 |
|
Icy Jupiter Moon Throws a Curve Ball at Formation Theories
June 01, 2005Scientists studying data from NASA's Galileo spacecraft have found that Jupiter's moon Amalthea is a pile of icy rubble less dense than water. Scientists expected moons closer to the planet to be rocky and not icy. The finding shakes up long-held theories of how moons form around giant planets.
"I was expecting a body made up mostly of rock. An icy component in a body orbiting so close to Jupiter was a surprise," said Dr. John D. Anderson, an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Anderson is lead author of a paper on the findings that appears in the current issue of the journal Science.
"This gives us important information on how Jupiter formed, and by implication, how the solar system formed," Anderson said.
Current models imply that temperatures were high at Amalthea's current position when Jupiter's moons formed, but this is inconsistent with Amalthea being icy. The findings suggest that Amalthea formed in a colder environment. One possibility is that it formed later than the major moons. Another is that the moon formed farther from Jupiter, either beyond the orbit of Jupiter's moon Europa or in the solar nebula at or beyond Jupiter's position. It would have then been transported or captured in its current orbit around Jupiter. Either of these explanations challenges models of moon formation around giant planets.
"Amalthea is throwing us a curve ball," said Dr. Torrence Johnson, co-author and project scientist for the Galileo mission at JPL. "Its density is well below that of water ice, and even with substantial porosity, Amalthea probably contains a lot of water ice, as well as rock." Analysis of density, volume, shape and internal gravitational stresses lead the scientists to conclude that Amalthea is not only porous with internal empty spaces but also contains substantial water ice.
One model for the formation of Jupiter's moons suggests that moons closer to the planet would be made of denser material than those farther out. That is based on a theory that early Jupiter, like a weaker version of the early Sun, would have emitted enough heat to prevent volatile, low-density material from condensing and being incorporated into the closer moons. Jupiter's four largest moons fit this model, with the innermost of them, Io, also the densest, made mainly of rock and iron.
Amalthea is a small red-tinted moon that measures about 168 miles in length and half that in width. It orbits about 181,000 kilometers (112,468 miles) from Jupiter, considerably closer than the Moon orbits Earth. Galileo passed within about 99 miles of Amalthea on Nov. 5, 2002. Galileo's flyby of Amalthea brought the spacecraft closer to Jupiter than at any other time since it began orbiting the giant planet on Dec. 7, 1995. After more than 30 close encounters with Jupiter's four largest moons, the Amalthea flyby was the last moon flyby for Galileo.
The Galileo spacecraft's 14-year odyssey came to an end on Sept. 21, 2003. JPL, a division of the California Institute of Technology in Pasadena, managed the Galileo mission for NASA.
Additional information about the mission is available online at: http://galileo.jpl.nasa.gov/ .
NASA Jet Propulsion Labratory
"Amalthea is throwing us a curve ball," said Dr. Torrence Johnson, co-author and project scientist for the Galileo mission at JPL. "Its density is well below that of water ice, and even with substantial porosity, Amalthea probably contains a lot of water ice, as well as rock." Analysis of density, volume, shape and internal gravitational stresses lead the scientists to conclude that Amalthea is not only porous with internal empty spaces but also contains substantial water ice.
One model for the formation of Jupiter's moons suggests that moons closer to the planet would be made of denser material than those farther out. That is based on a theory that early Jupiter, like a weaker version of the early Sun, would have emitted enough heat to prevent volatile, low-density material from condensing and being incorporated into the closer moons. Jupiter's four largest moons fit this model, with the innermost of them, Io, also the densest, made mainly of rock and iron.
Amalthea is a small red-tinted moon that measures about 168 miles in length and half that in width. It orbits about 181,000 kilometers (112,468 miles) from Jupiter, considerably closer than the Moon orbits Earth. Galileo passed within about 99 miles of Amalthea on Nov. 5, 2002. Galileo's flyby of Amalthea brought the spacecraft closer to Jupiter than at any other time since it began orbiting the giant planet on Dec. 7, 1995. After more than 30 close encounters with Jupiter's four largest moons, the Amalthea flyby was the last moon flyby for Galileo.
The Galileo spacecraft's 14-year odyssey came to an end on Sept. 21, 2003. JPL, a division of the California Institute of Technology in Pasadena, managed the Galileo mission for NASA.
Additional information about the mission is available online at: http://galileo.jpl.nasa.gov/ .
NASA Jet Propulsion Labratory
Planet Jupiter News and Current Planet Jupiter Events RSSLooking for life on Jupiter's icy moon Europa
While NASA and the European Space Agency focus on Mars rovers and future missions to search for life on the Red Planet, a determined core of scientists is lobbying for equal attention to a place they feel is just as likely to harbor life-Jupiter's icy moon Europa.
Jupiter: A cloudy mirror for the Sun?
Astronomers using the European Space Agency's XMM-Newton telescope have discovered that observing the giant planet Jupiter may actually give them an insight in to solar activity on the far side of the Sun! In research reported in the most recent edition of Geophysical Research Letters, they discovered that Jupiter's x-ray glow is due to x-rays from the Sun being reflected back off the planet's atmosphere.
New life discovered in the deep Mediterranean
Scientists have discovered a new group of microbes thriving in extreme conditions deep in the Mediterranean Sea. Their existence in such hostile environments hints at the possibility of life on other planets.
Moon and Four Planets in the Evening Sky - a Prelude to the Venus Transit
During the coming evenings, everybody under clear skies will be able to enjoy a beautiful view in the twilight. Right after sunset, planet Venus is visible as a brilliant point of light above the western horizon - and two other planets, Mars and Saturn, are seen to the left of Venus as somewhat less bright objects. More to the south and higher in the sky, planet Jupiter is also prominent. In the evenings of April 22 and 23, the thin crescent of the Moon will be located near Venus and Mars, further adding to the splendor of this sight (the drawing shows the configuration in the evening of Friday, April 23). One month later, around May 21, there will be another chance to witness this interesti
Will The Leonids Go Out With A Bang?
Anyone willing to brave the early morning cold on 19 November may be rewarded with one of Nature's most spectacular firework displays - a major meteor storm. This year's Leonid meteor shower is expected to provide the last great storm for at least 30 years, and possibly the biggest in the 21st century. With meteor numbers predicted to reach or even exceed 1000 per hour, this once-in-a-lifetime event should be worth waiting for if the skies are clear - despite the interference of a full Moon. The meteors in question are the Leonids, so-called because they seem to originate in the constellation of Leo. Commonly known as 'shooting stars', the fast-moving dust particles leave bright trails acr
Astronomers discover the wake of a planet around a nearby star
An international team of astronomers today report the discovery of a huge distorted disk of cold dust surrounding Fomalhaut - one of the brightest stars in the sky. The most likely cause of the distortion is the gravitational influence of a Saturn-like planet at a large distance from the star tugging on the disk. This provides some of the strongest evidence so far that Solar Systems similar in size, or even bigger than our own, are likely to exist. One hundred planets are already known to exist outside our Solar System - although none have yet been seen directly by a telescope. These planets have been nicknamed "hot-Jupiters" since they are roughly the size of the planet Jupiter, but have or
Disks around Failed Stars - a Question of Age
First Ground-Based Mid-Infrared Observations of Brown Dwarfs [1] A team of European astronomers [2] have observed eight Brown Dwarfs, i.e., small and faint objects also known as "failed stars", with the TIMMI2 infrared sensitive instrument at the ESO 3.6-m telescope on La Silla. From two of these, mid-infrared radiation is detected - for the first time ever from such objects with a ground-based telescope. While the younger Brown Dwarf, aged a few million years, is found to be surrounded by a dusty disk, no warm dust is present around the older ones. The new observations support the following formation hypothesis for Brown Dwarfs: they are born in the same way as "real" stars, by contraction
Infrared Images of an Infant Solar System
ESO telescopes have detected a strange-looking object. Using the ESO 3.6-m New Technology Telescope and the Very Large Telescope (VLT), a team of astronomers [1] have discovered a dusty and opaque disk surrounding a young solar-type star in the outskirts of a dark cloud in the Milky Way. It was found by chance during an unrelated research programme and provides a striking portrait of what our Solar System must have looked like when it was in its early infancy. Because of its unusual appearance, the astronomers have nicknamed it the "Flying Saucer". The new object appears to be a perfect example of a very young star with a disk in which planets are forming or will soon form, and located far a
Jupiter`s Electric Aurora
The planet Jupiter has spectacular rings of auroras around each pole but until now scientists have not been able to explain how they form. All auroras are caused by energetic charged particles crashing into the top of the atmosphere and making it glow. In the Earth's auroras, these particles come from the Sun in a flow of charged particles known as the solar wind. But this can't account for Jupiter's auroras because the solar wind does not reach to the region where the brightest are found. Space physicists from the University of Leicester have now proposed a new theory of how Jupiter's auroras are formed. An enormous disk of plasma gas rotates around Jupiter, flowing outwards from the moo
Aurorae and Volcanic Eruptions
Impressive thermal-infrared images have been obtained of the giant planet Jupiter during tests of a new detector in the ISAAC instrument on the ESO Very Large Telescope (VLT) at the Paranal Observatory (Chile). They show in particular the full extent of the northern auroral ring and part of the southern aurora. A volcanic eruption was also imaged on Io, the very active inner Jovian moon. Although these observations are of an experimental nature, they demonstrate a great potential for regular monitoring of the Jovian magnetosphere by ground-based telescopes together with space-based facilities. They also provide the added benefit of direct comparison with the terrestrial magnetosphere. The fu
More Planet Jupiter News Articles
 | Exploring Jupiter: The Astrological Key to Progress, Prosperity & Potential by Stephen Arroyo |
 | Jupiter: and How to Observe It (Astronomers' Observing Guides) by John W. McAnally ASTRONOMERS’ OBSERVING GUIDES provide up-to-date information for amateur astronomers who want to know all about what it is they are observing. This is the basis of the first part of the book. The second part details observing techniques for practical astronomers, working with a range of different... |
 | Destination: Jupiter by Seymour Simon When the unmanned spacecraft Galileo landed on Jupiter in 1995, what mysteries did it uncover?...Did you know that...Jupiter is so large that more than 1,300 planet Earths could fit inside.The Great Red Spot on the planet is actually an enormous hurricane that changes in size and color over the years.A person weighing 100 pounds on Earth would weigh 264 pounds on Jupiter.Life might exist on... |
 | Jupiter: The Planet, Satellites and Magnetosphere (Cambridge Planetary Science) This comprehensive volume summarizes current knowledge of the Jovian system, in view of recent scientific developments regarding the Galileo spacecraft, the Galileo probe, the Cassini spacecraft, the Hubble Space Telescope, and numerous ground-based and theoretical studies. Chapters by recognized authorities cover all aspects of Jupiter, its satellites and... |
 | Madalyn Aslan's Jupiter Signs: How to Improve Your Luck, Career, Health, Finance, Appearance, and Relationships through the New Astrology by Madalyn Aslan Madalyn Aslan has been hailed as the new Linda Goodman for a younger, contemporary audience and as the "Pollyanna psychic" (Isaac Mizrahi) we need today. In Madalyn Aslan's Jupiter Signs she describes how Jupiter is the planet governing luck, love, success, and money-and how the sign it was in at your birth can enrich you with secret strategies to change your life for the better in good times or... |
 | Jupiter Odyssey: The Story of NASA's Galileo Mission (Springer Praxis Books / Space Exploration) by David M. Harland Focusing on the Galileo Mission, the story will relate this remarkable spacecraft's protracted gestation and the ordeal of its long haul out to Jupiter and its ultimate triumph: 5 years exploration within the Jovian system. The story spans a full quarter of a century, drawing on the press conferences, technical papers and essays of engineers and scientists involved in the mission which provide a... |
 | Jupiter (Scholastic News Nonfiction Readers) by Christine Taylor-Butler |
 | The Depths of Space: The Story of the Pioneer Planetary Probes by Mark Wolverton Recounts the history of Pioneer 10, highlighting its scientific and technological achievements. Also features the exceptional people who made the program possible. DLC: Pioneer... |
 | The Worlds of Galileo: The Inside Story of Nasa's Mission to Jupiter by Michael Hanlon, Arthur C. Clarke In The Worlds of Galileo, readers can discover for themselves the photos that have allowed scientists to make some of the most important astronomical observations in recent years and follow the entire trajectory of the mission that transformed the way we see our... |
 | Manta's Gift by Timothy Zahn Jakob Faraday is exploring Jupiter when his small craft is suddenly jarred by contact with a living creature. Faraday realizes he has blundered into a herd of enormous manta/dolphin-like animals, the Qanska, which live in Jovian space. To learn more about the Qanska, Faraday challenges Matt Rainey, a recently crippled quadraplegic, to bond with a Qanska by being placed within the womb of a mother... |
| © 2008 BrightSurf.com |