Monday, 19 August 2013
NASA Probe Gets Close-Up Views of Large Hurricane on Saturn
In high-resolution pictures and video, scientists see the hurricane's eye is about 1,250 miles (2,000 kilometers) wide, 20 times larger than the average hurricane eye on Earth. Thin, bright clouds at the outer edge of the hurricane are traveling 330 mph(150 meters per second). The hurricane swirls inside a large, mysterious, six-sided weather pattern known as the hexagon.
"We did a double take when we saw this vortex because it looks so much like a hurricane on Earth," said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. "But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn's hydrogen atmosphere."
Scientists will be studying the hurricane to gain insight into hurricanes on Earth, which feed off warm ocean water. Although there is no body of water close to these clouds high in Saturn's atmosphere, learning how these Saturnian storms use water vapor could tell scientists more about how terrestrial hurricanes are generated and sustained.
Both a terrestrial hurricane and Saturn's north polar vortex have a central eye with no clouds or very low clouds. Other similar features include high clouds forming an eye wall, other high clouds spiraling around the eye, and a counter-clockwise spin in the northern hemisphere.
A major difference between the hurricanes is that the one on Saturn is much bigger than its counterparts on Earth and spins surprisingly fast. At Saturn, the wind in the eye wall blows more than four times faster than hurricane-force winds on Earth. Unlike terrestrial hurricanes, which tend to move, the Saturnian hurricane is locked onto the planet's north pole. On Earth, hurricanes tend to drift northward because of the forces acting on the fast swirls of wind as the planet rotates. The one on Saturn does not drift and is already as far north as it can be.
"The polar hurricane has nowhere else to go, and that's likely why it's stuck at the pole," said Kunio Sayanagi, a Cassini imaging team associate at Hampton University in Hampton, Va.
Scientists believe the massive storm has been churning for years. When Cassini arrived in the Saturn system in 2004, Saturn's north pole was dark because the planet was in the middle of its north polar winter. During that time, the Cassini spacecraft's composite infrared spectrometer and visual and infrared mapping spectrometer detected a great vortex, but a visible-light view had to wait for the passing of the equinox in August 2009. Only then did sunlight begin flooding Saturn's northern hemisphere. The view required a change in the angle of Cassini's orbits around Saturn so the spacecraft could see the poles.
"Such a stunning and mesmerizing view of the hurricane-like storm at the north pole is only possible because Cassini is on a sportier course, with orbits tilted to loop the spacecraft above and below Saturn's equatorial plane," said Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "You cannot see the polar regions very well from an equatorial orbit. Observing the planet from different vantage points reveals more about the cloud layers that cover the entirety of the planet."
Cassini changes its orbital inclination for such an observing campaign only once every few years. Because the spacecraft uses flybys of Saturn's moon Titan to change the angle of its orbit, the inclined trajectories require attentive oversight from navigators. The path requires careful planning years in advance and sticking very precisely to the planned itinerary to ensure enough propellant is available for the spacecraft to reach future planned orbits and encounters.
Cassini Spots Daytime Lightning on Saturn
July 18, 2012
PASADENA, Calif. - Saturn was playing the lightning storm blues. NASA's Cassini spacecraft has captured images of last year's storm on Saturn, the largest storm seen up-close at the planet, with bluish spots in the middle of swirling clouds. Those bluish spots indicate flashes of lightning and mark the first time scientists have detected lightning in visible wavelengths on the side of Saturn illuminated by the sun."We didn't think we'd see lightning on Saturn's day side - only its night side," said Ulyana Dyudina, a Cassini imaging team associate based at the California Institute of Technology in Pasadena. "The fact that Cassini was able to detect the lightning means that it was very intense."
Images can be found at http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org.
The storm occurred last year. The lightning flashes appear brightest in the blue filter of Cassini's imaging camera on March 6, 2011. Scientists aggressively heightened the blue tint of the image to determine its size and location. Scientists are still analyzing why the blue filter catches the lightning. It might be that the lightning really is blue, or it might be that the short exposure of the camera in the blue filter makes the short-lived lightning easier to see.
What scientists do know is that the intensity of the flash is comparable to the strongest flashes on Earth. The visible energy alone is estimated to be about 3 billion watts lasting for one second. The flash is approximately 100 miles (200 kilometers) in diameter when it exits the tops of the clouds. From this, scientists deduce that the lightning bolts originate in the clouds deeper down in Saturn's atmosphere where water droplets freeze. This is analogous to where lightning is created in Earth's atmosphere.
In composite images that show the band of the storm wrapping all the way around Saturn, scientists have seen multiple flashes. In one composite image, they recorded five flashes, and in another, three flashes.
"As summer storm season descends upon Earth's northern latitudes, Cassini provides us a great opportunity to see how weather plays out at different places in our solar system," said Linda Spilker, Cassini project scientist, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Saturn's atmosphere has been changing over the eight years Cassini has been at Saturn, and we can't wait to see what happens next."
Secrets of Molecule that Helped Build the Universe Exposed
A new study of one of the most fundamental molecules in the universe has given scientists clues into how the very first stars were formed.
For the first time, researchers have calculated the vibration patterns of a compound called H3+ (also known as a triatomic hydrogen ion), which consists of three hydrogen atoms sharing two electrons. Knowing how the molecule can vibrate allows scientists to predict which wavelengths of lightit will emit, giving them a way to identify its signature in astronomical observations.
H3+ is important because it is thought to have been prevalent in the universe just after the Big Bang that started things off around 13.7 billion years ago.
"Most of the universe consists of hydrogen in various forms," University of Arizona chemist Ludwik Adamowicz said in a statement, "but the H3+ ion is the most prevalent molecular ion in interstellar space. It's also one of the most important Molecules in existence."[Wacky Physics: The Coolest Little Particles in Nature]
H3+'s vibration and light-emitting qualities may have enabled it to transfer heat away from the first stars as they were in the process of forming, allowing them to coalesce without overheating and bursting apart.
"There wouldn't be any star formation if there weren't molecules that slowly cool down the forming star by emitting light," said Michele Pavanello, who was a University of Arizona graduate student when he worked on the project. "Astronomers think that the only molecule that could cool down a forming star in that particular time is H3+."
Adamowicz and Pavanello used a computer simulation to model the behavior of H3+, based on quantum mechanics.
"One has to involve a large amount of computations at the quantum mechanical level to predict those vibrations," Adamowicz said. "The role of theory is essentially to simulate those vibrations in the computer and then describe how the molecule is swinging or dancing."
Their simulations predicted numerous potential vibrations that would cause H3+ to emit photons of specific wavelengths, or energies. If telescope observations of a particular cloud in space reveal light of these wavelengths, then astronomers will know the cloud contains H3+.
The calculations should also help scientists understand the complicated physics of how stars form, especially the earliest stars in the universe.
"The only way we can predict how the stars form is if we know very well what the cooling abilities of H3+ are, and we cannot know its cooling ability until we know its vibrational spectrum," Pavanello said. "We need to know what these energy levels are. With this paper, we have pinpointed the energy levels up to a certain energy threshold that is already good enough to generate accurate predictions of the cooling ability of H3+."
For the first time, researchers have calculated the vibration patterns of a compound called H3+ (also known as a triatomic hydrogen ion), which consists of three hydrogen atoms sharing two electrons. Knowing how the molecule can vibrate allows scientists to predict which wavelengths of lightit will emit, giving them a way to identify its signature in astronomical observations.
H3+ is important because it is thought to have been prevalent in the universe just after the Big Bang that started things off around 13.7 billion years ago.
"Most of the universe consists of hydrogen in various forms," University of Arizona chemist Ludwik Adamowicz said in a statement, "but the H3+ ion is the most prevalent molecular ion in interstellar space. It's also one of the most important Molecules in existence."[Wacky Physics: The Coolest Little Particles in Nature]
H3+'s vibration and light-emitting qualities may have enabled it to transfer heat away from the first stars as they were in the process of forming, allowing them to coalesce without overheating and bursting apart.
"There wouldn't be any star formation if there weren't molecules that slowly cool down the forming star by emitting light," said Michele Pavanello, who was a University of Arizona graduate student when he worked on the project. "Astronomers think that the only molecule that could cool down a forming star in that particular time is H3+."
Adamowicz and Pavanello used a computer simulation to model the behavior of H3+, based on quantum mechanics.
"One has to involve a large amount of computations at the quantum mechanical level to predict those vibrations," Adamowicz said. "The role of theory is essentially to simulate those vibrations in the computer and then describe how the molecule is swinging or dancing."
Their simulations predicted numerous potential vibrations that would cause H3+ to emit photons of specific wavelengths, or energies. If telescope observations of a particular cloud in space reveal light of these wavelengths, then astronomers will know the cloud contains H3+.
The calculations should also help scientists understand the complicated physics of how stars form, especially the earliest stars in the universe.
"The only way we can predict how the stars form is if we know very well what the cooling abilities of H3+ are, and we cannot know its cooling ability until we know its vibrational spectrum," Pavanello said. "We need to know what these energy levels are. With this paper, we have pinpointed the energy levels up to a certain energy threshold that is already good enough to generate accurate predictions of the cooling ability of H3+."
Tuesday, 6 August 2013
Protons wander freely in icy gas giant cores
RSC - Chemistry World
If you squeeze ice hard enough, its protons fall off. That’s the conclusion of a new study by Malcolm Guthrie of the Carnegie Institution of Washington and colleagues. They used neutron scattering to look at ice while it is compressed between the teeth of a diamond anvil cell to pressures of more than 50 gigapascals (GPa) – equivalent to that in the depths of the Earth’s lower mantle. They find that under these conditions some of the protons in the water molecules become detached and take up positions in the small voids between the molecules.
The researchers say that the stray protons might have important implications for the nature of the icy interiors of the gas-giant planets such as Neptune and Uranus. It has been previously proposed that this ice might enter a ‘superionic’ phase in which there are relatively mobile hydrogen ions that can support proton currents and give rise to magnetic fields. The new findings suggest that such a phase might begin to form in a different manner from what was thought, and perhaps at a lower temperature.
‘If the results are correct – and that still needs to be demonstrated – then they have profound consequences for a huge amount of what we know about ice at high density, including its conductivity inside giant planets,’ says John Loveday of the University of Edinburgh, UK, a specialist on high-pressure solid-state physics.
The findings go against prevailing wisdom on how ice behaves under high pressure. The previous assumption was that, as the water molecules – connected in a three-dimensional network of hydrogen bonds – get squeezed closer together, eventually the hydrogen atoms will sit midway between two oxygens. So instead of being covalently bound to one and hydrogen-bonded to the other, it is bound equivalently by both. In this symmetrical arrangement, the water molecules lose their individual integrity.
But Guthrie and colleagues say that some water molecules fall apart well before that symmetrical arrangement is reached. Using neutron diffraction to locate where the protons are situated, they found that above about 13GPa some of these protons break away from their parent molecules and sit in ‘interstitial’ sites: small cavities within the hydrogen-bonded network.
A fragment of the crystal structure of the new ice is shown where oxygen atoms are blue and the molecular hydrogen atoms pink © Oak Ridge National Laboratory
In ordinary ice, called ice-I, there are large cavities in the middle of six-membered rings of water molecules. But at these high pressures ice adopts a different, denser structure called ice-VII, in which there are two, somewhat disorderly, interpenetrating networks. Guthrie and colleagues say that their new form of ice is like ice-VII but even less orderly, with some protons on average sitting in sites octahedrally coordinated to six oxygens. ‘This is another way in which density can be increased,’ explains Guthrie.
‘Current theory doesn't seem to predict this happening,’ he adds. ‘So there's a possibility that we've uncovered some new physics, possibly some quantum effect that allows the protons to “slip from the net” as it were.’ Another possibility is that the results simply won’t stand up, and Loveday reserves judgement. ‘The work is contrary to all expectation as to what will happen,’ he says. ‘That is of course not an argument to reject it, but it’s a reason to be skeptical. This is an extraordinary claim and it requires extraordinary proof.’
To study the high-pressure structure, the Carnegie team had to adapt their diamond-anvil cell to support neutron scattering in the sample. ‘We designed a new cell with about a 100 times larger volume than previous designs,’ says Guthrie. ‘This is still tiny for neutrons, so the second key was to use the high neutron flux of the Spallation Neutron Source at Oak Ridge National Laboratory. It still took around three years to get the technique working.’
If you squeeze ice hard enough, its protons fall off. That’s the conclusion of a new study by Malcolm Guthrie of the Carnegie Institution of Washington and colleagues. They used neutron scattering to look at ice while it is compressed between the teeth of a diamond anvil cell to pressures of more than 50 gigapascals (GPa) – equivalent to that in the depths of the Earth’s lower mantle. They find that under these conditions some of the protons in the water molecules become detached and take up positions in the small voids between the molecules.
The researchers say that the stray protons might have important implications for the nature of the icy interiors of the gas-giant planets such as Neptune and Uranus. It has been previously proposed that this ice might enter a ‘superionic’ phase in which there are relatively mobile hydrogen ions that can support proton currents and give rise to magnetic fields. The new findings suggest that such a phase might begin to form in a different manner from what was thought, and perhaps at a lower temperature.
‘If the results are correct – and that still needs to be demonstrated – then they have profound consequences for a huge amount of what we know about ice at high density, including its conductivity inside giant planets,’ says John Loveday of the University of Edinburgh, UK, a specialist on high-pressure solid-state physics.
The findings go against prevailing wisdom on how ice behaves under high pressure. The previous assumption was that, as the water molecules – connected in a three-dimensional network of hydrogen bonds – get squeezed closer together, eventually the hydrogen atoms will sit midway between two oxygens. So instead of being covalently bound to one and hydrogen-bonded to the other, it is bound equivalently by both. In this symmetrical arrangement, the water molecules lose their individual integrity.
But Guthrie and colleagues say that some water molecules fall apart well before that symmetrical arrangement is reached. Using neutron diffraction to locate where the protons are situated, they found that above about 13GPa some of these protons break away from their parent molecules and sit in ‘interstitial’ sites: small cavities within the hydrogen-bonded network.
A fragment of the crystal structure of the new ice is shown where oxygen atoms are blue and the molecular hydrogen atoms pink © Oak Ridge National Laboratory
In ordinary ice, called ice-I, there are large cavities in the middle of six-membered rings of water molecules. But at these high pressures ice adopts a different, denser structure called ice-VII, in which there are two, somewhat disorderly, interpenetrating networks. Guthrie and colleagues say that their new form of ice is like ice-VII but even less orderly, with some protons on average sitting in sites octahedrally coordinated to six oxygens. ‘This is another way in which density can be increased,’ explains Guthrie.
‘Current theory doesn't seem to predict this happening,’ he adds. ‘So there's a possibility that we've uncovered some new physics, possibly some quantum effect that allows the protons to “slip from the net” as it were.’ Another possibility is that the results simply won’t stand up, and Loveday reserves judgement. ‘The work is contrary to all expectation as to what will happen,’ he says. ‘That is of course not an argument to reject it, but it’s a reason to be skeptical. This is an extraordinary claim and it requires extraordinary proof.’
To study the high-pressure structure, the Carnegie team had to adapt their diamond-anvil cell to support neutron scattering in the sample. ‘We designed a new cell with about a 100 times larger volume than previous designs,’ says Guthrie. ‘This is still tiny for neutrons, so the second key was to use the high neutron flux of the Spallation Neutron Source at Oak Ridge National Laboratory. It still took around three years to get the technique working.’
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