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Wednesday, March 25, 2015

Black-hole 'Wind' Linked to a Galactic Gush of Star-forming Gas


By combining observations from the Japan-led Suzaku X-ray satellite and the European Space Agency's infrared Herschel Space Observatory, scientists have connected a fierce "wind" produced near a galaxy's monster black hole to an outward torrent of cold gas a thousand light-years across. The finding validates a long-suspected feedback mechanism enabling a supermassive black hole to influence the evolution of its host galaxy.

"This is the first study directly connecting a galaxy's actively 'feeding' black hole to features found at much larger physical scales," said lead researcher Francesco Tombesi, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park (UMCP). "We detect the wind arising from the luminous disk of gas very close to the black hole, and we show that it's responsible for blowing star-forming gas out of the galaxy's central regions."

This artist's rendering shows a galaxy being cleared of interstellar gas, the building blocks of new stars. New X-ray observations by Suzaku have identified a wind emanating from the black hole's accretion disk (inset) that ultimately drives such outflows.
Image Credit: ESA/ATG Medialab

Star formation takes place in cold, dense molecular clouds. By heating and dispersing gas that could one day make stars, the black-hole wind forever alters a large portion of its galaxy.

In a study published in the March 26 edition of Nature, Tombesi and his team report the connection in a galaxy known as IRAS F11119+3257, or F11119 for short. The galaxy is so distant, its light has been traveling to us for 2.3 billion years, or about half the present age of our solar system.

Like most galaxies, including our own Milky Way, F11119 hosts a supersized black hole, one estimated at 16 million times the sun's mass. The black hole's activity is fueled by a rotating collection of gas called an accretion disk, which is some hundreds of times the size of our planetary system. Closest to the black hole, the orbiting matter reaches temperatures of millions of degrees and is largely responsible for the galaxy's enormous energy output, which exceeds the sun's by more than a trillion times. The galaxy is heavily enshrouded by dust, so most of this emission reaches us in the form of infrared light.

A red-filter image of IRAS F11119+3257 (inset) from the University of Hawaii's 2.2-meter telescope shows faint features that may be tidal debris, a sign of a galaxy merger. Background: A wider view of the region from the Sloan Digital Sky Survey.

Image Credit: NASA's Goddard Space Flight Center/SDSS/S. Veilleux

The new findings resolve a long-standing puzzle. Galaxies show a correlation between the mass of their central black holes and stellar properties across a much larger region called the galactic bulge. Galaxies with more massive black holes usually possess bulges with proportionately greater stellar mass and faster-moving stars.

Black holes grow the same way their host galaxies do, by colliding and merging with their neighbors. But mergers disrupt galaxies, which leads to greatly enhanced star formation and sends a flood of gas toward the merged black hole. The process should scramble any simple relationship between the black hole's growth and the galaxy's evolution, yet it doesn't.

This animation illustrates how black-hole feedback works in quasars. Dense gas and dust in the center simultaneously fuels the black hole and shrouds it from view. The black-hole wind propels large-scale outflows of cold gas and powers a shock wave that clears gas and dust from the central galaxy.

Image Credit: NASA's Goddard Space Flight Center 

"These connections suggested the black hole was providing some form of feedback that modulated star formation in the wider galaxy, but it was difficult to see how," said team member Sylvain Veilleux, an astronomy professor at UMCP. "With the discovery of powerful molecular outflows of cold gas in galaxies with active black holes, we began to uncover the connection."

In 2013, Veilleux led a search for these outflows in a sample of active galaxies using the Herschel Space Observatory. In F11119, the researchers identified a strong outflow of hydroxyl molecules moving at about 2 million mph (3 million kph). Other studies using different trace molecules found similar flows.

In the present study, Tombesi, Veilleux and their colleagues estimate that this outflow operates up to 1,000 light-years from the galaxy's center and calculate that it removes enough gas to make 800 copies of our sun.

In May 2013, the team observed F11119 using Suzaku's X-ray Imaging Spectrometer, obtaining an effective exposure of nearly three days. The galaxy's spectrum indicates that X-ray-absorbing gas is racing outward from the innermost accretion disk at 170 million mph (270 million kph), or about a quarter the speed of light. The region is possibly half a billion miles (800 million km) from the brink of the black hole, and about as close to the point where not even light can escape as Jupiter is from the sun.

"The black hole is ingesting gas as fast as it can and is tremendously heating the accretion disk, allowing it to produce about 80 percent of the energy this galaxy emits," said co-author Marcio Meléndez, a research associate at UMCP. "But the disk is so luminous some of the gas accelerates away from it, creating the X-ray wind we observe."

Taken together, the disk wind and the molecular outflow complete the picture of black-hole feedback. The black-hole wind sets cold gas and dust into motion, giving rise to the molecular outflow. It also heats dust enshrouding the galaxy, leading to the formation of an outward-moving shock wave that sweeps away additional gas and dust.

When the black hole shines at its brightest, the researchers say, it's also effectively pushing away the dinner plate, clearing gas and dust from the galaxy's central regions and shutting down star formation there. Once the dust has been cleared out, shorter-wavelength light from the disk can escape more easily. 

Scientists think ultra-luminous infrared galaxies like F11119 represent an early phase in the evolution of quasars, a type of black-hole-powered galaxy with extreme luminosity across a broad wavelength range. According to this picture, the black hole will eventually consume its surrounding gas and gradually end its spectacular activity. As it does so, it will evolve from a quasar to a gas-poor galaxy with a relatively low level of star formation.
 
The researchers hope to detect and study this process in other galaxies and look forward to the improved sensitivity of Suzaku's successor, ASTRO-H. Expected to launch in 2016, ASTRO-H is being developed at the Institute of Space and Astronautical Science of the Japan Aerospace Exploration Agency (ISAS/JAXA), in collaboration with NASA Goddard and Japanese institutions.

NASA To Redirect Asteroids, Plans Revealed

NASA Wednesday announced more details in its plan for its Asteroid Redirect Mission (ARM), which in the mid-2020s will test a number of new capabilities needed for future human expeditions to deep space, including to Mars. NASA also announced it has increased the detection of near-Earth asteroids by 65 percent since launching its asteroid initiative three years ago.

The Asteroid Redirect Vehicle conducts one of the 1 km fly-bys that are used to characterize and image the asteroid with a resolution of up to 1 cm.
Credit: NASA

For ARM, a robotic spacecraft will capture a boulder from the surface of a near-Earth asteroid and move it into a stable orbit around the moon for exploration by astronauts, all in support of advancing the nation’s journey to Mars.

Microspine grippers on the end of the robotics arms are used to grasp and secure the boulder. The microspines use thousands of small spines to dig into the boulder and create a strong grip. An integrated drill will be used to provide final anchoring of the boulder to the capture mechanism.
Credit: NASA

"The Asteroid Redirect Mission will provide an initial demonstration of several spaceflight capabilities we will need to send astronauts deeper into space, and eventually, to Mars," said NASA Associate Administrator Robert Lightfoot. "The option to retrieve a boulder from an asteroid will have a direct impact on planning for future human missions to deep space and begin a new era of spaceflight."

Asteroid Capture:  Once the boulder is secured, the ARV will mechanically push off, or “hop,” from the surface and then use thrusters to ascend from the asteroid’s surface.
Credit: NASA

The agency plans to announce the specific asteroid selected for the mission no earlier than 2019, approximately a year before launching the robotic spacecraft. Before an asteroid is considered a valid candidate for the mission, scientists must first determine its characteristics, in addition to size, such as rotation, shape and precise orbit. NASA has identified three valid candidates for the mission so far: Itokawa, Bennu and 2008 EV5. The agency expects to identify one or two additional candidates each year leading up to the mission.

Asteroid Redirect Vehicle Landing: Once the boulder is secured, the Capture and Restraint System legs will provide a mechanical push off that will separate the boulder from the surface and provide an initial ascent without the use of thrusters to limit the amount of debris created.
Credit: NASA

Following its rendezvous with the target asteroid, the uncrewed ARM spacecraft will deploy robotic arms to capture a boulder from its surface. It then will begin a multi-year journey to redirect the boulder into orbit around the moon.

Close-up of the Asteroid Redirect Vehicle departing the asteroid after capturing a boulder from its surface. 
Credit: NASA

Throughout its mission, the ARM robotic spacecraft will test a number of capabilities needed for future human missions, including advanced Solar Electric Propulsion (SEP), a valuable capability that converts sunlight to electrical power through solar arrays and then uses the resulting power to propel charged atoms to move a spacecraft. This method of propulsion can move massive cargo very efficiently. While slower than conventional chemical rocket propulsion, SEP-powered spacecraft require significantly less propellant and fewer launches to support human exploration missions, which could reduce costs.

The asteroid redirect vehicle demonstrates the “gravity tractor” planetary defense technique on a hazardous-size asteroid. The gravity tractor method leverages the mass of the spacecraft to impart a gravitational force on the asteroid, slowly altering the asteroid’s trajectory. The demonstration is conducted after capturing the boulder and is referred to as the “enhanced gravity tractor” because the additional mass of the boulder enhances the force that can be transmitted to the asteroid. 
Credit: NASA

Future SEP-powered spacecraft could pre-position cargo or vehicles for future human missions into deep space, either awaiting crews at Mars or staged around the moon as a waypoint for expeditions to the Red Planet.

The Asteroid Redirect Vehicle travels toward a stable orbit around the moon with the captured asteroid boulder. The vehicle’s solar arrays collect power from the sun and convert it to energy to ionize and accelerate xenon propellant, resulting in the bright blue plume at the rear of the vehicle.

Credit: NASA

ARM's SEP-powered robotic spacecraft will test new trajectory and navigation techniques in deep space, working with the moon's gravity to place the asteroid in a stable lunar orbit called a distant retrograde orbit. This is a suitable staging point for astronauts to rendezvous with a deep space habitat that will carry them to Mars.

An astronaut, anchored to a foot restraint, prepares to investigate the asteroid boulder.

Credit: NASA

Before the piece of the asteroid is moved to lunar orbit, NASA will use the opportunity to test planetary defense techniques to help mitigate potential asteroid impact threats in the future. The experience and knowledge acquired through this operation will help NASA develop options to move an asteroid off an Earth-impacting course, if and when that becomes necessary.

In 2005, NASA's Deep Impact comet science mission tested technology that could assist in changing the course of a near-Earth object using a direct hit with a spacecraft. The ARM robotic spacecraft opens a new and second option for planetary defense using a technique called a gravity tractor. All mass exerts and experiences gravity and, in space, the gravitational attraction even between masses of modest size can significantly affect their motion. This means that by rendezvousing with the asteroid and holding a halo orbit in the appropriate direction, the ARM robotic spacecraft can slowly pull the asteroid without touching it. The effectiveness of this maneuver is increased, moreover, if mass is moved from the asteroid to the spacecraft by the capture of a boulder.

The Asteroid Redirect Vehicle descends to the asteroid’s surface following a series of dry-runs that are used to verify vehicle performance. 
Credit: NASA

It will take approximately six years for the ARM robotic spacecraft to move the asteroid mass into lunar orbit. In the mid-2020s, NASA's Orion spacecraft will launch on the agency’s Space Launch System rocket, carrying astronauts on a mission to rendezvous with and explore the asteroid mass. The current concept for the crewed mission component of ARM is a two-astronaut, 24-25 day mission.

This crewed mission will further test many capabilities needed to advance human spaceflight for deep space missions to Mars and elsewhere, including new sensor technologies and a docking system that will connect Orion to the robotic spacecraft carrying the asteroid mass. Astronauts will conduct spacewalks outside Orion to study and collect samples of the asteroid boulder wearing new spacesuits designed for deep space missions.

Collecting these samples will help astronauts and mission managers determine how best to secure and safely return samples from future Mars missions. And, because asteroids are made of remnants from the formation of the solar system, the returned samples could provide valuable data for scientific research or commercial entities interested in asteroid mining as a future resources.
 
In 2012, the president's NASA budget included, and Congress authorized, $20.4 million for an expanded NASA Near-Earth Object (NEO) Observations Program, increasing the resources for this critical program from the $4 million per year it had received since the 1990s. The program was again expanded in fiscal year 2014, with a budget of $40.5 million. NASA is asking Congress for $50 million for this important work in the 2016 budget.

"Asteroids are a hot topic," said Jim Green, director of NASA Planetary Science. "Not just because they could pose a threat to Earth, but also for their scientific value and NASA's planned mission to one as a stepping stone to Mars."

NASA has identified more than 12,000 NEOs to date, including 96 percent of near-Earth asteroids larger than 0.6 miles (1 kilometer) in size. NASA has not detected any objects of this size that pose an impact hazard to Earth in the next 100 years. Smaller asteroids do pass near Earth, however, and some could pose an impact threat. In 2011, 893 near-Earth asteroids were found. In 2014, that number was increased to 1,472.

In addition to NASA's ongoing work detecting and cataloging asteroids, the agency has engaged the public in the hunt for these space rocks through the agency's Asteroid Grand Challenge activities, including prize competitions. During the recent South by Southwest Festival in Austin, Texas, the agency announced the release of a software application based on an algorithm created by a NASA challenge that has the potential to increase the number of new asteroid discoveries by amateur astronomers.

 
Contacts and sources:
David E. Steitz / Karen Northon
NASA

Jupiter's Grand Attack on the Inner Solar System

Jupiter may have swept through the early solar system like a wrecking ball, destroying a first generation of inner planets before retreating into its current orbit, according to a new study published March 23 in Proceedings of the National Academy of Sciences. The findings help explain why our solar system is so different from the hundreds of other planetary systems that astronomers have discovered in recent years.

Jupiter is thought to have migrated inward toward the sun before retreating to its current position in the solar system. 
Photo credit: NASA/Cassini

"Now that we can look at our own solar system in the context of all these other planetary systems, one of the most interesting features is the absence of planets inside the orbit of Mercury," said Gregory Laughlin, professor and chair of astronomy and astrophysics at UC Santa Cruz and coauthor of the paper. "The standard issue planetary system in our galaxy seems to be a set of super-Earths with alarmingly short orbital periods. Our solar system is looking increasingly like an oddball."

The new paper explains not only the "gaping hole" in our inner solar system, he said, but also certain characteristics of Earth and the other inner rocky planets, which would have formed later than the outer planets from a depleted supply of planet-forming material.

Laughlin and coauthor Konstantin Batygin explored the implications of a leading scenario for the formation of Jupiter and Saturn. In that scenario, proposed by another team of astronomers in 2011 and known as the "Grand Tack," Jupiter first migrated inward toward the sun until the formation of Saturn caused it to reverse course and migrate outward to its current position. 

This diagram shows the orbital distribution of extrasolar planets smaller than Jupiter that have been detected by the Kepler mission, in comparison to the orbits of Mercury, Venus, Earth, and Mars. Most of these extrasolar planets are much closer to their host stars than the innermost planets of our solar system are to the sun.

Credit: Batygin and Laughlin, PNAS

Batygin, who first worked with Laughlin as an undergraduate at UC Santa Cruz and is now an assistant professor of planetary science at the California Institute of Technology, performed numerical calculations to see what would happen if a set of rocky planets with close-in orbits had formed prior to Jupiter's inward migration.

At that time, it's plausible that rocky planets with deep atmospheres would have been forming close to the sun from a dense disk of gas and dust, on their way to becoming typical "super-Earths" like so many of the exoplanets astronomers have found around other stars. As Jupiter moved inward, however, gravitational perturbations from the giant planet would have swept the inner planets (and smaller planetesimals and asteroids) into close-knit, overlapping orbits, setting off a series of collisions that smashed all the nascent planets into pieces.

"It's the same thing we worry about if satellites were to be destroyed in low-Earth orbit. Their fragments would start smashing into other satellites and you'd risk a chain reaction of collisions. Our work indicates that Jupiter would have created just such a collisional cascade in the inner solar system," Laughlin said.

The resulting debris would then have spiraled into the sun under the influence of a strong "headwind" from the dense gas still swirling around the sun. The ingoing avalanche would have destroyed any newly-formed super-Earths by driving them into the sun. A second generation of inner planets would have formed later from the depleted material that was left behind, consistent with evidence that our solar system's inner planets are younger than the outer planets. The resulting inner planets--Mercury, Venus, Earth, and Mars--are also less massive and have much thinner atmospheres than would otherwise be expected, Laughlin said.

"One of the predictions of our theory is that truly Earth-like planets, with solid surfaces and modest atmospheric pressures, are rare," he said.

Planet hunters have detected well over a thousand exoplanets orbiting stars in our galaxy, including nearly 500 systems with multiple planets. What has emerged from these observations as the "typical" planetary system is one consisting of a few planets with masses several times larger than the Earth's (called super-Earths) orbiting much closer to their host star than Mercury is to the sun. In systems with giant planets similar to Jupiter, they also tend to be much closer to their host stars than the giant planets in our solar system. The rocky inner planets of our solar system, with relatively low masses and thin atmospheres, may turn out to be fairly anomalous.

According to Laughlin, the formation of giant planets like Jupiter is somewhat rare, but when it occurs the giant planet usually migrates inward and ends up at an orbital distance similar to Earth's. Only the formation of Saturn in our own solar system pulled Jupiter back out and allowed Mercury, Venus, Earth, and Mars to form. Therefore, another prediction of the paper is that systems with giant planets at orbital periods of more than about 100 days would be unlikely to host multiple close-in planets, Laughlin said.

"This kind of theory, where first this happened and then that happened, is almost always wrong, so I was initially skeptical," he said. "But it actually involves generic processes that have been extensively studied by other researchers. There is a lot of evidence that supports the idea of Jupiter's inward and then outward migration. Our work looks at the consequences of that. Jupiter's 'Grand Tack' may well have been a 'Grand Attack' on the original inner solar system."

In a 2010 study, scientists say baby Jupiter was so strongly bashed by giant Earths that it lost part of its core. That would explain why Jupiter's core is disproportionately smaller today than sibling planet Saturn, says astronomer Douglas Lin, with the University of California in Santa Cruz.  

Scientists suspect that gas giant planets like Jupiter and Saturn started off with rocky and/or icy bodies about 10 times the mass of Earth. At that point, their gravitational muscles would be strong enough to begin pulling gas from the surrounding region, causing them to balloon in size over time. 

"In principle, all gas giants need to get to a critical core mass before they can start to accrete gas," Lin told Discovery News. "So the question is: Why is Jupiter's core mass so much smaller than Saturn's even though its total mass is so much bigger?" 

Working with computer models, astronomers Shu Lin Li of Peking University in China, Craig Agnor with Queen Mary University of London, and Lin came up with one possible answer: Perhaps Jupiter started off like Saturn, but lost part of its core as it evolved. The scientists calculated that if an object roughly five times the mass of Earth hit Jupiter, the impact would strike all the way to the planet's core. Add another three or four crashes and Jupiter's core would be eroded to roughly what it is today. 

"Jupiter has always had this problem because if we believe the numbers... the core seems to be too small -- so small that it cannot accrete gas efficiently in the solar nebula. This scenario gets around the problem," Lin said. 


Contacts and sources:
Tim Stephens
University of California in Santa Cruz

Monday, March 23, 2015

Darwinian Puzzle Key Found


Scientific screening techniques developed by our researchers have solved an important evolutionary puzzle that has baffled palaeontologists for more than a century.


Credit: York University

The remarkable technical feat casts new light on the origins of Toxodon and Macrauchenia, South American ungulates or hooved animals, described by Charles Darwin as the ‘strangest animals ever discovered’.

Previous attempts by scientists to pinpoint the origin of the animals using morphology-based analysis and DNA analysis of fossils had failed.

But techniques refined by experts in our BioArCh research facility and Centre of Excellence in Mass Spectrometry uncovered evidence that the animals were related to mammals like horses - rather than elephants and other African species as some taxonomists have maintained.

The breakthrough came when the researchers switched to analysing collagen samples, a structural protein that can survive around ten times longer than DNA. The team at York team screened 48 fossil bone samples of Toxodon platensis and Macrauchenia patachonica discovered in the 19th century in the same area as those recovered by Darwin.

Credit: W. Norton Publishers (in production).

Family tree

They produced sequences covering more than 90 per cent of the collagen molecule, providing a phylogenetic family ‘tree’ for the two species.

This is the first time the technique has produced molecular information based on protein sequences from the time of the last Ice Age, opening up the potential for further important evolutionary insights.

“People have been successful in retrieving collagen sequences from specimens dating up to four million years old and this is just the start,” said Professor Matthew Collins of BioArCh who carried out the sequencing work with Professor Jane Thomas-Oates, director of York’s Centre of Excellence in Mass Spectrometry. “In theory, with material recovered from permafrost conditions, we might be able to reach back ten million years or more.”

Exploring the evolutionary process

He added: “We now have the potential to address many more of these challenges and to explore the evolutionary process much further back in prehistory.”

The research team also included York PhD student Frido Welker and Dr Jessica Thomas from the University’s Department of Biology.

The Natural History Museum and the American Museum of Natural History led the project which was funded through the Systematics and Taxonomy research scheme (SynTax) supported by the Systematics Association, Linnean Society and the Biotechnology and Biological Sciences Research Council and the Natural Environment Research Council. The research is published in Nature.

Toxodon and Macrauchenia disappeared around 10,000 years ago. The 1.5 ton rhinoceros-sized Toxodon was the most common large-hoofed mammal to roam South America during the Late Pliocene and Plesistocene period over 16,500 years ago. The more nimble Macrauchenia, or ‘long llama’ resembled a humpless camel – but with a short trunk-like snout.

Charles Darwin collected fossils of the animals 180 years ago in Uruguay and Argentina during a stop-over on his famous journey on board The Beagle.


Contacts and sources:
Professor Mathew Collins

The Sound of Stars Discovered

A chance discovery by a team of researchers, including a University of York scientist, has provided experimental evidence that stars may generate sound.

Star formation in the Large Magellanic Cloud
 Credit; ESO 

The study of fluids in motion – now known as hydrodynamics – goes back to the Egyptians, so it is not often that new discoveries are made. However when examining the interaction of an ultra-intense laser with a plasma target, the team observed something unexpected.

Scientists including Dr John Pasley, of the York Plasma Institute in the Department of Physics at York, realised that in the trillionth of a second after the laser strikes, plasma flowed rapidly from areas of high density to more stagnant regions of low density, in such a way that it created something like a traffic jam. Plasma piled up at the interface between the high and low density regions, generating a series of pressure pulses: a sound wave.

However, the sound generated was at such a high frequency that it would have left even bats and dolphins struggling! With a frequency of nearly a trillion hertz, the sound generated was not only unexpected, but was also at close to the highest frequency possible in such a material – six million times higher than that which can be heard by any mammal!

Dr Pasley, who worked with scientists from the Tata Institute of Fundamental Research in Mumbai, India, and the Science and Technology Facilities Council’s Central Laser Facility in Oxfordshire, said: “One of the few locations in nature where we believe this effect would occur is at the surface of stars. When they are accumulating new material stars could generate sound in a very similar manner to that which we observed in the laboratory – so the stars might be singing – but, since sound cannot propagate through the vacuum of space, no-one can hear them.”

The technique used to observe the sound waves in the laboratory works very much like a police speed camera. It allows the scientists to accurately measure how fluid is moving at the point that is struck by the laser on timescales of less than a trillionth of a second.

Dr Alex Robinson from the Plasma Physics Group at STFC’s Central Laser Facility developed a numerical model to generate acoustic waves for the experiment. He said, “It was initially hard to determine the origin of the acoustic signals, but our model produced results that compared favourably with the wavelength shifts observed in the experiment. This showed that we had discovered a new way of generating sound from fluid flows. Similar situations could occur in plasma flowing around stars.”

The research was funded by the Engineering and Physical Sciences Research Council and the Tata Institute of Fundamental Research. It is published in Physical Review Letters.



Contacts and sources:
David Garner
University of York

Citaiton:  Terahertz acoustics in hot dense laser-plasmas by Amitava Adak, A. P. L. Robinson, Prashant Kumar Singh, et al is published in Physical Review Letters.

Doomsday Asteroid Strikes Found in Australia; Left World's Largest Impact Zone

A 400 kilometre-wide impact zone from a huge meteorite that broke in two moments before it slammed into the Earth has been found in Central Australia.

The crater from the impact millions of years ago has long disappeared. But a team of geophysicists has found the twin scars of the impacts – the largest impact zone ever found on Earth – hidden deep in the earth’s crust.

Dr Andrew Glikson with a sample of suevite - a rock with partially melted material formed during an impact. 

Image: D. Seymour

Lead researcher Dr Andrew Glikson from the ANU School of Archaeology and Anthropologysaid the impact zone was discovered during drilling as part of geothermal research, in an area near the borders of South Australia, Queensland and the Northern Territory.

“The two asteroids must each have been over 10 kilometres across – it would have been curtains for many life species on the planet at the time,” said Dr Glikson.

Their paper reports geophysical anomalies and intra-crystalline quartz lamellae in drill cores from the Warburton West Basin overlapping the border of South Australia and the Northern Territory. The pre-Upper Carboniferous ~ 450 × 300 km-large Warburton Basin, north-eastern South Australia, is marked by distinct eastern and western magnetic, gravity and low-velocity seismic tomography anomalies.

Warburton East and West sub-basins, northeast South Australia; the Birdsville Track Ridge divides the Warburton East Basin from the Warburton West Basin. 

Credit: Andrew Glikson et al.

The revelation of such ancient violent impacts may lead to new theories about the Earth’s history.

“Large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought,” Dr Glikson said.

The exact date of the impacts remains unclear. The surrounding rocks are 300 to 600 million years old, but evidence of the type left by other meteorite strikes is lacking.

For example, a large meteorite strike 66 million years ago sent up a plume of ash which is found as a layer of sediment in rocks around the world. The plume is thought to have led to the extinction of a large proportion of the life on the planet, including many dinosaur species.

Wharburton Basin 

Credit: Google Earth

However, a similar layer has not been found in sediments around 300 million years old, Dr Glikson said.

“It’s a mystery – we can’t find an extinction event that matches these collisions. I have a suspicion the impact could be older than 300 million years,” he said.

A geothermal research project chanced on clues to the impacts while drilling more than two kilometres into the earth’s crust.

The drill core contained traces of rocks that had been turned to glass by the extreme temperature and pressure caused by a major impact.

Magnetic modelling of the deep crust in the area traced out bulges hidden deep in the Earth, rich in iron and magnesium, corresponding to the composition of the Earth mantle.

“There are two huge deep domes in the crust, formed by the Earth’s crust rebounding after the huge impacts, and bringing up rock from the mantle below,” Dr Glikson said.

The two impact zones total more than 400 kilometres across, in the Warburton Basin in Central Australia. They extend through the Earth’s crust, which is about 30 kilometres thick in this area.

The research has been published in journal Tectonophysics.


Contacts and sources:
Dr Phil Dooley

Citation: Geophysical anomalies and quartz deformation of the Warburton West structure, central Australia: Authors:  A.Y. Glikson,  A.J. Meixner, B. Radke, I.T. Uysal, E. Saygin, J. Vickers, 
T.P. Mernagh 

Sunday, March 22, 2015

Prehistoric Stone Tools Bear 500,000-Year-Old Animal Residue

Tel Aviv Univeisty (TAU) discovers first direct evidence early flint tools were used to butcher animal carcasses.

Some 2.5 million years ago, early humans survived on a paltry diet of plants. As the human brain expanded, however, it required more substantial nourishment — namely fat and meat — to sustain it. This drove prehistoric man, who lacked the requisite claws and sharp teeth of carnivores, to develop the skills and tools necessary to hunt animals and butcher fat and meat from large carcasses.

An elephant rib bearing cutmarks associated with flint tools at the Revadim site.

Credit:  American Friends of Tel Aviv University (AFTAU)

Among elephant remains some 500,000 years old at a Lower Paleolithic site in Revadim, Israel, Prof. Ran Barkai and his graduate students Natasha Solodenko and Andrea Zupanchich of Tel Aviv University's Department of Archaeology and Ancient Near Eastern Cultures recently analyzed "handaxes" and "scrapers," universally shaped and sized prehistoric stone tools, replete with animal residue.

The research, published recently in PLOS One, represents the first scientifically verified direct evidence for the precise use of Paleolithic stone tools: to process animal carcasses and hides. The research was done in collaboration with Drs. Stella Ninziante Cesaro and Cristina Lemorini of La Sapienza, University of Rome, and Dr. Ofer Marder of Ben-Gurion University of the Negev.

Putting the puzzle together

"There are three parts to this puzzle: the expansion of the human brain, the shift to meat consumption, and the ability to develop sophisticated technology to meet the new biological demands. The invention of stone technology was a major breakthrough in human evolution," Prof. Barkai said. "Fracturing rocks in order to butcher and cut animal meat represents a key biological and cultural milestone.

"At the Revadim quarry, a wonderfully preserved site a half-million years old, we found butchered animal remains, including an elephant rib bone which had been neatly cut by a stone tool, alongside flint handaxes and scrapers still retaining animal fat. It became clear from further analyses that butchering and carcass processing indeed took place at this site."

Through use-wear analysis — examining the surfaces and edges of the tools to determine their function — and the Fourier Transform InfraRed (FTIR) residue analysis which harnesses infrared to identify signatures of prehistoric organic compounds, the researchers were able to demonstrate for the first time direct proof of animal exploitation by flint tools.

"Archaeologists have until now only been able to suggest scenarios about the use and function of such tools. We don’t have a time machine," Prof. Barkai said. "It makes sense that these tools would be used to break down carcasses, but until evidence was uncovered to prove this, it remained just a theory."

A prehistoric Swiss army knife

While the question of their function and production remained unanswered until now, there was little doubt that the handaxe and scraper, found at prehistoric sites all around the world, were distinct, used for specific purposes. By replicating the flint tools for a modern butchering experiment, and then comparing the replicas with their prehistoric counterparts, the researchers determined that the handaxe was prehistoric man's sturdy "Swiss army knife," capable of cutting and breaking down bone, tough sinew, and hide. The slimmer, more delicate scraper was used to separate fur and animal fat from muscle tissue.

"Prehistoric peoples made use of all parts of the animal," said Prof. Barkai. "In the case of the massive elephant, for example, they would have needed to use both tools to manage such a challenging task. The knowledge of how to make these tools was precious, and must have been passed along from generation to generation, because these tools were reproduced the same way across great territorial expanses and over hundreds of thousands of years.

"In this thousand-piece puzzle called archaeology, sometimes we find pieces that connect other pieces together. This is what we have found with the stone tools and animal bones."


Contacts and sources:

Did a Volcanic Cataclysm 40,000 Years Ago Trigger the Final Demise of the Neanderthals?

The Campanian Ignimbrite (CI) eruption in Italy 40,000 years ago was one of the largest volcanic cataclysms in Europe and injected a significant amount of sulfur-dioxide (SO2) into the stratosphere. Scientists have long debated whether this eruption contributed to the final extinction of the Neanderthals. This new study by Benjamin A. Black and colleagues tests this hypothesis with a sophisticated climate model.

This image shows annually averaged temperature anomalies in excess of 3°C for the first year after the Campanian Ignimbrite (CI) eruption compared with spatial distribution of hominin sites with radiocarbon ages close to that of the eruption.

Credit: B.A. Black et al. and the journal Geology

Black and colleagues write that the CI eruption approximately coincided with the final decline of Neanderthals as well as with dramatic territorial and cultural advances among anatomically modern humans. Because of this, the roles of climate, hominin competition, and volcanic sulfur cooling and acid deposition have been vigorously debated as causes of Neanderthal extinction.

They point out, however, that the decline of Neanderthals in Europe began well before the CI eruption: "Radiocarbon dating has shown that at the time of the CI eruption, anatomically modern humans had already arrived in Europe, and the range of Neanderthals had steadily diminished. Work at five sites in the Mediterranean indicates that anatomically modern humans were established in these locations by then as well."

"While the precise implications of the CI eruption for cultures and livelihoods are best understood in the context of archaeological data sets," write Black and colleagues, the results of their study quantitatively describe the magnitude and distribution of the volcanic cooling and acid deposition that ancient hominin communities experienced coincident with the final decline of the Neanderthals.

In their climate simulations, Black and colleagues found that the largest temperature decreases after the eruption occurred in Eastern Europe and Asia and sidestepped the areas where the final Neanderthal populations were living (Western Europe). Therefore, the authors conclude that the eruption was probably insufficient to trigger Neanderthal extinction.

However, the abrupt cold spell that followed the eruption would still have significantly impacted day-to-day life for Neanderthals and early humans in Europe. Black and colleagues point out that temperatures in Western Europe would have decreased by an average of 2 to 4 degrees Celsius during the year following the eruption. These unusual conditions, they write, may have directly influenced survival and day-to-day life for Neanderthals and anatomically modern humans alike, and emphasize the resilience of anatomically modern humans in the face of abrupt and adverse changes in the environment.


Contacts and sources:
Kea Giles
The Geological Society of America

Citation: Campanian Ignimbrite volcanism, climate, and the final decline of the Neanderthals
Benjamin A. Black et al., University of California, Berkeley, California, USA. Published online ahead of print on 19 March 2015; http://dx.doi.org/10.1130/G36514.1.

Milky Way's Center Harbors Supernova 'Dust Factory'

Sifting through the center of the Milky Way galaxy, astronomers have made the first direct observations - using an infrared telescope aboard a modified Boeing 747 - of cosmic building-block dust resulting from an ancient supernova.

"Dust itself is very important because it's the stuff that forms stars and planets, like the sun and Earth, respectively, so to know where it comes from is an important question," said lead author Ryan Lau, Cornell postdoctoral associate for astronomy, in research published March 19 in Science Express. "Our work strongly reinforces the theory that supernovae are producing the dust seen in galaxies of the early universe," he said.

Lau explains that one of astronomy's big questions is why galaxies - forming as recently as 1 billion years after the Big Bang - contain so much dust. The leading theory is that supernovae - stars that explode at the end of their lives - contain large amounts of metal-enriched material that, in turn, harbors key ingredients of dust, like silicon, iron and carbon.

The astronomers examined Sagittarius A East, a 10,000-year-old supernova remnant near the center of our galaxy. Lau said that when a supernova explodes, the materials in its center expand and form dust. This has been observed in several young supernova remnants - such as the famed SN1987A and Cassiopeia A. 

A time sequence of Hubble Space Telescope images, taken in the 15 years from 1994 to 2009, showing the collision of the expanding supernova remnant with a ring of dense material ejected by the progenitor star 20,000 years before the supernova.
Credit:  Mark McDonald - Larsson, J. et al. (2011). "X-ray illumination of the ejecta of supernova 1987A". Nature 474 (7352): 484–486., video compilation: Mark McDonald

In the turbulent supernova environment, scientists expect the churning dust to be destroyed. "That is theoretically," Lau said. "There have been no direct observations of any dust surviving the environment of the supernova remnant ... until now, and that's why our observations of an 'old' supernova are so important," he said.

 Astronomers have observed stars spinning around the supermassive black hole in Sagittarius A
Credit: ESA/Hubble

The astronomers captured the observations via FORCAST (the Faint Object Infrared Camera Telescope) aboard SOFIA (the Stratospheric Observatory for Infrared Astronomy), a modified Boeing 747 and a joint project of NASA, the German Aerospace Center and the Universities Space Research Association. It is the world's largest airborne astronomical observatory. Currently, no space-based telescope can observe at far-infrared wavelengths, and ground-based telescopes are unable to observe light at these wavelengths due to the Earth's atmosphere.

Cassiopeia A: A false color image composited of data from three sources. Red is infrared data from the Spitzer Space Telescope, orange is visible data from the Hubble Space Telescope, and blue and green are data from the Chandra X-ray Observatory. The cyan dot just off-center is the remnant of the star's core.

Credit: NASA/JPL-Caltech

Joining Lau on this research, "Old Supernova Dust Factory Revealed at the Galactic Center," are co-authors Terry Herter, Cornell professor of astronomy and principal scientific investigator on FORCAST; Mark Morris, University of California, Los Angeles; Zhiyuan Li, Nanjing University, China; and Joe Adams, NASA Ames Research Center.


Contacts and sources:
Syl Kacapyr
Cornell University

First Blood Test for Osteoarthritis Could Soon Be Available

The first blood test for osteoarthritis could soon be developed, thanks to research by the University of Warwick.

The research findings could potentially lead to patients being tested for osteoarthritis and diagnosed several years before the onset of physical symptoms.

Circles indicate joints that osteoarthritis most often affects.

Conducted by the University’s Medical School, the research identified a biomarker linked to both rheumatoid and osteoarthritis.

Whilst there are established tests for rheumatoid arthritis (RA), the newly identified biomarker could lead to one which can diagnose both rheumatoid arthritis and osteoarthritis (OA).

The research’s focus was citrullinated proteins (CPs), a biomarker suspected to be present in blood of people with early stage rheumatoid arthritis. It had previously been established that patients with RA have antibodies to CPs, but it was not thought that this was the same for those with OA.

In osteoarthritis, the cartilage between the bones in the joint breaks down (left image). Slowly, affected bones get bigger, as in the hand at right. 

Credit: American College of Rheumatology

However, the Warwick researchers found for the first time increased CPs levels in both early-stage OA and RA.

They then produced an algorithm of three biomarkers, CPs, anti-CP antibodies along with, the bone-derived substance, hydroxyproline.

Using the algorithm the researchers found that with a single test they could potentially detect and discriminate between the major types of arthritis at the early stages, before joint damage has occurred.

Commenting on the findings, lead researcher, Dr Naila Rabbani said:

“This is a remarkable and unexpected finding. It could help bring early-stage and appropriate treatment for arthritis which gives the best chance of effective treatment”.

Explaining the role of CPs in relation to both RA and OA and the importance of the algorithm to the research Dr Rabbani said:

“It has been long established that the autoimmunity of early-stage RA leads to antibodies to CPs, but the autoimmunity, and hence antibodies, are absent in early-stage OA. Using this knowledge and applying the algorithm of biomarkers we developed provides the basis to discriminate between these two major types of arthritis at an early stage”.

The ability to discriminate between RA and OA could provide a number of benefits to patients, including early diagnosis. 

Dr Rabbani said: “Detection of early stage-OA made the study very promising and we would have been satisfied with this only – but beyond this we also found we could detect and discriminate early-stage RA and other inflammatory joint diseases at the same.

 Wrist osteoarthritis
Credit: Wikipedia

“This discovery raises the potential of a blood test that can help diagnose both RA and OA several years before the onset of physical symptoms”.

The research, Biomarkers of early stage osteoarthritis, rheumatoid arthritis and musculoskeletal health, is published by Nature Scientific Reports.


Contacts and sources:
University of Warwick.

Friday, March 20, 2015

Black Holes and the Dark Sector Explained by Quantum Gravity


Ask any theoretical physicist on what are the most profound mysteries in physics and you will be surprised if she mentions anything other than Quantum Gravity and the Dark Sector. Questions such as how do we reconcile GR and Quantum Theory? What is Dark Matter? And what is Dark Energy? These are what keep most physicists awake late at night. Suggested solutions to these problems are manifold but all fall short of providing a satisfactory explanation.

This is a composite image of the Bullet Group showing galaxies, hot gas (shown in pink) and dark matter (indicated in blue).

Credit: ESA / XMM-Newton / F. Gastaldello (INAF/IASF, Milano, Italy) / CFHTLS.

The situation is set to change however as a new theory authored by Lic. Stuart Marongwe who holds a licentiate degree in physics and electronics from Jose Varona University in Havana, Cuba now stationed at the physics Department of McConnell College in Botswana, provides a self-consistent theory of Quantum Gravity which explains the Dark sector and is in agreement with observations.

The theory is known as Nexus in the sense that it provides a link between Quantum Theory and GR. This link manifests in the form of the Nexus graviton- a composite spin 2 particle of space-time which emerges naturally from the unification process. One remarkable feature of the Nexus graviton which distinguishes it from the graviton hypothesized in the Standard Model is that it is not a messenger particle but rather it induces a constant rotational motion on any test particle embedded within its confines. 

Moreover the Nexus graviton can also be considered as a globule of vacuum energy which can merge and de-merge with others in a process that resembles cytokineses in cell biology. The Nexus graviton is Dark Matter and constitutes space-time. The emission of a graviton of least energy by a high energy graviton results in the expansion of the high energy graviton as it assumes a lower energy state. This process manifests as Dark Energy and takes place throughout space-time as the theory explains.

This paper is significant in the sense that it sheds some light on some of the most perplexing questions in physics which include a quantum description of Black Holes without singularities inherent in classical GR.The solutions provided in this paper will certainly open doors to new physics.


Contacts and sources:
Philly Lim

Carolina Butcher: 9 Foot Long Crocodilian Ancestor Walked on Hind Legs



A newly discovered crocodilian ancestor may have filled one of North America's top predator roles before dinosaurs arrived on the continent. Carnufex carolinensis, or the "Carolina Butcher," was a 9-foot long, land-dwelling crocodylomorph that walked on its hind legs and likely preyed upon smaller inhabitants of North Carolina ecosystems such as armored reptiles and early mammal relatives.

This is a life reconstruction of Carnufex carolinensis.

Credit: Copyright Jorge Gonzales. Open access

Paleontologists from North Carolina State University and the North Carolina Museum of Natural Sciences recovered parts of Carnufex's skull, spine and upper forelimb from the Pekin Formation in Chatham County, North Carolina. Because the skull of Carnufex was preserved in pieces, it was difficult to visualize what the complete skull would have looked like in life. To get a fuller picture of Carnufex's skull the researchers scanned the individual bones with the latest imaging technology - a high-resolution surface scanner. Then they created a three-dimensional model of the reconstructed skull, using the more complete skulls of close relatives to fill in the missing pieces.

The Pekin Formation contains sediments deposited 231 million years ago in the beginning of the Late Triassic (the Carnian), when what is now North Carolina was a wet, warm equatorial region beginning to break apart from the supercontinent Pangea. "Fossils from this time period are extremely important to scientists because they record the earliest appearance of crocodylomorphs and theropod dinosaurs, two groups that first evolved in the Triassic period, yet managed to survive to the present day in the form of crocodiles and birds," says Lindsay Zanno, assistant research professor at NC State, director of the Paleontology and Geology lab at the museum, and lead author of a paper describing the find. "The discovery of Carnufex, one of the world's earliest and largest crocodylomorphs, adds new information to the push and pull of top terrestrial predators across Pangea."

Typical predators roaming Pangea included large-bodied rauisuchids and poposauroids, fearsome cousins of ancient crocodiles that went extinct in the Triassic Period. In the Southern Hemisphere, "these animals hunted alongside the earliest theropod dinosaurs, creating a predator pile-up," says Zanno. However, the discovery of Carnufex indicates that in the north, large-bodied crocodylomorphs, not dinosaurs, were adding to the diversity of top predator niches. "We knew that there were too many top performers on the proverbial stage in the Late Triassic," Zanno adds. "Yet, until we deciphered the story behind Carnufex, it wasn't clear that early crocodile ancestors were among those vying for top predator roles prior to the reign of dinosaurs in North America."

This image shows a reconstructed skull of Carnufex carolinensis. 3-D surface models of skull bones are shown in white. Grey areas are missing elements reconstructed from close relatives of Carnufex.

Credit:  Lindsay Zanno

As the Triassic drew to a close, extinction decimated this panoply of predators and only small-bodied crocodylomorphs and theropods survived. "Theropods were ready understudies for vacant top predator niches when large-bodied crocs and their relatives bowed out," says Zanno. "Predatory dinosaurs went on to fill these roles exclusively for the next 135 million years."

Still, ancient crocodiles found success in other places. "As theropod dinosaurs started to make it big, the ancestors of modern crocs initially took on a role similar to foxes or jackals, with small, sleek bodies and long limbs," says Susan Drymala, graduate student at NC State and co-author of the paper. "If you want to picture these animals, just think of a modern day fox, but with alligator skin instead of fur."


Contacts and sources:
 Tracey Peake
North Carolina State University

Thursday, March 19, 2015

Robot Model for Infant Learning Shows Bodily Posture May Affect Memory and Learning


An Indiana University cognitive scientist and collaborators have found that posture is critical in the early stages of acquiring new knowledge.

The study, conducted by Linda Smith, a professor in the IU Bloomington College of Arts and Sciences' Department of Psychological and Brain Sciences, in collaboration with a roboticist from England and a developmental psychologist from the University of Wisconsin-Madison, offers a new approach to studying the way "objects of cognition," such as words or memories of physical objects, are tied to the position of the body.

A robot is taught to distinguish between two objects as part of the research on the effect of body posture on infant learning.

 Credit: Photo by University of Plymouth

"This study shows that the body plays a role in early object name learning, and how toddlers use the body's position in space to connect ideas," Smith said. "The creation of a robot model for infant learning has far-reaching implications for how the brains of young people work."

The research, "Posture Affects How Robots and Infants Map Words to Objects," was published today in PLOS ONE, an open-access, peer-reviewed online journal.

Using both robots and infants, researchers examined the role bodily position played in the brain's ability to "map" names to objects. They found that consistency of the body's posture and spatial relationship to an object as an object's name was shown and spoken aloud were critical to successfully connecting the name to the object.

The new insights stem from the field of epigenetic robotics, in which researchers are working to create robots that learn and develop like children, through interaction with their environment. Morse applied Smith's earlier research to creating a learning robot in which cognitive processes emerge from the physical constraints and capacities of its body.

"A number of studies suggest that memory is tightly tied to the location of an object," Smith said. "None, however, have shown that bodily position plays a role or that, if you shift your body, you could forget."

To reach these conclusions, the study's authors conducted a series of experiments, first with Morse's robots, which were programmed to map the name of an object to the object through shared association with a posture, then with children age 12 to 18 months.

In one experiment, a robot was first shown an object situated to its left, then a different object to the right; then the process was repeated several times to create an association between the objects and the robot's two postures. Then with no objects in place, the robot's view was directed to the location of the object on the left and given a command that elicited the same posture from the earlier viewing of the object. Then the two objects were presented in the same locations without naming, after which the two objects were presented in different locations as their names were repeated. This caused the robot to turn and reach toward the object now associated with the name.

The robot consistently indicated a connection between the object and its name during 20 repeats of the experiment. But in subsequent tests where the target and another object were placed in both locations -- so as to not be associated with a specific posture -- the robot failed to recognize the target object. When replicated with infants, there were only slight differences in the results: The infant data, like that of the robot, implicated the role of posture in connecting names to objects.

"These experiments may provide a new way to investigate the way cognition is connected to the body, as well as new evidence that mental entities, such as thoughts, words and representations of objects, which seem to have no spatial or bodily components, first take shape through spatial relationship of the body within the surrounding world," Smith said.

Smith's research has long focused on creating a framework for understanding cognition that differs from the traditional view, which separates physical actions such as handling objects or walking up a hill from cognitive actions such as learning language or playing chess.

Additional research is needed to determine whether this study's results apply to infants only, or more broadly to the relationship between the brain, the body and memory, she added. The study may also provide new approaches to research on developmental disorders in which difficulties with motor coordination and cognitive development are well-documented but poorly understood.


Contacts and sources:
Kevin Fryling  

The Moon's Giant Volcanic Eruption

Scientists have produced a new map of the Moon's most unusual volcano showing that its explosive eruption spread debris over an area much greater than previously thought.

A team of astronomers and geologists, led by experts in the Institute for Computational Cosmology and Department of Earth Sciences at Durham University, UK, studied an area of the lunar surface in the Compton-Belkovich Volcanic Complex.

Image shows the area around the Compton-Belkovich Volcanic complex (with the vertical scale enhanced for clarity). The red region (approximately 35 km in diameter) is the volcanic complex and the green area is that containing the radioactive debris from the volcano's eruption, which stretches 300 km to the east.

Credit: Jack Wilson et al, Durham University

By mapping the radioactive element thorium which spewed out during the eruption they discovered that, with the help of the Moon's low gravity, debris from the unnamed volcano was able to cover an area the size of Scotland, or around 70,000 km2.

The eruption, which happened 3.5 billion years ago, threw rock five times further than the pyroclastic flow of molten rock and hot gases that buried the Roman city of Pompeii, the researchers added.

The findings are being presented by lead author and Durham University PhD student Jack Wilson to the 46th Lunar and Planetary Science Conference in Texas tomorrow (Thursday, March 19, 2015).

The research used data from NASA's Lunar Prospector spacecraft which first spotted the volcanic site in 1999 when it detected an isolated deposit of thorium on the Moon's far-side between the Compton and Belkovich impact craters.

Image shows the area around the Compton-Belkovich Volcanic complex (with the vertical scale enhanced for clarity). The red region (approximately 35km in diameter) is the volcanic complex and the green area is that containing the radioactive debris from the volcano's eruption, which stretches 300 km to the east.

Credit:  Jack Wilson, et al, Durham University

Since its discovery, the deposit had been hard to study because it is hidden beneath debris from meteorite impacts, but Lunar Prospector did detect gamma rays emitted by the thorium that can pass through up to a metre of rock.

Based on this information, the Durham-led team used a "pixon" image enhancement technique, originally designed to peer into the distant Universe, to sharpen the map and reveal the enormous size of the thorium deposit from the volcanic eruption.

Jack Wilson, a PhD student in Durham's Institute for Computational Cosmology, said he was surprised by the gigantic scale of the explosion.

He said: "Volcanoes were common in the early life of the Moon and in fact the dark 'seas' you can observe on the lunar surface were created by runny, iron-rich, lava that flooded large areas, filling in impact craters and low-lying ground.

"Eruption of viscous, light-coloured, iron-poor, lava, which creates steep-sided volcanic cones, was rare and observed only at a handful of sites such as this one. The explosive eruption of such lava is unknown elsewhere on the Moon, making this volcano unique.

"By mapping the radioactive content of the lava from this volcano we have been able to show that molten, radioactive rock was thrown far beyond the slopes of the volcano, reaching several hundred miles in one direction."

The research team is now planning to apply its mapping technique to the largest known volcano in the Solar system, Olympus Mons on Mars.

Rather than the radioactive element thorium, the researchers will be looking for hydrogen and the possible remnants of water ice from glaciers on the high slopes of the Red Planet.

The latest research used the DiRAC Data Centric system at Durham University, part of the DiRAC national supercomputing facility for research in astrophysics and particle physics funded by the Department for Business, Innovation and Skills through the Science and Technology Facilities Council and was supported by the Science and Technology Facilities Council and The Royal Society.


Contacts and sources: 
Leighton Kitson
Durham University

More Than a Million Stars Are Forming in Nearby Supernebula


More than a million young stars are forming in a hot, dusty cloud of molecular gases in a tiny galaxy near our own, an international team of astronomers has discovered.

The star cluster is buried within a supernebula in a dwarf galaxy known as NGC 5253, in the constellation Centaurus. The cluster has one billion times the luminosity of our sun, but is invisible in ordinary light, hidden by its own hot gases.

This is a Hubble Space Telescope image of galaxy NGC 5253. Superimposed is the gas (fuzzy red to yellow) as seen by the Submillimeter Array. The brightest part of the image is Cloud D.

Credit: Courtesy of Jean Turner

"We are stardust, and this cluster is a factory of stars and soot," said Jean Turner, a professor of physics and astronomy in the UCLA College and lead author of the research, which is published March 19 in the journal Nature. "We are seeing the dust that the stars have created. Normally when we look at a star cluster, the stars long ago dispersed all their gas and dust, but in this cluster, we see the dust.

"I've been searching for the gas cloud that is forming the supernebula and its star cluster for years," she said. "Now we have detected it."

The amount of dust surrounding the stars is extraordinary -- approximately 15,000 times the mass of our sun in elements such as carbon and oxygen.

"We were stunned," said Turner, who is chair of the department of physics and astronomy.

The cluster is about 3 million years old, which in astronomical terms, is remarkably young. It is likely to live for more than a billion years, she said.

The Milky Way has not formed gigantic star clusters for billions of years, Turner said. It is still forming new stars, but not in nearly such large numbers, she said. Some astronomers had believed that such giant star clusters could form only in the early universe.

The Milky Way has gas clouds, but nothing comparable to this galaxy's Cloud D -- see the bright white area in the photo -- which houses the enormous star cluster enshrouded in thick gas and dust, Turner said.

How much of a gas cloud gets turned into stars varies in different parts of the universe. In the Milky Way, the rate for gas clouds the size of Cloud D is less than 5 percent. In Cloud D, the rate is at least 10 times higher, and perhaps much more.

Turner and her colleagues conducted the research with the Submillimeter Array, a joint project of the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics, on Hawaii's Mauna Kea.

NGC 5253 has hundreds of large star clusters, including at least several that are young, the astronomers report. The most spectacular is found within Cloud D.

"We're catching this cluster at a special time," Turner said. "With a cluster this large, we would expect several thousand stars that would have become supernovae and exploded by now. We found no evidence of a supernova yet."

The cluster contains more than 7,000 massive "O" stars -- the most luminous of all known stars, each a million times brighter than our sun.

NGC 5253 has approximately nine times as much dark matter as visible matter -- a much higher rate than the inner parts of the Milky Way, Turner said.

In coming years, the cloud could be destroyed by stars that become supernovae, Turner said, "which would spin all of the gas and elements created by the stars into interstellar space."


Contacts and sources:
Stuart Wolpert 
UCLA


Iron Rain Splattered Earth Reveal Z Machine Researchers


Researchers at Sandia National Laboratories' Z machine have helped untangle a long-standing mystery of astrophysics: why iron is found spattered throughout Earth's mantle, the roughly 2,000-mile thick region between Earth's core and its crust.

Sandia's Z machine is the most powerful deliverer of bursts of electrical energy in the world.

Credit: Randy Montoya, photographer; courtesy, Sandia National Laboratories

At first blush, it seemed more reasonable that iron arriving from collisions between Earth and planetesimals -- ranging from several meters to hundreds of kilometers in diameter -- during Earth's late formative stages should have powered bullet-like directly to Earth's core, where so much iron already exists.

A second, correlative mystery is why the moon proportionately has much less iron in its mantle than does Earth. Since the moon would have undergone the same extraterrestrial bombardment as its larger neighbor, what could explain the relative absence of that element in the moon's own mantle?

To answer these questions, scientists led by Professor Stein Jacobsen at Harvard University and Professor Sarah Stewart at the University of California at Davis (UC Davis) wondered whether the accepted theoretical value of the vaporization point of iron under high pressures was correct. If vaporization occurred at lower pressures than assumed, a solid piece of iron after impact might disperse into an iron vapor that would blanket the forming Earth instead of punching through it. A resultant iron-rich rain would create the pockets of the element currently found in the mantle.

As for the moon, the same dissolution of iron into vapor could occur, but the satellite's weaker gravity would be unable to capture the bulk of the free-floating iron atoms, explaining the dearth of iron deposits on Earth's nearest neighbor.

Looking for experimental rather than theoretical values, researchers turned to Sandia's Z machine and its Fundamental Science Program, coordinated by Sandia manager Thomas Mattsson. This led to a collaboration among Sandia, Harvard University, UC Davis, and Lawrence Livermore National Laboratory (LLNL) to determine an experimental value for the vaporization threshold of iron that would replace the theoretical value used for decades.

Rick Kraus at LLNL (formerly at Harvard) and Sandia researchers Ray Lemke and Seth Root used Z to accelerate metals to extreme speeds using high magnetic fields. The researchers created a target that consisted of an iron plate 5 millimeters square and 200 microns thick, against which they launched aluminum flyer plates travelling up to 25 kilometers per second. At this impact pressure, the powerful shock waves created in the iron cause it to compress, heat up and -- in the zero pressure resulting from waves reflecting from the iron's far surface -- vaporize.

The result, published March 2 in Nature Geosciences under the title "Impact vaporization of planetesimal cores in the late stages of planet formation," shows the shock pressure experimentally required to vaporize iron is approximately 507 gigapascals (GPa), undercutting by more than 40 percent the previous theoretical estimate of 887 GPa. Astrophysicists say that this lower pressure is readily achieved during the end stages of planetary growth through accretion.

Principal investigator Kraus said, "Because planetary scientists always thought it was difficult to vaporize iron, they never thought of vaporization as an important process during the formation of the Earth and its core. But with our experiments, we showed that it's very easy to impact-vaporize iron."

He continued, "This changes the way we think of planet formation, in that instead of core formation occurring by iron sinking down to the growing Earth's core in large blobs (technically called diapirs), that iron was vaporized, spread out in a plume over the surface of the Earth and rained out as small droplets. The small iron droplets mixed easily with the mantle, which changes our interpretation of the geochemical data we use to date the timing of Earth's core formation."


Contacts and sources:
Neal Singer
Sandia Labs

Wednesday, March 18, 2015

"Mini Supernova" Explosion Could Have Big Impact

In Hollywood blockbusters, explosions are often among the stars of the show. In space, explosions of actual stars are a focus for scientists who hope to better understand their births, lives, and deaths and how they interact with their surroundings.

Credit:NASA/CXC/RIKEN/D.Takei et al

Using NASA’s Chandra X-ray Observatory, astronomers have studied one particular explosion that may provide clues to the dynamics of other, much larger stellar eruptions.

A team of researchers pointed the telescope at GK Persei, an object that became a sensation in the astronomical world in 1901 when it suddenly appeared as one of the brightest stars in the sky for a few days, before gradually fading away in brightness. Today, astronomers cite GK Persei as an example of a “classical nova,” an outburst produced by a thermonuclear explosion on the surface of a white dwarf star, the dense remnant of a Sun-like star.

A nova can occur if the strong gravity of a white dwarf pulls material from its orbiting companion star. If enough material, mostly in the form of hydrogen gas, accumulates on the surface of the white dwarf, nuclear fusion reactions can occur and intensify, culminating into a cosmic-sized hydrogen bomb blast. The outer layers of the white dwarf are blown away, producing a nova outburst that can be observed for a period of months to years as the material expands into space.

Classical novas can be considered to be “miniature” versions of supernova explosions. Supernovas signal the destruction of an entire star and can be so bright that they outshine the whole galaxy where they are found. Supernovas are extremely important for cosmic ecology because they inject huge amounts of energy into the interstellar gas, and are responsible for dispersing elements such as iron, calcium and oxygen into space where they may be incorporated into future generations of stars and planets.

Although the remnants of supernovas are much more massive and energetic than classical novas, some of the fundamental physics is the same. Both involve an explosion and creation of a shock wave that travels at supersonic speeds through the surrounding gas.

The more modest energies and masses associated with classical novas means that the remnants evolve more quickly. This, plus the much higher frequency of their occurrence compared to supenovas, makes classical novas important targets for studying cosmic explosions.

Chandra first observed GK Persei in February 2000 and then again in November 2013. This 13-year baseline provides astronomers with enough time to notice important differences in the X-ray emission and its properties.

This new image of GK Persei contains X-rays from Chandra (blue), optical data from NASA’s Hubble Space Telescope (yellow), and radio data from the National Science Foundation’s Very Large Array (pink). The X-ray data show hot gas and the radio data show emission from electrons that have been accelerated to high energies by the nova shock wave. The optical data reveal clumps of material that were ejected in the explosion. The nature of the point-like source on the lower left is unknown.

Over the years that the Chandra data span, the nova debris expanded at a speed of about 700,000 miles per hour. This translates to the blast wave moving about 90 billion miles during that period.

One intriguing discovery illustrates how the study of nova remnants can provide important clues about the environment of the explosion. The X-ray luminosity of the GK Persei remnant decreased by about 40% over the 13 years between the Chandra observations, whereas the temperature of the gas in the remnant has essentially remained constant, at about one million degrees Celsius. As the shock wave expanded and heated an increasing amount of matter, the temperature behind the wave of energy should have decreased. The observed fading and constant temperature suggests that the wave of energy has swept up a negligible amount of gas in the environment around the star over the past 13 years. This suggests that the wave must currently be expanding into a region of much lower density than before, giving clues to stellar neighborhood in which GK Persei resides.

A paper describing these results appeared in the March 10th issue of The Astrophysical Journal. The authors were Dai Takei (RIKEN, Spring-8 Center Japan), Jeremy Drake (Smithsonian Astrophysical Observatory), Hiroya Yamaguichi (Goddard Space Flight Center), Patrick Slane (Smithsonian Astrophysical Observatory), Yasunobu Uchimaya (Rikkyo University, Japan), Satoru Katsuda (Japanese Aerospace Exploration Agency).

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.



Contacts and sources:
Janet Anderson
Marshall Space Flight Center, Huntsvill

Aurora and Mysterious Dust Cloud Detected around Mars by NASA Spacecraft

NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has observed two unexpected phenomena in the Martian atmosphere: an unexplained high-altitude dust cloud and aurora that reaches deep into the Martian atmosphere.

Artist’s conception of MAVEN’s Imaging UltraViolet Spectrograph (IUVS) observing the “Christmas Lights Aurora" on Mars. MAVEN observations show that aurora on Mars is similar to Earth’s "Northern Lights" but has a different origin.

Image Credit: University of Colorado

The presence of the dust at orbital altitudes from about 93 miles (150 kilometers) to 190 miles (300 kilometers) above the surface was not predicted. Although the source and composition of the dust are unknown, there is no hazard to MAVEN and other spacecraft orbiting Mars.

"If the dust originates from the atmosphere, this suggests we are missing some fundamental process in the Martian atmosphere," said Laila Andersson of the University of Colorado's Laboratory for Atmospherics and Space Physics (CU LASP), Boulder, Colorado.

The cloud was detected by the spacecraft’s Langmuir Probe and Waves (LPW) instrument, and has been present the whole time MAVEN has been in operation. It is unknown if the cloud is a temporary phenomenon or something long lasting. The cloud density is greatest at lower altitudes. However, even in the densest areas it is still very thin. So far, no indication of its presence has been seen in observations from any of the other MAVEN instruments.

Possible sources for the observed dust include dust wafted up from the atmosphere; dust coming from Phobos and Deimos, the two moons of Mars; dust moving in the solar wind away from the sun; or debris orbiting the sun from comets. However, no known process on Mars can explain the appearance of dust in the observed locations from any of these sources.

A map of IUVS’s auroral detections in December 2014 overlaid on Mars’ surface. The map shows that the aurora was widespread in the northern hemisphere, not tied to any geographic location. The aurora was detected in all observations during a 5-day period.
 
Image Credit: University of Colorado

MAVEN's Imaging Ultraviolet Spectrograph (IUVS) observed what scientists have named "Christmas lights." For five days just before Dec. 25, MAVEN saw a bright ultraviolet auroral glow spanning Mars' northern hemisphere. Aurora, known on Earth as northern or southern lights, are caused by energetic particles like electrons crashing down into the atmosphere and causing the gas to glow.

"What's especially surprising about the aurora we saw is how deep in the atmosphere it occurs - much deeper than at Earth or elsewhere on Mars,” said Arnaud Stiepen, IUVS team member at the University of Colorado. “The electrons producing it must be really energetic."

The source of the energetic particles appears to be the sun. MAVEN's Solar Energetic Particle instrument detected a huge surge in energetic electrons at the onset of the aurora. Billions of years ago, Mars lost a global protective magnetic field like Earth has, so solar particles can directly strike the atmosphere. The electrons producing the aurora have about 100 times more energy than you get from a spark of house current, so they can penetrate deeply in the atmosphere.

The findings are being presented at the 46th Lunar and Planetary Science Conference in The Woodlands, Texas.

MAVEN was launched to Mars on Nov. 18, 2013, to help solve the mystery of how the Red Planet lost most of its atmosphere and much of its water. The spacecraft arrived at Mars on Sept. 21, and is four months into its one-Earth-year primary mission.

"The MAVEN science instruments all are performing nominally, and the data coming out of the mission are excellent," said Bruce Jakosky of CU LASP, Principal Investigator for the mission.

MAVEN is part of the agency's Mars Exploration Program, which includes the Opportunity and Curiosity rovers, the Mars Odyssey and Mars Reconnaissance Orbiter spacecraft currently orbiting the planet.

NASA's Mars Exploration Program seeks to characterize and understand Mars as a dynamic system, including its present and past environment, climate cycles, geology and biological potential. In parallel, NASA is developing the human spaceflight capabilities needed for its journey to Mars or a future round-trip mission to the Red Planet in the 2030’s.

MAVEN's principal investigator is based at the University of Colorado's Laboratory for Atmospheric and Space Physics, and NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN project. Partner institutions include Lockheed Martin, the University of California at Berkeley, and NASA's Jet Propulsion Laboratory.


Contacts and sources:
Nancy Neal-Jones / Bill Steigerwald
Goddard Space Flight Center

Jim Scott
University of Colorado, Boulder, Colorad

For images related to the findings, visit: http://www.nasa.gov/maven