Posted on by Fraser Cain

Methane and Water Overlap on Mars

Recent analyses of ESA?s Mars Express data reveal that concentrations of water vapour and methane in the atmosphere of Mars significantly overlap. This result, from data obtained by the Planetary Fourier Spectrometer (PFS), gives a boost to understanding of geological and atmospheric processes on Mars, and provides important new hints to evaluate the hypothesis of present life on the Red Planet.

PFS observed that, at 10-15 kilometres above the surface, water vapour is well mixed and uniform in the atmosphere. However, it found that, close to the surface, water vapour is more concentrated in three broad equatorial regions: Arabia Terra, Elysium Planum and Arcadia-Memnonia.

Here, the concentration is two to three times higher than in other regions observed. These areas of water vapour concentration also correspond to the areas where NASA?s Odyssey spacecraft has observed a water ice layer a few tens of centimetres below the surface, as Dr Vittorio Formisano, PFS principal investigator, reports.

New in-depth analysis of PFS data also confirms that methane is not uniform in the atmosphere, but concentrated in some areas. The PFS team observed that the areas of highest concentration of methane overlap with the areas where water vapour and underground water ice are also concentrated. This spatial correlation between water vapour and methane seems to point to a common underground source.

Initial speculation has taken the underground ice layer into account. This could be explained by the ?ice table? concept, in which geothermal heat from below the surface makes water and other material move towards the surface. It would then freeze before getting there, due to the very low surface temperature (many tens of degrees Celsius below zero).

Further investigations are needed to fully understand the correlation between the ice table and the presence and distribution of water vapour and methane in the atmosphere.

In other words, can the geothermal processes which ?feed? the ice table also bring water vapour and other gases, like methane, to the surface? Can there be liquid water below the ice table? Can forms of bacterial life exist in the water below the ice table, producing methane and other gases and releasing them to the surface and then to the atmosphere?

The PFS instrument has also detected traces of other gases in the Martian atmosphere. A report on these is currently under peer review. Further studies will address whether these gases can be linked to water and methane and help answer the unresolved questions. In-situ observations by future lander missions to Mars may provide a more exhaustive solution to the puzzle.

Original Source: ESA News Release

Posted on by Fraser Cain

Early Universe Might Not Have Been So Violent

The Universe has experienced far fewer collisions among galaxies than previously thought, according to a new analysis of Hubble Space Telescope data by an ANU researcher.

Astronomer Dr Alister Graham, from the Research School of Astronomy and Astrophysics, analysed a sample of galaxies located 100 million light years away ? and discovered that the number of violent encounters between large galaxies is around one-tenth of the number earlier studies had suggested.

Although theoretical models predict that fewer collisions were involved in the evolution of the universe, Dr Graham?s observations are the first that confirm these theories.

?The new result is in perfect agreement with popular models of hierarchical structure formation in our universe,? Dr Graham said. ?Galactically speaking, things appear to be a little safer out there.?

For years, astronomers have known the collision and merger of galaxies resulted in the formation of larger galaxies. The biggest of these galaxies appear largely devoid of stars at their cores, a phenomenon believed to result from the damage caused by the ?supermassive? black holes from the smaller galaxies as they merge near the centre of the new galaxy.

However, rather than requiring multiple mergers to clear away the stars from the heart of a galaxy, Dr Graham has shown just one collision between two galaxies is sufficient.

Using images from Hubble’s Wide Field Planetary Camera 2, Dr Graham was able to examine galaxies 100 million light years away, whose cores had not been depleted of stars, providing an important insight into star distributions before any major collisions occurred. By considering the overall galaxy structure, he was able to more accurately measure the sizes of the depleted cores in the galaxies.

The result: the mass of the deficit of stars at the galaxies centres equalled rather than exceeded the mass of the black hole.

?If there had been 10 mergers, we would have found a star deficit 10 times the mass of the central black hole. Many galaxies have large central black holes but no depleted cores. It is therefore not the case that every black hole is formed by gobbling up its surrounding stars. Instead, we?re observing the demolished cores of galaxies after the union of two massive cosmic wrecking balls.?

Although small satellite galaxies have been captured by our galaxy, the Milky Way, it has not experienced a recent major merger. If it had, the plane of its disk, visible as a faint wide ribbon in the night sky, would have been scattered and dispersed across the heavens. Such a fate is expected in about three billion years when the Milky Way collides with a neighbouring spiral galaxy, Andromeda.

The research was conducted during Dr Graham’s tenure at the University of Florida and was funded by NASA via a grant from the Space Telescope Science Institute in Baltimore. Dr Graham?s research will appear in the September 20 edition of Astrophysical Journal Letters.

Original Source: ANU News Release

Posted on by Fraser Cain

Genesis Recovery is Going Well

Genesis team scientists and engineers continue their work on the mission’s sample return canister in a specially constructed clean room at the U.S. Army Proving Ground in Dugway, Utah. As more of the capsule’s contents are revealed, the team’s level of enthusiasm for the amount of science obtainable continues to rise.

At present, the science canister that holds the majority of the mission’s scientific samples is lying upside down – on its lid. Scientists are very methodically working their way “up” from the bottom portion of the canister by trimming away small portions of the canister’s wall. The team continues to extract, from the interior of the science canister, small but potentially analyzable fragments of collector array material. One-half of a sapphire wafer was collected Tuesday – the biggest piece of collector array to date.

The mission’s main priority is to measure oxygen isotopes to determine which of several theories is correct regarding the role of oxygen in the formation of the solar system. Scientists hope to determine this with isotopes collected in the four target segments of the solar wind concentrator carried by the Genesis spacecraft. The condition of these segments will be better known over the next few days, after the canister’s solar wind concentrator is extricated. At this time, it is believed that three of these segments are relatively intact and that the fourth may have sustained one or more fractures. There are no concrete plans regarding the shipping date of the Genesis capsule or its contents from Dugway to the Johnson Space Center in Houston. The team continues its meticulous work and believes that a significant repository of solar wind materials may have survived that will keep the science community busy for some time.

The Genesis sample return capsule landed well within the projected ellipse path in the Utah Test and Training Range on Sept. 8, but its parachutes did not open. It impacted the ground at nearly 320 kilometers per hour (nearly 200 miles per hour).

News and information about Genesis is available on the Internet at http://www.nasa.gov/genesis. For background information about Genesis, visit http://genesismission.jpl.nasa.gov. For information about NASA on the Internet, visit http://www.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Wallpaper: Saturn’s Translucent Rings

Saturn’s ring shadows appear wrapped in a harmonious symphony with the planet in this color view from the Cassini spacecraft.

Saturn and its rings would nearly fill the space between Earth and the Moon. Yet, despite their great breadth, the rings are a few meters thick and, in some places, very translucent. This image shows a view through the C ring, which is closest to Saturn, and through the Cassini division, the 4,800-kilometer-wide gap (2,980-miles) that arcs across the top of the image and separates the optically thick B ring from the A ring. The part of the atmosphere seen through the gap appears darker and more bluish due to scattering at blue wavelengths by the cloud-free upper atmosphere.

The different colors in Saturn’s atmosphere are due to particles whose composition is yet to be determined. This image was obtained with the Cassini spacecraft narrow angle camera on July 30, 2004, at a distance of 7.6 million kilometers (4.7 million miles) from Saturn.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For images and information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. Images are also available at the Cassini imaging team home page, http://ciclops.org.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Seeing Our Sun’s Future in Other Stars

For more than 400 years, astronomers both professional and amateur have taken a special interest in observing Mira stars, a class of variable red giants famous for pulsations that last for 80-1,000 days and cause their apparent brightness to vary by a factor of ten times or more during a cycle.

An international team of astronomers led by Guy Perrin from the Paris Observatory/LESIA (Meudon, France) and Stephen Ridgway from the National Optical Astronomy Observatory (Tucson, Arizona, USA) has used interferometric techniques to observe the close environments of five Mira stars, and were surprised to find that the stars are surrounded by a nearly transparent shell of water vapor, and possibly carbon monoxide and other molecules. This shell gives the stars a deceptively large apparent size. By penetrating through this layer using the combined light of several telescopes, the team found that Mira stars are likely only half as large as formerly believed.

?This discovery resolves nagging inconsistencies between observations of the size of Mira stars, and models describing their composition and pulsations, which now can be seen to generally agree with each other,? Ridgway explains. ?The revised picture is that Mira stars are very luminous yet relatively normal stars of the asymptotic giant branch, but they have a resonant pulsation that drives their large variability.?

Mira stars are particularly interesting since they are similar in size to the Sun and they are undergoing a late stage of the same evolutionary path that all one-solar mass stars, including the Sun, will experience. Therefore, these stars illustrate the fate of our Sun five billion years from now. If such a star, including its surrounding shell, were located at the Sun?s position in our solar system, its vaporous shell would extend beyond the orbit of Mars.

Although they are really very large in diameter (up to a few hundred solar radii), red giant stars are point-like to unaided human eyes on Earth, and even the largest telescopes fail to distinguish their surfaces. This challenge can be overcome by combining signals from separate telescopes using a technique called astronomical interferometry that makes it possible to study very small details in the close surroundings of Mira stars. Ultimately, images of the observed stars can be reconstructed.

Mira stars are named after the first such known object, Mira (or Omicron Ceti). One possible explanation for their significant variability is that large amounts of material, including dust and molecules, are produced during each cycle. This material blocks much of the outgoing stellar radiation, until the material becomes diluted by expansion. The close environment of Mira stars is therefore very complex, and the characteristics of the central object are difficult to observe.

To study the close environment of these stars, the team led by Perrin and Ridgway carried out observations at the Infrared-Optical Telescope Array (IOTA) of the Smithsonian Astrophysical Observatory in Arizona. IOTA is a Michelson stellar interferometer, with two arms forming an L-shaped array. It operates with three collectors that can be located at different stations on each arm. In the present study, observations were made at several wavelengths using different telescope spacings ranging from 10 to 38 meters.

From these observations, the team was able to reconstruct the variation of the stellar brightness across the surface of each star. Details down to about 10 milli-arcseconds can be detected. For comparison, at the Moon?s distance, this would correspond to seeing features down to 20 meters in size.

The observations were made at near-infrared wavelengths that are of particular interest for the study of water vapor and carbon monoxide. The role played by these molecules was suspected some years ago by the team and independently confirmed by observations with the Infrared Space Observatory. The new observations using IOTA clearly demonstrate that Mira stars are surrounded by a molecular layer of water vapor and, in at least some cases, of carbon monoxide. This layer has a temperature of about 2,000 K and extends to about one stellar radius above the stellar photosphere, or roughly 50 percent of the observed diameter of the Mira stars in the sample.

Previous interferometric studies of Mira stars led to estimates of star diameters that were biased by the presence of the molecular layer, and were thus much overestimated. This new result shows that the Mira stars are about one-half as large as previously believed.

The new observations presented by the team are interpreted in the framework of a model that bridges the gap between observations and theory. The space between the star?s surface and the molecular layer very likely contains gas, like an atmosphere, but it is relatively transparent at the observed wavelengths. In visible light, the molecular layer is rather opaque, giving the impression that it is a surface, but in the infrared, it is thin and the star can be seen through it.

This model is the first ever to explain the structure of Mira stars over a wide range of spectral wavelengths from the visible to the mid-infrared and to be consistent with the theoretical properties of their pulsation. However, the presence of the layer of molecules far above the stellar surface is still somewhat mysterious. The layer is too high and dense to be supported purely by atmospheric pressure. The pulsations of the star probably play a role in producing the molecular layer, but the mechanism is not yet understood.

As Mira stars represent a late evolutionary stage of Sun-like stars, it will be very interesting to better describe the processes that occur in and around them, as a foreshadowing of the Sun?s own expected fate in the distant future. Mira stars eject large amounts of gas and dust into space, typically about one-third Earth mass per year, thus providing more than 75 percent of the molecules in the galaxy. The carbon, nitrogen, oxygen and other elements of which we are made were mostly produced in the interior of such stars (with heavier elements coming from supernovae), and are then returned to space via this mass loss to become part of new stars and planets. The maturing technique of interferometry is revealing details of the Mira atmosphere, bringing scientists close to observing and understanding the production and ejection of molecules and dust, as these stars recyle their contents on an astronomical scale.

The paper ?Unveiling Mira stars behind the molecules: Confirmation of the molecular layer model with narrow band near-infrared interferometry,? by Perrin et al., will appear in an upcoming issue of the journal Astronomy & Astrophysics.

Original Source: NOAO News Release

Posted on by Fraser Cain

NASA Centres Could Be Damaged by Ivan

NASA’s Stennis Space Center in Mississippi and the Michoud Assembly Facility in New Orleans are riding out Hurricane Ivan, which made landfall near Gulf Shores, Alabama, overnight. NASA has made preparations to secure important space flight hardware against damage.

Stennis, where Space Shuttle engines are tested before flight, is about 45 miles inland near the Mississippi-Louisiana border and is home to about 300 NASA personnel and 1,250 NASA contractors as well as employees from other agencies. Workers there were sent home Tuesday, Sept. 14 to prepare for the storm, and the center is not expected to open before Friday, Sept. 17. Information for Stennis employees will be posted on http://www.nasa.gov/stennis as it becomes available.

A team of about 50 essential personnel will ride out the storm at Stennis. Two flight-qualified Space Shuttle Main Engines at Stennis have been secured; one was put back into its container, and the other was wrapped in plastic. Two developmental engines were enclosed on their test stands and protected.

A ride-out team will also remain in place through the storm at Michoud, across the Mississippi-Louisiana border about 40 miles to the southwest of Stennis. The NASA facility, operated by Lockheed-Martin, manufactures and assembles the large Space Shuttle external fuel tanks, and is home to about 3,900 employees from NASA, Lockheed-Martin and other agencies. Lockheed Martin and NASA workers were dismissed Tuesday, Sept. 14. to make preparations at home, and the facility is not expected to open before Friday, Sept. 17. Contact information for Michoud employees is available at http://www.nasa.gov/marshall.

The shuttle fuel tanks at Michoud have been secured. Equipment has been moved indoors, facilities have been sandbagged, and important materials — such as insulating foam and adhesive — have been loaded onto trucks to be transported out of the area, if necessary.

KSC Recovering From Frances
Meanwhile, approximately 14,000 people returned to work at NASA’s Kennedy Space Center (KSC) this week, following an 11-day closure due to Hurricane Frances. Recovery efforts are already underway.

“We really saw our readiness for hurricanes Charley and Frances pay off,” said William Readdy, NASA’s associate administrator for space operations. “KSC was in the path of those two strong storms, and while some of our buildings were damaged, we made sure our workforce was safe and had no injuries. We were also able to protect our three Space Shuttles, our International Space Station components, and other key hardware.”

During the closure, the KSC Damage Assessment and Recovery Team (DART) completed initial damage assessments. KSC weathered sustained winds greater than 70 mph and gusts as high as 94 mph. A thorough assessment of KSC’s 900 facilities and buildings continues and could take weeks or months to complete.

The Vehicle Assembly Building (VAB), the Thermal Protection System Facility (TPSF) and the Processing Control Center (PCC) received significant damage. The Operations and Checkout Building, Vertical Processing Facility, Hangar AE, Hangar S, and Hangar AF Small Parts Facility received substantial damage.

Original Source: NASA News Release

Posted on by Fraser Cain

It’s Cold, But the View is Great

Australian researchers have shown that a ground-based telescope in Antarctica can take images almost as good as those from the Hubble Space Telescope, at a fraction of the cost.

“It represents arguably the most dramatic breakthrough in the potential for ground-based optical astronomy since the invention of the telescope,” says University of New South Wales Associate Professor Michael Ashley, who co-authored the Nature paper. “The discovery means that a telescope at Dome C on the Antarctic plateau could compete with a telescope two to three times larger at the best mid-latitude observatories, with major cost-saving implications. Dome C could become an important ‘test-bed’ for experiments and technologies that will later be flown as space missions. Indeed, for some projects, the site might be an attractive alternative to space based astronomy.”

Astronomical observations made by Australian astronomers at Dome C on the Antarctic Plateau, 3250 m above sea-level, prove that the site has less “star jitter” than the best mid-latitude observatories in Hawaii, Chile and the Canary Islands. While Antarctica has long been recognised as having characteristics that make it a potentially excellent site for astronomy, seeing conditions at the South Pole itself (latitude 90 degrees south) are poor due to atmospheric turbulence within 200 – 300 m of the ground.

By contrast, Dome C, located at latitude 75 degrees south, has several atmospheric and site characteristics that make it ideal for astronomical observations. The site’s atmospheric characteristics include low infrared sky emission, extreme cold and dryness, a high percentage of cloud free time, and low dust and aerosol content – features that confer significant benefits for all forms of astronomy, especially infrared and sub-millimetre.

Dome C is 400 m higher than the South Pole and further inland from the coast. Being a “dome” – a local maximum in the elevation of the terrain – it experiences much lower peak and average wind speeds, which has a profound beneficial effect on the performance of astronomical instruments. Like other regions on the Antarctic plateau, it shares the advantages of a lack of seismic activity and low levels of light pollution.

A key issue in considering where to locate new generation ground-based optical telescopes is to choose a site with excellent ‘seeing’. Seeing is defined as the amount of star jitter or sharpness of astronomical images, which is affected by atmospheric conditions close to Earth.

“The sharpness of the astronomical images at Dome C is two to three times better than at the very best sites currently used by astronomers, including those in Chile, Hawaii and the Canary Islands,” says A/Prof Ashley. “This implies a factor of ten increase in sensitivity. Put another way, an 8 metre infrared telescope on the Antarctic Plateau could achieve the sensitivity limits of a hypothetical 25 metre telescope anywhere else.

“It means there’s now a fantastic opportunity now for Australian astronomers to build world-beating telescopes at the site. I expect the romance and adventure of this combination of astronomy and Antarctica will inspire the next generation of young scientists.”

The observations at Dome C represent a stunning technical achievement, according to the paper’s lead author, Dr Jon S. Lawrence, a University of New South Wales Postdoctoral Fellow.

“We set up a self contained robotic observatory called AASTINO (Automated Astronomical Site Testing International Observatory) at Dome C in January 2004. Powered by two engines, the facility has heat and electrical power that allowed us to communicate with site testing equipment, computers and telescopes via an Iridium satellite network. The entire experiment was controlled remotely — we didn’t turn the telescope on until we returned home,” says Dr Lawrence. “When we left there in February we said goodbye to it knowing all that we could do was communicate with it by the phone and the Internet. If we’d needed to press a reset button on a computer or something, there was no way to do so, and the entire experiment could have failed.

“As it turns out, we’ve made some exceptional findings and published a paper in Nature before even returning to the site. We’re pretty thrilled about it.”

Original Source: UNSW News Release

Posted on by Fraser Cain

Comparing Satellite Images of Ivan and Frances

Seen through the eyes of the Multi-angle Imaging SpectroRadiometer aboard NASA’s Terra satellite, the menacing clouds of Hurricanes Frances and Ivan provide a wealth of information that can help improve hurricane forecasts.

The ability of forecasters to predict the intensity and amount of rainfall associated with hurricanes still requires improvement, particularly on the 24- to 48-hour timescales vital for disaster planning. Scientists need to better understand the complex interactions that lead to hurricane intensification and dissipation, and the various physical processes that affect hurricane intensity and rainfall distributions. Because uncertainties in representing hurricane cloud processes still exist, it is vital that model findings be evaluated against actual hurricane observations whenever possible. Two-dimensional maps of cloud heights such as those provided by the Multi-angle Imaging SpectroRadiometer offer an unprecedented opportunity for comparing simulated cloud fields against actual hurricane observations.

The newly released images of Hurricanes Frances and Ivan were acquired Sept. 4 and Sept. 5, 2004, respectively, when Frances’ eye sat just off the coast of eastern Florida and Ivan was heading toward the central and western Caribbean. They are available at: http://photojournal.jpl.nasa.gov/catalog/PIA04367.

The left-hand panel in each image pair is a natural-color view from the instrument’s nadir camera. The right-hand panels are computer-generated cloud-top height retrievals produced by comparing the features of images acquired at different view angles. When these images were acquired, clouds within Frances and Ivan had attained altitudes of 15 and 16 kilometers (9.3 and 9.9 miles) above sea level, respectively.

The instrument is one of several Earth-observing experiments aboard Terra, launched in December 1999. The instrument acquires images of Earth at nine angles simultaneously, using nine separate cameras pointed forward, downward and backward along its flight path. It observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. It was built and is managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif. JPL is a division of the California Institute of Technology in Pasadena.

More information about the Multi-angle Imaging SpectroRadiometer is available at: http://www-misr.jpl.nasa.gov/.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Stream of Particles from Io

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

Posted on by Fraser Cain

Radio Astronomy Will Get a Boost With the Square Kilometer Array

The project plans are being developed by a consortium of institutions headed up by Cornell, and funded by the National Science Foundation among others. The SKA plans are loosely based on the ideas being implemented by the Allen Telescope Array (ATA). The ATA is an array of 350 six meter dishes funded by Microsoft philanthropist Paul Allen specifically for SETI research. Note that the science and technology for using interferometers for radio has now reached a stage where this instrument can be built. While this transcontinental technique may be employable for microwaves in the decades ahead, infrared, optical, and x-ray interferometers (several connected telescopes) still require a short direct path of the light to follow, so that the images can be combined using optical, not electronic, means.

The 1.4 billion dollar SKA project should have a final design, and locations defined by 2007, with construction beginning by 2010, and it should be complete and operational by 2015. The array itself will have a core central array of 3300 dishes, and 160 outlying stations of about 7 dishes each covering a broad area of North and Central America.

When complete this tool will have the sensitivity of a single dish, 800 meters in diameter, which is on the order of a hundred times more sensitive than any steerable dish on the planet today. It is also about ten times the sensitivity of the giant dish at Arecibo, which is also operated by Cornell. At its shortest wavelength, the array will be able to image sources to a scale of 500 micro-arcseconds, which is about 15 light-years at the Andromeda galaxy [M31], or a few hundred AU when mapping nearby molecular clouds in our own galaxy.

With all this new detection capability will come a great deal of new science. This month, peer review journals and other sources are getting ready to print numerous papers proposing work that can be done with this instrument. Some of the science goals will help us observe the universe before the first stars formed, and will answer detailed questions about an epoch much earlier than will be seen by the upcoming James Webb Space Telescope. Among the science goals are: Mapping the star formation history and large-scale structure of the Universe, tracing the star formation history over cosmological time, and studying of the Sunyaev-Zel’dovich effect at high redshifts, which some say may have contaminated observed Cosmic Microwave background radiation, and altered the apparent age and dark matter density of the universe. Many of these observations will be done looking at the highly redshifted 21-cm line from neutral hydrogen.

Other science goals include tracing out the magnetic field structure in parsec to Megaparsec jets, in normal galaxies and in distant clusters of galaxies, as well as locate distant (z > 2) clusters, probing strong gravitational fields and the cosmological evolution of super-massive black holes, identifying radio transients 100 times fainter than we can now see, probing the scintillating universe and exploiting super-resolution phenomena, identifying the overall structure, discrete components, and turbulent and magnetic properties of the Milky Way and nearby galaxies, a Milky Way census of faint old pulsars and other compact objects, searching for brown dwarfs in the local Galactic environs and mapping thermal emission from nearby stars, as well as inventorying and tracking solar system debris such as asteroids, comets, and KBOs.

A recent paper points out that the SKA can be used to receive data rates hundreds of times faster than the current Deep Space Network from very distant space probes for short periods, such as from the ESA?s proposed tiny Pluto Orbiter Probe, or NASA?s New Horizons mission to the Kuiper belt.

The SKA will be a versatile instrument with capabilities far beyond what are available in today?s instruments. For radio astronomy, the SKA is the shape of things to come.

Links:
SKA site
SKA Design strawman paper
Allen Telescope Array website

Author: John A. Cross