Dusty shock waves generate planet ingredients

Using NASA’s Spitzer Space Telescope, astronomers have shown that shock waves around dusty young stars could be generating the raw materials needed for planet formation.

Astronomers detected tiny crystals, similar in make-up to quartz, around young stars just beginning to form planets. The cristobalite and tridymite crystals are already known to reside in comets, volcanic lava flows on Earth, and in some meteorites collected on Earth. They are thought to form in short-lived heating events followed by rapid cooling, conditions that are generated in shock waves.

Shock waves formed by colliding gas and dust in young planet-forming discs may force the creation of raw materials needed for planet growth. Image: ESO.

It is well known that planets are born out of swirling discs of dust and gas that surround young stars, building up from tiny grains into progressively larger planetisimals and eventually fully fledged planets in just a few millions of years. Forrest and colleagues used Spitzer to examine five young planet-forming discs around stars 400 light years away, and detected the high-temperature forms of silica, that is, cristobalite and tridymite, in planet forming discs for the first time. Silica is made of only silicon and oxygen and is the main ingredient in glass.

"Cristobalite and tridymite are essentially high-temperature forms of quartz," says Ben Sargent, one of the co-authors of the paper that describes the results that will appear in a future edition of the Astrophysical Journal. "If you heat quartz crystals, you'll get these compounds."

But these specific crystals require temperatures as high as 1,220 Kelvin to form, and the young planet-forming discs are only about 100 to 1,000 Kelvin, presenting something of a paradox. Since the crystals require a heating event that is followed by rapid cooling for their genesis, astronomers theorised that shock waves could be the culprit, creating violent, high speed collisions between the clouds of gas swirling around a young planetary disc and elevating the temperatures there.

"By studying these other star systems, we can learn about the very beginnings of our own planets 4.6 billion years ago," says William Forrest of the University of Rochester, New York.
"Spitzer has given us a better idea of how the raw materials of planets are produced very early on."

The findings are also in agreement with local evidence from our own Solar System. Spherical pebbles, called chondrules, found in ancient meteorites that have fallen to Earth are also thought to have been crystallised by shock waves in our Solar System's young planet-forming disc.

from:http://astronomynow.com/081112dustyshockwavesgenerateplanetingredients.html

Sub-millimetre astronomy reveals glowing stellar nurseries

By using sub-millimetre wavelength astronomy, astronomers have revealed the cold dense clouds of material that are the birth places of new stars.

Astronomers using the LABOCA camera on the 12 metre Atacama Pathfinder Experiment (APEX) telescope detected clumps of cold gas four times fainter than ever seen before, and which had been forced to collapse as an expanding bubble of ionised gas about ten light years across swept through the region known as RCW120.

Colour composite image of RCW120. The submillimetre emission is shown as the blue clouds surrounding the reddish glow of the ionised gas. Image: ESO/APEX/DSS2/ SuperCosmos.

RCW120 is located some 4,200 light years from Earth towards the constellation of Scorpius and hosts a hot, massive star in its centre. The star is emitting huge amounts of ultraviolet radiation, which ionises the surrounding gas, stripping the electrons from hydrogen atoms and producing the characteristic red glow of so-called H-alpha emission.

Accompanying the ionised region is a shock wave, which sweeps up a layer of the surrounding cold interstellar gas and cosmic dust. This layer becomes unstable and collapses under its own gravity into dense clumps, forming cold, dense clouds of hydrogen where new stars are born. Since the clouds are still extremely cold at just -250 degrees Celsius, their faint heat glow can only be seen at sub-millimetre wavelengths, demonstrating the importance of sub-millimetre astronomy in studying the earliest stages of stellar life. Moreover, since the brightness of the stellar clumps is a measure of their mass, this also means that astronomers can extend their studies to the least massive stars via sub-millimetre astronomy.

from:http://astronomynow.com/081112submillitreastronomyrevealsglowingstellarnurseries.html

Phoenix concludes Martian adventure

After more than five months on the Martian surface, NASA’s Phoenix Mars Lander has said its farewells to the Earth as the decline in solar power forces the spacecraft to shut down.

Phoenix last communicated with mission engineers on 2 November but there is still hope the lander will revive itself and phone home. In addition to shorter daylight hours, Phoenix must also contend with a dustier sky, greater cloud coverage and colder temperatures as the northern Mars summer turns to autumn.

One of Phoenix's major acheivements was finding a layer of ice just below the surface. The ice was seen to vapourise before its cameras in just a few Martian days. Image: NASA/JPL-Calech/University of Arizona/Texas A&M University.

Even though the practical side of the spacecraft’s work has concluded, mission scientists say that the analysis of data from the instruments is in its earliest stages. "Phoenix has given us some surprises, and I'm confident we will be pulling more gems from this trove of data for years to come," says Phoenix Principal Investigator Peter Smith of the University of Arizona.

Phoenix already notched up a first by landing farther north than any other spacecraft has dared on the Martian surface. Following its arrival on 25 May 2008, Phoenix has photographed, dug, scooped, baked, tasted and sniffed out the ingredients of the north polar soil, confirming the presence of water-ice in the Martian subsurface early in its mission. Phoenix is the first mission to directly ‘touch’ water-ice on Mars, which it found just a few centimetres below the surface, verifying the remote observations made by Mars Odyssey in 2002. The lander’s cameras returned over 25,000 images from panoramas to atomic level images of soil grains with the first atomic force microscope ever used outside Earth.

"Phoenix not only met the tremendous challenge of landing safely, it accomplished scientific investigations on 149 of its 152 Martian days as a result of dedicated work by a talented team," says Phoenix Project Manager Barry Goldstein at NASA's Jet Propulsion Laboratory. The mission was scheduled to last just three months, but continued for over five months.

During the first 90 Martian days after its May 25, 2008 landing in the north arctic plains of Mars, Phoenix dug several trenches in the workspace reachable with the lander's robotic arm. Image: NASA/JPL-Calech/University of Arizona/Texas A&M University.

One of Phoenix's science goals was to advance our understanding of Mars as a potentially habitable environment, either now or in the past. Supporting findings include documenting a mildly alkaline soil environment unlike any found by earlier Mars missions, finding small concentrations of salts that could be nutrients for life, discovering perchlorate salt, which has implications for ice and soil properties, and detecting calcium carbonate, a marker of effects of liquid water. Many of the minerals detected by both Phoenix and the Mars Exploration Rovers could only have formed in the presence of water, and scientists believe that by finding water, they will find clues to the history of life on Mars, should it ever have existed.

Phoenix also documented the Martian weather for the duration of the mission, observing snow descending from clouds, and providing extensive data on daily temperature, pressure, humidity and wind, as well as direct observations of haze, clouds, frost and dust devils. Coordinated with NASA's Mars Reconnaissance Orbiter, the duo performed simultaneous ground and orbital observations of Martian weather to provide context for both sets of recordings.

"Phoenix provided an important step to spur the hope that we can show Mars was once habitable and possibly supported life," says Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters in Washington. "Phoenix was supported by orbiting NASA spacecraft providing communications relay while producing their own fascinating science. With the upcoming launch of the Mars Science Laboratory, the Mars Program never sleeps."

Mars Science Laboratory will launch in late 2009 and will be winched down to the Martian surface by a rocket-powered ‘sky-crane’. The landing site has yet to be determined. You can read more about the Mars Science Laboratory in the Astronomy Now 2009 Yearbook, available to buy now
from:http://astronomynow.com/081111PhoenixconcludesMartianadventure.html

Early career planetary scientists explore Mars

Martian meteorites, surface process and the habitability of the red planet formed a key part of discussions at the UK Planetary Forum’s 6th Early Careers Planetary Scientists’ meeting held in London last week. Emily Baldwin reports on three up and coming PhD students and their extraterrestrial research.

The question of if and when water existed on Mars and its role in the history of the red planet is probably one of the most sought after answers in planetary science. Susan Conway of the Open University is studying the formation mechanisms of gullies on Mars by looking at similar examples here on the Earth. She suggests that since the current low average temperatures and pressures on Mars prevent the formation of liquid water, the discovery of recently active gullies on the surface of Mars presents a paradox.

Gullies like this on the Earth are usually formed by flowing water, but on Mars liquid water is unstable. Research into what has created the recent gullies on Mars is an active area of research for current early career scientists. Image: Malin Space Science Systems, MGS, JPL, NASA.

“The process forming gullies on Mars is unknown and it is through investigating the morphology of analogous sites on Earth that we hope to either rule out certain processes or find evidence for them occurring on Mars,” says Conway. Conway and colleagues undertook fieldwork in the Westfjords of Iceland where gullies share similarities with those on Mars, in terms of their shape and sinuosity (how much they bend and curve).

“In Iceland the gullies we have studied are formed by debris flow, a process by which a slurry of mud, rocks and water surges downslope. This process forms very distinctive landforms,” she says. By studying the Icelandic gullies, and comparing them with others from around the world, Conway found that the characteristics of Martian gullies shared many similarities with the terrestrial counterparts, meaning that debris flow as an active process on Mars – and possibly even including water – cannot be ruled out just yet. However, there is still a lot of work to be done, and Conway plans to study more gullies to increase the dataset.

“If we can show the morphology of the gullies on Mars is sufficiently similar to debris flow then we have a strong case for saying this process has been recently active on Mars,” she says. “This shows liquid water must have been present on the surface in the recent past, highlighting either that our current understanding of the behaviour of water under present Martian conditions is lacking or that our interpretation of the recent Martian climate is wrong.”

Earlier this year debris flows were reported on scarps on Mars that appeared as bright deposits in images taken by various orbiting Mars cameras separated by just a few years. After the initial excitement that this could have provided evidence for water on Mars, it turns out that dry debris flows, similar to an avalanche on Earth, are the most likely culprit. “The debris falls reported earlier this year do not form gullies,” comments Conway. “Due to the cold temperatures in this region, it is likely that these flows were entirely dry mass wasting.”

By studying environments on the Earth where volcanic activity and ice interact, such as in Iceland as shown here, scientists can learn about the potential habitability of similar environments on other planets such as Mars. Image: Clare Cousins.

Moving to astrobiology, but sticking with the watery theme, Claire Cousins of the Centre for Planetary Sciences at University College London presented her work on the potential for microbial colonisation on Mars, specifically where buried ice interacts with volcanic processes to give potentially life-giving heat to an otherwise harsh, frozen environment. “After an eruptive episode, subglacial volcanic systems produce a number of different environments that can be colonised by microbial life,” describes Cousins. “These include solidified lava, a lens of meltwater (which can be sustained by hydrothermal heating once the lava has cooled), and the overlying ice.”

The combination of geothermal energy and liquid water within a subsurface setting make subglacial volcanic systems an excellent refuge for life on Mars. “The presence of large amounts of water-ice plus widespread evidence for basaltic volcanism on Mars suggests the two must have interacted at some point in Martian history,” she says.

By performing experiments with microbes in simulated Martian icy conditions – which consisted of -30 degress Celsius temperatures, UV radiation and low pressure – and then subjecting the experiment to heat, Cousins and colleagues showed that the production of meltwater between the lava sample and the overlying ice offered a suitable environment for colonisation. “This strongly suggests this environmental setting could have been habitable on Mars at a time when volcanic activity and glaciers interacted,” she says.

However, problems may arise within the initial colonisation of a system because of the potential instability of these environments. “Once geothermal heat flow diminishes, or the overlying glacier retreats, the environments no longer exist,” says Cousins. That means that although you may have suitable environments, you need to somehow get the microbes there in the first place. Cousins comments that several volcanic systems can exist beneath the same glacier, therefore microbes could be transported via meltwater traveling through fractures and channels within the ice, thereby offering a solution to this problem.

“There is a lot of evidence that suggests subglacial volcanic activity occurred throughout Martian history, driving the need to understand these systems and resulting environments more fully,” adds Cousins. To date, only the top few centimetres of Martian soil have been probed; future missions such as ExoMars will include a drill to dig even deeper, and perhaps uncover potentially habitable environments buried at depth.

There is a lot of evidence for volcanic activity in Mars' past. Could volcanic activity combined with an icy environment at depth provide the magic ingredients for life? Claire Cousins of UCL has been finding out. Image: NASA.

While we have yet to return samples of Martian soil to the Earth, meteorites originating from the red planet are the next best thing, and give Julia Cartwright of the University of Manchester the tools to learn about the atmospheric and geological history of the planet. She studies a type of meteorite known as shergottites that account for over 80 percent of known Martian meteorites and which display evidence of undergoing a violent history. By looking at the composition, ratio and location of minerals contained within a meteorite, and the gases trapped within them, scientists can learn about the environment in which the meteorite originally formed, including details of the planet’s atmosphere and interior at the time of their genesis.

“The gases are incorporated into meteorites at some point in their histories, though the locations and trapping mechanisms of these gases has been heavily debated,” says Cartwright. The current theories propose that gases can form either within the mineral grains themselves, on the boundaries between grains or on the surfaces of the mineral, which relate to the mechanisms that put them there: either by being dissolved in the same magma that formed the grain, altered by water or formed in a high pressure event such as an impact, respectively.

Cartwright’s work on four different shergottites can answer questions regarding her meteorites’ ages and possible source locations. “The shergottites have very similar, young formation ages of 200-500 million years suggesting that they may have been formed in the same region and from the younger units on Mars, which only constitute a small proportion of the Martian surface. The shergottites also have very similar ejection ages of 1-4 million years, suggesting that they were ejected from Mars in just one of two ejection events.”

A photograph of a thin section of one of Cartwright’s Martian shergottite meteorites, with various minerals labelled. The left half of the image is shown in cross polarised light and the right side plane polarised light. By analysing the gases contained within meteorites, scientists can learn about the atmosphere and interior processes of Mars at the time the meteorite was formed and ejected from the planet. Image: Julia Cartwright.

But there is still work to be done to understand the processes that went into forming the different minerals contained within the meteorites, made all the more difficult by contamination by terrestrial processes resulting from the meteorites lying on the Earth’s surface for long periods of time. “Most meteorites will contain some sort of terrestrial component, though this will be determined by the amount of weathering that the meteorite has been subjected to,” she says. “Distinguishing between terrestrial and Martian weathering is very difficult, as similar minerals including clays, sulphates and carbonates are produced in both instances.”

Cartwright comments that a sample-return mission would be priceless regarding any further work on Mars. “Run in tandem to studies on meteorites, the information provided could be just the tip of the ice-berg when it comes to understanding not only the other planets in our Solar System, but our own planet Earth.”

Conway, Cousins and Cartwright were just three of twenty early career scientists presenting their work at the 6th UK Planetary Forum meeting, held at University College London on Monday 3 November. The UK Planetary Forum (UKPF) was founded in 1996 as a representative body of the planetary science community, and aims to promote planetary science in the UK amongst scientists and the public alike. For more information on the UKPF and for full listings of the talks presented, visit the UKPF website.

from:http://astronomynow.com/081108EarlycareerplanetaryscientistsexploreMars.html

ESO produces deepest UV image of the Universe

A new image from the European Southern Observatory (ESO) offers the deepest ground-based ultraviolet image of the Universe ever obtained.

The image contains more than 27 million pixels and reveals a cocktail of brightly coloured and varying shaped galaxies that make up the Chandra Deep Field South (CDF-S). The CDF-S is one of two regions selected as part of the Great Observatories Origins Deep Survey (GOODS), an effort of the worldwide astronomical community that unites the deepest observations from ground- and space-based facilities at all wavelengths from X-ray to radio. Its primary purpose is to provide astronomers with the most sensitive census of the distant Universe to assist in the fundamental study of the formation and evolution of galaxies.

The Chandra Deep Field South observed with ESO’s VIMOS and WFI instruments is the deepest image every taken in the U-band. The image covers a region 14.1 x 21.6 arcminutes. Image: ESO/ Mario Nonino, Piero Rosati and the ESO GOODS Team.

The image combines data obtained from 55 hours of observations with the VIMOS (Visible wide field Imager and Multi-Object Spectrograph) instrument on ESO’s Very Large Telescope (VLT) in the U- and R-bands, as well as data obtained in the B-band with the Wide-Field Imager (WFI) attached to the 2.2 metre Max Planck Gesellschaft/ESO telescope at La Silla. The U-band represents the boundary between visible and ultraviolet light, and in this image is the result of 40 hours of staring at the same region of the sky, resulting in the deepest image ever taken from the ground at this wavelength. At these depths, the sky is almost completely covered by galaxies, each one like our own Milky Way Galaxy, hosting hundreds of billions of stars.

Only a very few stars in this image actually belong to the Milky Way, though, and one can be seen to the left of the second brightest star towards the top of the field of view. It appears as a slightly elongated rainbow because the star moved while the data were being acquired in the different filters over several years.

Such a deep image unveils galaxies a billion times fainter than the unaided eye can see and over a range of colours not directly
observable by the human eye. The CDF-S has already been essential to the discovery of a large number of new galaxies that are so far away that they are seen as they were when the Universe was a youthful two billion years old.

from:http://astronomynow.com/081107ESOproducesdeepestultravioletimageoftheUniverse.html

Fingers and loops revealed in the Crab Nebula

The Chandra X-ray Observatory has captured the first clear view of the faint boundary of the Crab Nebula’s X-ray emitting pulsar wind nebula.

The Crab Nebula is located about 6,000 light years away in the constellation of Taurus and is powered by a rapidly rotating, highly magnetised neutron star, or pulsar (seen as a white dot near the centre of the image), the remnant of the gravitational collapse of a massive star that met its fate in a supernova explosion.

Chandra has captured a clear view of the faint boundary of the Crab Nebula’s X-ray emitting pulsar wind nebula. Image: NASA/CXC/SAO/F.Seward et al.

The Crab pulsar spins on its axis around 30 times a second, and this rapid rotation, combined with a strong magnetic field, generates an intense electromagnetic field that creates jets of radiation emanating from the poles of the pulsar, and a powerful wind flowing out in the equatorial direction.

As the magnetic pulsar wind slams into the body of the nebula, electrons and positrons (anti-electrons) spiral around the magnetic field lines and radiate away energy. An inner X-ray ring is thought to represent the shock wave that marks the boundary between the surrounding nebula and the flow of particles from the pulsar. Energetic electrons and positrons trapped within the star’s magnetic field move outward from this ring and brighten in an outer ring, producing a glow in X-rays, while many filamentary structures that contain hot gas permeate the nebula itself.

The Crab Nebula in visible light (left) and infrared (right) as seen by Hubble and Spitzer, respectively. The optical image also includes X-ray images (blue colour) from Chandra. The size of the X-ray image is smaller because the higher energy X-ray emitting electrons radiate away their energy more quickly than the lower energy optically emitting electrons as they move. Images: visible: ESA/NASA; Spitzer: NASA/JPL-Caltech/R. Gehrz (University of Minnesota).

The shock front is extremely dynamic, with its shape and position changing rapidly. Further out, fingers and loops of matter and bays that are void of matter all indicate that the magnetic field of the nebula and filaments of cooler matter are controlling the motion of the electrons and positrons. The particles can move rapidly along the magnetic field and travel several light years before radiating away their energy. In contrast, they move much more slowly perpendicular to the magnetic field, and travel only a short distance before losing their energy. The conspicuous dark bays on the lower right and left in the Chandra image are likely due to the effects of a remnant magnetic field from the Crab Nebula’s original progenitor star.

from: http://astronomynow.com/081107FingersandloopsintheCrabNebula.html

Phoenix in "precarious times" following power fault

NASA’s Phoenix Mars Lander tripped into safe mode yesterday in response to a low-power fault, and unexpectedly switched on to the ‘B-Side’ of its redundant electronics, shutting down one of its two batteries in the process.

During safe mode, the lander stops non-critical activities and awaits further instructions from the mission team. Engineers were able to kick start battery charging by sending commands from Earth to the failing lander, but the harsh weather conditions are taking their toll.

NASA's Mars Phoenix Lander is slowly shutting down as winter sets in. The mission, already in its fifth month of a 90 day mission, suffered a fault yesterday due to the
deteriorating weather conditions. Image: NASA/JPL-Calech/University of Arizona.

"This is a precarious time for Phoenix," says Phoenix Project Manager Barry Goldstein. "We're in the bonus round of the extended mission, and we're aware that the end could come at any time. The engineering team is doing all it can to keep the spacecraft alive and collecting science, but at this point survivability depends on some factors out of our control, such as the weather and temperatures on Mars."

Phoenix has recorded the lowest temperatures yet, dipping to -96 degrees Celsius at night and barely rising above -45 degrees Celsius in the day. Dust-storms and water-ice clouds add additional challenges, reducing the amount of sunlight reaching Phoenix’s solar panels, thereby restricting the amount of power the lander can generate. On Tuesday, low temperatures triggered Phoenix’s emergency battery heaters into action, creating another drain on precious power supplies.

"It could be a matter of days, or weeks, before the daily power generated by Phoenix is less than needed to operate the spacecraft," says JPL mission manager Chris Lewicki. "We have only a few options left to reduce the energy usage."

Only this week did mission leaders announce plans to turn off four heaters, one at a time, in an effort to preserve power. The faults experienced yesterday forced the engineers to shut down two heaters instead of one as originally planned, ceasing operations of the robotic arm, robotic arm camera and the thermal and evolved-gas analyser. The second heater served the lander's pyrotechnic initiation unit, which hasn't been used since landing.

Science activities will remain on hold for the rest of the week to allow the spacecraft to recharge and conserve power. It is still hoped that Phoenix will be able to perform meteorological observations at the very least, for some weeks to come.

from:http://www.astronomynow.com/081030phoenixinprecarioustimesfollowingpowerfault.html

Cassini’s imaging trick earned halloween treats from Enceladus

Following the success of the ‘skeet shoot’ imaging technique employed for the 11 August Enceladus fly-by, Cassini performed the same trick to obtain more high resolution images of the icy satellite this halloween.

Cassini captured more high resolution images of the prominent tiger stripes in the south polar region of Enceladus in a halloween encounter with Saturn’s enigmatic moon. Image: NASA/JPL/Space Science Institute.

While the 9 October fly-by focussed on the geyser-like plumes emanating from the so-called tiger stripes at the moon’s south pole, the halloween fly-by was set on obtaining high resolution images of the terrain from which the jets are erupting. The skeet shoot technique, named after an Olympic shooting event, works by initially pointing Cassini ahead of the moon, and ordering it to track a point in space while it waits for Enceladus to move into the camera’s field of view. Once the targeted region is in the line of fire, the camera shoots images of the high priority target regions in rapid succession.

For the 31 October fly-by, the ground track of the camera's pointing was selected to cut across two tiger stripes, known as sulci. The swath was chosen to pass over three particular segments of the tiger stripes that are known to be local hot spots and which are sites of previously observed eruptions. The results of the fly-by mean that the Cassini team have now observed six of eight jet sources, with the latest fly-by catching sources assigned tags VI and VII in and around the Baghdad sulci, as well as repeating observations of Damascus jet sources II and III. They noted that the region of the active tiger stripes is finely-fractured throughout and littered with icy blocks.

The source region for a jet (assigned the tag VI) was identified in the Baghdad Sulcus region. Image: NASA/JPL/Space Science Institute.

This image was captured at a resolution of just nine metres per pixel, the highest resolution of the halloween encounter. The image shows the south polar terrain in unprecedented detail, revealing fractured terrain littered with icy blocks. Image: NASA/JPL/Space Science Institute.

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from:http://www.astronomynow.com/081031cassiniimagingtricktoearnhalloweentreatfromenceladus.html

New mineral points to a wetter Mars

NASA's Mars Reconnaissance Orbiter (MRO) has observed a new category of minerals spread across large regions of Mars that point towards prolonged periods of water covering the red planet as recently as two billion years ago.

The new mineral, known as opaline silica, was detected on Mars by both the Spirit rover and by the MRO’s CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument earlier in the year, but in the November issue of the journal Geology, the CRISM team provide authoritative evidence for the presence of widespread opal and not some other water-containing (hydrated) mineral.

Opal like minerals have been detected in and around the giant Valles Marineris canyon system, appearing as a light-toned cream colour in this false colour image. The presence of opal in this location suggests water was present on the surface of Mars as recently as two billion years ago. Image: NASA/JPL-Caltech/Univ. of Arizona.

“Finding large outcrops of opal (hydrated silica) on Mars is a great discovery because it shows that the opal detected by the Spirit rover is not a unique occurrence and that this material is apparently quite common in some regions of Mars,” says lead author Dr Ralph Milliken of the Jet Propulsion Laboratory. “Also, the presence of opal and other silica-rich minerals has been predicted to exist on Mars by geochemical models, and now we've finally seen evidence of it on the surface from orbit.”

The hydrated mineral deposits are telltale signs of where and when water was present on ancient Mars, and the MRO observations reveal its presence in long outcrops in the relatively young plains outside of the large Valles Marineris canyon system, as well as some locations near dry river channels. “In some places the opal is found with iron sulfates, which tells us that the deposits may have formed from evaporation of very acidic water,” Milliken tells Astronomy Now. “However, in some locations we only see the opal, so in these places the water might not have been as acidic and may have been more favorable for life. Finding opal in these relatively young deposits tells us that there was liquid water on Mars as recently as 2-2.5 billion years ago, which means that the window for life or habitability on Mars has opened up a bit more than we previously thought.”

Until now, only two major groups of hydrated minerals, phyllosilicates and hydrated sulfates, had been observed by spacecraft orbiting Mars. Clay-like phyllosilicates formed more than 3.5 billion years ago where igneous rock came into prolonged contact with water, and are suited to trapping and preserving organic matter. Hydrated sulfates formed from the evaporation of salty and sometimes acidic water. The newly discovered opaline silicates are the youngest of the three types of hydrated minerals and formed where liquid water altered materials created by volcanic activity or meteorite impact on the Martian surface. The variations in the compositions of the minerals suggest that different types of watery environments created them, showing just how diverse conditions on Mars were in the last few billion years.

The key result of the opal discovery is the implication for the duration of water on Mars, and by association, the ‘extra’ time inferred for life to have taken hold on our neighbouring planet. "What's important is that the longer liquid water existed on Mars, the longer the window during which Mars may have supported life," says Milliken. "The opaline silica deposits would be good places to explore to assess the potential for habitability on Mars, especially in these younger terrains."

NASA’s Mars Science Laboratory will launch in 2009 and although the landing site is yet to be decided, it will be targeting sites most likely to yield signs of past life.

from:http://www.astronomynow.com/081030NewmineralpointstoawetterMars.html

Fireball captured by Canadian cameras

For the second time this year The University of Western Ontario’s Meteor Group has captured rare footage of a meteor streaking across the sky and possibly falling to the ground.

The meteor was tracked by all seven of Western’s Southern Ontario Meteor Network cameras at 5:28 am on Wednesday 15 October, local time. Western University astronomers suspect that some fraction of the meteor may have fallen to the ground, amounting to a few hundred grams in mass.

All seven cameras of the Meteor Network spotted this meteor streaking across the sky; this image was taken by the Orangeville camera number 6. The lights at the bottom are a moving aircraft. Video of the meteor is available here. Image: University of Western Ontario.

By studying the video footage, the astronomers concluded that the meteor penetrated the Earth’s atmosphere at an altitude of around 37 kilometres whereupon it slowed down considerably. Most meteoroids burn up by the time they hit an altitude of 60-70 kilometres from the ground, but in this case, one or more small meteorites could have made it to the ground intact. The surviving fragments are predicted to lie in a region north of Guelph. The trajectory of the meteor could also be tracked back to its pre-impact orbit, putting it into the typical Earth crossing asteroid type of a stony meteorite. Stony meteorites are composed mostly of silicate minerals and account for around 95 percent of all meteorites seen to fall to Earth.

In March, the same network of all-sky cameras captured a meteor careering towards the Parry Sound area. All-sky cameras consist of a fish eye lens that enables the whole sky to be imaged at once, as the name suggests. A network of three or more cameras allows the meteors to be located via triangulation.

The fireball is suspected to have shed meteorites in a region north of Guelph. Residents are encouraged to contact researchers at Western if they witnessed the event or if they have found fragments of the meteorite. Image: University of Western Ontario.

Just a week before the Canadian accomplishment, a three-metre wide asteroid was seen powering through the skies of northern Sudan as a glowing fireball (read our report here). Meteors streak across the sky on a daily basis, and when the Earth passes through the tail of a comet, we are treated to a meteor shower, such as the Perseids, Orionids, Leonids and Geminids, which offer the best displays. However, it is quite rare that meteoritic material reaches the ground intact, but finding this treasure allows scientists to sample the material of an extraterrestrial body, teaching us about the composition of the residents of our cosmic neighbourhood. The three-metre wide asteroid was a reminder that the Earth is also at risk from potentially devasting impacts without much notice, indeed, that case study was detected less than a day before it was due to penetrate the Earth's atmosphere.

from:http://www.astronomynow.com/081028FireballcapturedbyCanadiancameras.html

Double asteroid belt in Solar System clone

Spitzer observations have discerned two rocky asteroid belts and an icy outer ring surrounding our Sun’s doppelgänger Epsilon Eridani that could have been shaped by evolving planets.

"This system probably looks a lot like ours did when life first took root on Earth," says lead author of the study Dana Backman of the SETI Institute.

Click to enlarge. Our familiar Solar System compared with the similar layout of Epsilon Eridani's system. Both systems host asteroids (brown), comets (blue) and planets (white dots). Image: NASA/JPL-Caltech.

Epsilon Eridani, visible to the naked eye and located just 10.5 light years away in the constellation Eridanus, is marginally smaller and cooler than our own Sun, but at just 850 million years old is providing insight into how our Solar System evolved. It already shares striking similarities to the formation we are familiar with today, bearing an inner rocky asteroid belt at an equivalent distance from the central sun as our own inner Astroid Belt. An outer rocky belt containing around 20 times as much material also exists in the same position as Uranus.

A third ring of icy material spans a ring from 35 to 100 AU, mimicking the Kuiper belt of our own Solar System but with 100 times more material. But when our own Sun was a spritely 850 million years old, our icy reservoir probably looked much the same as Epsilon Eridani’s, prior to a dramatic clearing out of rocky material during the Heavy Bombardment Era, where material was flung into the inner planets and some even hurled out of the Solar System altogether.

"Epsilon Eridani looks a lot like the young Solar System, so it's
conceivable that it will evolve similarly," says Massimo Marengo of the Harvard-Smithsonian Center for Astrophysics.

Artist impression of the Epsilon Eridani solar system, exhibiting a double asteroid belt and a reservoir of icy cometary material. Image: NASA/JPL-Caltech.

The forming solar system was observed by the Spitzer Space Telescope, and revealed gaps between each of the rings orbiting the central star. Such gaps are best explained by the presence of planets that gravitationally mold the rings and sweep out material as they orbit their central star.

"Planets are the easiest way to explain what we're seeing," says Marengo. Indeed, the astronomers predict that three planets with masses between those of Neptune and Jupiter must be lurking in the system, and a candidate planet near the innermost ring already has been detected by radial velocity studies. A second planet is inferred near the outer asteroid belt at a distance of 20 AU, and a third at about 35 AU near the inner edge of the Kuiper Belt clone.

There is no doubt that the Epsilon Eridani system will be the first on many a planet hunter’s list, and as the resolving power of telescopes increases, astronomers hope to detect terrestrial and even Earth-mass planets orbiting inside the innermost asteroid belt for a true Solar System analogue.

from: http://www.astronomynow.com/081027DoubleasteroidbeltinSolarSystemclone.html

Rebooted Hubble scores a perfect 10

After numerous glitches with the software onboard Hubble, the world’s favourite space telescope is finally back online, and celebrates by capturing the perfect image.

Arp 147 lies in the constellation of Cetus, over 400 million light years away. This picture was assembled from WFPC2 images taken with three separate filters. The blue, visible-light, and infrared filters are represented by the colours blue, green, and red, respectively. Image: NASA, ESA, and M. Livio (STScI).

The Wide Field Planetary Camera 2 (WFPC2) captured this chance alignment of two galaxies that spell out the number ’10’. Together the interacting galaxies are known as Arp 147. The left-hand galaxy, the ‘1’, appears nearly edge on in our line of sight, and is relatively undisturbed apart from a smooth ring of starlight. The right-hand galaxy, representing the ‘0’, forms a ring of clumpy but intense star formation.

Astronomers speculate that the blue ring was created after the redder looking galaxy plunged through a galaxy on the right. The colliding galaxies would have created a powerful density wave that would have swept out the material into an expanding ring, stimulating star formation. The dusty reddish knot at the lower left of the blue ring probably marks the location of the original nucleus of the galaxy that was hit.

The galaxy pair was photographed on 27-28 October, demonstrating that Hubble is once again functioning as normal. Later today, NASA representatives will discuss the status of the upcoming repair mission, which was set back to early 2009 following technical problems with Hubble in the days before the mission was originally due to go ahead.

from:http://www.astronomynow.com/081030RebootedHubblescoresaperfect10.html

JCMT sees the dark hearts of bright galaxies

European astronomers using the James Clark Maxwell Telescope (JCMT) have gained important information on what are known as Ultraluminous Infrared Galaxies (ULIRGs), galaxies with a huge energy output but which are obscured by their massive dust and gas clouds.

Astronomers believe that this class of galaxy was much more common in the younger Universe than it is now, with their impressive energy output attributed to extremely rapid conversion of gas into young, luminous stars and to energetic processes associated with supermassive black holes. Using the HARP receiver on the JCMT, a team of astronomers from Wales, The Netherlands and Germany directly probed the physical conditions in the active inner regions of a number of ULIRGs by penetrating the thick dusty veil surrounding the galaxies and observing the submillimetre radiation.

Spectrum of hydrogen cyanide in a ULIRG obtained with the JCMT and its HARP receiver. The background image shows UGC5101 as observed with the ACS on board the Hubble Space Telescope and shows dust clouds obscuring the most luminous parts of the galaxy which can be seen as a red-brown band. Image: NASA, ESA, the Hubble Heritage STScI/AURA-ESA/Hubble Collaboration, and A. Evans, University of Virginia, Charlottesville/NRAO/Stony Brook University.

"The submillimetre radiation observed by the JCMT can penetrate the dust shroud obscuring the nuclear regions of the ULIRGs, but the spectral lines emitted from these regions are still very faint," says Dr Papadopoulos from Bonn University. "Therefore, we had to use the JCMT and its sensitive HARP receiver for up to 12 hours under very good atmospheric conditions, to detect just a single line in a single galaxy."

Among the molecular fingerprints that the team has observed are spectral lines of warm and dense carbon monoxide (CO) and of the formyl ion (HCO+). However, the most important spectral line detected is hydrogen cyanide (HCN), which originates from warm, dense and highly toxic hydrogen cyanide gas in the most active regions of the ULIRGs. These are the first spectra of this type from a substantial set of ULIRGs, and are surprisingly difficult to detect in many of these extreme objects. When interpreted together with the rest of the data, it becomes obvious that this spectral line probes the most extremely dense gas, the very immediate fuel of the massive star formation in these objects.

"Unlike other spectral lines which probe more remote gaseous regions in these galaxies which may not be actively forming stars, the hydrogen cyanide intensity changes dramatically from galaxy to galaxy," says Paul van der Werf of Leiden University in The Netherlands. "This depends on, and reveals, the intense gravitational tides and their effects on the densest of the gas phases in the centres of the ULIRGs."

The team is continuing its study of ULIRGs with the JCMT by observing the hot dense gas associated with the formation of young stars in these galactic powerhouses. "Even future satellites will not be able to supply us with all the information we need to probe the conditions within these galaxies: the JCMT with its large collecting area provides essential pieces in the puzzle," adds Kate Isaak of Cardiff University.

from: http://www.astronomynow.com/081105JCMTseesthedarkheartsofbrightgalaxies.html

Meteorites’ magnetism holds clues to planet birth

Magnetic records frozen into the cores of ancient meteorites have provided fresh insight into the planetary forming conditions at the beginning of the Solar System.

Benjamin Weiss of MIT and colleagues studied a group of the oldest known meteorites – angrites, basaltic rocks likely derived from main belt asteroids – to solve a longstanding mystery regarding the way planets form. The key result is that small planetary building blocks around 160 kilometres in diameter were still large enough to melt, separating out into a light crust and a heavier core. This heavy, iron-rich material began to turn over to produce a magnetic dynamo, the traces of which are still preserved in the meteorites that fell to Earth.

iPlanetary building blocks could have been differentiated into mini-planets with core, mantle and crust. Remnant magnetism from these planetesimals has been detected in ancient meteorites that fell to Earth. Image: NASA/JPL-Caltech.

"The magnetism in meteorites has been a longstanding mystery,” says Weiss. Indeed, until relatively recently, it was commonly thought that planetesimals — similar to the asteroids seen in the Solar System today — that came together to build planets were just homogenous, unmelted rocky material, with no large-scale structure. "Now we're realising that many of the things that were forming planets were mini-planets themselves, with crusts and mantles and cores."

The revelation has the potential to change key theories regarding the formation and evolution of planetary bodies in the early Solar System. Specifically, if the smaller bodies were already molten as they slammed together to build up larger planet-sized bodies, that could have implications for how different minerals are distributed in the Earth's crust, mantle and core today.

"In the last five or ten years our understanding of the early history of the Solar System has undergone a sort of mini-revolution, driven by analytical advances in geochemistry,” says Weiss. “In this study we used a geophysical technique to independently test many of these new ideas."

Events in the nascent Solar System took place at a fast rate and the fact that some of the angrite meteorites used in this study formed just three million years after the birth of the Solar System and show signs that their parent body had a magnetic field that was 20 to 40 percent as strong as Earth's today, has serious implications for the development of magnetic fields on planets.

"We are used to thinking of dynamo magnetic fields in rocky bodies as uncommon phenomena today,” says Weiss. “But it may be that short-lived planetesimal dynamos were widespread in the early Solar System." Because the magnetic record preserved in the angrite meteorites extends beyond the expected lifetime of the circumstellar disc, the magnetic fields must have been generated inside the body from which the meteorites were derived, possibly by an early magnetic dynamo in the planetesimal’s rapidly formed metallic core.

The results of the study are published in the 31 October edition of the journal Science.

from: http://www.astronomynow.com/081105meteoritesmagnetismholdscluestoplanetbirth.html

Rare impact craters revealed in Martian polar terrain

New HiRISE images have revealed two rare sightings of impact craters in the Mars’ northern polar regions.

In the first image, an unusual solitary mound protruding from a depression in a slope in Mars’ north polar layered terrain was brought to the attention of HiRISE scientists. Mars’ layered terrain is made up from stacks of ice and dust several kilometres thick, and is thought to contain much of the planet’s water reservoir. Its formation is believed to be strongly linked to atmospheric processes, and scientists believe the deposits record details of climate changes on the red planet.

This cater surprised scientists because of its location in the north layered terrain where craters are rare, its non-circular shape possibly arising from flowing ice deforming the bowl-shaped cavity, and the mound of bright ice rising out of the crater. The surrounding terrain has lost most of its ice cover, whereas that in the crater could be protected by the crater walls. The image is colour enhanced to show ice as blue/white and the surrounding terrain as yellow. Image: NASA/JPL/University of Arizona.

The new HiRISE image shows an exposed 500 metre thick section of this layering, and part of what could be the remnant of a once buried impact crater. The image reveals a 40 metre high conical mound sticking out of the slope that is made up of polygonal blocks as big as 10 metres across. The blocks are covered with reddish dust, but otherwise resemble ice-rich blocks seen in other images of the north polar layered deposits.

"The mound may be the remnant of a buried impact crater, which is now being exhumed," says planetary scientist Shane Byrne from the Lunar and Planetary Laboratory in Arizona. Impact craters would have been buried by ice as the layered deposits accumulated, with layers wrapping around and infilling the crater. But this is a rare case, since almost no craters exist on the surface of this terrain. "In this case, erosion formed a trough that uncovered one of these structures,” continues Byrne. “For reasons that are poorly understood right now, the ice beneath the site of the crater is more resistant to this erosion, so that as this trough formed, ice beneath the old impact site remained, forming this isolated hill."

This is the crater seen against the vast expanse of the north polar cap. Colours have been enhanced to show dusty regions as red and ice of large grain sizes as blue. A smooth area stretching away from the crater to the upper right of the image may be caused by winds around the crater or by fine-grained ice and frost blowing out of the crater. Image: NASA/JPL/University of Arizona.

In another new HiRISE image a second impact crater 115 metres in diameter is witnessed on the north polar cap itself, where such features are hardly ever observed. The deficit of impact craters in these high northern latitudes suggests that either the north polar cap is only about 100,000 years old or that crater impacts into the ice disappear as the ice relaxes over time.

Since the Mars Reconnaissance Orbiter's HiRISE camera began operations in 2006, it has returned more than 8,200 gigapixel-sized images of the Martian surface that are giving planetary scientists brand new insight into the geology of the red planet

from:http://www.astronomynow.com/081021RareimpactcratersrevealedinMartianpolarterrain.html

The stellar nursery with a massive heart

A new ESO image reveals the vast stellar nursery of Gum 29, which hosts a small cluster of stars bearing one of the most massive double star systems known to man.

This image was obtained with the Wide Field Imager (WFI) camera attached to the 2.2-metre Max-Planck/ESO telescope through four different filters (B, V, R, and H-alpha), and shows the amazing intricacies of the vast stellar nursery Gum 29. At its centre lies the cluster of young stars Westerlund 2. Image: ESO.

Gum 29, named for it being the 29th entry in astronomer Colin Stanley Gum’s catalogue, is a vast region of ionised hydrogen gas that spans over 200 light years. Known as the H-II region, the hydrogen gas has been stripped of its electrons by the intense breath of hot young stars radiating in its centre. The new image was captured with the Wide Field Imager (WFI) camera attached to the 2.2 metre Max-Planck telescope at the European Southern Observatory (ESO)’s La Silla site in Chile.

A young and little-known star cluster – Westerlund 2 – is embedded within the belly of Gum 29 at a distance of 26,000 light years from Earth, corresponding to a location within the outer edge of the Carina spiral arm of our Milky Way Galaxy. It is thought to be just one or two million years old. Two stars in the bottom right of Westerlund 2 form a double star system of huge proportions at 82 and 83 times the mass of our Sun respectively, and rotating around each other in approximately 3.7 days. They are amongst the most massive stars known to astronomers.

Marked in the image is a double stellar system in the Westerlund 2 cluster. The two stars have masses of 82 and 83 times that of our Sun and are amongst the most massive stars known to astronomers. Image: ESO.

Intense scrutiny of this pair has also revealed their identity as Wolf-Rayet stars, massive stars that are expelling huge quantities of material as they near the end of their lives. Observations made in X-rays have subsequently shown that streams of material from each star continually collide, creating a blaze of X-ray radiation.

COROT sees sunquakes in other stars

The CNES/ESA Earth orbiting COROT satellite has applied the technique of seismology to the study of stellar interiors, probing the interiors of three stars beyond our own Sun for the first time.

COROT can detect ‘starquakes’, acoustic waves generated deep within a star that ripple across the star’s surface, altering its brightness. By studying these variations, a star’s mass, age and structure can be determined. Image: CNES.

Like the propagation of seismic waves on Earth providing information about our planet's interior, sound waves travelling throughout the Sun and other stars carry information about what is happening below the surface. The study of these waves propagating through a star is known as helioseismology, and has already been used to generate complex models of the interior conditions on our Sun, showing that different layers of our home star rotate at different speeds to generate the Sun’s magnetic field, and that jet streams of plasma run thousands of kilometres below the surface.

Oscillations of the Sun’s surface can also be tracked by direct observations and related to interior processes by the tool of helioseismology. Similar oscillations can be observed on other stars by watching for variations in the light emitted by the star as the surface wobbles, revealing both the internal structure of the star and the way energy is transported from the core to the surface.

"Other techniques to estimate stellar oscillations have been used from the ground, but they are limited in what they can do," says Malcolm Fridlund, ESA Project Scientist for COROT at ESA's European Space Research and Technology Centre (ESTEC). "Adverse weather conditions, plus the fact that you cannot observe stars during daytime, oblige ground astronomers to interrupt their observations.”

COROT consists of a 27 centimetre telescope and was launched in December 2006. Image: CNES/D. Ducros.

The COROT satellite allows uninterrupted viewing from afar, and with high sensitivity instruments such as a 4-CCD camera capable of recording tiny variations of light intensity emitted from a star, COROT offers a new view of our stellar neighbourhood. In the new study, three Sun-like stars were scrutinized by COROT: HD499933, HD181420 and HD181906, revealing 'sunquakes' rumbling inside their interiors.

"The fact that COROT succeeded in probing the interior of Sun-like stars with direct measurements for the first time is a huge leap in understanding stars in general", says Fridlund. "In addition, this will help us to understand, by comparison, our own Sun even better."

COROT was launched at the end of 2006 and was designed as both a planet hunter and star surveyor, having clocked up six exoplanets to date with the aim of surveying around 120,000 stars for exoplanets, and over a hundred stars for stellar seismology studies.

from:http://www.astronomynow.com/081024COROTseessunquakesinotherstars.html