Posted on by Fraser Cain

Water Once Drenched Regions of Mars

Image credit: NASA/JPL
Scientists have concluded the part of Mars that NASA’s Opportunity rover is exploring was soaking wet in the past.

Evidence the rover found in a rock outcrop led scientists to the conclusion. Clues from the rocks’ composition, such as the presence of sulfates, and the rocks’ physical appearance, such as niches where crystals grew, helped make the case for a watery history.

“Liquid water once flowed through these rocks. It changed their texture, and it changed their chemistry,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science instruments on Opportunity and its twin, Spirit. “We’ve been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion.”

Dr. James Garvin, lead scientist for Mars and lunar exploration at NASA Headquarters, Washington, said, “NASA launched the Mars Exploration Rover mission specifically to check whether at least one part of Mars ever had a persistently wet environment that could possibly have been hospitable to life. Today we have strong evidence for an exciting answer: Yes.”

Opportunity has more work ahead. It will try to determine whether, besides being exposed to water after they formed, the rocks may have originally been laid down by minerals precipitating out of solution at the bottom of a salty lake or sea.

The first views Opportunity sent of its landing site in Mars’ Meridiani Planum region five weeks ago delighted researchers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., because of the good fortune to have the spacecraft arrive next to an exposed slice of bedrock on the inner slope of a small crater.

The robotic field geologist has spent most of the past three weeks surveying the whole outcrop, and then turning back for close-up inspection of selected portions. The rover found a very high concentration of sulfur in the outcrop with its alpha particle X-ray spectrometer, which identifies chemical elements in a sample. “The chemical form of this sulfur appears to be in magnesium, iron or other sulfate salts,” said Dr. Benton Clark of Lockheed Martin Space Systems, Denver. “Elements that can form chloride or even bromide salts have also been detected.”

At the same location, the rover’s Moessbauer spectrometer, which identifies iron-bearing minerals, detected a hydrated iron sulfate mineral called jarosite. Germany provided both the alpha particle X- ray spectrometer and the Moessbauer spectrometer. Opportunity’s miniature thermal emission spectrometer has also provided evidence for sulfates.

On Earth, rocks with as much salt as this Mars rock either have formed in water or, after formation, have been highly altered by long exposures to water. Jarosite may point to the rock’s wet history having been in an acidic lake or an acidic hot springs environment.

The water evidence from the rocks’ physical appearance comes in at least three categories, said Dr. John Grotzinger, sedimentary geologist from the Massachusetts Institute of Technology, Cambridge: indentations called “vugs,” spherules and crossbedding.

Pictures from the rover’s panoramic camera and microscopic imager reveal the target rock, dubbed “El Capitan,” is thoroughly pocked with indentations about a centimeter (0.4 inch) long and one-fourth or less that wide, with apparently random orientations. This distinctive texture is familiar to geologists as the sites where crystals of salt minerals form within rocks that sit in briny water. When the crystals later disappear, either by erosion or by dissolving in less-salty water, the voids left behind are called vugs, and in this case they conform to the geometry of possible former evaporite minerals.

Round particles the size of BBs are embedded in the outcrop. From shape alone, these spherules might be formed from volcanic eruptions, from lofting of molten droplets by a meteor impact, or from accumulation of minerals coming out of solution inside a porous, water-soaked rock. Opportunity’s observations that the spherules are not concentrated at particular layers in the outcrop weigh against a volcanic or impact origin, but do not completely rule out those origins.

Layers in the rock that lie at an angle to the main layers, a pattern called crossbedding, can result from the action of wind or water. Preliminary views by Opportunity hint the crossbedding bears hallmarks of water action, such as the small scale of the crossbedding and possible concave patterns formed by sinuous crestlines of underwater ridges.

The images obtained to date are not adequate for a definitive answer. So scientists plan to maneuver Opportunity closer to the features for a better look. “We have tantalizing clues, and we’re planning to evaluate this possibility in the near future,” Grotzinger said.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington.

For information about NASA and the Mars mission on the Internet, visit http://www.nasa.gov. Images and additional information about the project are also available at http://marsrovers.jpl.nasa.gov and http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Black Holes Maintain Their Information

Image credit: NASA
Stephen Hawking and Kip Thorne may owe John Preskill a set of encyclopedias.

In 1997, the three cosmologists made a famous bet as to whether information that enters a black hole ceases to exist — that is, whether the interior of a black hole is changed at all by the characteristics of particles that enter it.

Hawking?s research suggested that the particles have no effect whatsoever. But his theory violated the laws of quantum mechanics and created a contradiction known as the ?information paradox.?

Now physicists at Ohio State University have proposed a solution using string theory, a theory which holds that all particles in the universe are made of tiny vibrating strings.

Samir Mathur and his colleagues have derived an extensive set of equations that strongly suggest that the information continues to exist — bound up in a giant tangle of strings that fills a black hole from its core to its surface.

The finding suggests that black holes are not smooth, featureless entities as scientists have long thought.

Instead, they are stringy ?fuzzballs.?

Mathur, professor of physics at Ohio State, suspects that Hawking and Thorne won?t be particularly surprised by the outcome of the study, which appears in the March 1 issue of the journal Nuclear Physics B.

In their wager, Hawking, professor of mathematics at the University of Cambridge, and Thorne, professor of theoretical physics at Caltech, bet that information that enters a black hole is destroyed, while Preskill — also a professor of theoretical physics at Caltech — took the opposite view. The stakes were a set of encyclopedias.

?I think that most people gave up on the idea that information was destroyed once the idea of string theory rose to prominence in 1995,? Mathur said. ?It?s just that nobody has been able to prove that the information survives before now.?

In the classical model of how black holes form, a supermassive object, such as a giant star, collapses to form a very small point of infinite gravity, called a singularity. A special region in space surrounds the singularity, and any object that crosses the region?s border, known as the event horizon, is pulled into the black hole, never to return.

In theory, not even light can escape from a black hole.

The diameter of the event horizon depends on the mass of the object that formed it. For instance, if the sun collapsed into a singularity, its event horizon would measure approximately 3 kilometers (1.9 miles) across. If Earth followed suit, its event horizon would only measure 1 centimeter (0.4 inches).

As to what lies in the region between a singularity and its event horizon, physicists have always drawn a blank, literally. No matter what type of material formed the singularity, the area inside the event horizon was supposed to be devoid of any structure or measurable characteristics.

And therein lies the problem.

?The problem with the classical theory is that you could use any combination of particles to make the black hole — protons, electrons, stars, planets, whatever — and it would make no difference. There must be billions of ways to make a black hole, yet with the classical model the final state of the system is always the same,? Mathur said.

That kind of uniformity violates the quantum mechanical law of reversibility, he explained. Physicists must be able to trace the end product of any process, including the process that makes a black hole, back to the conditions that created it.

If all black holes are the same, then no black hole can be traced back to its unique beginning, and any information about the particles that created it is lost forever at the moment the hole forms.

?Nobody really believes that now, but nobody could ever find anything wrong with the classical argument, either,? Mathur said. ?We can now propose what went wrong.?

In 2000, string theorists named the information paradox number eight on their top-ten list of physics problems to be solved during the next millennium. That list included questions such as ?what is the lifetime of a proton?? and ?how can quantum gravity help explain the origin of the universe??

Mathur began working on the information paradox when he was an assistant professor at the Massachusetts Institute of Technology, and he attacked the problem full time after joining the Ohio State faculty in 2000.

With postdoctoral researcher Oleg Lunin, Mathur computed the structure of objects that lie in-between simple string states and large classical black holes. Instead of being tiny objects, they turned out to be large. Recently, he and two doctoral students — Ashish Saxena and Yogesh Srivastava — found that the same picture of a ?fuzzball? continued to hold true for objects more closely resembling a classic black hole. Those new results appear in Nuclear Physics B.

According to string theory, all the fundamental particles of the universe — protons, neutrons, and electrons — are made of different combinations of strings. But as tiny as strings are, Mathur believes they can form large black holes through a phenomenon called fractional tension.

Strings are stretchable, he said, but each carries a certain amount of tension, as does a guitar string. With fractional tension, the tension decreases as the string gets longer.

Just as a long guitar string is easier to pluck than a short guitar string, a long strand of quantum mechanical strings joined together is easier to stretch than a single string, Mathur said.

So when a great many strings join together, as they would in order to form the many particles necessary for a very massive object like a black hole, the combined ball of string is very stretchy, and expands to a wide diameter.

When the Ohio State physicists derived their formula for the diameter of a fuzzy black hole made of strings, they found that it matched the diameter of the black hole event horizon suggested by the classical model.

Since Mathur?s conjecture suggests that strings continue to exist inside the black hole, and the nature of the strings depends on the particles that made up the original source material, then each black hole is as unique as are the stars, planets, or galaxy that formed it. The strings from any subsequent material that enters the black hole would remain traceable as well.

That means a black hole can be traced back to its original conditions, and information survives.

This research was supported in part by the U.S. Department of Energy.

Original Source: Ohio State University News Release

Posted on by Fraser Cain

Both Rovers Working on Rocks

Image credit: NASA/JPL
Spirit Status for sol 55
Spirit used its rock abrasion tool for brushing the dust off three patches of a rock called “Humphrey,” during its 55th sol on Mars, ending at 5:53 p.m. Saturday, PST. Before applying the wire-bristled brush, the rover inspected the surface of the rock with its microscope and with its alpha particle X-ray spectrometer, which identifies elements that are present. Brushing three different places on a rock one right after another was an unprecedented use of the rock abrasion tool, designed to provide a larger cleaned area for examining.

Afterwards, Spirit rolled backward 85 centimeters (2.8 feet) to a position from which it could use its miniature thermal emission spectrometer on the cleaned areas for assessing what minerals are present. Due to caution about potential hazards while re-approaching “Humphrey,” the rover moved only part of the way back. Plans for sol 56, ending at 6:33 p.m. Sunday, PST, call for finishing that re-approach and further inspecting the brushed areas. If all goes well, the rock abrasion tool’s diamond-toothed grinding wheel will cut into the rock on sol 57 to expose fresh interior material.

For wake-up music on sol 55, controllers chose “Brush Your Teeth,” by Cathy Fink and Marcy Marxer, and “Knock Three Times,” by Tony Orlando and Dawn.

Opportunity Status for sol 35
During its 35th sol on Mars, ending at 6:14 a.m. Sunday, PST, Opportunity manipulated the microscopic imager at the tip of its arm for eight observations of the fine textures of an outcrop-rock target called “Guadalupe.” The observations include frames to be used for developing stereo and color views.

Opportunity also used its Moessbauer spectrometer and, after an overnight switch, its alpha particle X-ray spectrometer to assess the composition of the interior material of “Guadalupe” exposed yestersol by a grinding session with the rock abrasion tool.

The panoramic camera up on the rover’s mast captured a new view toward the eastern horizon beyond the crater where Opportunity is working, for use in evaluating potential drive directions after the rover leaves the crater.

Jimmy Cliff’s “I Can See Clearly Now,” was played in the mission support area at JPL as Opportunity’s sol 35 wake-up music.

Plans for sol 36, ending at 6:54 a.m. Monday, PST, called for finishing the close-up inspection of “Guadalupe,” then backing up enough to give the panoramic camera and miniature emission spectrometer good views of the area where the rock interior has been exposed by grinding.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Simulating Titan’s Atmosphere in the Lab

Image credit: ESA
It takes at least three elements to harbor life as we know it: water, energy and an atmosphere. Among Mars and the moons around both Jupiter and Saturn, there is evidence of one or two of these three elements, but less is known if a complete set is available. Only Saturn’s moon, Titan, has an atmosphere comparable to Earth’s in pressure, and is much thicker than the martian one (1% of Earth’s sea level pressure).

The most interesting point about simulations of Titan’s hydrocarbon haze is that this smoggy component contains molecules called tholins (from the Greek word, muddy) that can form the foundations of the building blocks of life. For example, amino acids, one of the building blocks of terrestrial life, form when these red-brown smog-like particles are placed in water. As Carl Sagan pointed out, Titan may be regarded as a broad parallel to the early terrestrial atmosphere with respect to its chemistry and in this way, it is certainly relevant to the origins of life.

This summer, NASA’s Cassini spacecraft, launched in 1997, is scheduled to go into orbit around Saturn and its moons for four years. In early 2005, the piggybacking Huygens probe is scheduled to plunge into the hazy Titan atmosphere and land on the moon’s surface. There are 12 instruments onboard the Cassini Spacecraft orbiter, and 6 instruments onboard the Huygens Probe. The Huygens probe is geared primarily towards sampling the atmosphere. The probe is equipped to take measurements and record images for up to a half an hour on the surface. But the probe has no legs, so when it sets down on Titan’s surface its orientation will be random. And its landing may not be by a site bearing organics. Images of where Cassini is in its current orbit are continuously updated and available for view as the mission progresses.

Astrobiology Magazine had an opportunity to talk with research scientist, Jean-Michel Bernard of the University of Paris, about how to simulate Titan’s complex chemistry in a terrestrial test tube. His simulations of Titan’s environment build on the classic prebiotic soup, first pioneered fifty years ago by University of Chicago researchers, Harold Urey and Stanley Miller.

Astrobiology Magazine (AM): What first stimulated your interest in the atmospheric chemistry of Titan?

Jean-Michel Bernard (JB): How do two simple molecules (nitrogen and methane) create a very complex chemistry? Does chemistry become biochemistry? The recent discoveries of life in extreme conditions on Earth (bacteria in the South Pole at -40?C and archaea at more than +110?C in the vicinity of hydrothermal sources) allow to suppose that life could be present on other worlds and other conditions.

Titan has astrobiological interest because it is the only satellite in the solar system with a dense atmosphere. Titan’s atmosphere is made of nitrogen and methane. The energetic particles coming from the Sun and Saturn’s environment allow complex chemistry, such as formation of hydrocarbons and nitriles. The particles also generate a permanent haze around the satellite, rains of methane, winds, seasons Recently, lakes of hydrocarbons seem to have been detected on Titan’s surface. I think that this discovery, if it is confirmed by the Cassini-Huygens mission, will be of great interest.

It would make Titan an analog to the Earth, since it would have an atmosphere (gas), lakes (liquid), haze and soil (solid), the three necessary environments for the appearance of life.

The composition of Titan’s haze is unknown. Only optical data are available and they are difficult to analyze due to the complexity of this carbonaceous material. Many experiments have been carried out in order to mimic the chemistry of Titan’s atmosphere, most notably the aerosols analogs named “tholins” by Carl Sagan’s group. It seems that tholins could be involved in the origin of life. Indeed, hydrolysis of these Titan aerosol analogs gives rise to the formation of amino acids, the precursors of life.

AM: Can you describe your experimental simulation for extending the Miller-Urey experiments in a way that is customized for Titan’s low temperatures and unique chemistry?

JB: Since the Miller-Urey experiments, many experimental simulations of supposed prebiotic system have been carried out. But after the retrieval of Voyager’s data, it appeared necessary to come back to this approach to simulate Titan’s atmosphere. Then several scientists carried out such simulation experiments by introducing a nitrogen-methane mixture in a system like Miller’s apparatus. But a problem became obvious due to the difference between the experimental conditions and Titan’s conditions. The pressure and temperature were not representative of Titan’s environment. Then we decided to carry out experiments which reproduce the pressure and the temperature of Titan’s stratosphere: a gas mixture of 2% of methane in nitrogen, a low pressure (about 1 mbar) and a cryogenic system in order to have a low temperature. Furthermore, our system is placed in a glove box containing pure nitrogen in order to avoid contamination by ambient air of the solid products.

AM: What do you consider the best energy source for triggering Titan’s synthetic chemistry: the magnetosphere of Saturnian particles, solar radiation, or something else?

JB: Scientists debate about what energy source would best simulate the energy sources in Titan’s atmosphere. Ultraviolet (UV) radiation? Cosmic rays? Electrons and other energetic particles coming from Saturn’s magnetosphere? All these sources are involved, but their occurence depends of the altitude: extreme ultraviolet radiation and electrons in the ionosphere, UV light in the stratosphere, while cosmic rays occur in the troposphere.

I think the appropriate question should be: What is the experimental goal? If it is to understand the hydrogen cyanide (HCN) chemistry in Titan’s stratosphere, a simulation with UV radiation of HCN is appropriate. If the goal is to determine the effects of electric fields generated by galactic cosmic rays in the troposphere, a corona discharge of a simulated Titan-atmosphere is preferable.

In studying Titan’s stratospheric conditions, we chose to use an electric discharge in our simulation. This choice is contested by a minority of scientists because the main energy source in Titan’s stratosphere is UV radiation. But our results validated our experiment. We detected all the organic species observed on Titan. We predicted the presence of CH3CN (acetonitrile) before its observation. We detected for the first time dicyanoacetylene, C4N2, an unstable molecule at room temperature that has also been detected in Titan’s atmosphere. The middle infrared signature of the solid products created in our experiment was in line with Titan observations.

AM: How are your results part of the planned atmospheric testing for the Cassini-Huygens probe?

JB: After collaborating with a team from the Observatoire Astronomique de Bordeaux in France, we determined the dielectric constants of aerosol analogs. This will allow us to estimate how Titan’s atmosphere and surface properties could affect the performance of the Cassini-Huygens radar experiments. The altimeter onboard the Huygens probe could be affected by the aerosol properties, but complementary experiments must be carried out to confirm this result.

Two years ago, we introduced a gas mixture, N2/CH4/CO (98/1.99/0.01). The goal was to determine the impact of carbon monoxide, the most abundant oxygenated compound on Titan. Surprisingly, we detected oxirane in the gaseous phase as the major oxygenated product. This unstable molecule was discovered in the interstellar medium but theoretical models do not predict it for Titan’s chemistry. Yet maybe this molecule is present on Titan.

Currently, we are analyzing the first molecules, radicals, atoms and ions (or ‘species’) created inside our experimental reactor. We are using infrared spectrometry and UV-visible emission to study excited species like CN, CH, NH, C2, HCN, C2H2. Next, we will observe the correlation between the abundance of these species and the structures of the solid products. . Coupling these experimental results with a theoretical model developed in collaboration with the University of Porto in Portugal, we will have a better understanding about the chemistry occurring into the experimental reactor. This will allow us to analyze the Cassini-Huygens data and Titan’s haze formation.

Our team is involved at the mission science level as well, as one of the scientists of the mission is also in our group at the Laboratoire Inter-Universitaire des Syst?mes Atmosph?riques, LISA). Our laboratory tholins will be used as guides to calibrate several of the instruments on the Huygens probe and the Cassini orbiter.

There are 18 instruments on board the probe and orbiter. Calibration tests are needed for gas chromatography and mass spectroscopy [GC-MS]. The GC-MS will identify and measure chemicals in Titan’s atmosphere.

Calibration tests are also needed for the Aerosol Collector and Pyrolyser (ACP). This experiment will draw in aerosol particles from the atmosphere through filters, then heat the trapped samples in ovens to vaporize volatiles and decompose the complex organic materials.

The Composite Infrared Spectrometer (CIRS), a thermal measuring instrument on the orbiter, also needs to be calibrated. Compared to previous deep space missions, the spectrometer onboard Cassini-Huygens is a significant improvement, with a spectral resolution ten times higher than the Voyager spacecraft’s spectrometer.

AM: Do you have future plans for this research?

JB: Our next step is an experiment developed by Marie-Claire Gazeau, called “SETUP”. The experiment has two parts: a cold plasma in order to dissociate nitrogen, and a photochemical reactor in order to photodissociate methane. This will give us a better global simulation of Titan’s condition.

Original Source: NASA Astrobiology Magazine

Posted on by Fraser Cain

New Insights Into Martian Atmosphere

Image credit: Joint Astronomy Center
Astronomers have detected hydrogen peroxide (H2O2) in the atmosphere of Mars for the first time. This is the first time that a chemical catalyst of this sort has been found in a planetary atmosphere other than the Earth’s. Catalysts control the reactions of the most important chemical cycles in the Earth’s atmosphere. The result shows that scientists’ knowledge of the Earth’s atmosphere can be used to explain the chemistry of atmospheres on other planets, and vice versa. The work is announced in the March issue of the journal “Icarus”. The observations were made at the James Clerk Maxwell Telescope (JCMT), situated near the 14000-ft summit of Mauna Kea in Hawaii.

Dr Todd Clancy, at the Space Science Institute (SSI) in Boulder, Colorado, led the research team. He says “Mars is one of three observable terrestrial atmospheres. Unlike Venus, Mars is hospitable enough to be considered a possible human habitat in the future. And unlike the Earth, Mars is not extensively explored and so presents an opportunity to discover new and exciting phenomena.”

Dr Brad Sandor, also at SSI, explains “We took advantage of the excellent 2003 opposition of Mars, when the Earth and Mars passed close by each other in their orbits around the sun, to measure Martian atmospheric H2O2 for the first time.”

The Earth’s atmosphere has been studied much more than that of Mars. Scientists have had to rely on their terrestrial experience to guess how the Martian atmosphere reacts to solar radiation, and how its overall photochemical balance is controlled.

Models predicted that hydrogen peroxide was the key catalytic chemical that controls Mars atmospheric chemistry. Until now, scientists were unable to detect the predicted amount of H2O2, so some researchers argued that the models were wrong.

However, the new measurements of hydrogen peroxide made with the JCMT agree with the predictions of standard photochemistry. Dr Clancy continues “We have largely confirmed that the chemical balance of the Mars atmosphere is determined by the products of the photolysis of water vapor, without the need for special or unknown changes to current theory.”

Dr Gerald Moriarty-Schieven of the National Research Council of Canada worked on the project with Dr Clancy and Dr Sandor, and is based at the Joint Astronomy Centre in Hawaii, which operates the JCMT. He explains more about the JCMT observations: “The 2003 opposition was especially favorable since it occurred when Mars was closest to the sun in its orbit, and hence unusually close to us as we passed by. Mars was at its warmest, when the most H2O2 is available to observe, and the JCMT can make especially sensitive H2O2 measurements.”

What impact does this result have for the search for life on Mars? Dr Clancy says “Hydrogen peroxide is actually used as an antiseptic here on Earth, and so it would tend to retard any biological activity on the surface on Mars. For this reason, as well as the ultraviolet radiation and lack of water, bacteria-like organisms are not expected to be viable on the surface. Most arguments for finding life on Mars now center on subsurface regions.”

Original Source: JACH News Release

Posted on by Fraser Cain

Mars Express’ Image of Hecates Tholus

Image credit: ESA
The colour image (with north at the top) shows the summit caldera of Hecates Tholus, the northernmost volcano of the Elysium volcano group. The volcano reveals multiple caldera collapses. On the flanks of Hecates Tholus, several flow features related to water (lines radiating outwards) and pit chains related to lava can be observed. The volcano has an elevation of 5300 m, the caldera has a diameter of maximum 10 km and a depth of 600 m. The image centre is located at 150? East and 31.7? North.

Credits: ESA/DLR/FU Berlin (G. Neukum)

Original Source: ESA News Release

Posted on by Fraser Cain

Record for Furthest Galaxy is Broken Again

Image credit: ESO
Using the ISAAC near-infrared instrument on ESO’s Very Large Telescope, and the magnification effect of a gravitational lens, a team of French and Swiss astronomers [2] has found several faint galaxies believed to be the most remote known.

Further spectroscopic studies of one of these candidates has provided a strong case for what is now the new record holder – and by far – of the most distant galaxy known in the Universe.

Named Abell 1835 IR1916, the newly discovered galaxy has a redshift of 10 [3] and is located about 13,230 million light-years away. It is therefore seen at a time when the Universe was merely 470 million years young, that is, barely 3 percent of its current age.

This primeval galaxy appears to be ten thousand times less massive than our Galaxy, the Milky Way. It might well be among the first class of objects which put an end to the Dark Ages of the Universe.

This remarkable discovery illustrates the potential of large ground-based telescopes in the near-infrared domain for the exploration of the very early Universe.

Digging into the past
Like palaeontologists who dig deeper and deeper to find the oldest remains, astronomers try to look further and further to scrutinise the very young Universe. The ultimate quest? Finding the first stars and galaxies that formed just after the Big Bang.

More precisely, astronomers are trying to explore the last “unknown territories”, the boundary between the “Dark Ages” and the “Cosmic Renaissance”.

Rather shortly after the Big Bang, which is now believed to have taken place some 13,700 million years ago, the Universe plunged into darkness. The relic radiation from the primordial fireball had been stretched by the cosmic expansion towards longer wavelengths and neither stars nor quasars had yet been formed which could illuminate the vast space. The Universe was a cold and opaque place. This sombre era is therefore quite reasonably dubbed the “Dark Ages”.

A few hundred million years later, the first generation of stars and, later still, the first galaxies and quasars, produced intense ultraviolet radiation, gradually lifting the fog over the Universe.

This was the end of the Dark Ages and, with a term again taken over from human history, is sometimes referred to as the “Cosmic Renaissance”.

Astronomers are trying to pin down when – and how – exactly the Dark Ages finished. This requires looking for the remotest objects, a challenge that only the largest telescopes, combined with a very careful observing strategy, can take up.

Using a Gravitational Telescope
With the advent of 8-10 meter class telescopes spectacular progress has been achieved during the last decade. Indeed it has since become possible to observe with some detail several thousand galaxies and quasars out to distances of nearly 12 billion light-years (i.e. up to a redshift of 3 [3]). In other words astronomers are now able to study individual galaxies, their formation, evolution, and other properties over typically 85 % of the past history of the Universe.

Further in the past, however, observations of galaxies and quasars become scarce. Currently, only a handful of very faint galaxies are seen approximately 1,200 to 750 million years after the Big Bang (redshift 5-7). Beyond that, the faintness of these sources and the fact their light is shifted from the optical to the near infrared has so far severely limited the studies.

An important breakthrough in this quest for the earliest formed galaxy has now been achieved by a team of French and Swiss astronomers [2] using ESO’s Very Large Telescope (VLT) equipped with the near-infrared sensitive instrument ISAAC. To accomplish this, they had to combine the light amplification effect of a cluster of galaxies – a Gravitational Telescope – with the light gathering power of the VLT and the excellent sky conditions prevailing at Paranal.

Searching for distant galaxies
The hunt for such faint, elusive objects demands a particular approach.

First of all, very deep images of a cluster of galaxies named Abell 1835 were taken using the ISAAC near-infrared instrument on the VLT. Such relatively nearby massive clusters are able to bend and amplify the light of background sources – a phenomenon called Gravitational Lensing and predicted by Einstein’s theory of General Relativity.

This natural amplification allows the astronomers to peer at galaxies which would otherwise be too faint to be seen. In the case of the newly discovered galaxy, the light is amplified approximately 25 to 100 times! Combined with the power of the VLT it has thereby been possible to image and even to take a spectrum of this galaxy. Indeed, the natural amplification effectively increases the aperture of the VLT from 8.2-m to 40-80 m.

The deep near-IR images taken at different wavelengths have allowed the astronomers to characterise the properties of a few thousand galaxies in the image and to select a handful of them as potentially very distant galaxies. Using previously obtained images taken at the Canada-France-Hawaii Telescope (CFHT) on Mauna Kea and images from the Hubble Space Telescope, it has then been verified that these galaxies are indeed not seen in the optical. In this way, six candidate high redshift galaxies were recognised whose light may have been emitted when the Universe was less than 700 million years old.

To confirm and obtain a more precise determination of the distance of one of these galaxies, the astronomers obtained Director’s Discretionary Time to use again ISAAC on the VLT, but this time in its spectroscopic mode. After several months of careful analysis of the data, the astronomers are convinced to have detected a weak but clear spectral feature in the near-infrared domain. The astronomers have made a strong case that this feature is most certainly the Lyman-alpha emission line typical of these objects. This line, which occurs in the laboratory at a wavelength of 0.1216 ?m, that is, in the ultraviolet, has been stretched to the near infrared at 1.34 ?m, making Abell 1835 IR1916 the first galaxy known to have a redshift as large as 10.

The most distant galaxy known to date
This is the strongest case for a redshift in excess of the current spectroscopically confirmed record at z=6.6 and the first case of a double-digit redshift. Scaling the age of the Universe to a person’s lifetime (80 years, say), the previous confirmed record showed a four-year toddler. With the present observations, we have a picture of the child when he was two and a half years old.

From the images of this galaxy obtained in the various wavebands, the astronomers deduce that it is undergoing a period of intense star formation. But the amount of stars formed is estimated to be “only” 10 million times the mass of the sun, approximately ten thousand times smaller than the mass of our Galaxy, the Milky Way.

In other words, what the astronomers see is the first building block of the present-day large galaxies. This finding agrees well with our current understanding of the process of galaxy formation corresponding to a successive build-up of the large galaxies seen today through numerous mergers of “building blocks”, smaller and younger galaxies formed in the past.

It is these building blocks which may have provided the first light sources that lifted the fog over the Universe and put an end to the Dark Ages.

For Roser Pell?, from the Observatoire Midi-Pyr?n?es (France) and co-leader of the team, “these observations show that under excellent sky conditions like those at ESO’s Paranal Observatory, and using strong gravitational lensing, direct observations of distant galaxies close to the Dark Ages are feasible with the best ground-based telescopes.”

The other co-leader of the team, Daniel Schaerer from the Geneva Observatory and University (Switzerland), is excited: “This discovery opens the way to future explorations of the first stars and galaxies in the early Universe.”

More information
The information presented in this Press Release is based on a research article in the European research journal “Astronomy & Astrophysics” (A&A, volume 416, page L35; “ISAAC/VLT observations of a lensed galaxy at z=10.0” by Roser Pell?, Daniel Schaerer, Johan Richard, Jean-Fran?ois Le Borgne, and Jean-Paul Kneib). It is available on the web at the EDP web site.

Additional explanations and images are available on the authors’ web page, at http://obswww.unige.ch/sfr and http://webast.ast.obs-mip.fr/galaxies/

Original Source: ESO News Release

Posted on by Fraser Cain

Closest Youngest Star Found

Image credit: UC Berkeley
Astronomers at the University of California, Berkeley, have discovered the nearest and youngest star with a visible disk of dust that may be a nursery for planets.

The dim red dwarf star is a mere 33 light years away, close enough that the Hubble Space Telescope or ground-based telescopes with adaptive optics to sharpen the image should be able to see whether the dust disk contains clumps of matter that might turn into planets.

“Circumstellar disks are signposts for planet formation, and this is the nearest and youngest star where we directly observe light reflected from the dust produced by extrasolar comets and asteroids – i.e., the objects that could possibly form planets by accretion,” said Paul Kalas, assistant research astronomer at UC Berkeley and lead author of a paper reporting the discovery.

“We’re waiting for the summer and fall observing season to go back to the telescopes and study the properties of the disk in greater detail. But we expect everyone else to do the same thing – there will be lots of follow-up.”

A paper announcing the discovery will be published online in Science Express this week, and will appear in the printed edition of the journal in March. Coauthors with Kalas are Brenda C. Matthews, a post-doctoral researcher with UC Berkeley’s Radio Astronomy Laboratory, and astronomer Michael C. Liu of the University of Hawaii. Kalas also is affiliated with the Center for Adaptive Optics at UC Santa Cruz.

The young M-type star, AU Microscopium (AU Mic), is about half the mass of the sun but only about 12 million years old, compared to the 4.6 billion year age of the sun. The team of astronomers found the star while searching for dust disks around stars emitting more than expected amounts of infrared radiation, indicative of a warm, glowing dust cloud.

The image of AU Mic, obtained last October with the University of Hawaii’s 2.2-meter telescope atop Mauna Kea, shows an edge-on disk of dust stretching about 210 astronomical units from the central star – about seven times farther from the star than Neptune is from the sun. One astronomical unit, or AU, is the average distance from the Earth to the sun, about 93 million miles.

“When we see scattered infrared light around a star, the inference is that this is caused by dust grains replenished by comets and asteroid collisions,” Kalas said. Because 85 percent of all stars are M-type red dwarfs, the star provides clues to how the majority of planetary systems form and evolve.

Other nearby stars, such as Gliese 876 at 16 light years and epsilon-Eridani at 10 light years, wobble, providing indirect evidence for planets. But images of debris disks around stars are rare. AU Mic is the closest dust disk directly imaged since the discovery 20 years ago of a dust disk around beta-Pictoris, a star about 2.5 times the mass of the sun and 65 light years away. Though the two stars are in opposite regions of the sky, they appear to have been formed at the same time and to be traveling together through the galaxy, Kalas said.

“These sister stars probably formed together in the same region of space in a moving group containing about 20 stars,” Kalas said. This represents an unprecedented opportunity to study stars formed under the same conditions, but of masses slightly larger and slightly smaller than the sun.

“Theorists are excited, too, at the opportunity to understand how planetary systems evolve differently around high-mass stars like beta-Pictoris and low-mass stars like AU Mic,” he said.

The pictures of AU Mic were obtained by blocking glare from the star with a coronagraph like that used to view the sun’s outer atmosphere, or corona. The eclipsing disk on the University of Hawaii’s 2.2-meter telescope blocked view of everything around the star out to about 50 AU. At this distance in our solar system, only the Kuiper Belt of asteroids and the more distant Oort cloud, the source of comets, would be visible.

Kalas said that sharper images from the ground or space should show structures as close as 5 AU, which means a Jupiter-like planet or lump in the dusty disk would be visible, if present.

“With the adaptive optics on the Lick 120-inch telescope or the Keck 10-meter telescopes, or with the Hubble Space Telescope, we can improve the sharpness by 10 to 100 times,” Kalas said.

In a companion paper accepted for publication in The Astrophysical Journal, the Berkeley-Hawaii team reports indirect evidence for a relatively dust-free hole within about 17 AU of the star. This would be slightly inside the orbit of Uranus in our own solar system.

“Potential evidence for the existence of planets comes from the infrared spectrum, where we notice an absence of warm dust grains,” he said. “That means that grains are depleted within about 17 AU radius from the star. One mechanism to clear out the dust disk within 17 AU radius is by planet-grain encounters, where the planet removes the grains from the system.”

“The dust missing from the inner regions of AU Mic is the telltale sign of an orbiting planet. The planet sweeps away any dust in the inner regions, keeping the dust in the outer region at bay,” said Liu.

Aside from further observations with the 2.2-meter telescope in Hawaii, Kalas and his colleagues plan to use the Spitzer Space Telescope, an infrared observatory launched last August by the National Aeronautics and Space Administration (NASA), to conduct a more sensitive search for gas.

The research was supported by the NASA Origins Program and the National Science Foundation’s Center for Adaptive Optics.

Original Source: UC Berkeley News Release

Posted on by Fraser Cain

Opportunity Watches a Sunset on Mars

Image credit: NASA/JPL
Dust gradually obscures the Sun during a blue-sky martian sunset seen in a sequence of newly processed frames from NASA’s Mars Exploration Rover Opportunity.

“It’s inspirational and beautiful, but there’s good science in there, too,” said Dr. Jim Bell of Cornell University, Ithaca, N.Y., lead scientist for the panoramic cameras on Opportunity and its twin, Spirit.

The amount of dust indicated by Opportunity’s observations of the Sun is about twice as much as NASA’s Mars Pathfinder lander saw in 1997 from another site on Mars.

The sunset clip uses several of the more than 11,000 raw images that have been received so far from the 18 cameras on the two Mars Exploration Rovers and publicly posted at http://marsrovers.jpl.nasa.gov. During a briefing today at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., Bell showed some pictures that combine information from multiple raw frames.

A patch of ground about half the area of a coffee table, imaged with the range of filters available on Opportunity’s panoramic camera, has soil particles with a wide assortment of hues — “more spectral color diversity than we’ve seen in almost any other data set on Mars,” Bell said.

Opportunity is partway through several days of detailed observations and composition measurements at a portion of the rock outcrop in the crater where it landed last month. It used its rock abrasion tool this week for the first time, exposing a fresh rock surface for examination. That surface will be studied with its alpha particle X-ray spectrometer for identifying chemical elements and with its Moessbauer spectrometer for identifying iron-bearing minerals. With that rock-grinding session, all the tools have now been used on both rovers.

Dr. Ray Arvidson of Washington University, St. Louis, deputy principal investigator for the rovers’ science work, predicted that in two weeks or so, Opportunity will finish observations in its landing-site crater and be ready to move out to the surrounding flatland. At about that same time, Spirit may reach the rim of a larger crater nicknamed “Bonneville” and send back pictures of what’s inside. “We’ll both be at the rims of craters,” he said of the two rovers’ science teams, “one thinking about going in and the other thinking about going out onto the plain.”

Not counting occasional backup moves, Spirit has driven 171 meters (561 feet) from its lander. It has about half that distance still to go before reaching the crater rim. The terrain ahead looks different than what’s behind, however. “It’s rockier, but we’re after rocks,” Arvidson said.

Spirit can traverse the rockier type of ground in front of it, said Spirit Mission Manager Jennifer Harris of JPL. As it approached the edge of a small depression in the ground earlier this week, the rover identified the slope as a potential hazard, and “did the right thing” by stopping and seeking an alternate route, she said.

However, engineers are also planning to transmit new software to both rovers in a few weeks to improve onboard navigation capabilities. “We want to be more robust for the terrain we’re seeing,” Trosper said. The software revisions will also allow engineers to turn off a heater in Opportunity’s arm, which has been wasting some power by going on during cold hours even when not needed.

As it heads toward “Bonneville” to look for older rocks from beneath the region’s current surface layer, Spirit is stopping frequently to examine soil and rocks along the way. Observations with its microscope at one wavy patch of windblown soil allowed scientists to study how martian winds affect the landscape. Coarser grains are concentrated on the crests, with finer grains more dominant in the troughs, a characteristic of “ripples” rather than of dunes, which are shaped by stronger winds. “This gives us a better understanding of the current erosion process due to winds on Mars,” said Shane Thompson, a science team collaborator from Arizona State University, Tempe.

The rovers’ main task is to explore their landing sites for evidence in the rocks and soil about whether the sites’ past environments were ever watery and possibly suitable for sustaining life.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Wallpaper: Cassini’s Latest View of Saturn

Image credit: NASA/JPL
Four months before its scheduled arrival at Saturn, the Cassini- Huygens spacecraft sent its best color postcard back to Earth of the ringed world. The spacecraft is expected to send weekly postcards, as it gets closer to the ringed giant.

The view from Cassini shows Saturn growing larger and more defined as the spacecraft nears a July 1, 2004, arrival date. On February 9, Cassini’s narrow angle camera, one of two cameras onboard the spacecraft, took a series of exposures through different filters, which were combined to form the color image released today.

“We very much want everyone to enjoy Cassini’s tour of this magnificent planetary system,” said Dr. Carolyn Porco, leader of the Cassini imaging science team at the Space Science Institute in Boulder, Colo. “And I can say right now the views out the window will be stunning.”

Cassini was 69.4 million kilometers (43.2 million miles) from Saturn when the images were taken. The smallest features visible in the image are approximately 540 kilometers (336 miles) across. Finer details in the rings and atmosphere than previously seen are beginning to emerge and will grow in sharpness and clarity over the coming months. The thickness of the middle B ring of Saturn, and the comparative translucence of the outer A ring, when seen against the planet, as well as subtle color differences in the finely-banded Saturn atmosphere, are more apparent.

“I feel like a kid on a road trip at the beginning of our tour,” said Dr. Dennis Matson, project scientist for the Cassini-Huygens mission to Saturn and its largest moon Titan. “We’ve been driving this car for nearly 3.5 billion kilometers (2.2 billion miles) and it’s time to get off and explore this ringed world and its many moons. I can hardly wait, but in the meantime, these weekly color images offer a glimpse of our final destination.”

In the coming months, imaging highlights will include near daily, multi-wavelength imaging of Saturn and its rings; imaging of Titan beginning in April; Titan movie sequences starting in late May, when the resolution exceeds that obtainable from Earth; and a flyby of Saturn’s distant moon, Phoebe, in June, at a spacecraft altitude of 2,000 kilometers (1,243 miles).

Through Cassini, about 260 scientists from 17 countries hope to gain a better understanding of Saturn, its famous rings, its magnetosphere, Titan, and its other icy moons. “Cassini is probably the most ambitious exploration mission ever launched and is the fruit of an active international collaboration,” said Dr. Andre Brahic, imaging team member and professor at Universit? Paris 7-Denis Diderot, France. “It should be the prelude of our future, the exploration of our surroundings by humanity.”

Cassini will begin a four-year prime mission in orbit around Saturn when it arrives July 1. It will release its piggybacked Huygens probe about six months later for descent through Titan’s thick atmosphere. The probe could impact in what may be a liquid methane ocean.

JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Office of Space Science, Washington. The Space Science Institute is a non-profit organization of scientists and educators engaged in research in astrophysics, planetary science, Earth sciences, and in integrating research with education and public outreach. Cassini- Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency.

For the first image and other weekly images on the Internet each Friday, visit:

http://www.nasa.gov/

http://saturn.jpl.nasa.gov

http://ciclops.org/

For information about Cassini-Huygens on the Internet, visit:

http://saturn.jpl.nasa.gov/

Original Source: NASA/JPL News Release