Subtly shaded map of moon reveals titanium treasure troves

ScienceDaily (Oct. 7, 2011) — A map of the Moon combining observations in visible and ultraviolet wavelengths shows a treasure trove of areas rich in Titanium ores. Not only is titanium a valuable element, it is key to helping scientists unravel the mysteries of the Moon's interior.

Mark Robinson and Brett Denevi is presenting the results from the Lunar Reconnaissance Orbiter mission at the joint meeting of the European Planetary Science Congress and the American Astronomical Society's Division for Planetary Sciences.

"Looking up at the Moon, its surface appears painted with shades of grey -- at least to the human eye. But with the right instruments, the Moon can appear colourful," said Robinson, of Arizona State University. "The maria appear reddish in some places and blue in others. Although subtle, these colour variations tell us important things about the chemistry and evolution of the lunar surface. They indicate the titanium and iron abundance, as well as the maturity of a lunar soil."

The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) is imaging the surface in seven different wavelengths at a resolution of between 100 and 400 metres per pixel. Specific minerals reflect or absorb strongly certain parts of the electromagnetic spectrum, so the wavelengths detected by LROC WAC help scientists better understand the chemical composition of the lunar surface.

Robinson and his team previously developed a technique using Hubble Space Telescope images to map titanium abundances around a small area centred on the Apollo 17 landing site. Samples around the site spanned a broad range of titanium levels. By comparing the Apollo data from the ground with the Hubble images, the team found that the titanium levels corresponded to the ratio of ultraviolet to visible light reflected by the lunar soils.

"Our challenge was to find out whether the technique would work across broad areas, or whether there was something special about the Apollo 17 area," said Robinson.

Robinson's team constructed a mosaic from around 4000 LROC WAC images collected over one month. Using the technique they had developed with the Hubble imagery, they used the WAC ratio of the brightness in the ultraviolet to visible light to deduce titanium abundance, backed up by surface samples gathered by Apollo and Luna missions.

The highest titanium abundances in similar kinds of rocks on Earth are around one percent or less. The new map shows that in the mare, titanium abundances range from about one percent to a little more than ten percent. In the highlands, everywhere titanium is less than one percent. The new titanium values match those measured in the ground samples to about one percent.

"We still don't really understand why we find much higher abundances of titanium on the Moon compared to similar types of rocks on Earth. What the lunar titanium-richness does tell us is something about the conditions inside the Moon shortly after it formed, knowledge that geochemists value for understanding the evolution of the Moon," said Robinson.

Lunar titanium is mostly found in the mineral ilmenite, a compound containing iron, titanium and oxygen. Future miners living and working on the Moon could break down ilmenite to liberate these elements. In addition, Apollo data shows that titanium-rich minerals are more efficient at retaining particles from the solar wind, such as helium and hydrogen. These gases would also provide a vital resource for future human inhabitants of lunar colonies.

"The new map is a valuable tool for lunar exploration planning. Astronauts will want to visit places with both high scientific value and a high potential for resources that can be used to support exploration activities. Areas with high titanium provide both -- a pathway to understanding the interior of the Moon and potential mining resources," said Robinson.

The new maps also shed light on how space weather changes the lunar surface. Over time, the lunar surface materials are altered by the impact of charged particles from the solar wind and high-velocity micrometeorite impacts. Together these processes work to pulverize rock into a fine powder and alter the surface's chemical composition and hence its colour. Recently exposed rocks, such as the rays that are thrown out around impact craters, appear bluer and have higher reflectance than more mature soil. Over time this 'young' material darkens and reddens, disappearing into the background after about 500 million years.

"One of the exciting discoveries we've made is that the effects of weathering show up much more quickly in ultraviolet than in visible or infrared wavelengths. In the LROC ultraviolet mosaics, even craters that we thought were very young appear relatively mature. Only small, very recently formed craters show up as fresh regolith exposed on the surface," said Denevi, of Johns Hopkins University Applied Physics Laboratory.

The mosaics have also given important clues to why lunar swirls -- sinuous features associated with magnetic fields in the lunar crust -- are highly reflective. The new data suggest that when a magnetic field is present, it deflects the charged solar wind, slowing the maturation process and resulting in the bright swirl. The rest of the Moon's surface, which does not benefit from the protective shield of a magnetic field, is more rapidly weathered by the solar wind. This result may suggest that bombardment by charged particles may be more important than micrometeorites in weathering the Moon's surface.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Europlanet Media Centre, via AlphaGalileo.

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Cosmic weight watching reveals black hole-galaxy history

ScienceDaily (Sep. 29, 2011) — Using state-of-the-art technology and sophisticated data analysis tools, a team of astronomers from the Max Planck Institute for Astronomy has developed a new and powerful technique to directly determine the mass of an active galaxy at a distance of nearly 9 billion light-years from Earth. This pioneering method promises a new approach for studying the co-evolution of galaxies and their central black holes. First results indicate that for galaxies, the best part of cosmic history was not a time of sweeping changes.

One of the most intriguing developments in astronomy over the last few decades is the realization that not only do most galaxies contain central black holes of gigantic size, but also that the mass of these central black holes are directly related to the mass of their host galaxies. This correlation is predicted by the current standard model of galaxy evolution, the so-called hierarchical model, as astronomers from the Max Planck Institute for Astronomy have recently shown.

When astronomers look out to greater and greater distances, they look further and further into the past. Investigating this black hole-galaxy mass correlation at different distances, and thus at different times in cosmic history, allows astronomers to study galaxy and black hole evolution in action.

For galaxies further away than 5 billion light-years (corresponding to a redshift of z > 0.5), such studies face considerable difficulties. The typical objects of study are so-called active galaxies, and there are well-established methods to estimate the mass of such a galaxy's central black hole. It is the galaxy's mass itself that is the challenge: At such distances, standard methods of estimating a galaxy's mass become exceedingly uncertain or fail altogether.

Now, a team of astronomers from the Max Planck Institute for Astronomy, led by Dr Katherine Inskip, has, for the first time, succeeded in directly "weighing" both a galaxy and its central black hole at such a great distance using a sophisticated and novel method. The galaxy, known to astronomers by the number J090543.56+043347.3 (which encodes the galaxy's position in the sky) has a distance of 8.8 billion light-years from Earth (redshift z = 1.3).

The astronomers succeeded in measuring directly the so-called dynamical mass of this active galaxy. The key idea is the following: A galaxy's stars and gas clouds orbit the galactic centre; for instance, our Sun orbits the centre of the Milky Way galaxy once every 250 million years. The stars' different orbital speeds are a direct function of the galaxy's mass distribution. Determine orbital speeds and you can determine the galaxy's total mass.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Max-Planck-Gesellschaft.

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K. J. Inskip, K. Jahnke, H.-W. Rix, G. van de Ven. Resolving the Dynamical Mass of a z ~ 1.3 Quasi-stellar Object Host Galaxy Using SINFONI and Laser Guide Star Assisted Adaptive Optics. The Astrophysical Journal, 2011; 739 (2): 90 DOI: 10.1088/0004-637X/739/2/90

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Cosmic weight watching reveals black hole-galaxy history

ScienceDaily (Sep. 29, 2011) — Using state-of-the-art technology and sophisticated data analysis tools, a team of astronomers from the Max Planck Institute for Astronomy has developed a new and powerful technique to directly determine the mass of an active galaxy at a distance of nearly 9 billion light-years from Earth. This pioneering method promises a new approach for studying the co-evolution of galaxies and their central black holes. First results indicate that for galaxies, the best part of cosmic history was not a time of sweeping changes.

One of the most intriguing developments in astronomy over the last few decades is the realization that not only do most galaxies contain central black holes of gigantic size, but also that the mass of these central black holes are directly related to the mass of their host galaxies. This correlation is predicted by the current standard model of galaxy evolution, the so-called hierarchical model, as astronomers from the Max Planck Institute for Astronomy have recently shown.

When astronomers look out to greater and greater distances, they look further and further into the past. Investigating this black hole-galaxy mass correlation at different distances, and thus at different times in cosmic history, allows astronomers to study galaxy and black hole evolution in action.

For galaxies further away than 5 billion light-years (corresponding to a redshift of z > 0.5), such studies face considerable difficulties. The typical objects of study are so-called active galaxies, and there are well-established methods to estimate the mass of such a galaxy's central black hole. It is the galaxy's mass itself that is the challenge: At such distances, standard methods of estimating a galaxy's mass become exceedingly uncertain or fail altogether.

Now, a team of astronomers from the Max Planck Institute for Astronomy, led by Dr Katherine Inskip, has, for the first time, succeeded in directly "weighing" both a galaxy and its central black hole at such a great distance using a sophisticated and novel method. The galaxy, known to astronomers by the number J090543.56+043347.3 (which encodes the galaxy's position in the sky) has a distance of 8.8 billion light-years from Earth (redshift z = 1.3).

The astronomers succeeded in measuring directly the so-called dynamical mass of this active galaxy. The key idea is the following: A galaxy's stars and gas clouds orbit the galactic centre; for instance, our Sun orbits the centre of the Milky Way galaxy once every 250 million years. The stars' different orbital speeds are a direct function of the galaxy's mass distribution. Determine orbital speeds and you can determine the galaxy's total mass.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Max-Planck-Gesellschaft.

Journal Reference:

K. J. Inskip, K. Jahnke, H.-W. Rix, G. van de Ven. Resolving the Dynamical Mass of a z ~ 1.3 Quasi-stellar Object Host Galaxy Using SINFONI and Laser Guide Star Assisted Adaptive Optics. The Astrophysical Journal, 2011; 739 (2): 90 DOI: 10.1088/0004-637X/739/2/90

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Science & the Public: HIPPO reveals climate surprises

Swooping pole-to-pole plane flights uncover unexpected trends in pollutant releases and spreadWeb edition : Thursday, September 8th, 2011 Pollutant snifferThis aircraft sampled air at different altitudes along paths that ran from pole to pole looking for climate-altering pollutants.©UCAR/Carlye Calvin

A major pollution-mapping program that ends September 9 has turned up startling trends in climate-warming gases and soot. The data it collected over the past five years from a National Science Foundation aircraft show the tropics periodically belch huge plumes of nitrous oxide — a potent greenhouse gas — into the upper atmosphere. Arctic measurements show that the recent record summer retreats of ice cover have allowed seas there to exhale unexpected amounts of methane, another potent greenhouse gas.

Then there’s soot. Parts of the supposedly pristine Arctic skies host dense clouds of these black carbon particles. During some flights, “We were immersed in essentially clouds of black carbon that were dense enough that you could barely see the ground,” recalls Stephen Wofsy of Harvard University, a principal investigator in the program. “It was like landing in Los Angeles — except that you were 8 kilometers above the surface of the Arctic Ocean.”

Until a few years ago, scientists interested in mapping global emissions of climate-altering pollutants had to rely on Earth-based sensors or satellites’ eyes on the skies. Neither could identify at what altitude the pollutants tended to congregate. They also missed many highly localized or seasonal plumes of natural pollutants.

That all changed when a federal-university research partnership got access to NSF’s research plane: HIAPER (for High Performance Instrumented Airborne Platform for Environmental Research). Throughout a number of periodic runs, this aircraft repeatedly swooped up and down — from 150 meters above Earth’s surface to heights sometimes exceeding 13.7 kilometers (45,000 feet). All along the way, its instruments measured more than 50 greenhouse gases and black carbon.

The unparalleled altitude- and latitude- specific data collected as part of this program — named HIPPO (for HIAPER Pole-to-Pole Observations) — will soon be made available to researchers generally, notes Wofsy. He expects scientists will mine its data for many years, looking for additional climate trends.

Sky-truthing carbon dioxide levels
A primary goal of HIPPO was to investigate how well airborne pollutant concentrations match what computer models had predicted should exist. In some cases, as for soot, HIPPO data pointed to serious problems — oversimplifications — in those models. In other instances, such as for oxygen movement in and out of oceans, the new data generally validated computer predictions.

Currently, land plants and the oceans absorb roughly half of all carbon dioxide emitted, notes Britton Stephens, a scientist with the National Center on Atmospheric Research in Boulder, Colo. But details on which parts of which ecosystems do it, under what circumstances and how efficiently remains somewhat of an open book. Simply put: “We don’t understand their behavior at the current time well enough to predict their behavior into the future,” he says.

So airborne observations have been repeatedly compared to what computer models predict. And one example of where the models need fine tuning involves carbon dioxide, HIPPO indicates.

Little ice, lots of methaneHIPPO ties unexpected release of methane to loss of summer Arctic sea-ice cover (and 2011 may be record loss, Wofsy says).iStockPhoto

It revealed “large plumes of carbon dioxide over the Arctic,” Stephens reported Sept. 7 at a news briefing. These plumes didn’t come from the Arctic, he says, but bled into Arctic skies from industrial centers throughout the Northern Hemisphere.

“This was a bit of a surprise,” he says, because models had suggested that much of the carbon dioxide should have been sucked up by plants and seas close to where the gas was being emitted.

Another instance of where the models appear to fall short is on how well the mixing of near-surface parcels of air homogenize carbon dioxide concentrations.

Stephens pointed to data collected earlier this week by the HIAPER aircraft during a run from Kona, Hawaii, to Anchorage, Alaska. “This is the time of year when we see peak uptake [of the gas]” as a result of photosynthesis in land plants, he explains. And HIPPO indeed observed a large depletion of carbon dioxide near the surface, he notes — except “we were measuring it over the middle of the Pacific Ocean.”

Computer analyses had predicted a greater degree of mixing of clean and polluted air parcels, he says. Instead, there were sharp gradients in the gas among closely sampled regions.

Elsewhere, HIPPO offered welcome confirmation of a different model prediction: large plumes of oxygen coming out of the southern oceans during the austral summer. Stephens attributes these massive releases to the uptake of carbon dioxide by photosynthetic bacteria in the warming seas. Currently, it’s winter in the South. And HIPPO has just measured the opposite trend, Stephens says: a seasonal absorption of oxygen by oceans there.

Similar trends for these gases have been observed before throughout the Northern Hemisphere. But HIPPO shows that this normal pattern of winter absorption of oxygen and summer absorption of carbon dioxide “is somewhat decoupled” in the southern oceans. Indeed, Stephens concludes, at times “it was almost more significant that we measured an anti-correlation between oxygen and carbon dioxide than the actual numbers [of how much of either was present].”

Other revelations
More unexpected, Wofsy says, was the March 2010 finding of “a significant excess over the tropics of greenhouse gases — especially nitrous oxide — very high up in the atmosphere. That hadn’t been predicted by any models.”

So radical were the data that his team rushed them into print. Those data show a “bulge” in nitrous oxide emissions between the equator and 20° North latitude.

“It is clear that the enhanced nitrous oxide seen at altitude is a product of tropical emissions lofted to the middle and upper troposphere by convection,” the authors conclude in the Aug. 6, 2011, Geophysical Research Letters.  HIPPO data alone cannot confirm whether the release of this gas represents a “winking on and off” of emissions on time scales of days to weeks, the researchers said, or whether the releases occur more chronically but only occasionally shoot up to altitudes of between 2 kilometers and 14 kilometers.

The best explanation for these data, Wofsy and his coauthors write, is that rainfall or regional flooding spurs production of the gas (probably by soil microbes) — and when this coincides with sharp atmospheric updrafts, the pollutant is propelled high into the skies.

Something too new to fully understand (although a report on it is being prepared for publication), Wofsy says, is a finding of notable concentrations of methane in the Arctic’s atmosphere that trace back to the sea.

“Oceanographers have known for some time that there is production of methane in surface waters of the Arctic,” he says, but “it’s never been observed in the atmosphere.” Those oceanographic data, he says, suggest a source for this methane other than sediments or the melting of icy gas hydrates.

The phenomenon also appears very widespread. “We observed that the ocean surface releases methane to the atmosphere all over the whole of the Arctic Ocean,” Wofsy says.

Climate scientists have been concerned about whether the Arctic Ocean's loss of summer ice cover might lead, through some feedback mechanisms, to boosting the release of methane. Concludes Wofsy: Thanks to HIPPO, “This hypothesized feedback has been observed for the first time.” And there are hints, he adds, that methane’s source may be something other than melting of gas hydrates.

One notable take-home message from HIPPO: Climate-altering pollution from the Northern Hemisphere — home to 95 percent of humanity — has been migrating everywhere, even into southern skies, says James Elkins of the National Oceanic and Atmospheric Administration, in Boulder. The data are “just very persuasive.”

Indeed, Wofsy adds, after reviewing HIPPO data, you’re left with an impression that pollution associated with human activities has exerted “an overwhelming influence” on Earth’s atmosphere. And that’s not, he adds, reassuring.

Found in: Climate Change, Earth, Environment and Molecules

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First habitable exoplanet? Climate simulation reveals new candidate that could support Earth-like life

ScienceDaily (May 16, 2011) — The planetary system around the red dwarf Gliese 581, one of the closest stars to the Sun in the galaxy, has been the subject of several studies aiming to detect the first potentially habitable exoplanet. Two candidates have already been discarded, but a third planet, Gliese 581d, can be considered the first confirmed exoplanet that could support Earth-like life. This is the conclusion of a team of scientists from the Institut Pierre Simon Laplace (CNRS, UPMC, ENS Paris, Ecole Polytechnique) in Paris, France, whose study is published in The Astrophysical Journal Letters.

Are there other planets inhabited like Earth, or at least habitable? The discovery of the first habitable planet has become a quest for many astrophysicists who look for rocky planets in the "habitable zone" around stars, the range of distances in which planets are neither too cold nor too hot for life to flourish.

In this quest, the red dwarf star Gliese 581 has already received a huge amount of attention. In 2007, scientists reported the detection of two planets orbiting not far from the inner and outer edge of its habitable zone. While the more distant planet, Gliese 581d, was initially judged to be too cold for life, the closer-in planet was thought to be potentially habitable by its discoverers. However, later analysis by atmospheric experts showed that if it had liquid oceans like Earth, they would rapidly evaporate in a 'runaway greenhouse' effect similar to that which gave Venus the hot, inhospitable climate it has today. A new possibility emerged late in 2010, when a team of observers led by Steven Vogt at the University of California, Santa Cruz, announced that they had discovered a new planet, which they dubbed Gliese 581g, or 'Zarmina's World'. This planet, they claimed, had a mass similar to that of Earth and was close to the centre of the habitable zone. For several months, the discovery of the first potential Earth twin outside the Solar System seemed to have been achieved. Unfortunately, later analysis by independent teams has raised serious doubts on this extremely difficult detection. Many now believe that Gliese 581g may not exist at all. Instead, it may simply be a result of noise in the ultra-fine measurements of stellar 'wobble' needed to detect exoplanets in this system.

Today, it is finally Gliese 581g's big brother -- the larger and more distant Gliese 581d -- which has been shown to be the confirmed potentially habitable exoplanet by Robin Wordsworth, François Forget and co-workers from Laboratoire de Météorologie Dynamique (CNRS, UPMC, ENS Paris, Ecole Polytechnique) at the Institute Pierre Simon Laplace in Paris. Although it is likely to be a rocky planet, it has a mass at least seven times that of Earth, and is estimated to be about twice its size. At first glance, Gliese 581d is a pretty poor candidate in the hunt for life: it receives less than a third of the stellar energy Earth does and may be tidally locked, with a permanent day and night side. After its discovery, it was generally believed that any atmosphere thick enough to keep the planet warm would become cold enough on the night side to freeze out entirely, ruining any prospects for a habitable climate.

To test whether this intuition was correct, Wordsworth and colleagues developed a new kind of computer model capable of accurately simulating possible exoplanet climates. The model simulates a planet's atmosphere and surface in three dimensions, rather like those used to study climate change on Earth. However, it is based on more fundamental physical principles, allowing the simulation of a much wider range of conditions than would otherwise be possible, including any atmospheric cocktail of gases, clouds and aerosols.

To their surprise, they found that with a dense carbon dioxide atmosphere -- a likely scenario on such a large planet -- the climate of Gliese 581d is not only stable against collapse, but warm enough to have oceans, clouds and rainfall. One of the key factors in their results was Rayleigh scattering, the phenomenon that makes the sky blue on Earth. In the Solar System, Rayleigh scattering limits the amount of sunlight a thick atmosphere can absorb, because a large portion of the scattered blue light is immediately reflected back to space. However, as the starlight from Gliese 581 is red, it is almost unaffected. This means that it can penetrate much deeper into the atmosphere, where it heats the planet effectively due to the greenhouse effect of the CO2 atmosphere, combined with that of the carbon dioxide ice clouds predicted to form at high altitudes. Furthermore, the 3D circulation simulations showed that the daylight heating was efficiently redistributed across the planet by the atmosphere, preventing atmospheric collapse on the night side or at the poles.

Scientists are particularly excited by the fact that at 20 light years from Earth, Gliese 581d is one of our closest galactic neighbours. For now, this is of limited use for budding interstellar colonists -- the furthest-travelled human-made spacecraft, Voyager 1, would still take over 300,000 years to arrive there. However, it does mean that in the future telescopes will be able to detect the planet's atmosphere directly. While Gliese 581d may be habitable there are other possibilities; it could have kept some atmospheric hydrogen, like Uranus and Neptune, or the fierce wind from its star during its infancy could even have torn its atmosphere away entirely. To distinguish between these different scenarios, Wordsworth and co-workers came up with several simple tests that observers will be able to perform in future with a sufficiently powerful telescope.

If Gliese 581d does turn out to be habitable, it would still be a pretty strange place to visit -- the denser air and thick clouds would keep the surface in a perpetual murky red twilight, and its large mass means that surface gravity would be around double that on Earth. But the diversity of planetary climates in the galaxy is likely to be far wider than the few examples we are used to from the Solar System. In the long run, the most important implication of these results may be the idea that life-supporting planets do not in fact need to be particularly like Earth at all.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by CNRS (Délégation Paris Michel-Ange).

Journal Reference:

Robin D. Wordsworth, François Forget, Franck Selsis, Ehouarn Millour, Benjamin Charnay, Jean-Baptiste Madeleine. Gliese 581d is the first discovered terrestrial-mass exoplanet in the habitable zone. The Astrophysical Journal, 2011; 733 (2): L48 DOI: 10.1088/2041-8205/733/2/L48

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

First habitable exoplanet? Climate simulation reveals new candidate that could support Earth-like life

ScienceDaily (May 16, 2011) — The planetary system around the red dwarf Gliese 581, one of the closest stars to the Sun in the galaxy, has been the subject of several studies aiming to detect the first potentially habitable exoplanet. Two candidates have already been discarded, but a third planet, Gliese 581d, can be considered the first confirmed exoplanet that could support Earth-like life. This is the conclusion of a team of scientists from the Institut Pierre Simon Laplace (CNRS, UPMC, ENS Paris, Ecole Polytechnique) in Paris, France, whose study is published in The Astrophysical Journal Letters.

Are there other planets inhabited like Earth, or at least habitable? The discovery of the first habitable planet has become a quest for many astrophysicists who look for rocky planets in the "habitable zone" around stars, the range of distances in which planets are neither too cold nor too hot for life to flourish.

In this quest, the red dwarf star Gliese 581 has already received a huge amount of attention. In 2007, scientists reported the detection of two planets orbiting not far from the inner and outer edge of its habitable zone. While the more distant planet, Gliese 581d, was initially judged to be too cold for life, the closer-in planet was thought to be potentially habitable by its discoverers. However, later analysis by atmospheric experts showed that if it had liquid oceans like Earth, they would rapidly evaporate in a 'runaway greenhouse' effect similar to that which gave Venus the hot, inhospitable climate it has today. A new possibility emerged late in 2010, when a team of observers led by Steven Vogt at the University of California, Santa Cruz, announced that they had discovered a new planet, which they dubbed Gliese 581g, or 'Zarmina's World'. This planet, they claimed, had a mass similar to that of Earth and was close to the centre of the habitable zone. For several months, the discovery of the first potential Earth twin outside the Solar System seemed to have been achieved. Unfortunately, later analysis by independent teams has raised serious doubts on this extremely difficult detection. Many now believe that Gliese 581g may not exist at all. Instead, it may simply be a result of noise in the ultra-fine measurements of stellar 'wobble' needed to detect exoplanets in this system.

Today, it is finally Gliese 581g's big brother -- the larger and more distant Gliese 581d -- which has been shown to be the confirmed potentially habitable exoplanet by Robin Wordsworth, François Forget and co-workers from Laboratoire de Météorologie Dynamique (CNRS, UPMC, ENS Paris, Ecole Polytechnique) at the Institute Pierre Simon Laplace in Paris. Although it is likely to be a rocky planet, it has a mass at least seven times that of Earth, and is estimated to be about twice its size. At first glance, Gliese 581d is a pretty poor candidate in the hunt for life: it receives less than a third of the stellar energy Earth does and may be tidally locked, with a permanent day and night side. After its discovery, it was generally believed that any atmosphere thick enough to keep the planet warm would become cold enough on the night side to freeze out entirely, ruining any prospects for a habitable climate.

To test whether this intuition was correct, Wordsworth and colleagues developed a new kind of computer model capable of accurately simulating possible exoplanet climates. The model simulates a planet's atmosphere and surface in three dimensions, rather like those used to study climate change on Earth. However, it is based on more fundamental physical principles, allowing the simulation of a much wider range of conditions than would otherwise be possible, including any atmospheric cocktail of gases, clouds and aerosols.

To their surprise, they found that with a dense carbon dioxide atmosphere -- a likely scenario on such a large planet -- the climate of Gliese 581d is not only stable against collapse, but warm enough to have oceans, clouds and rainfall. One of the key factors in their results was Rayleigh scattering, the phenomenon that makes the sky blue on Earth. In the Solar System, Rayleigh scattering limits the amount of sunlight a thick atmosphere can absorb, because a large portion of the scattered blue light is immediately reflected back to space. However, as the starlight from Gliese 581 is red, it is almost unaffected. This means that it can penetrate much deeper into the atmosphere, where it heats the planet effectively due to the greenhouse effect of the CO2 atmosphere, combined with that of the carbon dioxide ice clouds predicted to form at high altitudes. Furthermore, the 3D circulation simulations showed that the daylight heating was efficiently redistributed across the planet by the atmosphere, preventing atmospheric collapse on the night side or at the poles.

Scientists are particularly excited by the fact that at 20 light years from Earth, Gliese 581d is one of our closest galactic neighbours. For now, this is of limited use for budding interstellar colonists -- the furthest-travelled human-made spacecraft, Voyager 1, would still take over 300,000 years to arrive there. However, it does mean that in the future telescopes will be able to detect the planet's atmosphere directly. While Gliese 581d may be habitable there are other possibilities; it could have kept some atmospheric hydrogen, like Uranus and Neptune, or the fierce wind from its star during its infancy could even have torn its atmosphere away entirely. To distinguish between these different scenarios, Wordsworth and co-workers came up with several simple tests that observers will be able to perform in future with a sufficiently powerful telescope.

If Gliese 581d does turn out to be habitable, it would still be a pretty strange place to visit -- the denser air and thick clouds would keep the surface in a perpetual murky red twilight, and its large mass means that surface gravity would be around double that on Earth. But the diversity of planetary climates in the galaxy is likely to be far wider than the few examples we are used to from the Solar System. In the long run, the most important implication of these results may be the idea that life-supporting planets do not in fact need to be particularly like Earth at all.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by CNRS (Délégation Paris Michel-Ange).

Journal Reference:

Robin D. Wordsworth, François Forget, Franck Selsis, Ehouarn Millour, Benjamin Charnay, Jean-Baptiste Madeleine. Gliese 581d is the first discovered terrestrial-mass exoplanet in the habitable zone. The Astrophysical Journal, 2011; 733 (2): L48 DOI: 10.1088/2041-8205/733/2/L48

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

NASA's Galileo reveals magma 'ocean' beneath surface of Jupiter's moon

ScienceDaily (May 12, 2011) — A new analysis of data from NASA's Galileo spacecraft has revealed that beneath the surface of Jupiter's volcanic moon Io is an "ocean" of molten or partially molten magma.

The finding, from a study published May 13 in the journal Science, is the first direct confirmation of such a magma layer on Io and explains why the moon is the most volcanic object known in the solar system. The research was conducted by scientists from UCLA, UC Santa Cruz and the University of Michigan-Ann Arbor.

"The hot magma in Io's ocean is millions of times better at conducting electricity than rocks typically found on the Earth's surface," said the study's lead author, Krishan Khurana, a former co-investigator on Galileo's magnetometer team and a research geophysicist with UCLA's Institute of Geophysics and Planetary Physics. "Just like the waves beamed from an airport metal detector bounce off metallic coins in your pocket, betraying their presence to the detector, Jupiter's rotating magnetic field continually bounces off the molten rocks in Io's interior. The bounced signal can be detected by a magnetometer on a passing spacecraft.

"Scientists are excited that we finally understand where Io's magma is coming from and have an explanation for some of the mysterious signatures we saw in some of Galileo's magnetic field data," Khurana added. "It turns out Io was continually giving off a 'sounding signal' in Jupiter's rotating magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface."

Io's volcanoes are the only known active magma volcanoes in the solar system other than those on Earth; Io produces about 100 times more lava each year than all of Earth's volcanoes. While those on Earth occur in localized hotspots like the "Ring of Fire" around the Pacific Ocean, Io's volcanoes are distributed all over its surface. A global magma ocean lying beneath about 20 to 30 miles (30 to 50 km) of Io's crust helps explain the moon's activity.

"It has been suggested that both the Earth and moon may have had similar magma oceans billions of years ago, at the time of their formation, but they have long since cooled," said Torrence Johnson, who was Galileo's project scientist, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and who was not directly involved in the study. "Io's volcanism informs us how volcanoes work and provides a window in time to styles of volcanic activity that may have occurred on the Earth and moon during their earliest history."

Io's volcanoes were discovered by NASA's Voyager spacecraft in 1979. The energy for the volcanic activity comes from the squeezing and stretching of the moon by Jupiter's gravity as Io orbits the immense planet, the largest in the solar system.

Galileo was launched in 1989 and began orbiting Jupiter in 1995. After a successful mission, the spacecraft was intentionally sent into Jupiter's atmosphere in 2003. The unexplained signatures appeared in the magnetic-field data taken from Galileo fly-bys of Io in October 1999 and February 2000, during the final phase of the mission.

"But at the time, models of the interaction between Io and Jupiter's immense magnetic field, which bathes the moon in charged particles, were not yet sophisticated enough for us to understand what was going on in Io's interior," said study co-author Xianzhe Jia of the University of Michigan.

Recent work in mineral physics showed that a group of what are known as "ultramafic" rocks become capable of carrying substantial electrical current when melted. These rocks are igneous in origin -- that is, they are formed through the cooling of magma. On Earth, ultramafic rocks are believed to derive from the mantle. The finding led Khurana and colleagues to test the hypothesis that the strange signature was produced by an electrical current flowing in a molten or partially molten layer of this kind of rock.

Tests showed that the signatures detected by Galileo were consistent with a rock like lherzolite, an igneous rock rich in silicates of magnesium and iron found, for example, in Spitzbergen, Norway. The magma ocean layer on Io appears to be more than 30 miles (50 km) thick, making up at least 10 percent of the moon's mantle by volume. The blistering temperature of the magma ocean probably exceeds 2,200 degrees Fahrenheit (1,200 degrees Celsius).

Additional co-authors on the paper are Christopher T. Russell, professor of geophysics and space physics in UCLA's Department of Earth and Space Sciences; Margaret Kivelson, professor emeritus of space physics in UCLA's Department of Earth and Space Sciences; Gerald Schubert, professor of geophysics and planetary physics in UCLA's Department of Earth and Space Sciences; and Francis Nimmo, associate professor of Earth and planetary sciences at UC Santa Cruz.

The Galileo mission was managed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, for NASA.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - Los Angeles. The original article was written by Jia-Rui Cook.

Journal Reference:

Krishan K. Khurana, Xianzhe Jia, Margaret G. Kivelson, Francis Nimmo, Gerald Schubert, Christopher T. Russell. Evidence of a Global Magma Ocean in Io’s Interior. Science, 2011; DOI: 10.1126/science.1201425

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

NASA's Galileo reveals magma 'ocean' beneath surface of Jupiter's moon

ScienceDaily (May 12, 2011) — A new analysis of data from NASA's Galileo spacecraft has revealed that beneath the surface of Jupiter's volcanic moon Io is an "ocean" of molten or partially molten magma.

The finding, from a study published May 13 in the journal Science, is the first direct confirmation of such a magma layer on Io and explains why the moon is the most volcanic object known in the solar system. The research was conducted by scientists from UCLA, UC Santa Cruz and the University of Michigan-Ann Arbor.

"The hot magma in Io's ocean is millions of times better at conducting electricity than rocks typically found on the Earth's surface," said the study's lead author, Krishan Khurana, a former co-investigator on Galileo's magnetometer team and a research geophysicist with UCLA's Institute of Geophysics and Planetary Physics. "Just like the waves beamed from an airport metal detector bounce off metallic coins in your pocket, betraying their presence to the detector, Jupiter's rotating magnetic field continually bounces off the molten rocks in Io's interior. The bounced signal can be detected by a magnetometer on a passing spacecraft.

"Scientists are excited that we finally understand where Io's magma is coming from and have an explanation for some of the mysterious signatures we saw in some of Galileo's magnetic field data," Khurana added. "It turns out Io was continually giving off a 'sounding signal' in Jupiter's rotating magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface."

Io's volcanoes are the only known active magma volcanoes in the solar system other than those on Earth; Io produces about 100 times more lava each year than all of Earth's volcanoes. While those on Earth occur in localized hotspots like the "Ring of Fire" around the Pacific Ocean, Io's volcanoes are distributed all over its surface. A global magma ocean lying beneath about 20 to 30 miles (30 to 50 km) of Io's crust helps explain the moon's activity.

"It has been suggested that both the Earth and moon may have had similar magma oceans billions of years ago, at the time of their formation, but they have long since cooled," said Torrence Johnson, who was Galileo's project scientist, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and who was not directly involved in the study. "Io's volcanism informs us how volcanoes work and provides a window in time to styles of volcanic activity that may have occurred on the Earth and moon during their earliest history."

Io's volcanoes were discovered by NASA's Voyager spacecraft in 1979. The energy for the volcanic activity comes from the squeezing and stretching of the moon by Jupiter's gravity as Io orbits the immense planet, the largest in the solar system.

Galileo was launched in 1989 and began orbiting Jupiter in 1995. After a successful mission, the spacecraft was intentionally sent into Jupiter's atmosphere in 2003. The unexplained signatures appeared in the magnetic-field data taken from Galileo fly-bys of Io in October 1999 and February 2000, during the final phase of the mission.

"But at the time, models of the interaction between Io and Jupiter's immense magnetic field, which bathes the moon in charged particles, were not yet sophisticated enough for us to understand what was going on in Io's interior," said study co-author Xianzhe Jia of the University of Michigan.

Recent work in mineral physics showed that a group of what are known as "ultramafic" rocks become capable of carrying substantial electrical current when melted. These rocks are igneous in origin -- that is, they are formed through the cooling of magma. On Earth, ultramafic rocks are believed to derive from the mantle. The finding led Khurana and colleagues to test the hypothesis that the strange signature was produced by an electrical current flowing in a molten or partially molten layer of this kind of rock.

Tests showed that the signatures detected by Galileo were consistent with a rock like lherzolite, an igneous rock rich in silicates of magnesium and iron found, for example, in Spitzbergen, Norway. The magma ocean layer on Io appears to be more than 30 miles (50 km) thick, making up at least 10 percent of the moon's mantle by volume. The blistering temperature of the magma ocean probably exceeds 2,200 degrees Fahrenheit (1,200 degrees Celsius).

Additional co-authors on the paper are Christopher T. Russell, professor of geophysics and space physics in UCLA's Department of Earth and Space Sciences; Margaret Kivelson, professor emeritus of space physics in UCLA's Department of Earth and Space Sciences; Gerald Schubert, professor of geophysics and planetary physics in UCLA's Department of Earth and Space Sciences; and Francis Nimmo, associate professor of Earth and planetary sciences at UC Santa Cruz.

The Galileo mission was managed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, for NASA.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - Los Angeles. The original article was written by Jia-Rui Cook.

Journal Reference:

Krishan K. Khurana, Xianzhe Jia, Margaret G. Kivelson, Francis Nimmo, Gerald Schubert, Christopher T. Russell. Evidence of a Global Magma Ocean in Io’s Interior. Science, 2011; DOI: 10.1126/science.1201425

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Huge dry ice deposit on Mars: NASA orbiter reveals big changes in Red Planet's atmosphere

ScienceDaily (Apr. 22, 2011) — NASA's Mars Reconnaissance Orbiter has discovered the total amount of atmosphere on Mars changes dramatically as the tilt of the planet's axis varies. This process can affect the stability of liquid water, if it exists on the Martian surface, and increase the frequency and severity of Martian dust storms.

Researchers using the orbiter's ground-penetrating radar identified a large, buried deposit of frozen carbon dioxide, or dry ice, at the Red Planet's south pole. The scientists suspect that much of this carbon dioxide enters the planet's atmosphere and swells the atmosphere's mass when Mars' tilt increases. The findings are published in the journal Science.

The newly found deposit has a volume similar to Lake Superior's nearly 3,000 cubic miles (about 12,000 cubic kilometers). The deposit holds up to 80 percent as much carbon dioxide as today's Martian atmosphere. Collapse pits caused by dry ice sublimation and other clues suggest the deposit is in a dissipating phase, adding gas to the atmosphere each year. Mars' atmosphere is about 95 percent carbon dioxide, in contrast to Earth's much thicker atmosphere, which is less than .04 percent carbon dioxide.

"We already knew there is a small perennial cap of carbon-dioxide ice on top of the water ice there, but this buried deposit has about 30 times more dry ice than previously estimated," said Roger Phillips of Southwest Research Institute in Boulder, Colo. Phillips is deputy team leader for the Mars Reconnaissance Orbiter's Shallow Radar instrument and lead author of the report.

"We identified the deposit as dry ice by determining the radar signature fit the radio-wave transmission characteristics of frozen carbon dioxide far better than the characteristics of frozen water," said Roberto Seu of Sapienza University of Rome, team leader for the Shallow Radar and a co-author of the new report. Additional evidence came from correlating the deposit to visible sublimation features typical of dry ice.

"When you include this buried deposit, Martian carbon dioxide right now is roughly half frozen and half in the atmosphere, but at other times it can be nearly all frozen or nearly all in the atmosphere," Phillips said.

An occasional increase in the atmosphere would strengthen winds, lofting more dust and leading to more frequent and more intense dust storms. Another result is an expanded area on the planet's surface where liquid water could persist without boiling. Modeling based on known variation in the tilt of Mars' axis suggests several-fold changes in the total mass of the planet's atmosphere can happen on time frames of 100,000 years or less.

The changes in atmospheric density caused by the carbon-dioxide increase also would amplify some effects of the changes caused by the tilt. Researchers plugged the mass of the buried carbon-dioxide deposit into climate models for the period when Mars' tilt and orbital properties maximize the amount of summer sunshine hitting the south pole. They found at such times, global, year-round average air pressure is approximately 75 percent greater than the current level.

"A tilted Mars with a thicker carbon-dioxide atmosphere causes a greenhouse effect that tries to warm the Martian surface, while thicker and longer-lived polar ice caps try to cool it," said co-author Robert Haberle, a planetary scientist at NASA's Ames Research Center in Moffett Field, Calif. "Our simulations show the polar caps cool more than the greenhouse warms. Unlike Earth, which has a thick, moist atmosphere that produces a strong greenhouse effect, Mars' atmosphere is too thin and dry to produce as strong a greenhouse effect as Earth's, even when you double its carbon-dioxide content."

The Shallow Radar, one of the Mars Reconnaissance Orbiter's six instruments, was provided by the Italian Space Agency, and its operations are led by the Department of Information Engineering, Electronics and Telecommunications at Sapienza University of Rome. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter project for NASA's Science Mission Directorate at the agency's headquarters in Washington. Lockheed Martin Space Systems in Denver built the spacecraft.

For more information about the Mars Reconnaissance Orbiter mission, visit http://www.nasa.gov/mro .

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA/Jet Propulsion Laboratory.

Journal Reference:

Roger J. Phillips, Brian J. Davis, Kenneth L. Tanaka, Shane Byrne, Michael T. Mellon, Nathaniel E. Putzig, Robert M. Haberle, Melinda A. Kahre, Bruce A. Campbell, Lynn M. Carter, Isaac B. Smith, John W. Holt, Suzanne E. Smrekar, Daniel C. Nunes, Jeffrey J. Plaut, Anthony F. Egan, Timothy N. Titus, and Roberto Seu. Massive CO2 Ice Deposits Sequestered in the South Polar Layered Deposits of Mars. Science, 2011; DOI: 10.1126/science.1203091

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here