitions. The f irst part, "Medici Collection," starts with armillary spheres, astrolabes and similar instruments, followed by maps and codexes. There are numerous examples of compasses, dividers, quadrants, nocturnals (instruments used to determine the time based on the position of a star, like a sun dial), and perspective and surveying instruments, both civilian and military. The show also discusses science in the age of Galileo. The second part of the exhibition is called "Galileo's Telescope" and features one of the two known surviving telescopes that Galileo used during his lifetime. The 400-year-old telescope was Galileo's observing telescope rather than his more ornate presentation telescope. Also featured are drawings of the Moon by Galileo with annotations, charts of Jupiter's moons with measurements of position relative to time and manuscripts with possible explanations for Saturn's rings. There are abundant hands-on sections with telescopes, lenses and lasers demonstrating how the different types of telescopes work, and their strengths and weaknesses. Interactive video screens highlight the signif icant discoveries of Galileo's time and their impact on science. At the end of the exhibit there's a short introduction to the problem of determining longitude at sea and Galileo's Jovilabe. The Jovilabe was meant to determine longitude by f inding the time, using the positions of Jupiter's moons. Not discussed in the exhibition, but mentioned as you exit the show, is the issue of church and science, and Galileo's trial. The exhibition has free audioguides through the use of a cell phone. At the end of my visit I checked out other activities related to the International Year of Astronomy and was pleasantly surprised by the Fels Planetarium show "Two Small Pieces of Glass," which tells the story of two teenagers going to a local star party, and their discoveries and learning about telescopes and their history. This brings me to the PBS documentary "400 Years of the Telescope, A Journey of Science, Technology and Thought," an hour-long show recently broadcast. The f ilm featured several prominent scientists and scientif ic historians, including Hayden Planetarium director Neil de Grasse Tyson as narrator and such historical f igures as Galileo and Newton. The show covered advances in astronomy since Galileo f irst used a telescope to look at the sky 400 years ago. The creation and science behind telescopes were explained in detail, as well as the differences between refractors and reflectors, their history, mechanical diff iculties encountered in manufacturing them and their associated discoveries. There was also emphasis on advances since the Hubble Space Telescope started to operate, and the importance of having a f ixed-up and upgraded Hubble or some other more advanced instrument looking at the sky. The superb illustrations and animations in the documentary helped explain, in very simple language, concepts somewhat diff icult to understand when presented for the f irst time, such as expansion of the universe, adaptive optics and interferometers. The show overall was very entertaining and captivating, but also very educational and almost guaranteed to inspire future astronomers. A companion book to the show has been published, by well-known astronomy writer Donald Goldsmith. It's "400 Years of the Telescope: A Journey of Science, Technology and Thought." g Rosenberg continued from page 3 Work has proceeded slowly on development of the club's class, Rosenberg said, but in June, "we'll present the f irst part of a PowerPoint presentation dealing with our understanding of the solar system from prehistoric man to the space age. This will be free to all members." Rosenberg also pointed to the success of the club's lecture series, including standing-room-only for talks by Robert Nemiroff of Astronomy Picture of the Day, and AAA member and Hayden Planetarium director Neil de Grasse Tyson, who spoke on Pluto. At the annual meeting last year, Tyson created a $3,000 matching fund to benef it the club and honor Fred Hess. Contributions from members quickly achieved the fund's target. "As the f irst fruit," Rosenberg noted, "we've bought a CCD imager which, when inserted into a telescope in place of an eyepiece, converts incoming photons into images that can be seen on a computer monitor. This is a terrif ic educational tool. Many people can see images at once. Hard-to-recognize objects such as lunar craters or moons of Jupiter can be pointed out." The club has ordered a dozen Galileoscopes, simple scopes similar to, but easier to use, than the one Galileo used. These should arrive in June and will be featured at observing sessions, Rosenberg said. He noted that he's sent letters in support of light-pollution legislation to the governor and key legislators in Albany, and urged members to do the same. g

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Balloon-Borne Scope Delves into Early Universe
Several years ago, a team of scientists hoping to f igure out how the galaxies formed launched a revolutionary new telescope under a NASA high-altitude balloon to unlock the evolution of the universe. The BLAST (Balloon-borne LargeAperture Sub-millimeter Telescope) mission, which staged long-duration flights over Sweden in 2005 and Antarctica in 2006, is the subject of a documentary, "BLAST!" being shown in New York this month. Filmmaker Paul Devlin followed the story of his brother, Mark, a University of Pennsylvania professor of astronomy and astrophysics, and the project's principal investigator. Mark Devlin was in charge of a collaboration that designed the telescope. Flying the telescope above much of the atmosphere allowed the BLAST team to peer into the distant universe at wavelengths nearly unattainable from the ground. The study has uncovered dust-enshrouded galaxies that hide about half the cosmic starlight. In the 1980s and 1990s, certain galaxies called ultraluminous infrared galaxies were found to be forming hundreds of times more stars than our own local galaxies. These starburst galaxies, 7 billion-10 billion light-years away, were thought to make up the far infrared background discovered by the COBE satellite. The BLAST study combined telescope survey measurements at wavelengths below 1 millimeter with Spitzer data at much shorter infrared wavelengths. Results conf irm that all the far infrared background comes from individual distant galaxies, solving a question of the radiation's origin. Thus, as much as half the universe's light energy is infrared from young, forming galaxies. BLAST's extragalactic survey, at wavelengths of 0.25, 0.35 and 0.5 millimeters, provided new limits on the abundance and brightness of starburst galaxies for both the low- and highredshift universe. The instrument has a 2-meter primary mirror along with a camera made of hundreds of bolometers, sensitive detectors cooled to 0.3 degrees above absolute zero. With three wavelength bands operating, BLAST determined the spectrum of submillimeter light coming from distant galaxies. This measurement gave the temperature of each galaxy and, ultimately, its estimated rate of star formation. In one 11-day balloon flight, BLAST found more than 10 times the total number of submillimeter starburst galaxies detected in a decade of ground-based observations. The study documented a large population of cold clouds of gas and dust, many cooled to less than -260 C, which form the birthplace of stars. The New 11 at the IFC one showing Village, 12th June 12-18. York premiere of "BLAST!" is Thursday, June Center, 6th Avenue and 3rd Street. There will be on that day. The f ilm then moves to Cinema Street east of 5th Avenue, for f ive shows a day

Images, photographs, sky maps and the complete study are available at http://www.blastexperiment.info/. If yiou want further information on the f ilm, proceed to info@blastthemovie.com. g

Astronomical League Slates August Convention in NY
The Astronomical League convention comes to our area August 8 and 9 at Hofstra University, Hempstead, N. Y. It's cosponsored by the AmateurObservers' Society of New York, and Hofstra's physics and astronomy department. The program will include guest speakers with expertise in such areas as astrophysics, exobiology, astronomy hardware, observing techniques, astronomy art, astronomy history and radio astronomy. The many speakers include David Levy, "A Night Watchman's Journey: My Life and Hard Times as a Comet Hunter"; NASA Goddard's Nancy Kiang, "Astronomical Detection of Life on Other Worlds: Biosignatures of Photosynthesis"; author Phil Harrington, "Nights of Future Passed," which reviews the amateur telescope over the 20th century; Al Nagler, president and founder of Tele Vue Optics; Tony Pirera, founder and president of Spectrum Thin Films, where coatings have been deposited on f ilters for NASA space probes, such as the Mars Phoenix Lander; astronomy writer/educator Joe Rao, "Great Comets of the Last 400 Years"; and Dr. Michael Inglis of Suffolk County Community College, on detection of extremely high-energy rays. Other session topics include "Dark Skies as a Universal Resource," "Night-Sky Network Materials for Astronomy Education," "Recent Developments on20Jupiter," "Amateur Imaging of Mercury" and "Variable Star Observing." The convention will also feature astronomy vendors. Pre-convention activities starting August 2 include tours of the Hayden Planetarium and Brookhaven National Laboratories. Early convention registration, at a discount, is open until July 1. Info: www.alcon2009.org. g

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The Continuing Saga of the Twin Martian Rovers
By Dan Harrison
Addressing the Explorers Club May 2, Cornell astronomy professor Dr. Steven Squyres noted that the twin Martian rovers Spirit and Opportunity were in day 1,895 of their 90-day mission. Squyres, lead scientist for the Mars Exploration Rover Project, had no way of knowing that just four days later, on May 6, Spirit would get stuck in sandy soil and would be delayed in its voyage towards Goddard Crater, 250 meters south of its location when he spoke and a possible volcanicexplosion crater. But Squyres' outline of the rovers' achievements in what's been the greatest overland trek of a planet--they were designed to go 600 meters--was hardly diminished by that news. After all, the rovers have sustained several glitches and have continued their duties. In his talk to the Explorers Club, Squyres noted that there have been previous stalls in the Martian sand. Vehicles on Earth have simulated the predicaments by being partially put in sand, clay and earth. This was even used to guide scientists in extracting a robot from a sand dune. "The optimal technique," Squyres observed, is to do what many earthlings do: "put it into reverse and gun it." Outlining highlights from the rovers' f ive years on Mars, Squyres noted that Spirit found a dry riverbed flowing into Gusev Crater. "We wanted to f ind sedimentary rocks but found igneous rocks. We still think sedimentary rocks are down there but are covered by lava." When Spirit climbed Husband Hill, it saw layering materials that could only have formed by the action of water, Squyres said. "About 1,200 days into the mission, soil popped up like snow. It was 91% pure silicone, evidence of a hot-spring deposit. " A key to the rovers' longevity has been the Martian winds. At one point, Squyres recalled, dust led to decreased power. "We thought Spirit was close to the end, but we hit the windy season so lower power was less of a problem because the rover's solar ar rays had been cleaned off by the wind." Opportunity's landing site was chosen by chemistry. "Hematite is a chemical that serves as a beacon since water may have been present," Squyres said. "Layered bedrock is right near the impact crater. The layering is f ine grain, and we found hematite right away. We found rocks made of hematite and evidence that water soaked the ground. Ripples that transported rocks were evidence of water. So water blew across the surface and headed across the countryside." Opportunity is heading for Endeavor Crater after having visited the Eagle, Victoria and Endurance craters. Endeavor is much older than Victoria and Endurance, so it may provide a look at bedrock. The rover, having spent two years exploring Victoria, has adduced evidence that not only did water shape much of the crater's region, but that liquid water could have formed in well-below-freezing temperatures if there were enough minerals in it. Meanwhile, getting Spirit unstuck was proving diff icult at press time. On the science end, the exact makeup of the dirt the rover is stuck in isn't known. Spirit is sampling its surroundings to provide clues. On the mechanical end, Spirit's right front wheel has been dead for three years. That makes it harder to use the f ive remaining wheels to pull the rover out." In his remarks to the Explorers Club, Squyres said that Spirit and Opportunity have lasted so long due to "very good hardware, overengineering and luck due to windy gusts that boost power by cleaning the vehicles, especially Spirit. The next rover, slated for launch in 2011, will have a different payload that will be able to detect organic molecules if they are there. The rover will be powered by nuclear, not solar. That means "we don't need solar ar rays and don't need wind gusts to clean the craft." Asked how long he thought the rovers might continue, Squyres, as if ready for the question, replied, "My wife keeps asking me that." g

AAA Officers for 2009-10
President - Richard Rosenberg Vice President - Rik Davis Treasurer - Thomas Haeberle Financial Secretary - Alice Barner Recording Secretary - Edward Fox Corresponding Secretary - Ron McCullough

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Review: The Intense Scientific Disputes about Europa
By Katherine Avakian
"Unmasking Europa: The Search for Life on Jupiter's Ocean Moon" (Copernicus Books, $27.50) by Richard Greenberg, is a richly detailed book stating the author's strong belief that this is largely an oceanic world with a thin and permeable shell of ice, presenting an environment for possible life. Greenberg, professor of planetary science at the University of Arizona, was on the imaging team for the Galileo mission, which arrived at the Jupiter system in 1995. The spaceship was crash landed into Jupiter in 2004 to avoid contaminating Europa. The book is replete with images from that mission and by Voyager 2 as it flew past Jupiter in 1979. Another segment of the imaging team, viewed by Greenberg as the "establishment," came up with a different view of Europa, one in which ice tens of kilometers thick blankets and isolates the ocean below. How this viewpoint dominated despite Greenberg's evidence is spelled out. It's not a pretty picture. Indeed, of a prior book on Europa geared to the academic science community, he says, "Some individuals beholden to the U. S. planetary exploration establishment really hated it....They didn't like what I had to say about how science is done in the context of a major big-ticket space mission...." Greenberg's presentation of the scientif ic makeup of Europa is believable. It's about the size of our Moon. Its close proximity to Jupiter, with some 300 times the mass of Earth, generates great tides on Europa. This tidal action produces heat which keeps most of its water liquid. The tidal action also stresses the moon, causing its surface to crack, creating systems of ridges as water from below rushes up. Over long periods of time, the cracks open and close each Europan day (3 1/2 Earth days), pushing up newly-formed ice each day to build these ridges which overlay older ones. "Tracking the ridges gives us a way to unravel the history of the cracking of Europa's crust. From the paths that the ridges take over the surface, we can read the history of the stress of tides." Greenberg describes other areas of "thermal disruption," such as Conamara Chaos, "where the crust briefly melted, allowing blocks of surface ice to float to slightly displaced locations before refreezing...." These areas of chaos replace an earlier surface with a "lumpy, bumpy matrix with somewhat displaced rafts." Europa's few large impact craters show evidence pointing to a thin ice covering, Greenberg states. Craters such as Tyre and Callanish "record impact penetration to liquid water, which resulted in temporary exposure of the ocean to the surface. Blocks of crust were broken apart and dislodged, then locked into place as the exposed water refroze." He notes the presence of the same type of lumpy matrix and broken rafts that characterize areas of chaos. The only difference in their formation is an impact from above in one case and heating from below in the other. On the other hand, proponents of a thick-ice theory believe that convection within the ice and cryovolcanism could produce areas of chaos as well as other small upwellings. Greenberg admits convection is "possible in an ice crust, but only if the ice meets certain criteria," such as fluidity involving temperature and size of ice-crystal grains. The ice crust also needs to be thick enough for vertical motion to take place. He concludes convection is "plausible, although by no means a certainty or even a likelihood." Greenberg also points out why cryovolcanism is improbable on Europa. Since liquid water is denser than ice, it would remain below unless there were "pressure chambers to force the liquid upward." In any event, "the watery magma could not come from the global ocean. The ocean could not be pressurized enough to reach the surface...." "It seems bizarre that political clout would be used to promote a scientif ically weak position," but that's what happened. Those who didn't get on the thick-ice bandwagon paid a price. Although Greenberg was a member of the Galileo imaging team, he always felt marginalized. He wasn't among those plan