The DPS fully supports the plan for Solar System exploration just released by the National Research Council "New Frontiers in the Solar System: An Integrated Exploration Strategy". The DPS was actively involved in the Survey, providing ad-hoc reports written by its members as input to the NRC Survey Panels. The Survey provides a science community consensus on priorities for planetary missions and ground-based research for the next decade.
The key overall recommendations for non-Mars planetary missions are
1) maintenance of the Discovery program of low-cost (total mission
cost less than $325M) missions at a flight rate of one every 18 months,
2) start of a New Frontiers line of medium-cost (less than $650M)
competitively procured missions to be implemented as in the Discovery
program, but selected from a prioritized list provided by the Survey,
with a flight rate of about one every 3 years, and
3) one large-cost mission (greater than $650M) per decade.
The recommended large-cost mission is the Europa Geophysical Explorer, a version of the JPL Europa Orbiter concept. The recommended medium-cost New Frontiers missions are in priority order 1) KBO/Pluto Explorer, 2) Lunar South Polar Aitken Basin Sample Return, 3) Jupiter Polar Orbiter with Probes, 4) Venus In-Situ Explorer, and 5) Comet Surface Sample Return. The prioritized list of New Frontiers missions includes more than three missions to provide flexibility for technology and budgetary developments over the next ten years. In addition to the Discovery program of low-cost missions, the Survey recommends extension of the Cassini mission beyond its prime mission termination in 2007.
The Survey contains a separate set of prioritized recommendations for the Mars Exploration Program. After the launch of the Mars Reconnaissance Orbiter in 2005, there are two recommendations for the low-cost category of missions 1) a Mars Scout program of competitively procured missions implemented in the same manner as Discovery, with a flight rate of one Scout launch at every other Mars opportunity (one every 52 months) beginning in 2007, and 2) a Mars upper atmosphere orbiter. In the medium class category, the recommendations are for a Mars Smart Lander launch in 2009 and a Mars Long-lived Lander Network that could be implemented by international cooperation. The Survey recommends that these missions be implemented in a manner to build towards a Mars Sample Return mission early in the next decade. The Lunar South Polar Aitken Basin Sample Return mission should also be implemented in a manner to provide appropriate technological development for a Mars Sample Return.
There are also recommendations on fundamental research and analysis including a gradual increase in grant programs, recommendations on mission data analysis, the Deep Space Network, and technology development with an endorsement of the nuclear power and propulsion technologies initiative, and recommendations on ground-based support programs including a recommendation to share development and operations of a Large Synoptic Survey Telescope with the NSF. Implementation of the recommendations in this Survey would provide for a broad, integrated program of scientific exploration throughout the Solar System and enable new scientific discoveries addressing some of the most compelling scientific questions in planetary science.
The Division for Planetary Sciences of the American Astronomical Society endorses this report and looks forward to seeing its provisions implemented.
The full report is posted at http://www.nap.edu and has been posted at the community decadal website: http://www.aas.org/dps/decadal/
The DPS is the world's largest professional organization dedicated to the exploration of the Solar System.
The DPS fully supports the plan for Solar System exploration just released by the National Research Council "New Frontiers in the Solar System: An Integrated Exploration Strategy". The DPS was actively involved in the Survey, providing ad-hoc reports written by its members as input to the NRC Survey Panels. The Survey provides a science community consensus on priorities for planetary missions and ground-based research for the next decade.
The key overall recommendations for non-Mars planetary missions are
1) maintenance of the Discovery program of low-cost (total mission
cost less than $325M) missions at a flight rate of one every 18 months,
2) start of a New Frontiers line of medium-cost (less than $650M)
competitively procured missions to be implemented as in the Discovery
program, but selected from a prioritized list provided by the Survey,
with a flight rate of about one every 3 years, and
3) one large-cost mission (greater than $650M) per decade.
The recommended large-cost mission is the Europa Geophysical Explorer, a version of the JPL Europa Orbiter concept. The recommended medium-cost New Frontiers missions are in priority order 1) KBO/Pluto Explorer, 2) Lunar South Polar Aitken Basin Sample Return, 3) Jupiter Polar Orbiter with Probes, 4) Venus In-Situ Explorer, and 5) Comet Surface Sample Return. The prioritized list of New Frontiers missions includes more than three missions to provide flexibility for technology and budgetary developments over the next ten years. In addition to the Discovery program of low-cost missions, the Survey recommends extension of the Cassini mission beyond its prime mission termination in 2007.
The Survey contains a separate set of prioritized recommendations for the Mars Exploration Program. After the launch of the Mars Reconnaissance Orbiter in 2005, there are two recommendations for the low-cost category of missions 1) a Mars Scout program of competitively procured missions implemented in the same manner as Discovery, with a flight rate of one Scout launch at every other Mars opportunity (one every 52 months) beginning in 2007, and 2) a Mars upper atmosphere orbiter. In the medium class category, the recommendations are for a Mars Smart Lander launch in 2009 and a Mars Long-lived Lander Network that could be implemented by international cooperation. The Survey recommends that these missions be implemented in a manner to build towards a Mars Sample Return mission early in the next decade. The Lunar South Polar Aitken Basin Sample Return mission should also be implemented in a manner to provide appropriate technological development for a Mars Sample Return.
There are also recommendations on fundamental research and analysis including a gradual increase in grant programs, recommendations on mission data analysis, the Deep Space Network, and technology development with an endorsement of the nuclear power and propulsion technologies initiative, and recommendations on ground-based support programs including a recommendation to share development and operations of a Large Synoptic Survey Telescope with the NSF. Implementation of the recommendations in this Survey would provide for a broad, integrated program of scientific exploration throughout the Solar System and enable new scientific discoveries addressing some of the most compelling scientific questions in planetary science.
The Division for Planetary Sciences of the American Astronomical Society endorses this report and looks forward to seeing its provisions implemented.
The full report is posted at http://www.nap.edu and has been posted at the community decadal website: http://www.aas.org/dps/decadal/
The DPS is the world's largest professional organization dedicated to the exploration of the Solar System.
PASADENA, Calif., May 28, 2002 (AScribe Newswire) -- The final images are in, and the resulting portrait of Jupiter's moon Io, after a challenging series of observations by NASA's Galileo spacecraft, is a peppery world of even more plentiful and diverse volcanoes than scientists imagined before Galileo began orbiting Jupiter in 1995. Now that Galileo's observations of Io have ended, scientists are focusing on trying to understand the big picture of how Io works by examining details.
Thirteen previously unknown active volcanoes dot infrared images from Galileo's final successful flyby of Io, volcanologist Dr. Rosaly Lopes of NASA's Jet Propulsion Laboratory reported today at the spring meeting of the American Geophysical Union in Washington, D.C. That brings the total number of known Ionian hot spots to 120. Galileo images revealed 74 of them.
"We expected maybe a dozen or two," said Dr. Torrence Johnson, Galileo project scientist at JPL in Pasadena, Calif. That expectation was based on discoveries by NASA's Voyager spacecraft in 1979 and 1980, and subsequent ground-based observations.
"The volcanoes on Io have displayed an assortment of eruption styles, but recent observations have surprised us with the frequency of both giant plumes and crusted-over lakes of molten lava," said planetary scientist Dr. Alfred McEwen of the University of Arizona, Tucson.
Galileo's latest images, which also show tall slopes
crumbling and surface deposits from two eruptions' recent
giant plumes, are available online from JPL at
http://www.jpl.nasa.gov/images/io and from the University of
Arizona Lunar and Planetary Laboratory at
http://pirlwww.lpl.arizona.edu/Galileo/Releases.
Some high-resolution views taken as Galileo skimmed past Io on Oct. 16, 2001, are aiding analysis of the connection between volcanism and the rise and fall of mountains on Io. Few of Io's volcanoes resemble the crater-topped volcanic peaks seen on Earth and Mars, said planetary scientist Dr. Elizabeth Turtle of the University of Arizona. Most of Io's volcanic craters are in relatively flat regions, not near mountains, but nearly half of the mountains Io does have sit right beside volcanic craters.
"It appears that the process that drives mountain-building -- perhaps the tilting of blocks of crust - -- also makes it easier for magma to get to the surface," Turtle said. She showed a new image revealing that material slumping off a mountain named Tohil Mons has not piled up in a crater below, suggesting that the crater floor has been molten more recently than any landslides have occurred. Galileo's infrared-mapping instrument has detected heat from the crater, indicating an active or very recent eruption.
From the analysis of Galileo's observations, scientists are developing an understanding of how that distant world resurfaces itself differently than our world does.
"On Earth, we have large-scale lateral transport of the crust by plate tectonics," McEwen said. "Io appears to have a very different tectonic style dominated by vertical motions. Lava rises from the deep interior and spreads out over the surface. Older lavas are continuously buried and compressed until they must break, with thrust faults raising the tall mountains. These faults also open new pathways to the surface for lava to follow, so we see complex relations between mountains and volcanoes, like at Tohil."
"Io is a weird place," Johnson said. "We've known that since even before Voyager, and each time Galileo has given us a close look, we get more surprises. Galileo has vastly increased our understanding of Io even though the mission was not originally slated to study Io."
Extensions to Galileo's original two-year orbital mission included six swings close to Io, where exposure to Jupiter's intense radiation belts stresses electronic equipment on board the spacecraft. Researchers presented some results today from two Io encounters in the second half of 2001. Observations were not made successfully during Galileo's final Io flyby, in January 2002, because effects of the radiation belts put the spacecraft into a precautionary standby mode during the crucial hours of the encounter.
Galileo will make its last flyby of a moon when it passes close to Amalthea, a small inner satellite of Jupiter, on November 5. No imaging is planned for that flyby. With fuel for altering its course and pointing its antenna nearly depleted, the long-lived spacecraft will then loop one last time away from Jupiter and perish in a final plunge into Jupiter's atmosphere in September 2003.
Additional information about Galileo, Jupiter and
Jupiter's moons is available online at
http://galileo.jpl.nasa.gov.
JPL, a division of the California Institute of Technology in Pasadena, manages Galileo for NASA's Office of Space Science, Washington, D.C.
University of Hawaii press release, May 17, 2002
Web Site: http://www.ifa.hawaii.edu/~sheppard/satellites/jup.html
Summary
University of Hawaii astronomers announce the
discovery of 11 new satellites of Jupiter. These
new satellites, when added to the eleven discovered
the previous year by the Hawaii team, bring the
total of known Jupiter satellites to 39. This is
more than any other planet.
Discoveries
The new satellites were discovered during mid-December
of 2001 by a team led by Scott S. Sheppard and David
Jewitt from the University of Hawaii's Institute for
Astronomy and including Jan Kleyna of Cambridge
University, England. They used the Canada-France-Hawaii
(3.6 meter) telescope with one of the largest digital
imaging cameras in the world, the "12K", to obtain
sensitive images of a wide area around Jupiter. The
digital images were processed using high speed computers
and then searched with an efficient computer algorithm.
Candidate satellites were monitored in the succeeding
months at the University of Hawaii 2.2-meter telescope
to confirm their orbits and to reject closer asteroids
masquerading as satellites. Orbits of the new
satellites were fitted by both Robert Jacobson at the
NASA Jet Propulsion Laboratory and Brian Marsden at
the Minor Planet Center. The satellites were formally
announced by the International Astronomical Union on
Circular No. 7900 (May 16, 2002).
Properties
The 11 new objects all belong to the so-called
"irregular satellite" class, meaning that they have
large semi-major axes, eccentricities and inclinations.
All are retrograde (they orbit in the direction
opposite to the rotation of the planet), and possess
similar semi-major axes (about 300 Jupiter radii or
20 million km) The estimated diameters are between
about 2 and 4 kilometers, assuming a 4% albedo. As
yet, nothing is known about their surface properties,
compositions or densities, but they are presumed to
be rocky objects like the asteroids.
The new discoveries bring the known total of Jupiter satellites to 39, of which 31 are irregulars. (The 8 regular satellites include 4 large objects discovered by Galileo and 4 small objects on circular orbits interior to that of Io). Jupiter's nearest rival for having the largest number of known satellites is Saturn, with 30 (of which 13 are irregular).
Significance
The large, elongated and inclined orbits of the
irregular satellites strongly suggest an origin by
capture. Since no efficient contemporary capture
mechanisms are known, it is likely that the irregular
satellites were acquired when Jupiter was young,
possibly still in the process of condensing down to
its equilibrium size. The precise mechanism of
capture remains unidentified but there are two
leading theories for the capture process. In the
gas drag hypothesis, passing asteroids are slowed by
friction with proto-Jupiter's bloated atmosphere.
Those which do not burn up in the atmosphere like
meteors are trapped in looping orbits like those of
the new satellites. In the mass growth hypothesis,
the rapid growth of Jupiter leads to capture of
nearby, co-moving planetesimals. Both processes
would have operated in the first million years of
the solar system.
The irregular satellites are grouped into distinct dynamical families or clusters. This suggests that individual satellites are pieces of a few precursor bodies that have been shattered. The disruptions occurred either during the process of capture or possibly after capture due to collisions with Jupiter-crossing comets. Future measurements of the size distribution, surface properties and orbits of the satellites will help determine how they formed.
Press Release 3/13/02
PASADENA, Calif., March 13 (AScribe Newswire) -- A dark patch of hydrocarbon haze, wider than Earth, develops and swirls in a new movie clip from ultraviolet images taken by NASA's Cassini spacecraft of Jupiter's upper atmosphere, or stratosphere.
Observations in the ultraviolet part of the light spectrum reveal features in Jupiter's stratosphere that are transparent in the visible-light portion of the spectrum. One surprise is the dark vortex whose birth and migration can be seen during the 11-week span of the movie taken while Cassini was approaching Jupiter in late 2000. Development of this feature resembles development of ozone holes in Earth's stratosphere in that both processes appear to occur only within confined masses of high-altitude polar air. The similarity may help scientists understand both processes better.
The movie clip and a still image mapping all 360 degrees of Jupiter in ultraviolet are available online from NASA's Jet Propulsion Laboratory, Pasadena, Calif., at
http://www.jpl.nasa.gov/images/jupiter
and from the Cassini imaging team, based at the Boulder, Colo., campus of the Southwest Research Institute, at
http://ciclops.lpl.arizona.edu/ .
Cassini made its closest pass to Jupiter on Dec. 30, 2000, gaining a gravitational boost for reaching its main destination, Saturn, in 2004. More information about the mission is available at http://saturn.jpl.nasa.gov . Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini and Galileo missions for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena.
PASADENA, Calif., Jan. 18, 2002 (AScribe News) -- NASA's Galileo spacecraft resumed gathering scientific information on Jan. 17 Pacific Time) after commands radioed from Earth took the Jupiter orbiter out of the passive standby mode it entered, causing it to miss taking photos of Io.
Galileo passed within about 102 kilometers (63 miles) of Jupiter's moon Io on January 17. Planned observations for the remainder of the spacecraft's current swing near Jupiter include a series of images of the planet's atmosphere, a farewell color study of its icy moon Europa and navigational imaging of the small moon Amalthea.
Galileo hit its target point for the Io flyby so accurately that a scheduled post-encounter firing of thrusters to fine-tune the trajectory was cancelled as unnecessary, said Dr. Eilene Theilig, Galileo project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The close flyby was calculated to use Io's gravity to put Galileo on course for its next encounters. Galileo will pass near Amalthea in November 2002 and plunge to its demise in Jupiter's crushing atmosphere in September 2003.
"As expected, visiting Io has proved to be a challenging and risky endeavor," Theilig said. "It's disappointing not to get the observations of Io that were planned for this encounter, but I am very proud of the flight team that has kept Galileo functioning in orbit more than three times longer than originally planned and revived it once more yesterday."
Galileo detected a computer reset and placed itself in a standby or "safe" mode on January 17 at 13:41 Universal Time (5:41 PacificTime), about half an hour before its closest approach to Io. The reset was apparently caused by exposure to the intense radiation environment at Io's distance from Jupiter. Since the spacecraft began orbiting Jupiter in 1995, it has endured a cumulative radiation exposure about three-and-a-half times what it was originally designed to withstand.
NASA has repeatedly extended Galileo's original two-year mission in orbit. The spacecraft is now nearly out of the hydrazine propellant needed to keep its antenna pointed toward Earth. Knowing they would eventually lose contact and control of the spacecraft, the Galileo team chose the planned impact with Jupiter to ensure there was no chance the spacecraft might hit Europa. One of Galileo's important discoveries has been the likelihood of a melted saltwater ocean under Europa's icy crust, making that moon of great interest for future study of the possibility of extraterrestrial life.
Additional information about the Galileo mission is available at http://galileo.jpl.nasa.gov .
Galileo was launched from the Space Shuttle Atlantis on Oct. 18, 1989. After a long journey to Jupiter, Galileo began orbiting the huge planet on Dec. 7, 1995, and successfully completed its two-year primary mission in 1997. That has been followed by three mission extensions. JPL, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C.
NASA's Galileo orbiter will dart past Jupiter's moon Io on January 17 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 since they were first seen in 1979 by NASA's Voyager spacecraft and especially during the six years that Galileo has been orbiting Jupiter. 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. "An orbital mission like Galileo gives you the advantage of getting to examine interesting places repeatedly over a period of time. That's been great for studying Io, since it keeps changing so much."
The Galileo flight team at JPL aimed the orbiter to skim just 100 kilometers (62 miles) above Io's multicolored surface at 9:09 a.m. EST on Jan. 17. "The reason we're going so close is to put Galileo on a ballistic trajectory for impact into Jupiter in September 2003," Theilig said.
Galileo has operated in orbit more than three times longer than its originally planned mission. The resilient spacecraft has survived about three and a half times as much exposure to radiation from Jupiter's radiation belts as it was designed to withstand. In its 33 loops around Jupiter, it has flown near Io six times previously and near the other three of Jupiter's planet-sized moons - Europa, Ganymede and Callisto - a total of 27 times.
The tour has relied on expert navigators to calculate several moves in advance, using each moon's gravity to help adjust the spacecraft's trajectory toward its various encounters.
However, the propellant supply needed for steering the spacecraft and keeping its antenna pointed toward Earth is now nearly exhausted. To avoid even a slim chance that Galileo could crash into Europa after its mission ends, NASA has decided to send it to a controlled demise in the crushing pressure of Jupiter's dense atmosphere. Galileo had earlier found evidence that Europa has a deep ocean of melted saltwater under its frozen surface, heightening interest in keeping Europa pristine for later studies of its potential for harboring extraterrestrial life.
Before its final plunge, Galileo will make the first close flyby of Amalthea, a small, inner moon of Jupiter, in November 2002.
This week, Galileo will make direct measurements of the charged particles and magnetic environment around Io. Also, its camera and instruments for infrared and thermal imaging have been programmed to make observations during the flyby. As much of the data as possible will be transmitted to Earth from the spacecraft's tape recorder in coming months, Theilig said.
Io, like Earth's Moon, always keeps the same side facing inward toward its planet. On Thursday, Galileo will be in position for its best-ever look at the Jupiter-facing side of Io. "We're hoping to see areas we haven't seen well since Voyager imaged them back in 1979," said JPL's Dr. Torrence Johnson, Galileo project scientist. "We'd like to know more about rates of change for volcanic features on Io." New observations are also planned for a previously inactive volcano that unexpectedly lofted a tall plume last summer.
On this swing through the inner portion of the Jovian system, Galileo will also examine storms on Jupiter itself and the Io torus, a doughnut-shaped band of charged particles encircling Jupiter at Io's distance from the planet.
A sporadic malfunction has affected performance of Galileo's camera since mid-2000, apparently due to radiation damage to an electronic component. The camera worked flawlessly during the most recent Io encounter in October 2001, but each time Galileo swings as close to Jupiter as Io's orbit, odds increase for more serious damage to the spacecraft from exposure to the planet's radiation belts.
Io is the innermost of Jupiter's four large moons. Heat from tidal flexing powered by Jupiter's gravitational pull makes it the most volcanically active world in the solar system, with an estimated 200 to 300 volcanoes rapidly resurfacing it.
Galileo left Earth aboard the space shuttle Atlantis in 1989. JPL, a division of the California Institute of Technology in Pasadena, Calif., manages the Galileo mission for NASA's Office of Space Science in Washington.
Additional information about the mission is available online at: http://galileo.jpl.nasa.gov
A slumping cliff, migrating eruptions and churning lava lakes appear in new images of Jupiter's sizzling moon Io from NASA's Galileo spacecraft.
The images and explanatory captions are available online at
<http://www.jpl.nasa.gov/images/io
> from NASA's Jet Propulsion Laboratory,
Pasadena, Calif. Images are also online at
<
http://pirlwww.lpl.arizona.edu/missions/Galileo/releases>,
the University of
Arizona Galileo Imaging Team members' web site.
A high-resolution view of a cliff named Telegonus gives information about erosion on a world that has neither surface water nor wind. The cliff is slumping outward due to gravity.
The Tvashtar area on northern Io, where no volcanic activity was seen prior to December 1999, now has a cluster of hot spots. An infrared mapping image from Galileo's Aug. 6, 2001, flyby of Io shows that the surface within the Tvashtar area is hot at the sites observed in 1999 and 2000, as well as at newly observed sites. "The most explosive phase of the Tvashtar eruption may have ceased, but these observations reveal that the area is still active," said Dr. Rosaly Lopes, a volcanologist at JPL. Tvashtar appears to be an example of a volcanic site where activity starts vigorously then gradually declines, similar to many eruptions on Earth, she said.
Io's most powerful volcano, Loki, offers a contrasting style of eruption. The Loki hot spot brightens and fades over periods of several months, possibly in periodic cycles, a pattern not known on Earth. Scientists have proposed that Loki is either an active lava lake or a caldera whose floor is flooded by frequent lava flows.
Infrared mapping images of Loki from Galileo's Oct. 16, 2001, flyby of Io weigh in favor of the lava lake interpretation. They show a concentration of high temperatures along one edge, like a glowing shoreline. This suggests that hotter lava from underneath is showing through where a cooler lava crust is breaking up as it hits the crater wall. High-resolution nighttime pictures of another of Io's hot spots, Pele, also show the apparent overturning of cooler crust on a lava lake.
A Hubble NICMOS infrared set of images shows Jupiter's atmosphere, its ring, and its moon Metis.
The very first asteroids to be discovered were named after the major heroes of the Trojan War without regard for Greek vs Trojan (Achilles, Patroclus, Hector, Nestor). At this early point, 1906-7, presumably, astronomers didn't know that many, many more asteroids would be discovered, and so weren't thinking about a large-scale naming scheme that would have the leading group of asteroids as the 'Greek army' and the trailing group as the 'Trojan army'. Asteroids named after the first four do appear consistent with this naming scheme.
For more information, see http://cfa-www.harvard.edu/cfa/ps/lists/JupiterTrojans.html.
http://saturn.jpl.nasa.gov
http://ciclops.org
or simply
http://ciclops.org
Chandra observed Saturn for about 20 hours in April of 2003. The spectrum, or distribution with energy of the X-rays, was found to be very similar to that of X-rays from the Sun.
"This indicates that Saturn's X-ray emission is due to the scattering of solar X-rays by Saturn's atmosphere," said Jan-Uwe Ness, of the University of Hamburg in Germany and lead author of a paper discussing the Saturn results in an upcoming issue of Astronomy & Astrophysics. "It's a puzzle, since the intensity of Saturn's X-rays requires that Saturn reflects X-rays fifty times more efficiently than the Moon."
The observed 90 megawatts of X-ray power from Saturn's equatorial region is roughly consistent with previous observations of the X-radiation from Jupiter's equatorial region. This suggests that both giant, gaseous planets reflect solar X-rays at unexpectedly high rates. Further observations of Jupiter will be needed to test this possibility.
The weak X-radiation from Saturn's south-polar region presents another puzzle (the north pole was blocked by Saturn's rings during this observation). Saturn's magnetic field, like that of Jupiter, is strongest near the poles. X-radiation from Jupiter is brightest at the poles because of auroral activity due to the enhanced interaction of high-energy particles from the Sun with its magnetic field. Since spectacular ultraviolet polar auroras have been observed to occur on Saturn, Ness and colleagues expected that Saturn's south pole might be bright in X-rays. It is not clear whether the auroral mechanism does not produce X-rays on Saturn, or for some reason concentrates the X-rays at the north pole.
"Another interesting result of the observation is that Saturn's rings were not detected in X-rays," noted Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, a coauthor of the paper. "This requires Saturn's rings to be less efficient at scattering X-rays than the planet itself."
The same team detected X-radiation from Saturn using the European Space Agency's XMM-Newton Observatory. Although these observations could not locate the X-rays on Saturn's disk, the intensity of the observed X-rays was very similar to what was found with Chandra and consistent with a marginal detection of X-rays from Saturn reported in 2000 using the German Roentgensatellite ( ROSAT).
The research team, which used Chandra's ACIS instrument to observed Saturn, also included J. Schmitt (Univ. of Hamburg) as well as Konrad Dennerl and Vadim Burwitz (Max Planck Institute, Garching Germany). 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.
http://chandra.harvard.edu/photo/2004/saturn/
We're nearly there.
LPL Press Release, November 1, 2002, from Carolyn Porco
Colleagues, Friends, and Fans of Cassini,
Cassini has sighted Saturn, and today the Imaging Team is releasing a color composite image of the planet and its moon, Titan, taken from a distance of 285 million kilometers....twice the distance from the Sun to the Earth.
After an adventurous 7-year long tour among the planets, the Cassini-Huygens spacecraft will arrive at Saturn in July 2004. Once there, Cassini will parachute the Huygens probe to Saturn's biggest satellite, Titan. Titan is thought to have an atmosphere similar to the primitive Earth. However, both the probe and the Cassini-Huygens team are not in idle state until 2004. They have plenty of things to keep them busy.
http://sci.esa.int/content/news/index.cfm?aid=1&cid=1&oid=30362
PASADENA, Calif., Feb. 11 (AScribe Newswire) -- NASA's Cassini spacecraft continues to fly in good health with less than 29 months to go before it becomes the first Earth envoy to enter orbit around Saturn.
Last month, Cassini completed a 40-day period of data collection as part of a multi-year search for gravitational waves. The data comes from radio transmissions between Cassini and stations of NASA's Deep Space Network in California, Spain and Australia.
The experiment used frequencies both in the X-band, which is the band commonly used by interplanetary spacecraft, and in the higher-frequency Ka-band, a new band for the Deep Space Network. Data was successfully collected for 90 percent of the possible transmission time in the Ka-band, a promising beginning for future uses of that band by Cassini and other spacecraft. In the traditional X-band, data was received for 98 percent of the possible time over the 40-day
Gravitational waves are ripples in the fabric of space and time that are set off by acceleration of massive bodies, such as black holes or supernovas. Their existence has been confirmed indirectly, but never detected experimentally. This search assesses the Doppler effect on radio waves traveling between Cassini and Earth. The Doppler effect is how the frequency of a transmission is affected by the relative speed between the sender and receiver, such as the raised pitch of an approaching train's whistle.
Scientists are looking for barely perceptible fluctuations that would be caused in Cassini's speed relative to Earth if gravitational waves of certain wavelengths were traveling through the solar system. They expect analysis of the data to take months. Cassini will be used for two more periods of gravitational wave investigation before it reaches Saturn.
Engineers are making progress at correcting a problem of haze on the spacecraft's narrow-angle camera. Warming the camera for a week to a temperature just above freezing has significantly reduced the problem, so that treatment will be repeated for a longer period beginning March 5.
"We're fully confident it is going to get better," said Robert Mitchell, Cassini-Huygens program manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The usual operating temperature for the camera is minus 90 Celsius (minus 130 Fahrenheit). Haze on its optics appeared when it was cooled to that temperature after a routine-maintenance heating of the instrument to 30 C (86 F). That occurred following flawless imaging of Jupiter for several months of 2000 and 2001. Heating the camera again, but to only 4 C (39 F), is removing the haze. Test images taken of a star in late January showed the improvement.
Cassini will reach Saturn on July 1, 2004, and release its piggybacked Huygens probe about six months later for descent through the thick atmosphere of the moon Titan on Jan. 14, 2005. Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Office of Space Science, Washington, D.C. Additional information about Cassini-Huygens is available online at http://saturn.jpl.nasa.gov .
[Cornell University Press Release, October 2000]
An international team of eight "satellite hunters," astronomers who pluck tiny specks of light out of the distant solar system, has discovered four new outer moons of Saturn orbiting at least 15 million kilometers (more than 9 million miles) from the surface of the giant planet.
The discovery gives Saturn a total of 22 known moons, surpassing the 21 orbiting Uranus. Nothing is known about the four new moons except for their brightness. Estimates of their size -- between 10 and 50 kilometers (6-30 miles) across -- are based on assumptions of their reflectivity. Observed from Earth-bound observatories, the moons appear as faint dots of light moving around the planet.
Members of the team, including former Cornell University researcher Brett Gladman and Cornell professors of astronomy Joseph Burns and Philip Nicholson, warn that the findings are still preliminary. They also note that they might have discovered several other objects that could be Saturnian moons. Other members of the team include Jean-Marc Petit and Hans Scholl of the Observatoire de la Cote d'Azur, France; J.J. Kavelaars of McMaster University, Canada; and Matthew Holman and Brian Marsden of the Harvard-Smithsonian Center for Astrophysics.
The discovery of the four new moons was made using a technique developed by Gladman while he was a student at Cornell. Gladman, who now works for the Centre National de la Recherche Scientifique in France, obtained his Ph.D. at Cornell. The technique, which also was used in the discovery of the five new Uranian moons, uses light-sensitive semiconductors, called charge-coupled devices, attached to telescopes to detect the distant points of light. Several of these digital images, taken once every hour, are then compared, using computer software to pick out a moving point of light against the known star background of the sky.
Between 1997 and 1999, the same team discovered a total of five new moons of Uranus. All five, like the newly discovered four outer moons of Saturn, are irregular satellites. Burns notes that an irregular satellite's orbit is "long and looping," unlike the orbit of an inner moon, which is nearly circular and lies in the planet's equatorial plane.
The great distance that the moons orbit from Saturn, says Nicholson, indicates that the moons were captured into orbit after the planet formed, unlike the larger regular satellites that are thought to have coalesced from a disk of dust and gas that surrounded the planet as it formed.
Until this latest discovery, Saturn was known to have only one irregular, outer satellite, Phoebe, which was discovered by W. Pickering 102 years ago. Nicholson notes that Phoebe is traveling in a retrograde orbit, that is, in the opposite direction to the spin of Saturn. All regular satellites move on prograde orbits that follow the direction of the spin of their parent planet. "We look for such patterns because it's easier to capture objects from a solar orbit into a retrograde than onto a prograde orbit," says Nicholson. "If you could demonstrate statistically that retrograde orbits were favored, that would help confirm some theories of capture."
The first two candidates for newly discovered satellites of Saturn were spotted by Gladman using the European Southern Observatory's 2.2 meter telescope in Chile on Aug. 7. Gladman and Kavelaars "recovered" the two objects Sept 23 and 24 at the Canada-France-Hawaii 3.5 meter telescope on Mauna Kea, Hawaii. They also found two new candidates. Additional confirming observations were made at other telescopes.
Related World Wide Web sites: The following sites provide additional information on this news release.
Brett Gladman: ( http://www.obs-nice.fr/saturn).
McMaster University: ( http://pinks.physics.mcmaster.ca/Saturn).
The Cassini spacecraft's radio cannot satisfactorily pick up the entire radio band over which the Huygens Probe is to send it signals to relay, Cassini project officials disclosed in October 2000. There is the danger, therefore, that some of the data that the Huygens Probe is to send as it plunges into Titan's atmosphere for 2.5 hours in November 2004 wile be lost. It turns out that the bandpass of the Cassini receiver is not as wide as the design called for. The equipment cannot be fixed or bypassed, but engineers hope that signal processing can find a way to save the rest of the data. They may even have to change the time and angle at which the Probe is deployed. The Huygens probe and the receiver on Cassini were supplied by the European Space Agency, and the problem was discovered in tests they carried out. They hope to have a proposed solution in the summer of 2001.
The good news is that the camera on Cassini is working very well. It supplied a clear, sharp image of Jupiter from its current distance of 52 million miles.
At present, Cassini is to go into orbit around Saturn on July 1, 2004, and the Probe is to be deployed on November 30, 2004.
On October 9, 2000, the Cassini Imaging Team released its first color image of Jupiter seen through the eyes of Cassini. It can be found at the updated Imaging Team website
http://ciclops.lpl.arizona.edu/
Atmospheric features on Uranus and Neptune are revealed in images taken with the Space Telescope Imaging Spectrograph and the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope. A wider view of Uranus reveals the planet's faint rings and several of its satellites. The observations were taken in August 2003.
At first glance, the top row of images makes the planets appear like twins. But the bottom row reveals that Uranus and Neptune are two different worlds. Uranus's rotational axis, for example, is tilted almost 90 degrees to Neptune's axis. The south poles of Uranus and Neptune are at the left and bottom, respectively. Both are tilted slightly toward Earth. Uranus also displays more contrast between both hemispheres. This may be caused by its extreme seasons.
Both planets display a banding structure of clouds and hazes aligned parallel to the equator. Additionally, a few discrete cloud features appear bright orange or red. The color is due to methane absorption in the red part of the spectrum. Methane is third in abundance in the atmospheres of Uranus and Neptune after hydrogen and helium, which are both transparent. Colors in the bands correspond to variations in the altitude and thickness of hazes and clouds. The colors allow scientists to measure the altitudes of clouds from far away.
The bright satellite on the lower right corner is Ariel, which has a snowy white surface. Five small satellites with dark surfaces can be seen just outside the rings. Clockwise from the top, they are: Desdemona, Belinda, Portia, Cressida, and Puck. Even fainter satellites were imaged in deeper exposures, also taken with the Advanced Camera in August 2003.
Image credit: NASA and Erich Karkoschka, University of Arizona
Electronic image files and additional information are available at:Astronomers have discovered two of the smallest moons yet found around Uranus. The new moons, uncovered by NASA's Hubble Space Telescope, are about 8 to 10 miles across (12 to 16 km) -- about the size of San Francisco.
The two moons are so faint they eluded detection by the Voyager 2 spacecraft, which discovered 10 small satellites when it flew by the gas giant planet in 1986. The newly detected moons are orbiting even closer to the planet than the five major Uranian satellites, which are several hundred miles wide. The two new satellites are the first inner moons of Uranus discovered from an Earth-based telescope in more than 50 years. The International Astronomical Union (IAU) will announce the finding today. The Hubble telescope observations also helped astronomers confirm the discovery of another tiny moon that had originally been spotted in Voyager pictures.
"It's a testament to how much our Earth-based instruments have improved in 20 plus years that we can now see such faint objects 1.7 billion miles (2.8 billion km) away," says Mark Showalter, a senior research associate at Stanford University in Stanford, Calif., who works at the NASA Ames Research Center, in Moffett Field, Calif. Showalter and Jack Lissauer, a research scientist at the NASA Ames Research Center, used Hubble's Advanced Camera for Surveys (ACS) to make the discovery. The images were taken Aug. 25, 2003.
The newly discovered moons are temporarily designated as S/2003 U 1 and S/2003 U 2 until the IAU formally approves their discovery. S/2003 U 1 is the larger of the two moons, measuring 10 miles (16 km) across. The Hubble telescope spotted this moon orbiting between the moons Puck, the largest satellite found by Voyager, and Miranda, the innermost of the five largest Uranian satellites. Astronomers previously thought this region was empty space. S/2003 U 1 is 60,600 miles (97,700 km) away from Uranus, whirling around the giant planet in 22 hours and 9 minutes.
The smallest Uranian moon yet found, S/2003 U 2, is 8 miles (12 km) wide. Its orbital path is just 200 to 450 miles (300 to 700 km) from the moon Belinda. S/2003 U 2 is 46,400 miles (74,800 km) away from Uranus and circles the planet in 14 hours and 50 minutes. The tiny moon is part of a densely crowded field of 11 other moons, all discovered from pictures taken by the Voyager spacecraft.
"The inner swarm of 13 satellites is unlike any other system of planetary moons," says co-investigator Jack Lissauer. "The larger moons must be gravitationally perturbing the smaller moons. The region is so crowded that these moons could be gravitationally unstable. So, we are trying to understand how the moons can coexist with each other."
One idea is that some of the moons are young and formed through collisions with wayward comets. For example, the Hubble telescope spotted two small moons orbiting very close to the moon Belinda. One of them is the newly detected moon, S/2003 U 2, which is traveling inside Belinda's orbit. The other, designated S/1986 U 10, was found in 1999 by astronomer Erich Karkoschka of the University of Arizona, who uncovered the satellite in Voyager pictures. But the finding required confirmation by an Earth-based telescope. This is the first time this moon has been seen since Voyager snapped a picture of it. S/1986 U 10 is 750 miles (1,200 km) away from Belinda.
"Not all of Uranus's satellites formed over 4 billion years ago when the planet formed," Lissauer says. "The two small moons orbiting close to Belinda, for example, probably were once part of Belinda. They broke off when a comet smashed into Belinda."
The astronomers hope to refine the orbits of the newly discovered moons with further observations. "The orbits will show how the moons interact with one another, perhaps showing how such a crowded system of satellites can be stabilized," Showalter explains. "This could provide further insight into how the moon system formed. Refining their orbits also could reveal whether these moons have any special role in confining or 'shepherding' Uranus's 10 narrow rings."
Astronomers stretched the limit of Hubble's ACS to find the tiny satellites. "These moons are 40 million times fainter than Uranus," Showalter says. "The moons are at 25th magnitude and Uranus is at sixth magnitude. They are blacker than asphalt, if their composition is like the other small, inner moons. So they don't reflect much light. Even with the sensitivity and high resolution of Hubble's ACS, we had to overexpose the images of Uranus to pinpoint the moons."
The newly detected moons, when approved by the IAU, will bring the Uranian satellite total to 24. Uranus ranks third in the number of IAU-certified moons behind Jupiter (38) and Saturn (30). Excluding the outer moons that travel in elongated orbits and are probably captured asteroids, Uranus holds the record for the most satellites with 18 in its inner system. All of them have nearly circular orbits. Saturn is second with 17.
Electronic images, movies, and additional information are available at:
http://hubblesite.org/newscenter/2003/29
http://amesnews.arc.nasa.gov/
SEDS (Students for the Exploration and Development of Space) Homepage
http://skyandtelescope.com/news/current/article_932_1.asp
William Sheehan reports on "newly discovered documents from the 1840s" that show that John Couch Adams's predictions were uncertain and waivering, and were not of the certainty or quality that LeVerrier's had nor that would have permitted Neptune to be discovered observationally the way it actually was. Apparently, the British kept the documents secret, but the file has now been returned to the Royal Greenwich Observatory archives, which are at the University Library of the University of Cambridge, where they are being studied by Nick Kollerstrom, an astronomer at the University of London.
Springtime is blooming on Neptune! This might sound like an oxymoron because Neptune is the farthest and coldest of the major planets. But NASA Hubble Space Telescope observations are revealing an increase in Neptune's brightness in the southern hemisphere, which is considered a harbinger of seasonal change, say astronomers.
Observations of Neptune made over six years by a group of scientists from the University of Wisconsin-Madison and NASA's Jet Propulsion Laboratory (JPL) show a distinct increase in the amount and brightness of the banded cloud features located mostly in the planet's southern hemisphere.
"Neptune's cloud bands have been getting wider and brighter," says Lawrence A. Sromovsky, a senior scientist at University of Wisconsin- Madison's Space Science and Engineering Center and a leading authority on Neptune's atmosphere. "This change seems to be a response to seasonal variations in sunlight, like the seasonal changes we see on Earth."
The findings are reported in the May, 2003 issue of Icarus, a leading planetary science journal.
Neptune, the eighth planet from the Sun, is known for its weird and violent weather. It has massive storm systems and ferocious winds that sometimes gust to 900 miles per hour, but the new Hubble observations are the first to suggest that the planet undergoes a change of seasons.
Using Hubble, the Wisconsin team made three sets of observations of Neptune. In 1996, 1998, and 2002, observations of a full rotation of the planet were obtained. The images showed progressively brighter bands of clouds encircling the planet's southern hemisphere. The findings are consistent with observations made by G.W. Lockwood at the Lowell Observatory, which show that Neptune has been gradually getting brighter since 1980.
Neptune's near-infrared brightness is much more sensitive to high altitude clouds than its visible brightness. The recent trend of increasing cloud activity on Neptune has been qualitatively confirmed at near-infrared wavelengths with Keck Telescope observations from July 2000 to June 2001 by H. Hammel and co-workers. Near-infrared observations at NASA's Infrared Telescope Facility on Mauna Kea, Hawaii are planned for this summer to further characterize changes in the high-altitude cloud structure.
"In the 2002 images, Neptune is clearly brighter than it was in 1996 and 1998," Sromovsky says, "and is dramatically brighter at near-infrared wavelengths. The greatly increased cloud activity in 2002 continues a trend first noticed in 1998."
Like the Earth, Neptune would have four seasons: "Each hemisphere would have a warm summer and a cold winter, with spring and fall being transitional seasons, which may or may not have specific dynamical features," the Wisconsin scientist explains.
Unlike the Earth, however, the seasons of Neptune last for decades, not months. A single season on the planet, which takes almost 165 years to orbit the Sun, can last more than 40 years. If what scientists are observing is truly seasonal change, the planet will continue to brighten for another 20 years.
Also like Earth, Neptune spins on an axis that is tilted at an angle toward the Sun. The tilt of the Earth, at a 23.5-degree inclination, is the phenomenon responsible for the change of seasons. As the Earth orbits the Sun over the course of a year, the planet is exposed to patterns of solar radiation that mark the seasons. Similarly, Neptune is inclined at a 29-degree angle and the northern and southern hemispheres alternate in their positions relative to the Sun.
What is remarkable, according to Sromovsky, is that Neptune exhibits any evidence of seasonal change at all, given that the Sun, as viewed from the planet, is 900 times dimmer than it is from Earth. The amount of solar energy a hemisphere receives at a given time is what determines the season.
"When the Sun deposits heat energy into an atmosphere, it forces a response. We would expect heating in the hemisphere getting the most sunlight. This in turn could force rising motions, condensation and increased cloud cover," Sromovsky notes.
Bolstering the idea that the Hubble images are revealing a real increase in Neptune's cloud cover consistent with seasonal change is the apparent absence of change in the planet's low latitudes near its equator.
"Neptune's nearly constant brightness at low latitudes gives us confidence that what we are seeing is indeed seasonal change as those changes would be minimal near the equator and most evident at high latitudes where the seasons tend to be more pronounced."
Despite the new insights into Neptune, the planet remains an enigma, says Sromovsky. While Neptune has an internal heat source that may also contribute to the planet's apparent seasonal variations and blustery weather, when that is combined with the amount of solar radiation the planet receives, the total is so small that it is hard to understand the dynamic nature of Neptune's atmosphere.
There seems, Sromovsky says, to be a "trivial amount of energy available to run the machine that is Neptune's atmosphere. It must be a well-lubricated machine that can create a lot of weather with very little friction."
In addition to Sromovsky, authors of the Icarus paper include Patrick M. Fry and Sanjay S. Limaye, both of University of Wisconsin-Madison's Space Science and Engineering Center; and Kevin H. Baines of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Electronic images and additional information are available at:
http://hubblesite.org/news/2003/17
More detailed information and pictures are available at
http://www.ssec.wisc.edu/media/Neptune2003.htm
MADISON. A progressive increase in the brightness of the planet Neptune suggests that, like Earth, the distant planet has seasons.
Observations of Neptune made during a six-year period with NASA's Hubble Space Telescope by a group of scientists from the University of Wisconsin-Madison and NASA's Jet Propulsion Laboratory (JPL) show that the planet is exhibiting a significant increase in brightness. The changes, observed mostly in the planet's southern hemisphere, show a distinct increase in the amount and brightness of the banded cloud features that are a distinctive feature of the planet.
"Neptune's cloud bands have been getting wider and brighter," says Lawrence A. Sromovsky, a senior scientist at UW-Madison's Space Science and Engineering Center and a leading authority on Neptune's atmosphere. "This change seems to be a response to seasonal variations in sunlight, like the seasonal changes we see on Earth."
The findings are reported in the May 2003 issue of Icarus, a leading planetary science journal.
Neptune, the eighth planet from the sun, is known for its weird and violent weather. It has massive storm systems and ferocious winds that sometimes gust to 900 miles per hour, but the new Hubble observations are the first to suggest that the planet undergoes a change of seasons.
Using Hubble, the Wisconsin team made three sets of observations of Neptune. In 1996, 1998 and 2002, they obtained observations of a full rotation of the planet. The images showed progressively brighter bands of clouds encircling the planet's southern hemisphere. The findings are consistent with observations made by G.W. Lockwood at the Lowell Observatory, which show that Neptune has been gradually getting brighter since 1980.
"In 2002 images, Neptune is clearly brighter than it was in 1996 and 1998," Sromovsky says, "and is dramatically brighter at near infrared wavelengths. The greatly increased cloud activity in 2002 continues a trend first noticed in 1998."
Like the Earth, Neptune would have four seasons: "Each hemisphere would have a warm summer and a cold winter, with spring and fall being transitional seasons, which may or may not have specific dynamical features, the Wisconsin scientist explains.
Unlike the Earth, however, the seasons of Neptune last for decades, not months. A single season on the planet, which takes almost 165 years to orbit the sun, can last more than 40 years. If what scientists are observing is truly seasonal change, the planet will continue to brighten for another 20 years.
Also like Earth, Neptune spins on an axis that is tilted at an angle toward the sun. The tilt of the Earth, at a 23.5-degree inclination, is the phenomenon responsible for the change of seasons. As the Earth spins on its axis and orbits the sun during the course of a year, the planet is exposed to patterns of solar radiation that mark the seasons.
Similarly, Neptune is inclined at a 29-degree angle and the northern and southern hemispheres alternate in their positions relative to the sun.
What is remarkable, according to Sromovsky, is that Neptune exhibits any evidence of seasonal change at all, given that the sun, as viewed from the planet, is 900 times dimmer than the sun as seen from the Earth. The amount of solar energy a hemisphere receives at a given time is what determines the season.
"When the sun deposits heat energy into an atmosphere, it forces a response. In the hemisphere getting the most sunlight, we would expect heating, which in turn could force rising motions, condensation and increased cloud cover," Sromovsky notes.
Bolstering the idea that the Hubble images are revealing a real increase in Neptune's cloud cover consistent with seasonal change is the apparent absence of change in the planet's low latitudes near its equator.
"Neptune's nearly constant brightness at low latitudes gives us confidence that what we are seeing is indeed seasonal change, as those changes would be minimal near the equator and most evident at high latitudes where the seasons tend to be more pronounced."
Despite the new insights into Neptune, the planet remains an enigma, says Sromovsky. While Neptune has an internal heat source that may also contribute to the planet's apparent seasonal variations and blustery weather, when that is combined with the amount of solar radiation the planet receives, the total is so small that it is hard to understand the dynamic nature of Neptune's atmosphere.
There seems, Sromovsky says, to be a "trivial amount of energy available to run the machine that is Neptune's atmosphere. It must be a well-lubricated machine that can create a lot of weather with very little friction."
In addition to Sromovsky, authors of the Icarus paper include Patrick M. Fry and Sanjay S. Limaye, both of UW-Madison's Space Science and Engineering Center, and Kevin H. Baines of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Le Verrier is honored with a statue in the courtyard of L'Observatoire de Paris, and with a street also on Paris's Left Bank.
University of California, Berkeley, Press Release
Pasadena - Astronomers taking advantage of new adaptive optics on the W. M. Keck II Telescope in Hawaii have obtained the best pictures yet of the planet Neptune, showing an atmosphere rich with dynamic features such as vortices, waves and narrowly spaced bands of clouds similar to those present around Jupiter.
The team - which included astronomers from the University of California, Berkeley; Lawrence Livermore National Laboratory (LLNL); the California Institute of Technology, or Caltech; and UCLA - captured near infrared pictures of the giant ice planet on five nights between June 8 and 28. They hoped to track characteristics of very bright features previously seen on the planet, but the images were beyond their expectations.
"We've never seen the detail we see now," said team leader Imke de Pater, a professor of astronomy and of earth and planetary science at UC Berkeley. "This shows us how much structure there is in the planet's atmosphere, how dynamic it is - as dynamic as Jupiter."
The team also presented new near infrared pictures of the planet Uranus that mark the first ground-based detection of the faint rings around that planet.
Adaptive optics is a relatively new technology which compensates for blurring caused by turbulence in the atmosphere. Such a system was recently installed at the Keck telescope, and works extremely well, said Macintosh of LLNL. Thanks to this technology, the team was able to see not only the large-scale bright features on Neptune but also a wealth of small-scale features: narrow bands of brightness encircling the planet, waves within those bands, and regions where the bands move apart and come together as if they were separated by a vortex. Similar structures appear in infrared images of Jupiter, around structures that correspond to vortices in visible images.
Neptune's atmosphere is a puzzle, UC Berkeley's Martin said, showing signs of transient storms and wind speeds reaching 400 meters/second at the equator - 30 times the wind speeds on Jupiter. The team has yet to explain most of the features, such as what causes the brightest features (often referred to as storms), why wind speeds are so high on Neptune and what tremendous energy source is driving weather on the planet. These are the types of questions researchers hope analysis of these data will answer.
An exciting prospect for this research is the opportunity to track the atmospheric features of Neptune over time using ground-based telescopes. Previous wind speed measurements were based on Voyager spacecraft data and data from the Hubble Space Telescope. Preliminary analyses of the June data indicate that wind speed measurements are similar to those made by Voyager.
Ultimately, these data, along with fluid dynamical models of the atmosphere, may give some hints as to the internal structure of Neptune and perhaps even indications of its formation and history. Such questions are of particular interest since extra-solar planet hunters are seeing hints of many solar systems with multiple planets orbiting their sun.
The team also took spectral measurements of Neptune to obtain information about the composition of the atmosphere.
Neptune, the eighth planet from the Sun, has an atmosphere composed primarily of hydrogen, helium and methane. The methane condenses into methane cloud layers in the same way water condenses into clouds in Earth's atmosphere.
Using the same adaptive optics system, the team also made the first ground-based detection of the faint rings around Uranus on June 17. The faint rings are those encircling the planet closer than the bright epsilon ring. According to de Pater, the researchers also saw numerous small cloud features well above, in altitude, the south polar methane haze layer.
These features, located at high northern latitudes in regions of the atmosphere which only recently emerged into sunlight after a 40-some year darkness, could be tracked during several hours. The derived wind speeds suggest the winds at high northern latitudes to be similar in strength to those at high southern latitudes. The overall wind profile is strikingly similar to that derived for Neptune from Voyager data, except that the extreme wind speeds on Uranus are roughly half those found on Neptune.
Among the team's other collaborators were Professors Michael Brown of Caltech and Andrea Ghez of UCLA.
This research was supported in part by the National Science Foundation and in part by the U.S. Department of Energy at Lawrence Livermore National Laboratory.
For photos:
http://www.berkeley.edu/news/media/download/nep_index.html.