Category: Jupiter

Scientists have obtained new insight into the unique power source for many of Jupiter’s auroras, the most spectacular and active auroras in the Solar System. Extended monitoring of the giant planet with NASA’s Chandra X-ray Observatory detected the presence of highly charged particles crashing into the atmosphere above its poles.

X-ray spectra measured by Chandra showed that the auroral activity was produced by ions of oxygen and other elements that were stripped of most of their electrons. This implies that these particles were accelerated to high energies in a multimillion-volt environment above the planet’s poles. The presence of these energetic ions indicates that the cause of many of Jupiter’s auroras is different from auroras produced on Earth or Saturn.

“Spacecraft have not explored the region above the poles of Jupiter, so X-ray observations provide one of the few ways to probe that environment,” said Ron Elsner of the NASA Marshall Space Center in Huntsville, Alabama, and lead author on a recently published paper describing these results in the Journal for Geophysical Research. “These results will help scientists to understand the mechanism for the power output from Jupiter’s auroras, which are a thousand times more powerful than those on Earth.”

Electric voltages of about 10 million volts, and currents of 10 million amps – a hundred times greater than the most powerful lightning bolts – are required to explain the X-ray observations. These voltages would also explain the radio emission from energetic electrons observed near Jupiter by the Ulysses spacecraft.

On Earth, auroras are triggered by solar storms of energetic particles, which disturb Earth’s magnetic field. Gusts of particles from the Sun can also produce auroras on Jupiter, but unlike Earth, Jupiter has another way of producing auroras. Jupiter’s rapid rotation, intense magnetic field, and an abundant source of particles from its volcanically active moon, Io, create a huge reservoir of electrons and ions. These charged particles, trapped in Jupiter’s magnetic field, are continually accelerated down into the atmosphere above the polar regions where they collide with gases to produce the aurora, which are almost always active on Jupiter.

If the particles responsible for the aurora came from the Sun, they should have been accompanied by large number of protons, which would have produced an intense ultraviolet aurora. Hubble ultraviolet observations made during the Chandra monitoring period showed relatively weak ultraviolet flaring. The combined Chandra and Hubble data indicate that this auroral activity was caused by the acceleration of charged ions of oxygen and other elements trapped in the polar magnetic field high above Jupiter’s atmosphere.

Chandra observed Jupiter in February 2003 for four rotations of the planet (approximately 40 hours) during intense auroral activity. These Chandra observations, taken with its Advanced CCD Imaging Spectrometer, were accompanied by one-and-a-half hours of Hubble Space Telescope observations at ultraviolet wavelengths.

The research team also included Noe Lugaz, Hunter Waite, and Tariq Majeed (University of Michigan, Ann Arbor), Thomas Cravens (University of Kansas, Lawrence), Randy Gladstone (Southwest Research Institute, San Antonio, Texas), Peter Ford (Massachusetts Institute of Technology, Cambridge), Denis Grodent (University of Liege, Belgium), Anil Bhardwaj (Marshall Space Flight Center) and Robert MacDowell and Michael Desch (Goddard Space Flight Center, Greenbelt, Md.)

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA’s Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

Original Source: Chandra News Release

The first ground based infrared spectrum of Jupiter’s moon Amalthea reveals that it must have formed far from its current location. This new result, based on observations with the Subaru telescope and the NASA Infrared Telescope Facility by a team of researchers from the National Astronomical Observatory of Japan, the University of Hawaii, and the University of Tokyo, sheds new light on our Solar System’s turbulent past.

Planets like Earth and Jupiter formed from the disk of gas and dust swirling around the Sun at the time of its birth. Rocky planets like Earth formed in the high temperature environment close to the Sun, while large gaseous planets like Jupiter formed in the cooler regions farther away. Similarly, Jupiter, the largest planet in the solar system, probably had its own disk of gas and dust. The four moons of Jupiter discovered by Galileo (Io, Europa, Ganymede, and Callisto) are likely to have been born from this disk.

In addition to the Galilean moons, Jupiter has two other types of satellites: four small inner moons orbiting Jupiter within the orbit of Io, the inner most Galilean satellite, and at least fifty five small outer moons outside the orbit of Callisto, the outer most Galilean satellite. All the outer satellites have tell-tale orbits that reveal that they must have been captured by Jupiter during or after the formation of the planet and its larger moons.

The origin of the four small inner moons remain a mystery, however. They have orbits compatible with the hypothesis that they formed in orbit around Jupiter like the Galilean moons. On the other hand, their small irregular shapes and their comparatively low reflectivity and low densities resemble asteroids and suggest that they were captured by Jupiter’s gravitational pull just like the outer moons.

The mystery persists because of the challenge inherent in observing Jupiter’s small inner moons from Earth. The moons are small and therefore faint, and they are obscured by the bright glare from Jupiter. Although NASA’s space probes Voyager and Galileo have captured detailed images of Jupiter’s small inner moons, these data have been insufficient for resolving the question of their origin.

Naruhisa Takato from the National Astronomical Observatory of Japan and his collaborators have now had success in obtaining the first infrared spectrum of two of Jupiter’s small inner moons, Amalthea and Thebe. To obtain a spectrum over a wide range of infrared wavelengths, the group combined the strengths of two instruments on two telescopes on the summit of Mauna Kea, Hawaii. For high resolution spectroscopy at wavelengths longer than 3 ?m ,the group used the Infrared Camera and Spectrograph on the Subaru telescope. For shorter wavelengths, the group used SpeX on the NASA IRTF, which has broad wavelength coverage.

The new spectrum of Amalthea shows the characteristic signatures of water. The most likely location of this water is within water containing hydrous minerals. Such minerals typically form in low temperature environments, ruling out the possibility that Amalthea could have formed in the high temperature environment of Jupiter’s immediate neighborhood while the planet was forming and where Amalthea
now is.

If Amalthea did not form near its present location, where did it come from? The surface of Amalthea resembles regions of Callisto that are not covered by ice. This suggests that Amalthea may have been one of the many small “micro-satellites” orbiting Jupiter that was sucked into an inner orbit when the Galilean moons formed. However, the spectrum of Amalthea has similarities with asteroids orbiting the Sun, suggesting that is was a “micro-planet” that was pulled into Jupiter’s orbit when Jupiter itself was forming.

Takato says “although we think Jupiter’s moons formed as an assembly of many smaller bodies, the same way we think planets formed from ‘planetesimals’, until now we have not found any example of the original building blocks of a planet’s moon. However, our results strengthen the argument that Amalthea is one of the few remaining pieces of the material that formed the Galilean moons. Amalthea may have ended up in orbit close to Jupiter rather than get incorporated into a larger moon or Jupiter itself. If this is the case, Amalthea would be the first known example of a ‘satellitesimal.'”

Original Source: Subaru News Release

At first glance, Jupiter looks like it has a mild case of the measles. Five spots – one colored white, one blue, and three black – are scattered across the upper half of the planet.

Closer inspection by NASA’s Hubble Space Telescope reveals that these spots are actually a rare alignment of three of Jupiter’s largest moons – Io, Ganymede, and Callisto – across the planet’s face.

In this image, the telltale signatures of this alignment are the shadows [the three black circles] cast by the moons. Io’s shadow is located just above center and to the left; Ganymede’s on the planet’s left edge; and Callisto’s near the right edge. Only two of the moons, however, are visible in this image. Io is the white circle in the center of the image, and Ganymede is the blue circle at upper right. Callisto is out of the image and to the right.

On Earth, we witness a solar eclipse when our Moon’s shadow sweeps across our planet’s face as it passes in front of our Sun. Jupiter, however, has four moons roughly the same size as Earth’s Moon. The shadows of three of them occasionally sweep simultaneously across Jupiter. The image was taken March 28, 2004, with Hubble’s Near Infrared Camera and Multi-Object Spectrometer.

Seeing three shadows on Jupiter happens only about once or twice a decade. Why is this triple eclipse so unique?

Io, Ganymede, and Callisto orbit Jupiter at different rates. Their shadows likewise cross Jupiter’s face at different rates. For example, the outermost moon Callisto orbits the slowest of the three satellites. Callisto’s shadow moves across the planet once for every 20 shadow crossings of Io. Add the crossing rate of Ganymede’s shadow and the possibility of a triple eclipse becomes even more rare. Viewing the triple shadows in 2004 was even more special, because two of the moons were crossing Jupiter’s face at the same time as the three shadows.

Jupiter appears in pastel colors in this photo because the observation was taken in near-infrared light. Astronomers combined images taken in three near-infrared wavelengths to make this color image. The photo shows sunlight reflected from Jupiter’s clouds. In the near infrared, methane gas in Jupiter’s atmosphere limits the penetration of sunlight, which causes clouds to appear in different colors depending on their altitude.

Studying clouds in near-infrared light is very useful for scientists studying the layers of clouds that make up Jupiter’s atmosphere. Yellow colors indicate high clouds; red colors lower clouds; and blue colors even lower clouds in Jupiter’s atmosphere. The green color near the poles comes from a thin haze very high in the atmosphere. Ganymede’s blue color comes from the absorption of water ice on its surface at longer wavelengths. Io’s white color is from light reflected off bright sulfur compounds on the satellite’s surface.

“I’m increasingly aware that some of the most interesting things in astronomy and astrophysics, for instance, can change the way people understand the universe, how it got started and where it’s going. I found those Voyager pictures of the moons of Jupiter incredibly exciting, these beautiful color pictures showing volcanoes on the surface”. -Robert C. Richardson, Nobel Laureate, Physics, Cornell, (1996)

In viewing this rare alignment, astronomers also tested a new imaging technique. To increase the sharpness of the near-infrared camera images, astronomers speeded up Hubble’s tracking system so that Jupiter traveled through the telescope’s field of view much faster than normal. This technique allowed scientists to take rapid-fire snapshots of the planet and its moons. They then combined the images into one single picture to show more details of the planet and its moons.

Original Source: NASA Astrobiology

NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., selected Northrop Grumman Space Technology, Redondo Beach, Calif., as the contractor for co-designing the proposed Prometheus Jupiter Icy Moons Orbiter (JIMO) spacecraft. The contract award is for approximately $400 million, covering work through mid-2008.

The Prometheus JIMO mission is part of an ambitious mission to orbit and explore three planet-sized moons, Callisto, Ganymede and Europa, of Jupiter. The moons may have vast oceans beneath their icy surfaces. A nuclear reactor would enable the mission, which would launch in the next decade.

JIMO would be the first NASA mission using nuclear electric propulsion, which would enable the spacecraft to orbit each icy world to perform extensive investigations of their composition, history, and potential for sustaining life.

The JIMO mission, integrated with the Vision for Space Exploration, also develops and demonstrates technologies and capabilities in direct support to implement the Vision, including space nuclear electric power systems and nuclear electric propulsion systems.

“We have assembled an exceptional team of professionals to take us into the next phase of the mission. To see the mission evolve is rewarding, and I am confident a good team is in place to move us forward,” said John Casani, project manager for the JIMO mission at JPL.

Under the contract, Northrop Grumman will work with a government team to complete the preliminary design for the spacecraft. The work includes developing hardware, software and test activities for the design of the non-nuclear portion of the spacecraft. It also includes developing the interfaces for the spacecraft, space reactor, and science instruments. The contractor is responsible for the integration of government-owned and provided technologies into the spacecraft. They are also responsible for assembly, integration, and testing of the space system in accordance with applicable government requirements.

The government team will co-design the spacecraft with the contractor. NASA will supply the launch vehicle. The Department of Energy’s Office of Naval Reactors, Washington, will own and be responsible for the space reactor.

The government team includes JPL, NASA’s Ames Research Center, Moffett Field, Calif.; Glenn Research Center, Cleveland; Kennedy Space Center, Fla.; Langley Research Center, Hampton, Va.; and Marshall Space Flight Center, Huntsville, Ala. Also the Office of Naval Reactors, which includesing Knolls Atomic Power Laboratory, Schenectady, N.Y.; Bettis Laboratory, Pittsburgh; and supporting Department of Energy national laboratories.

The mission instruments will be procured competitively via a NASA Announcement of Opportunity. Three crosscutting themes, identified by a NASA-chartered science definition team, drive the proposed JIMO investigations.

The themes are: evaluate the degree subsurface oceans are present on these moons; study the chemical composition of the moons, including organic materials, and the surface processes that affect them; and scrutinize the entire Jupiter system, particularly the interactions between Jupiter, the moons’ atmospheres and interiors.

JIMO is managed by JPL and is part of NASA’s Prometheus Program, a program studying a series of initiatives to develop power systems and technologies for space exploration in support of the Vision for Space Exploration.

JPL, a division of the California Institute of Technology, manages the proposed JIMO mission for NASA’s Exploration Systems Mission Directorate, Washington.

For more information about the mission or NASA, visit:
http://spacescience.nasa.gov/missions/prometheus.htm
NASA JIMO Mission
http://www.nasa.gov

Original Source: NASA JPL News Release

Jupiter’s moon Io is peppered with volcanoes, the hottest, most active volcanoes in our solar system. Sizzling vents spew plumes of gas and dust as much as 400 km high. They surge, spit, subside and surge again, non-stop.

The towering plumes, outlined by graceful arcs of rising and falling ash, are eerily beautiful. Their tops jut into space, freezing. Beneath them, scientists believe, it snows. Sulfurous flakes crystallize in the plume-tops and drift gently down to coat Io’s colorful terrain.

High above the falling snow something unexpected happens: At the apex of the plumes, some of the ash and dust that ought to turn around and fall … doesn’t. Defying gravity, it keeps going up, not slowing but accelerating, 2 times, 10 times, hundreds of times faster than a speeding bullet, away from Io and into deep space.

Passing spacecraft beware: Io is shooting at you.

The Ulysses spacecraft, a joint mission of NASA and the European Space Agency, made the discovery in 1992 when, approaching Jupiter, it was hit by a breakneck stream of volcano dust.

“What a surprise,” recalls Harold Krueger of the Max Planck Institute in Heidelberg, the principle investigator for Ulysses’ dust detector. “We expected to encounter dust,” he says. The solar system is littered with flakes from comets and asteroids. “But nothing like this.”

The dust came in a tight stream, like water from a garden hose, and it was moving extraordinarily fast, about 300 km/s (670,000 mph). “This makes it some of the fastest-moving material in the solar system,” says Krueger, “second only to the solar wind.” Fortunately the dust-bits were small, similar in size to particles in cigarette smoke, so they didn’t penetrate the ship’s hull in spite of their extreme velocity.

At first, no one suspected Io. Ulysses was 100 million kilometers from Io when the stream blew by, supposedly beyond the reach of volcanic plumes. Plus, the speed of the dust didn’t make sense. Particles emerge from Io’s vents traveling 1 or 2 km/s, not 300 km/s.

Baffled, researchers considered several possibilities: Could Jupiter’s dark rings be responsible? There’s plenty of dust there, but how could rings manufacture fast-moving jets? Comet Shoemaker-Levy 9 was another suspect. The comet flew so close to Jupiter in 1992 that it was torn apart. Comets are known to produce streams of dust, but not so fast as the stream that hit Ulysses.

NASA’s Galileo spacecraft eventually solved the puzzle. Like Ulysses, Galileo was pelted by dust when it approached Jupiter in 1995. Unlike Ulysses, which merely flew past the giant planet, Galileo settled into orbit. As data accumulated over a period of years, scientists were able to correlate volcanic activity with dust events, and they showed, furthermore, that dust streams were modulated by Io’s orbital motion.

The source was definitely Io.

Regarding the extreme velocity of the dust: “Jupiter is responsible for that,” explains Krueger.

Jupiter is not only a giant planet, but also a giant magnet, which spins once every 9 hours and 55 minutes. Spinning magnetic fields produce electric fields, and the electric fields around Jupiter are intense. Io-dust, like dust on your computer monitor, is electrically charged, so Jupiter’s electric forces naturally accelerate the grains. 300 km/s is no problem.

In 2000 when the Cassini spacecraft sailed past Jupiter en route to Saturn, it too was hit. Cassini’s dust detector is more capable than Ulysses’. In addition to mass, speed, charge and trajectory, it can also measure elemental composition. Cassini found hints of sulfur, silicon, sodium and potassium–all signs of volcanic origin.

“This raises an interesting possibility,” says Krueger. “We can analyze the hot interior of Io from a great distance.” There’s no need to get too close to the sizzling vents when you can catch the ash millions of miles away.

Io dust can even reach Earth, says Krueger, but don’t expect a meteor shower. Bright meteors such as Perseids and Leonids are caused by sand-sized comet dust. Io dust is much smaller. A typical grain is only 10 billionths of a meter wide. If a bit of it disintegrated in Earth’s atmosphere, you probably wouldn’t notice.

End of story? Not quite.

Ulysses visited Jupiter again in early 2004 and once again the craft was pelted. Io’s volcanoes were still at work. But something was wrong: The dust was shooting in the wrong direction.

“Io dust is supposed fly out of Jupiter’s equatorial plane,” says Krueger, “because that’s the way the accelerating electric fields point.” This time Ulysses approached Jupiter’s north pole (75 degrees north latitude to be exact) where no dust should go. Yet the spacecraft was pelted anyway.

Jupiter, it seems, flings Io-dust in every direction, which is hard to understand, says Krueger. Future missions to the giant planet might unravel the mystery. Every blast of dust will remind: we’ve still got a lot to learn.

Original Source: NASA Science Article

Scientists have discovered irregular lumps beneath the icy surface of Jupiter’s largest moon, Ganymede. These irregular masses may be rock formations, supported by Ganymede’s icy shell for billions of years. This discovery comes nearly a year after the orchestrated demise of NASA’s Galileo spacecraft into Jupiter’s atmosphere and more than seven years after the data were collected.

Researchers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and the University of California, Los Angeles, report their findings in a paper that will appear in the Aug. 13 issue of the journal Science.

The findings have caused scientists to rethink what the interior of Ganymede might contain. The reported bulges reside in the interior, and there are no visible surface features associated with them. This tells scientists that the ice is probably strong enough, at least near the surface, to support these possible rock masses from sinking to the bottom of the ice for billions of years. But this anomaly could also be caused by piles of rock at the bottom of the ice.

“The anomalies could be large concentrations of rock at or underneath the ice surface. They could also be in a layer of mixed ice and rock below the surface with variations in the amount of rock,” said Dr. John Anderson, a scientist and the paper’s lead author at JPL. “If there is a liquid water ocean inside Ganymede’s outer ice layer there might be variations in its depth with piles of rock at the ocean bottom. There could be topographic variations in a hidden rocky surface underlying a deep outer icy shell. There are many possibilities, and we need to do more studies.”

Dr. Gerald Schubert, co-author at UCLA, said “Although we don’t yet have anything definitive about the depth at this point, we did not expect Ganymede’s ice shell to be strong enough to support these lumpy mass concentrations. Thus, we expect that the irregularities would be close to the surface where the ice is coldest and strongest, or at the bottom of the thick ice shell resting on the underlying rock. It would really be a surprise if these masses were deep and in the middle of the ice shell.”

Ganymede has three main layers. A sphere of metallic iron at the center (the core), a spherical shell of rock (mantle) surrounding the core, and a spherical shell of mostly ice surrounding the rock shell and the core. The ice shell on the outside is very thick, maybe 800 kilometers (497 miles) thick. The surface is the very top of the ice shell. Though it is mostly ice, the ice shell might contain some rock mixed in. Scientists believe there must be a fair amount of rock in the ice near the surface. Variations in this amount of rock may be the source of these possible rock formations.

Scientists stumbled on the results by studying Doppler measurements of Ganymede’s gravity field during Galileo’s second flyby of the moon in 1996. Scientists were measuring the effect of the moon’s gravity on the spacecraft as it flew by. They found unexpected variations.

“Believe it or not, it took us this long to straighten out the anomaly question, mostly because we were analyzing all 31 close flybys for all four of Jupiter’s large moons,” said Anderson. “In the end, we concluded that there is only one flyby, the second flyby of Ganymede, where mass anomalies are evident.”

Scientists have seen mass concentration anomalies on one other moon before, Earth’s, during the first lunar orbiter missions in the 1960s. The lunar mass concentrations during the Apollo moon mission era were due to lava in flat basins. However, scientists cannot draw any similarities between these mass concentrations and what they see at Ganymede.

“The fact that these mass anomalies can be detected with just flybys is significant for future missions,” said Dr. Torrence Johnson, former Galileo project scientist. “With this type of information you could make detailed gravity and altitude maps that allow us to actually map structures within the ice crust or on the rocky surface. Knowing more about the interior of Ganymede raises the level of importance of looking for gravity anomalies around Jupiter’s moons and gives us something to look for. This might be something NASA’s proposed Jupiter Icy Moons Orbiter Mission could probe into deeper.”

The paper was co-authored by Dr. Robert A. Jacobson and Eunice L. Lau of JPL, with Dr. William B. Moore and Jennifer L. Palguta of UCLA. JPL is a division of the California Institute of Technology in Pasadena. JPL designed and built the Galileo orbiter, and operated the mission. For images and information about the Galileo mission, visit http://galileo.jpl.nasa.gov.

Image credit: NASA/JPL
The hottest spot in the solar system is neither Mercury, Venus, nor St. Louis in the summer. Io, one of the four satellites that the Italian astronomer Galileo discovered orbiting Jupiter almost 400 years ago, takes that prize. The Voyager spacecraft discovered volcanic activity on Io over 20 years ago and subsequent observations show that Io is the most volcanically active body in the solar system. The Galileo spacecraft, named in honor of the astronomer Galileo, found volcanic hot spots with temperatures as high as 2,910 Fahrenheit (1,610 Celsius).

Now computer models of volcanic eruptions on Io performed by researchers at Washington University in St. Louis show that the lavas are so hot that they are vaporizing sodium, potassium, silicon and iron and probably other gases as well into its atmosphere.

Using an updated version of MAGMA, a versatile computer program he developed 15 years ago with a Harvard University colleague, Bruce Fegley, Jr., Ph.D., professor of earth and planetary sciences in Arts & Sciences at Washington University in St. Louis, found that some of these elements are vaporized at least partly as single-atom gases. Others are vaporized in different molecular forms, for instance, silicon monoxide, silicon dioxide and iron monoxide.

“Reaction of these gases with sulfur and chlorine species in volcanic gases could lead to the formation of such unusual gases as sodium chloride, potassium chloride, magnesium dichloride and iron dichloride, ” Fegley said.

In 2000, Fegley and former Washington University colleague Mikhail Zolotov, Ph.D., now at Arizona Sate University, predicted formation of sodium chloride and potassium chloride vapor in volcanic gases on Io. Three years later astronomers found sodium chloride gas on Io. However, these observations were not sensitive enough to detect the less abundant potassium chloride vapor.

Now Fegley has found that sodium and potassium in Ionian volcanic gases are being vaporized from the hot lavas. Fegley and research assistant Laura Schaefer of Washington University used data from the Galileo mission and Earth-based observations from high-powered telescopes in their NASA-funded research. They published their results in the May 2004 issue of Icarus, the leading planetary science journal.

“We’re basically doing geology on Io using data from telescopes on Earth, which shows that observations like this can compete with expensive space missions,” said Fegley. “It’s amazing how hot and how volcanically active Io is. It is 30 times more active than Earth. It’s the hottest body outside of the sun in the solar system.”

The innermost of the four major satellites of Jupiter – there are at least 16 – Io gets its high rate of volcanism from tidal interactions with Jupiter, which has the strongest magnetic field of all the planets. Over 100 active volcanoes have been identified on Io. Hotspots there have temperatures as high as 1,600 degrees Celsius. This is several hundred degrees hotter than terrestrial volcanoes like Kilauea in Hawaii, which has a temperature of about 1,000 Celsius (1,830 Fahrenheit).

Fegley and Schaefer found that silicon monoxide is the major silicon-bearing gas over the lavas.

“The interesting thing about this is that astronomers have observed silicon monoxide in other environments in interstellar space, most notably in the atmospheres of cool stars,” said Fegley.

Astronomical observations of actively erupting volcanoes on Io may be able to detect the silicon monoxide gas in its atmosphere.

Fegley and Schaefer recommend an Io volcanic probe mission to directly measure the pressure, temperature and composition of gases of Pele, one of Io’s most active volcanoes. Such an endeavor is “feasible using present technology,” Fegley said. “It would vastly expand our knowledge of the most volcanically active body in the solar system.”

The volcanic probe mission would represent an advance in the effort to unveil some of Io’s mysteries, such as how the satellite, about the size of our own Moon, can maintain its high magma temperatures without being nearly totally molten, and how does Io maintain a strong enough lithosphere to support mountains higher than Mount Everest?

Original Source: WUSTL News Release

Image credit: NASA/JPL
NASA has issued its mission design requirements to three industry teams for a proposed mission to Jupiter and its three icy moons. The requirements are also the first product formulated by NASA’s new Office of Exploration Systems in Washington.

The Jupiter Icy Moons Orbiter is a spacecraft with an ambitious proposed mission that would orbit three planet-sized moons of Jupiter — Callisto, Ganymede and Europa — that may harbor vast oceans beneath their icy surfaces. The mission would be powered by a nuclear reactor and launched sometime in the next decade.

Associate Administrator retired Rear Adm. Craig E. Steidle of NASA’s Office of Exploration Systems said, “The Jupiter Icy Moons Orbiter requirements represent our new way of doing business, tracing exploration strategies to the technology maturation programs that will enable this exciting mission and the other missions that make up Project Constellation.”

The Request for Proposal was released this week to the three previously qualified industry teams led by Boeing, Huntington Beach, Calif.; Lockheed Martin, Denver; and Northrop Grumman, Redondo Beach, Calif. These three companies are currently working under study contracts investigating conceptual designs for the mission. The proposals are due July 16, 2004.

The scope of the initial contract is to co-design the spacecraft through the preliminary design with the government team. A contract modification will be issued after preliminary design to implement the design, to integrate and test the spacecraft and to integrate the spacecraft with the reactor module and mission module. JPL would be responsible for delivering the mission module, which would include instruments procured competitively via a NASA announcement of opportunity. The launch vehicle will be supplied by NASA. The Department of Energy’s Office of Naval Reactors would be responsible for the reactor module. To ensure the technologies demonstrated are consistent and coordinated with the Vision for Space Exploration, Project Constellation is managed within the Office of Exploration Systems.

“Although the Jupiter Icy Moons Orbiter mission may not launch until the next decade, the study of revolutionary new technologies in spacecraft design is underway in the areas of power conversion and heat rejection, electric propulsion, radiation hardened electronics and materials, and telecommunications,” said Karla Clark, industry studies lead and deep space avionics project manager for the Jupiter Icy Moons Orbiter Mission.

Three cross-cutting science themes identified by the NASA- chartered science definition team would drive the proposed Jupiter Icy Moons Orbiter science investigations. The themes are to evaluate the degree to which subsurface oceans are present on these worlds; to study the chemical composition of the moons, including organic materials, and the surface processes that affect them; and to scrutinize the entire Jupiter system, particularly the interactions between Jupiter and the moons’ atmospheres and interiors.

“The scientists have told us what they want,” said John Casani, project manager for the Jupiter Icy Moons Orbiter mission at JPL. “When you consider the five-to-eight year trip to Jupiter, going from one moon to the next, not only flying by but orbiting each moon, this will require a unique nuclear power and electric propulsion system. The large amount of power required for electric propulsion could be used in orbit to power a significantly enhanced suite of instruments not even conceivable with previous power systems.”

The Jupiter Icy Moons Orbiter mission is part of NASA’s Project Prometheus, a program studying a series of initiatives to develop power systems and technologies for space exploration. The Jupiter Icy Moons Orbiter, managed by JPL, would be the first NASA mission utilizing nuclear electric propulsion, which would enable the spacecraft to orbit each of these icy worlds to perform extensive investigations of their makeup, history and potential for sustaining life. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the proposed Jupiter Icy Moons Orbiter mission for NASA’s Office of Exploration Systems, Washington, D.C.

For more information visit: http://spacescience.nasa.gov/missions/prometheus.htm or: NASA JIMO Mission

Original Source: NASA/JPL News Release

Image credit: NASA/JPL
If a University of California, Berkeley, physicist’s vision of Jupiter is correct, the giant planet will be in for a major global temperature shift over the next decade as most of its large vortices disappear.

But fans of the Great Red Spot can rest easy. The most famous of Jupiter’s vortices – which are often compared to Earth’s hurricanes – will stay put, largely because of its location near the planet’s equator, says Philip Marcus, a professor at UC Berkeley’s Department of Mechanical Engineering.

Using whirlpools and eddies for comparison, Marcus bases his forecast on principals learned in junior-level fluid dynamics and on the observation that many of Jupiter’s vortices are literally vanishing into thin air.

“I predict that due to the loss of these atmospheric whirlpools, the average temperature on Jupiter will change by as much as 10 degrees Celsius, getting warmer near the equator and cooler at the poles,” says Marcus. “This global shift in temperature will cause the jet streams to become unstable and thereby spawn new vortices. It’s an event that even backyard astronomers will be able to witness.”

According to Marcus, the imminent changes signal the end of Jupiter’s current 70-year climate cycle. His surprising predictions are published in the April 22 issue of the journal Nature.

Jupiter’s stormy atmosphere has a dozen or so jet streams that travel in alternating directions of east and west, and that can clock speeds greater than 330 miles per hour. As on Earth, vortices on Jupiter that rotate clockwise in the northern hemisphere are considered anticyclones, while those that spin counterclockwise are cyclones. The opposite is true in the southern hemisphere, where clockwise vortices are cyclones and counterclockwise spinners are anticyclones.

The Great Red Spot, located in the southern hemisphere, holds title as Jupiter’s largest anticyclone; spanning 12,500 miles wide, it is large enough to swallow Earth two to three times over.

Unlike the cyclonic storms on Jupiter, Earth’s hurricanes and storms are associated with low-pressure systems and dissipate after days or weeks. The Great Red Spot, in comparison, is a high-pressure system that has been stable for more than 300 years, and shows no signs of slowing down.

About 20 years ago, Marcus developed a computer model showing how the Great Red Spot emerged out of and endured in the chaotic turbulence of Jupiter’s atmosphere. His efforts to explain the dynamics governing it and other vortices on Jupiter led to his current projection of the planet’s impending climate change.

He says the current 70-year cycle began with the formation of three distinct anticyclones – the White Ovals – that developed south of the Great Red Spot in 1939. “The birth of the White Ovals was seen through telescopes on Earth,” he says. “I believe we’re in for a similar treat within the next 10 years.”

Marcus says the first stage of the climate cycle involves the formation of vortex streets which straddle the westward jet streams. Anticyclones form on one side of the street, while cyclones form on the other side, with no two vortices rotating in the same direction directly adjacent to each other.

Most of the vortices slowly decay with turbulence. By stage two of the cycle, some vortices become weak enough to get trapped in the occasional troughs, or Rossby waves, that form in the jet stream. Multiple vortices can get caught in the same trough. When they do, they travel bunched together, and turbulence can easily make them merge. When the vortices are weak, trapping and merging continues until only one pair is left on each vortex street.

The noted disappearance of two White Ovals, one in 1997 or 1998 and a second in 2000, exemplified the merging of the vortices in stage two, and as such, signaled the “beginning of the end” of Jupiter’s current climate cycle, says Marcus.

Why would the merger of vortices affect global temperature? Marcus says the relatively uniform temperature of Jupiter – where the temperatures at the poles are nearly the same as they are at the equator – is due to the chaotic mixing of heat and airflow from the vortices.

“If you knock out a whole row of vortices, you stop all the mixing of heat at that latitude,” says Marcus. “This creates a big wall and prevents the transport of heat from the equator to the poles.”

Once enough vortices are gone, the planet’s atmosphere will warm at the equator and cool at the poles by as much as 10 degrees Celsius in each region, which is stage three of the climate cycle.

This temperature change destabilizes the jet streams, which will react by becoming wavy. The waves steepen and break up, like they do at the beach, but they then roll up into new large vortices in the cycle’s fourth stage. In the fifth and final stage of the climate cycle, the new vortices decrease in size, and they settle into the vortex streets to begin a new cycle.

The weakening of the vortices is due to turbulence and happens gradually over time. It takes about half a century for newly formed vortices to gradually shrink down enough to be caught up in a jet stream trough, says Marcus.

Fortunately, the Great Red Spot’s proximity to the equator saves it from destruction. Unlike Jupiter’s other vortices, the Great Red Spot survives by “eating” its neighboring anticyclones, says Marcus.

Marcus notes that his theory of Jupiter’s climate cycle relies on the existence of a roughly equal number of cyclones and anticyclones on the planet.

Since the telltale signs of vortices are the clouds they create, it was easy to miss the presence of long-lived cyclones, says Marcus. He explains that unlike an anticyclone’s distinct spot, cyclones create patterns of filamentary clouds that are less clearly defined.

“On the face of it, it is easy to think that Jupiter is dominated by anticyclones because their spinning clouds show up clearly as bull’s-eyes,” says Marcus.

In the paper in Nature, Marcus presents a computer simulation showing that the warm center and cooler perimeter of a cyclone creates the appearance of the filamentary clouds. In contrast, anticyclones have cold centers and warmer perimeters. Ice crystals that form in the anticyclone’s center swell up and move to the sides where they melt, creating a darker swirl surrounding a lighter colored center.

Marcus approaches the study of planetary atmospheres from the untraditional viewpoint of a fluid dynamicist. “I’m basing my predictions on the relatively simple laws of vortex dynamics instead of using voluminous amounts of data or complex atmospheric models,” says Marcus.

Marcus says the lesson of Jupiter’s climate could be that small disturbances can cause global changes. However, he cautions against applying the same model to Earth’s climate, which is influenced by many different factors, both natural and manmade.

“Still, it’s important to have different ‘labs’ for climate,” says Marcus. “Studying other worlds helps us better understand our own, even if they are not directly analogous.”

Marcus’s research is supported by grants from the NASA Origins Program, the National Science Foundation Astronomy and Plasma Physics Programs and the Los Alamos National Laboratory.

Original Source: UC Berkeley News Release

Image credit: NASA/JPL
Investigations into lava lakes on the surface of Io, the intensely volcanic moon that orbits Jupiter, may provide clues to what Earth looked like in its earliest phases, according to researchers at the University at Buffalo and NASA’s Jet Propulsion Laboratory.

“When I look at the data, it becomes startlingly suggestive to me that this may be a window onto the primitive history of Earth,” said Tracy K. P. Gregg, Ph.D., assistant professor of geology in the UB College of Arts and Sciences.

“When we look at Io, we may be seeing what Earth looked like when it was in its earliest stages, akin to what a newborn baby looks like in the first few seconds following birth,” she added.

Gregg and Rosaly M. Lopes, Ph.D., research scientist at JPL, gave a presentation about Io’s volcano, Loki, on Tuesday (March 16, 2004) at the Lunar and Planetary Science Conference in Houston.

Scientists have been interested in Loki, considered the most powerful volcano in the solar system, because of debate over whether or not it is an active lava lake, where molten lava is in constant contact with a large reservoir of magma stored in the planet’s crust.

Using models developed to investigate temperature changes on active lava lakes on Earth, Gregg and Lopes have concluded that Loki behaves quite differently from terrestrial lava lakes.

Gregg suggests that Loki and other lava lakes on Io might be more similar volcanologically to fast-spreading mid-ocean ridges on Earth, like the Southern East Pacific Rise.

According to Gregg, plate tectonics on Earth make these features long — as in thousands of kilometers — and narrow — as in less than 10 kilometers wide. Io, on the other hand, has no plate tectonics and a similar release of heat and magma would be circular, like Loki.

“These lava lakes could be an Ionian version of mid-ocean ridges,” functioning the way these ridges do on Earth, spilling huge amounts of lava on its surface, thus generating new crust, she said.

During the most intense periods of its eruption cycle, Gregg said, Loki churns out about 1,000 square meters of lava — about the size of a soccer field — per second.

“All planets start out hot and spend their ‘lifetimes’ trying to get cold,” explained Gregg.

This effort by planets to “chill,” she explained, is an attempt to attain a similar temperature to that of outer space, which is 4 Kelvin, or minus 269 degrees Celsius.

On Earth, she explained, the shifting of the planet’s tectonic plates, which focus the eruption of volcanoes at their boundaries, function to cool down the planet’s surface.

Io never developed plate tectonics because it is stuck in an incessant orbit between Jupiter and Europa, another of the Jovian planet’s moons.

“Io just never grew up,” she said, “since it’s continually being pushed around by Jupiter and Europa.”

But, she added, Earth only developed plate tectonics after it had been in existence for perhaps 200 to 500 million years.

Gregg and Lopes analyzed data obtained by the Galileo spacecraft, which orbited Jupiter for 14 years, finally disintegrating in Jupiter’s atmosphere last fall.

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Original Source: University at Buffalo News Release