Posted on by Fraser Cain

A Giant Lightning Storm At Saturn

The strongest lightning storm ever been recorded was found at Saturn. Image credit: NASA/JPL/SSI Click to enlarge
Imagine an electrical storm larger than the continental United States in which the lightning bolts are more than 1,000 times stronger than conventional lightning, and you’ll have a good idea of the lightning storm — the strongest of its kind ever seen — that University of Iowa space scientists and their colleagues currently are tracking at Saturn with the Cassini spacecraft.

UI Professor Donald Gurnett, principal investigator for the Radio and Plasma Wave Science investigation (RPWS), along with UI researchers William Kurth and Georg Fischer, have been tracking the storm since Jan. 23.

“It is clear that this is the strongest lightning activity that we’ve seen yet with Cassini since it has arrived at Saturn. In fact, the flash rate even exceeds the rate observed by Voyager 1 back in 1980 and the intensities are at least as large, if not larger,” Gurnett says. “Since Cassini was over the night side of Saturn and in a difficult position to image clouds, amateur astronomers were asked if they had seen evidence of a storm cloud recently.”

He adds that within hours, two amateurs near Paris had posted a beautiful image of a white cloud at southern latitudes on Saturn that they had obtained early on Jan. 25, at a location consistent with the source of the lightning radio emissions being observed by Cassini. Cassini has now imaged the storm that RPWS and the Earth-based amateurs have seen.

Kurth notes that the Iowa-built RPWS instrument detects radio emissions the same way that a car radio picks up the crackle and pop of a summer thunderstorm on Earth.

“With Cassini we have learned that lightning storms can emerge suddenly and last for several weeks or even a month”, says Fischer, a UI postdoctoral research scholar. “On the other hand, we have only observed a single smaller lightning storm throughout 2005, which is remarkably different compared to what we know about terrestrial thunderstorms.”

RPWS team member and UI alumnus Michael Kaiser of NASA’s Goddard Space Flight Center, Greenbelt, Md., suggests that the storm has varied in intensity, but continued with some 25 episodes occurring since he first noticed the storm on Jan. 23.

The researchers say that the origin of such storms is unknown, but may be related to Saturn’s warm interior. Gurnett says that scientists hope to locate the storm with greater precision in the coming weeks when Cassini is scheduled to fly closer to the planet.

Gurnett’s RPWS team colleagues, in addition to Fischer, Kurth, and Kaiser, are Philippe Zarka and Alain Lecacheux of the Observatory of Paris, Meudon, France; and Bill Farrell of Goddard Space Flight Center, Greenbelt, Md.

The radio sounds of Saturn’s lightning can be heard by visiting the Space Audio Web site at: http://www-pw.physics.uiowa.edu/space-audio. More information about the Cassini Radio and Plasma Wave Science investigation can be found at http://cassini.physics.uiowa.edu/cassini/. A Podcast of this story and other Cassini mission information is available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

The Cassini 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, Calif., manages the Cassini mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.

Original Source: University of Iowa News Release

Posted on by Fraser Cain

Interstellar Particles Reproduced in the Lab

Image of a GEMS in an interplanetary dust particle. Image credit: NASA Click to enlarge
For the first time, a team of French scientists were able to reproduce the structure of the exotic GEMS in the laboratory. The results of their experiments will soon be published in Astronomy & Astrophysics. GEMS (glass with embedded metal and sulphides) is a major component of primitive interplanetary dust. To understand its origin is one of the primary objectives of planetary science, and especially of the recently successful Stardust mission.

In a coming issue, Astronomy & Astrophysics presents new laboratory results that provide some important clues to the possible origins of exotic mineral grains in interplanetary dust. Studying interplanetary grains is currently a hot topic within the framework of the NASA Stardust mission, which recently brought back some samples of these grains. They are among the most primitive material ever collected. Their study will lead to a better understanding of the formation and evolution of our Solar System.

Through dedicated laboratory experiments aimed at simulating the possible evolution of cosmic materials in space, C. Davoisne and her colleagues explored the origin of the so-called GEMS (glass with embedded metal and sulphides). GEMS is a major component of the primitive interplanetary dust particles (IDPs). They are a few 100 nm in size and are composed of a silicate glass that includes small, rounded grains of iron/nickel and metal sulphide. A small fraction of the GEMS (less than 5%) have presolar composition and could therefore have an interstellar origin. The remainder have solar composition and may have been formed or processed in the early Solar System. The varied compositions of the GEMS make it difficult to arrive at a consensus regarding their origin and formation process.

The team first postulates that the GEMS precursors originated in the interstellar medium and were progressively heated in the protosolar nebula. To test the validity of this hypothesis a joint experimental project involving two French laboratories, the Laboratoire de Structure et Propri?t?s de l?Etat Solide (LSPES) in Lille and the Institut d?Astrophysique Spatiale (IAS) in Orsay, was set up. Z. Djouadi, at the IAS, heated various amorphous samples of olivine ((Mg,Fe)2SiO4) under high vacuum and at temperatures ranging from 500 to 750?C. After heating, the samples show microstructures that closely resemble those of the GEMS, with rounded iron nanograins that are seen to be embedded in a silicate glass.

This is the first time that a GEMS-like structure has been reproduced by laboratory experiments. There, they show that the iron oxide (FeO) component of the amorphous silicates has undergone a chemical reaction known as reduction, in which the iron gains electrons and releases its oxygen, to precipitate in a metallic form. Since the GEMS component in IDPs is usually closely associated with carbonaceous matter, the reaction FeO + C –> Fe + CO will be at the source of the metallic iron nanograins in these IDP?s. Such conditions may have been encountered in the primitive solar nebula. This reaction has been known of for centuries by metallurgists, but the originality of the LSPES/IAS approach is the application of material science concepts to extreme astrophysical environments.

In addition, the scientists found that, in the heated sample, practically no iron remains in the silicate glass, since all the iron has migrated into the metal grains. The team is thus able to explain why the dust observed around evolved stars and in comets is mainly composed of magnesium-rich silicates where iron is apparently lacking. Indeed, iron in metallic spherules becomes totally undetectable by the usual remote spectroscopic techniques. This work could therefore provide an important and new insight into the composition of interstellar grains as well.

The team shows that GEMS could form through a specific heating process that would affect grains of various origins. The process may be very common and could occur both in the Solar System and around other stars. The GEMS could thus have diverse origins. Scientists now eagerly await the analysis of grains collected by Stardust to find out for certain that some GEMS truly come from the interstellar medium.

Original Source: A&A News Release

Posted on by Fraser Cain

Telesto’s Smooth Surface

The tiny Trojan moon Telesto. Image credit: NASA/JPL/SSI Click to enlarge
The Cassini spacecraft passed within a cosmic stone’s throw of Telesto in October, 2005 capturing this shot of the tiny Trojan moon.

Telesto (24 kilometers, or 15 miles across) appears to be mantled in fine, icy material, although a few craters and some outcrops and/or large boulders are visible. Its smooth surface does not appear to retain the record of intense cratering that most of Saturn’s other moons possess.

The image was taken in polarized green light with the Cassini spacecraft narrow-angle camera on Oct. 11, 2005, at a distance of approximately 14,500 kilometers (9,000 miles) from Telesto. The image scale is 86 meters (283 feet) per pixel.

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 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 operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Modifying Gravity to Account for Dark Matter

Current theories may not describe our Universe very accurately. Image credit: Brussels Museum of Fine Arts, and Space Telescope Institute. Click to enlarge
A Chinese astronomer from the University of St Andrews has fine-tuned Einstein’s groundbreaking theory of gravity, creating a ‘simple’ theory which could solve a dark mystery that has baffled astrophysicists for three-quarters of a century.

A new law for gravity, developed by Dr Hong Sheng Zhao and his Belgian collaborator Dr Benoit Famaey of the Free University of Brussels (ULB), aims to prove whether Einstein’s theory was in fact correct and whether the astronomical mystery of Dark Matter actually exists. Their research was published on February 10th in the US-based Astrophysical Journal Letters. Their formula suggests that gravity drops less sharply with distance as in Einstein, and changes subtly from solar systems to galaxies and to the universe.

Theories of the physics of gravity were first developed by Isaac Newton in 1687 and refined by Albert Einstein’s general theory of relativity in 1905 to allow light bending. While it is the earliest-known force, gravity is still very much a mystery with theories still unconfirmed by astronomical observations in space.

The ‘problem’ with the golden laws of Newton and Einstein is whilst they work very well on earth, they do not explain the motion of stars in galaxies and the bending of light accurately. In galaxies, stars rotate rapidly about a central point, held in orbit by the gravitational attraction of the matter in the galaxy. However astronomers found that they were moving too quickly to be held by their mutual gravity – so not enough gravity to hold the galaxies together instead stars should be thrown off in all directions!

The solution to this, proposed by Fritz Zwicky in 1933, was that there was unseen material in the galaxies, making up enough gravity to hold the galaxies together. As this material emits no light astronomers call it ‘Dark Matter’. It is thought to account for up to 90% of matter in the Universe. Not all scientists accept the Dark Matter theory however. A rival solution was proposed by Moti Milgrom in 1983 and backed up by Jacob Bekenstein in 2004. Instead of the existence of unseen material, Milgrom proposed that astronomers understanding of gravity was incorrect. He proposed that a boost in the gravity of ordinary matter is the cause of this acceleration.

Milgrom’s theory has been worked on by a number of astronomers since and Dr Zhao and Dr Famaey have proposed a new formulation of his work that overcomes many of the problems previous versions have faced.

They have created a formula that allows gravity to change continuously over various distance scales and, most importantly, fits the data for observations of galaxies. To fit galaxy data equally well in the rival Dark Matter paradigm would be as challenging as balancing a ball on a needle, which motivated the two astronomers to look at an alternative gravity idea.

Legend has it that Newton began thinking about gravity when an apple fell on his head, but according to Dr Zhao, “It is not obvious how an apple would fall in a galaxy. Mr Newton’s theory would be off by a large margin – his apple would fly out of the Milky Way. Efforts to restore the apple on a nice orbit around the galaxy have over the years led to two schools of thoughts: Dark Matter versus non-Newtonian gravity. Dark Matter particles come naturally from physics, with beautiful symmetries and explain cosmology beautifully; they tend to be everywhere. The real mystery is how to keep them away from some corners of the universe. Also Dark Matter comes hand- in-hand with Dark Energy. It would be more beautiful if there were one simple answer to all these mysteries”.

Dr Zhao, a PPARC Advanced Fellow at University of St Andrews, School of Physics and Astronomy, and member of the Scottish Universities Physics Alliance (SUPA), continued “There has always been a fair chance that astronomers might rewrite the law of gravity. We have created a new formula for gravity which we call ‘the simple formula’, and which is actually a refinement of Milgrom’s and Bekenstein’s. It is consistent with galaxy data so far, and if its predictions are further verified for solar system and cosmology, it could solve the Dark Matter mystery. We may be able to answer common questions such as whether Einstein’s theory of gravity is right and whether the so-called Dark Matter actually exists”.

“A non-Newtonian gravity theory is now fully specified on all scales by a smooth continuous function. It is ready for fellow scientists to falsify. It is time to keep an open mind for new fields predicted in our formula while we continue our search for Dark Matter particles.”

The new formula will be presented to an international workshop at Edinburgh’s Royal Observatory in April, which will be given the opportunity to test and debate the reworked theory. Dr Zhao and Dr Famaey will demonstrate their new formula to an audience of Dark Matter and gravity experts from ten different countries.

Dr Famaey commented “It is possible that neither the modified gravity theory, nor the Dark Matter theory, as they are formulated today, will solve all the problems of galactic dynamics or cosmology. The truth could in principle lie in between, but it is very plausible that we are missing something fundamental about gravity, and that a radically new theoretical approach will be needed to solve all these problems. Nevertheless, our formula is so attractively simple that it is tempting to see it as part of a yet unknown fundamental theory. All galaxy data seem to be explained effortlessly”.

Original Source: PPARC News Release

Posted on by Fraser Cain

Volcanoes Helped Slow Ocean Warming Trend

The June 12, 1991 eruption column from Mount Pinatubo, Philippines. Image credit: Richard P. Hoblitt/USGS Click to enlarge
Ocean temperatures might have risen even higher during the last century if it weren’t for volcanoes that spewed ashes and aerosols into the upper atmosphere, researchers have found. The eruptions also offset a large percentage of sea level rise caused by human activity.

Using 12 new state-of-the-art climate models, the researchers found that ocean warming and sea level rise in the 20th century were substantially reduced by the 1883 eruption of the Krakatoa volcano in Indonesia. Volcanic aerosols blocked sunlight and caused the ocean surface to cool.

“That cooling penetrated into deeper layers of the ocean, where it remained for decades after the event,” said Peter Gleckler, an atmospheric scientist at Lawrence Livermore National Laboratory (LLNL). “We found that volcanic effects on sea level can persist for many decades.”

Gleckler, along with LLNL colleagues Ben Santer, Karl Taylor and Krishna AchutaRao and collaborators from the National Center for Atmospheric Research, the University of Reading and the Hadley Centre, tested the effects of volcanic eruptions on recent climate models. They examined model simulations of the climate from 1880 to 2000, comparing them with available observations.

External “forcings,” such as changes in greenhouse gases, solar irradiance, sulphate and volcanic aerosols, were included in the models.

Oceans expand and contract depending on the ocean temperature. This causes sea level to increase when the water is warmer and to recede in cooler temperatures.

The volume average temperature of oceans (down to 300 meters) worldwide has warmed by roughly .037 degrees Celsius in recent decades due to increasing atmospheric greenhouse gases. While seemingly small, this corresponds to a sea level rise of several centimeters and does not include the effect of other factors such as melting glaciers. That sea level jump, however, would have been even greater if it weren’t for volcanic eruptions over the last century, Gleckler said.

“The ocean warming suddenly drops,” he said. “Volcanoes have a big impact. The ocean warming and sea level would have risen much more if it weren’t for volcanoes.”

Volcanic aerosols scatter sunlight and cause the ocean surface temperature to cool, an anomaly that is gradually subducted into deeper layers, where it remains for decades.

The experiments studied by Gleckler’s team also included the more recent 1991 Mt. Pinatubo eruption in the Philippines, which was comparable to Krakatoa in terms of its size and intensity. While similar ocean surface cooling resulted from both eruptions, the heat-content recovery occurred much more quickly in the case of Pinatubo.

“The heat content effects of Pinatubo and other eruptions in the late 20th century are offset by the observed warming of the upper ocean, which is primarily due to human influences,” Gleckler said.

The research appears in the Feb. 9 issue of the journal Nature.

Founded in 1952, Lawrence Livermore National Laboratory has a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy’s National Nuclear Security Administration.

Original Source: Lawrence Livermore National Laboratory

Posted on by Fraser Cain

Dig a Big Hole on Mars to Search for Life

THOR will search for water ice in potentially habitable zones. Image credit: NASA Click to enlarge
A proposed new robotic mission to Mars plans to make the first exploration of subsurface water ice in a potentially habitable zone.

If approved, the Tracing Habitability, Organics and Resources (THOR) project ? a low-cost mission designed for NASA’s Mars Scout program ? aims to send a projectile at high speed into the Martian surface while observing the impact and its aftermath. The mission would be led by ASU, in partnership with the Jet Propulsion Laboratory (JPL).

The THOR mission, planned for launch in 2011, aims to use a direct approach to excavating material from beneath the surface of Mars: blasting it out.

“The mission’s goal is to expose snow and ice in a previously unexplored part of Mars: the deep subsurface,” says THOR’s principal investigator, Phil Christensen of ASU’s Mars Space Flight Facility. “We’ll do this by blowing a crater at least 30 feet deep in the Martian ground.”

Besides finding underground water, he says, THOR also proposes to look for organic compounds, including methane, which Earth-based telescopes and other Mars spacecraft have detected in the Martian atmosphere.

The mission aims to use a two-part spacecraft, which consists of an “impactor” probe and an observer craft. The impactor is a simple projectile made of pure Arizona copper. The observer spacecraft will carry it until shortly before reaching Mars. After being released from the observer, the impactor will streak through the Martian atmosphere to an impact site lying between 30 degrees and 60 degrees latitude, in either the northern or southern hemisphere of the Red Planet.

“In many areas of Mars’ middle latitudes, we see tantalizing evidence of dust-covered layers of snow or ice,” Christensen says. “THOR will aim for this material.”

The suspected ice-rich layers were deposited during the past 50,000 to 1 million years, as the Martian climate changed because of orbital variations.

According to the mission plan, when the impactor slams into the ground, it will dig a crater more than 30 feet (10 meters) deep. The observer spacecraft will study the debris plume jetting from the impact site.

The observer’s instruments will include a visible-light camera and an infrared spectrometer. In addition to studying the plume, the spectrometer’s role is to search the Martian atmosphere for organic materials and gases, such as methane.

In the past, Christensen notes, Mars has been studied using fly-by and orbiter spacecraft, and with landers. While highly valuable, such missions have only scratched the surface, he says.

“The time has come to take Martian studies a step further ? and deeper,” Christensen says. “This unexplored region of Mars may provide chemical and mineral clues to tell us about habitable areas on the planet.”

“The THOR mission plans to use a straightforward, low-risk approach to reach the Martian subsurface,” says JPL’s David Spencer, the study lead engineer for THOR.

Spencer is the former mission manager for Deep Impact, the comet mission that pioneered the impact technique.

In comparing the two missions, Spencer says, “With such a large target region on Mars, delivering THOR’s impactor will be less challenging than the Deep Impact comet encounter.”

Christensen sees THOR’s scientific value continuing far beyond the impact.

“THOR’s crater will remain a test-site for all current Mars spacecraft and those in years to come,” he says. “The crater might also be visited on the ground by a future Mars rover, sometime in the next decade.”

NASA’s Mars Scouts are competitively proposed missions designed to advance the goals of NASA’s Mars exploration program. The Mars Scout Program is managed by JPL for NASA’s Office of Space Science, based in Washington.

Original Source: ASU News Release

Posted on by Fraser Cain

Titanic Complexity

Titan’s complex atmosphere. Image credit: NASA/JPL/SSI Click to enlarge
This view of Titan reveals structure in the moon’s complex atmosphere. The geometry of the Cassini spacecraft’s view of Titan during this flyby was similar to that of Voyager 1’s pass in 1980.

The view has been greatly contrast-enhanced and shows intriguing structure in the north of Titan (5,150 kilometers, or 3,200 miles across) that is also clearly visible in a violet light view (see PIA07701) taken at about the same time.

The color view was created by combining images taken using red, green and blue spectral filters. The images were taken with the Cassini spacecraft wide-angle camera on Dec. 26, 2005, at a distance of approximately 193,000 kilometers (120,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 29 degrees. The image scale is 11 kilometers (7 miles) per pixel.

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 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 operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Ancient Impact Might Have Created the “Man In The Moon”

The Moon. Image credit: NASA Click to enlarge
Ohio State University planetary scientists have found the remains of ancient lunar impacts that may have helped create the surface feature commonly called the “man in the moon.”

Their study suggests that a large object hit the far side of the moon and sent a shock wave through the moon’s core and all the way to the Earth-facing side. The crust recoiled — and the moon bears the scars from that encounter even today.

The finding holds implications for lunar prospecting, and may solve a mystery about how past impacts on Earth affect it’s geology today.

The early Apollo missions revealed that the moon isn’t perfectly spherical. Its surface is warped in two spots; an earth-facing bulge on the near side is complemented by a large depression on the Moon’s far side. Scientists have long wondered whether these surface features were caused by Earth’s gravity tugging on the moon early in its existence, when its surface was still molten and malleable.

According to Laramie Potts and Ralph von Frese, a postdoctoral researcher and professor of geological sciences respectively at Ohio State , these features are instead remnants from ancient impacts.

Potts and von Frese came to this conclusion after they used gravity fluctuations measured by NASA’s Clementine and Lunar Prospector satellites to map the moon’s interior. They reported the results in a recent issue of the journal Physics of the Earth and Planetary Interiors.

They expected to see defects beneath the moon’s crust that corresponded to craters on the surface. Old impacts, they thought, would have left marks only down to the mantle, the thick rocky layer between the moon’s metallic core and its thin outer crust. And that’s exactly what they saw, at first.

Potts pointed to a cross-sectional image of the moon that the scientists created using the Clementine data. On the far side of the moon, the crust looks as though it was depressed and then recoiled from a giant impact, he said. Beneath the depression, the mantle dips down as he and von Frese would expect it to do if it had absorbed a shock.

Evidence of the ancient catastrophe should have ended there. But some 700 miles directly below the point of impact, a piece of the mantle still juts into the moon’s core today.

That was surprising enough. “People don’t think of impacts as things that reach all the way to the planet’s core,” von Frese said.

But what they saw from the core all the way to the surface on the near side of the moon was even more surprising. The core bulges, as if core material was pushed in on the far side and pulled out into the mantle on the near side. Above that, an outward-facing bulge in the mantle, and above that — on the Earth-facing side of the moon — sits a bulge on the surface.

To the Ohio State scientists, the way these features line up suggests that a large object such as an asteroid hit the far side of the moon and sent a shock wave through the core that emerged on the near side.

The scientists believe that a similar, but earlier impact occurred on the near side.

Potts and von Frese suspect that these events happened about four billion years ago, during a period when the moon was geologically active — with its core and mantle still molten and magma flowing.

Back then, the moon was much closer to the Earth than it is today, Potts explained, so the gravitational interactions between the two were stronger. When magma was freed from the Moon’s deep interior by the impacts, Earth’s gravity took hold of it and wouldn’t let go.

So the warped surfaces on the near and far sides of the moon and the interior features that connect them are all essentially signs of injuries that never healed.

“This research shows that even after the collisions happened, the Earth had a profound effect on the moon,” Potts said.

The impacts may have created conditions that led to a prominent lunar feature.

The “man in the moon” is a collection of dark plains on the Earth-facing side of the moon, where magma from the moon’s mantle once flowed out onto the surface and flooded lunar craters. The moon has long since cooled, von Frese explained, but the dark plains are a remnant of that early active time — “a frozen magma ocean.”

How that magma made it to the surface is a mystery, but if he and Potts are right, giant impacts could have created a geologic “hot spot” on the moon ? a site where magma bubbles to the surface. Some time between when the impacts occurred and when the moon solidified, some magma escaped the mantle through cracks in the crust and flooded the nearside surface and formed a lunar ?hot spot?.

A hot spot on Earth forms the volcanoes that make the Hawaiian island chain. The Ohio State scientists wondered: could similar ancient impacts have penetrated the Earth, and caused the hot spots that exist here today? von Frese thinks that it’s possible.

“Surely Earth was peppered with impacts, too,” he said. “Evidence of impacts here is obscured, but there are hot spots like Hawaii . Some hot spots have corresponding hot spots on the opposite side of the Earth. That could be a consequence of this effect.”

He and Potts are exploring the idea, by studying gravitational anomalies under the Chicxulub Crater on Mexico ‘s Yucatan Peninsula . A giant asteroid struck the spot some 65 million years ago, and is believed to have set off an environmental chain reaction that killed the dinosaurs.

NASA funded this research. The space agency has been charged with returning astronauts to the moon to prospect for valuable gases and minerals.

But even today, scientists don’t entirely know what the moon is made of ? not down to the core, anyway. They can calculate where certain minerals should be, given the conditions they believe existed when the moon formed. But impacts like the one Potts and von Frese discovered have since shuffled materials around. Gravity measurements, they said, will play a key role as scientists figure out what materials lie within the moon, and where.

“We don’t fully understand the way these minerals settle out under temperature and pressure, so the exact composition of the moon is difficult to determine. We have to use gravity measurements to calculate the density of materials, and then use that information to extrapolate the likely composition,” Potts said.

von Frese said a lunar base would be needed before scientists can more completely answer these questions.

Potts agreed. “Once we have more rock samples and soil samples, we will have a lot more to go on. Nothing is better than having a person on the ground,” he said.

Original Source: OSU News Release

Posted on by Fraser Cain

Integral Uses the Earth to Search for Cosmic Radiation

Artist’s impression of Integral observing Earth. Image credit: ESA Click to enlarge
Cosmic space is filled with continuous, diffuse high-energy radiation. To find out how this energy is produced, the scientists behind ESA’s Integral gamma-ray observatory have tried an unusual method: observing Earth from space.

During a four-phase observation campaign started on 24 January this year, continued until 9 February, Integral has been looking at Earth. Needing complex control operations from the ground, the satellite has been kept in a fixed orientation in space, while waiting for Earth to drift through its field of view.

Unusually, the main objective of these observations is not Earth itself, but what can be seen in the background when Earth moves in front of the satellite. This is the origin of the diffuse high-energy radiation known as the ‘cosmic X-ray background’.

Until now with Integral, this was never studied simultaneously with such a broad band of energy coverage since the 1970s, and certainly not with such advanced instruments.

Astronomers believe that the ‘cosmic X-ray background’ is produced by numerous supermassive and accreting black holes, distributed throughout deep space. These powerful monsters attract matter, which is then hugely accelerated and so emit high energy in the form of gamma- and X-rays.

X-ray observatories such as ESA’s XMM-Newton and NASA’s Chandra have been able to identify and directly count a large number of individual sources ? likely black holes ? that already account for more than 80 percent of the measured cosmic diffuse X-ray background.

However, very little is known about the origin of the highest energy band of this cosmic radiation, above the range of these two satellites. This is spread out in the form of high-energy X- and gamma-rays, within the reach of Integral.

It is believed that most of the gamma-ray background emission is produced by individual supermassive black holes too, but scientists need to couple this emission with clearly identified sources to make a definitive statement. In fact, other sources such as far-away galaxies or close weak sources could be also be responsible.

Identifying the individual sources in the gamma-ray range that make up the diffuse cosmic background is much more difficult than counting the individual X-ray sources. In fact, the powerful gamma-rays cannot be focused with lenses or mirrors, because they simply pass straight through.

So to produce a gamma-ray image of a source, Integral uses a ‘mask’ technique – an indirect imaging method that consists of detecting the shadow of a mask placed on top of the telescope, as projected by a gamma-ray source.

During the observations, the scientists used Earth’s disk as an ‘extra mask’. Earth naturally blocks, or shades, the highest energy flux from millions of distant black holes.

Their combined flux can be accurately measured in an indirect way, that is by measuring the amplitude and the energy spectrum of the energy drop when Earth passes through Integral’s field of view. Once this is known, scientists can eventually try to connect the radiation to individual sources.

All the observations were very successful, as all the gamma-ray and X-ray instruments on board Integral (IBIS, SPI and JEM-X) recorded clear and unambiguous signals in line with expectations.

The Integral scientists are already proceeding with the analysis of the data. The aim is to ultimately understand the origin of the highest energy background radiation and, possibly, provide new clues on the history of growth of super-massive black holes since the early epochs of the Universe.

Original Source: ESA Portal

Posted on by Fraser Cain

What’s Up This Week – February 13 – February 19, 2006

Lunar halo. Image credit: Steve Mandel. Click to enlarge.
Monday, February 13 – Tonight is Full Moon. During the month of February the upper northern hemisphere is often heavy with snow. Native Indian tribes of the north and east called February’s Full Moon the Full Snow Moon. Some tribes also referred to this Moon as the Full Hunger Moon as artic weather conditions often made hunting and food gathering very unproductive.

Tonight let’s have a look at a pair of single stars that make up Gemini (the Twins): Castor and Pollux.

In Greek mythology, Castor and Pollux were fathered by the Greek god Zeus (Jupiter) who took the form of a swan and came upon a beautiful mortal woman. Pollux later grew up to become a skilled boxer and Castor, a master horseman. The two brothers were inseparable. It is said that they rescued the beautiful Helen from Troy, traveled with Jason and the Argonauts, and ultimately found themselves in a mortal battle with another pair of twin brothers over a beautiful woman. Pollux was so grief stricken at Castor’s death that he cried out to Zeus and offered up his own immortality in exchange for Castor’s life. Zeus took pity on the twins and placed them in the sky. You can see them tonight with your own eyes joined seemingly eternally together in Gemini.

As you observe this pair note that although Castor is almost half a magnitude fainter than Pollux, Bayer gave that star the title “Alpha Geminorum.” Which one do you think appears brighter? There’s more about both stars to come.

Tuesday, February 14 – Happy Valentine’s Day! Today is the birth date of Fritz Zwicky. Born in 1898, Zwicky was the first astronomer to identify supernovae as a separate class of objects. His insights also proposed the possibility of neutron stars. Among his many achievements, Zwicky catalogued galaxy clusters and designed jet engines. He also suggested the redshift displayed in the spectra of distant galaxies could be caused by something other than universal expansion.

Tonight’s lunar feature for telescopes and binoculars is crater Langrenus. Named for the Belgian engineer and mathematician Michel Florent van Langren, crater Langrenus is easily found along the terminator slightly south of central. At this time its 132 km expanse will appear shallow and display a luminous central peak.

Since you have your scope out, why not turn it towards one of the brightest double stars in the night sky – Alpha Geminorum. It’s true. One of the twins is a twin! Separated by a little more than 3 arc seconds, this true binary pair of 2nd magnitude stars make Castor a splendid study – even in the smallest scopes.

Wednesday, February 15 – Born on this day in 1564 was the man who “fathered” modern astronomy – Galileo Galilei. Almost 4 centuries ago, Galileo became the first scientist to use a telescope for astronomical purposes and his first study was the Moon. His words, “Most beautiful and admirable is it to see the Moon’s luminous form… At nearly thirty diameters – some 900 times greater in region – anyone can perceive that the Moon is not covered with a smooth and uniform surface but in fact reveals great mountainous shelves, deep cavities, and gorges just like those of the Earth,” still echo true today.

Tonight the tiny crater named for Galileo will be visible on the surface, but seeing it – even in a telescope – will be a challenge. Look to the fully illuminated western edge. Almost central and caught on the edge of Oceanus Procellarum, you will see a small, bright ring. This is crater Reiner. You will find Galileo just a short hop to the northwest as a tiny, washed out feature. What a shame the cartographers did not pick a more vivid feature to honor the great Galileo!

Galileo is noted for making many wondrous discoveries, but did you know that he may have been the first astronomer to see the Trapezium in M42? Galileo included three of the four stars in a sketch based on what is probably a low power (27x) view of the Great Nebula. Tonight celebrate that unheralded discovery by using the lowest possible magnification and the smallest telescope you can find to get the “Galileo-eye view” of the Trapezium.

Thursday, February 16 – Today celebrates the birth of Francois Arago. Born in 1786, Arago was an early and enthusiastic supporter of the wave theory of light. His scientific achievements were many – including the 1811 invention of the polariscope. Arago was also a practiced astronomer and wrote 4 volumes entitled Astronomie Populaire in the mid-1800s. Arago’s polariscope revealed that light could be organized in such a way as to cause photons to have a similar electromagnetic orientation. Polarized light viewed through his polariscope could come close to disappearing when the instrument was rotated. Many amateur astronomers use polarizing filters to reduce the amount of glare from the Moon, but did you know that even starlight can be polarized?

In celebration of Arago’s birth, why not go out and have a look at one such star – Merope in the Pleiades. As you observe Merope keep in mind that its light doesn’t begin polarized. In passing through the Merope Nebula, it becomes filtered. Try using a polarized filter and compare the view without.

On this day in 1948, Gerard Kuiper was celebrating the discovery of Miranda – one of Uranus’ moons. At magnitude 16, few of us will ever see Kuiper’s discovery for ourselves. With Uranus now close to the Sun (near Lambda Aquarii), even it will be hard to see!

Friday, February 17 – For SkyWatchers this morning, many of you will have the opportunity to watch the Moon occult bright Spica – Alpha Virginis. Be sure to check with IOTA for times and locales.

Early evening means dark skies, so let’s take the opportunity to revisit two of the three Messier open clusters in Auriga and compare them with the similar, but fainter, NGC 1893.

NGC 1893 is similar to M36 in size, but four times fainter. On a good night, a small telescope can resolve more than a dozen faint stars in this 13,000 light-year distant open cluster. To find it, look around 3 degrees southwest of M38 and west of M36. The three clusters form an even triangle in the sky. In large binoculars or a rich-field telescope, the trio can be seen together as nebulous mists sprinkled with faint stars. Remember this cluster is also four times more distant than the Messier objects it shares Auriga with. It is estimated to be 10 million years old and it’s still in the process of giving birth to new stars. Reflection nebula IC 410 is also part of the NGC 1893. See if you can spot it!

Saturday, February 18 – On this day in 1930, a young man named Clyde Tombaugh was very busy with some photographic plates taken with the Lowell Observatory’s 13″ telescope. His reward? The discovery of Pluto!

Clyde discovered Pluto on a set of plates centered on the star Delta Geminorum – Wasat – a star lying very near the path the Sun takes across the sky. While we can’t see Pluto tonight, we can study this fine 3.5 magnitude star and its disparate companion.

Once you’ve studied Wasat, you may notice Saturn gracing the early evening sky. As you observe Saturn’s magnificent ring system and four or five brightest moons, give some thought to distance and size. If our solar system was measured in units based on the Saturn-Sun distance – rather than Earth-Sun, Pluto would be 3.4 AUs from Sol. At 2274 kilometers in diameter, Pluto is less than half the size of Saturn’s largest satellite – Titan!

For deep sky, have a look at the rich open cluster NGC 2129. Located about a fingerwidth west of M35, at low power it may appear in the same field as Propus – 1 Geminorum. A rich-field scope or binoculars will frame M35 and NGC 2129 together.

Sunday, February 19 – Today is the birthday of Nicolas Copernicus. Born in 1473, Copernicus envisioned the modern solar system model which explained the retrograde motion of the outer planets. Considering this was well over 530 years ago, and in a rather unenlightened time, his revolutionary thinking is astounding. If you are up later, you can see the mighty crater named for Copernicus on the lunar surface almost central and west of the terminator.

But, before the Moon rises tonight, let’s turn our telescopes towards Saturn – one solar system body whose motion through the heavens exemplifies much of what Copernicus hoped his concept could explain! Among the “seven classical planets,” Saturn moves the slowest, taking almost two and a half years to move the thirty degrees related to each of the twelve “stations” planets pass through as they circle the ecliptic. Because of its slow pace, Saturn is often associated with “Chronos,” or Father Time, who wields his scythe and harvests a 30 year-long generation of humankind. Right now, Saturn is stationed in Cancer the Crab – one of the twelve “zodiacal,” or “animal signs” of the ecliptic. The Crab is joined with eleven other animals – preceded by neighboring Gemini, “the twin men,” and followed by Leo, “the solitary Lion.” By putting the Sun in the center of all this – rather than the Earth – Copernicus freed human thinking from the more ancient Ptolemaic system and allowed the solar Lion to stand at the center of things instead.

So, have another look at Saturn. Enjoy its low-contrast southern equatorial belt, subtly mottled blue polar region, and fine system of four easily seen satellites each moving much more rapidly around Saturn than the planet itself does around the Sun. Then think “Wow, that Copernicus guy would really have enjoyed seeing this!”

May all your journeys be at light speed… ~Tammy Plotner. Contibuting writer: Jeff Barbour @ astro.geekjoy.com