Hidden Oceans on Jupiter's Icy Moon Europa May Explain Strange Terrain

Churning seas beneath the icy surface of Jupiter's moon Europa might explain the chaotic jumble of cracks and ridges around its equator, scientists say.

These findings hint Europa may be even more habitable for alien life than previously thought, researchers added.

Europa is nearly the size of Earth's moon. Under an icy crust maybe 10 to 15 miles (15 to 25 kilometers) thick, investigators think Europa possesses an ocean perhaps up to 100 miles (160 km) deep. Since there is life virtually wherever there is water on Earth, researchers have long entertained the notion that Europa could support life.

Europa's icy shell would hide its ocean from view. However, clues about how this underground ocean behaves might be deduced from the moon's crust, especially areas known as chaos terrains, where the ice has mysteriously warped and broken into jumbled blocks. These strange regions cover up to 40 percent of Europa's surface, clustered mostly around the Jovian moon's equator.

The origins of chaos terrain are strongly debated, but scientists think the way heat flows in the ocean beneath such terrain is critical to the explanation. To see what behavior from the underground ocean might be giving rise to chaos terrain, planetary geophysicist Krista Soderlund at the University of Texas at Austin and her colleagues devised computer models of how sea currents might circulate.

Past simulations of Europa's ocean assumed its currents flowed in a two-dimensional pattern. This pattern channeled the moon's heat to high latitudes away from the equator.

However, the new model assumed currents that flowed in a three-dimensional manner. This model suggested Europa had an ocean that roiled or convected intensely, with turbulence and heat flow strongest at low latitudes near the equator.

The scientists found two reasons why three-dimensional patterns of flow would cause ocean heat to concentrate near the equator. First, the ocean convects more vigorously there. 

"One way to think about this is to consider the classic example of a boiling pot of water," Soderlund said. "If the pot is much larger than the burner, water will convect more vigorously at the center than near the edges."

Second, three-dimensional patterns of flow cause systems of currents to form at low latitudes. These systems "are similar to Hadley cells on Earth, where warm material rises at the equator, cools and sinks again at higher latitudes," Soderlund explained.                                                                                                                                           

The researchers suggest ocean heat drives melting and disruption of the ice on Europa. The concentration of heat near the equator could explain why chaos terrain is clustered there.

And intensely turbulent oceans would have "implications for potential habitability," Soderlund said. "The currents would enhance the transport of nutrients from the seafloor to the ice shell, especially at low latitudes."

The European Space Agency's JUICE probe and NASA's conceived Europa Clipper mission to visit Jupiter could help scientists better understand Europa and other icy moons and see if the research team's model of Europa is correct, Soderlund added.

The scientists detailed their findings online Dec. 1 in the journal Nature Geoscience.

Source of Article: Space.com

Elusive Dark Matter May Have Already Been Found

The mysterious dark matter that makes up most of the matter in the universe may already have been detected with superconducting circuits, researchers say.

Dark matter is currently one of the greatest mysteries in the cosmos — an invisible substance thought to make up five-sixths of all matter in the universe. The scientific consensus right now is that dark matter is composed of a new type of particle, one that interacts very weakly at best with all the known forces of the universe, except gravity. As such, dark matter is invisible and nearly completely intangible, mostly only detectable via the gravitational pull it exerts.

A number of ongoing experiments based on massive sensor arrays buried underground are attempting to identify the weak signals dark matter is expected to give off when it experiences a rare collision with other particles. So far, none of these studies have detected any dark matter fingerprints. 

Now, theoretical physicist Christian Beck at Queen Mary University of London suggests much smaller bench top detectors might be capable of detecting axions, which are leading theoretical candidates for dark matter particles.

Recent theoretical research suggests axions may condense together, essentially forming super-particles that physicists call Bose-Einstein condensates. "I started thinking not about the behavior of single axions, but [about] the collective behavior of many axions coupled together," Beck said.

Beck noted the equations describing the motion of these axions were very similar to those governing a special kind of circuit known as an S/N/S Josephson junction, a device made of two superconductors separated by a thin layer of metal. (Superconductors are materials in which electricity can flow without any resistance.)

Beck calculated that axions could leave behind a detectable electrical signal when they pass through these devices. "This opens up a new way of searching for axions that people haven't thought about before," he said.

If this notion is true, Beck said that the evidence may already have appeared — in a 2004 experiment exploring noise levels in S/N/S Josephson junctions that revealed a signal of unknown origin. If that signal came from an axion, Beck calculated, it would mean these particles have masses less than four-billionths those of electrons.

To confirm or refute the idea that axions generated the 2004 signal, further experiments are needed, ones paying special focus to shielding from any external radiation, since axions cannot be shielded against.

In addition, the Earth is expected to move faster through the galaxy's halo of dark matter in June and slower in December, so if the signals come from axions, the number of such signals these devices detect should rise and fall over the year.

"I want to now collaborate with my experimental colleagues to do the tests I suggested," Beck said.

Beck is scheduled to detail his findings online Dec. 2 in the journal Physical Review Letters.

Source of Article: Space.com

Radiation on Mars 'Manageable' for Manned Mission, Curiosity Rover Reveals

The risk of radiation exposure is not a show-stopper for a long-term manned mission to Mars, new results from NASA's Curiosity rover suggest.

A mission consisting of a 180-day cruise to Mars, a 500-day stay on the Red Planet and a 180-day return flight to Earth would expose astronauts to a cumulative radiation dose of about 1.01 sieverts, measurements by Curiosity's Radiation Assessment Detector (RAD) instrument indicate.

To put that in perspective: The European Space Agency generally limits its astronauts to a total career radiation dose of 1 sievert, which is associated with a 5-percent increase in lifetime fatal cancer risk.

"It's certainly a manageable number," said RAD principal investigator Don Hassler of the Southwest Research Institute in Boulder, Colo., lead author of a study that reports the results today (Dec. 9) in the journal Science.

A 1-sievert dose from radiation on Mars would violate NASA's current standards, which cap astronauts' excess-cancer risk at 3 percent. But those guidelines were drawn up with missions to low-Earth orbit in mind, and adjustments to accommodate trips farther afield may be in the offing, Hassler said.

"NASA is working with the National Academies' Institute of Medicine to evaluate what appropriate limits would be for a deep-space mission, such as a mission to Mars," Hassler told SPACE.com. "So that's an exciting activity."

The new results represent the most complete picture yet of the radiation environment en route to Mars and on the Red Planet's surface. They incorporate data that RAD gathered during Curiosity's eight-month cruise through space and the rover's first 300 days on Mars, where it touched down in August 2012.

The RAD measurements cover two different types of energetic-particle radiation — galactic cosmic rays (GCRs), which are accelerated to incredible speeds by far-off supernova explosions, and solar energetic particles (SEPs), which are blasted into space by storms on our own sun.

RAD's data show that astronauts exploring the Martian surface would accumulate about 0.64 millisieverts of radiation per day. The dose rate is nearly three times greater during the journey to Mars, at 1.84 millisieverts per day.

But Mars' radiation environment is dynamic, so Curiosity's measurements thus far should not be viewed as the final word, Hassler stressed. For example, RAD's data have been gathered near the peak of the sun's 11-year activity cycle, a time when the GCR flux is relatively low (because solar plasma tends to scatter galactic cosmic rays).

Curiosity's radiation measurements should help NASA plan out a manned mission to Mars, which the space agency hopes to pull off by the mid-2030s, Hassler said. And they should also inform the search for signs of past or present life on the Red Planet — another top NASA priority.

For example, the new RAD results suggest that microbial life is unlikely to exist right at the Martian surface, Hassler said. But future missions may not have to drill too deeply underground to find pockets of Mars life, if it ever existed.

"These measurements do tell us that we think it could be viable to find signs of possible extant or past life as shallow as 1 meter deep," Hassler said.

The new study is one of six papers published in Science today that report new results from Curiosity. Most of the other studies present evidence that the rover has found an ancient freshwater lake that could have supported microbial life for tens of thousands, and perhaps millions, of years.

Source of Article: Space.com

Ancient Mars Lake Could Have Supported Life, Curiosity Rover Shows

NASA's Curiosity rover has found evidence of an ancient Martian lake that could have supported life as we know it for long stretches — perhaps millions of years.

This long and skinny freshwater lake likely existed about 3.7 billion years ago, researchers said, suggesting that habitable environments were present on Mars more recently than previously thought.

"Quite honestly, it just looks very Earth-like," said Curiosity lead scientist John Grotzinger, of the California Institute of Technology in Pasadena.

"You've got an alluvial fan, which is being fed by streams that originate in mountains, that accumulates a body of water," Grotzinger told SPACE.com. "That probably was not unlike what happened during the last glacial maximum in the Western U.S."

Habitable Mars

The lake once covered a small portion of the 96-mile-wide (154 kilometers) Gale Crater, which the 1-ton Curiosity rover has been exploring since touching down on the Red Planet in August 2012.

The main task of Curiosity's $2.5 billion mission is to determine whether Gale Crater could ever have supported microbial life. The rover team achieved that goal months ago, announcing in March that a spot near Curiosity's landing site called Yellowknife Bay was indeed habitable billions of years ago.

The new results, which are reported today (Dec. 9) in six separate papers in the journal Science, confirm and extend Curiosity's landmark discovery, painting a more complete picture of the Yellowknife Bay area long ago.

This picture emerged from Curiosity's analysis of fine-grained sedimentary rocks called mudstones, which generally form in calm, still water. The rover obtained powdered samples of these rocks by drilling into Yellowknife Bay outcrops.

The mudstones contain clay minerals that formed in the sediments of an ancient freshwater lake, researchers said. Curiosity also spotted some of the key chemical ingredients for life in the samples, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon.

The lake could have potentially supported a class of microbes called chemolithoautotrophs, which obtain energy by breaking down rocks and minerals. Here on Earth, chemolithoautotrophs are commonly found in habitats beyond the reach of sunlight, such as caves and hydrothermal vents on the ocean floor.

"It is exciting to think that billions of years ago, ancient microbial life may have existed in the lake's calm waters, converting a rich array of elements into energy," Sanjeev Gupta of Imperial College London, co-author of one of the new papers, said in a statement.

An icy Martian lake?

The shallow ancient lake may have been about 30 miles long by 3 miles wide (50 by 5 kilometers), Grotzinger said. Based on the thickness of the sedimentary deposits, the research team estimates that the lake existed for at least tens of thousands of years — and perhaps much longer, albeit on a possibly on-and-off basis.

Taking into account the broader geological context, "you could wind up with an assemblage of rocks that represent streams, lakes and ancient groundwater systems — so for times when the lake might have been dry, the groundwater's still there. This could have gone on for millions or tens of millions of years," Grotzinger said.

The lack of weathering on Gale Crater's rim suggests that the area was cold when the lake existed, he added, raising the possibility that a layer of ice covered the lake on a permanent or occasional basis. But such conditions wouldn't be much of a deterrent to hardy microbes.

"These are entirely viable habitable environments for chemolithoautotrophs," Grotzinger said.

Researchers still don't know if the Gale Crater lake hosted organisms of any kind; Curiosity was not designed to hunt for signs of life on Mars. But if chemolithoautotrophs did indeed dominate the lake, it would put an alien twist on a superficially familiar environment.

"You can imagine that, if life evolved on Mars and never got beyond the point of chemolithoautotrophy, then in the absence of competition from other types of microbes, these systems might have been dominated by that type of metabolic pathway," Grotzinger said. "And that's an un-Earth-like situation."

Source of Article: Space.com

You Can't Get Entangled Without a Wormhole: Physicist Finds Entanglement Instantly Gives Rise to a Wormhole

Quantum entanglement is one of the more bizarre theories to come out of the study of quantum mechanics -- so strange, in fact, that Albert Einstein famously referred to it as "spooky action at a distance."

Essentially, entanglement involves two particles, each occupying multiple states at once -- a condition referred to as superposition. For example, both particles may simultaneously spin clockwise and counterclockwise. But neither has a definite state until one is measured, causing the other particle to instantly assume a corresponding state. The resulting correlations between the particles are preserved, even if they reside on opposite ends of the universe.

But what enables particles to communicate instantaneously -- and seemingly faster than the speed of light -- over such vast distances? Earlier this year, physicists proposed an answer in the form of "wormholes," or gravitational tunnels. The group showed that by creating two entangled black holes, then pulling them apart, they formed a wormhole -- essentially a "shortcut" through the universe -- connecting the distant black holes.

Now an MIT physicist has found that, looked at through the lens of string theory, the creation of two entangled quarks -- the building blocks of matter -- simultaneously gives rise to a wormhole connecting the pair.

The theoretical results bolster the relatively new and exciting idea that the laws of gravity holding together the universe may not be fundamental, but arise from something else: quantum entanglement.

Julian Sonner, a senior postdoc in MIT's Laboratory for Nuclear Science and Center for Theoretical Physics, has published his results in the journal Physical Review Letters, where it appears together with a related paper by Kristan Jensen of the University of Victoria and Andreas Karch of the University of Washington.

The tangled web that is gravity

Ever since quantum mechanics was first proposed more than a century ago, the main challenge for physicists in the field has been to explain gravity in quantum-mechanical terms. While quantum mechanics works extremely well in describing interactions at a microscopic level, it fails to explain gravity -- a fundamental concept of relativity, a theory proposed by Einstein to describe the macroscopic world. Thus, there appears to be a major barrier to reconciling quantum mechanics and general relativity; for years, physicists have tried to come up with a theory of quantum gravity to marry the two fields.

"There are some hard questions of quantum gravity we still don't understand, and we've been banging our heads against these problems for a long time," Sonner says. "We need to find the right inroads to understanding these questions."

A theory of quantum gravity would suggest that classical gravity is not a fundamental concept, as Einstein first proposed, but rather emerges from a more basic, quantum-based phenomenon. In a macroscopic context, this would mean that the universe is shaped by something more fundamental than the forces of gravity.

This is where quantum entanglement could play a role. It might appear that the concept of entanglement -- one of the most fundamental in quantum mechanics -- is in direct conflict with general relativity: Two entangled particles, "communicating" across vast distances, would have to do so at speeds faster than that of light -- a violation of the laws of physics, according to Einstein. It may therefore come as a surprise that using the concept of entanglement in order to build up space-time may be a major step toward reconciling the laws of quantum mechanics and general relativity.

Tunneling to the fifth dimension

In July, physicists Juan Maldacena of the Institute for Advanced Study and Leonard Susskind of Stanford University proposed a theoretical solution in the form of two entangled black holes. When the black holes were entangled, then pulled apart, the theorists found that what emerged was a wormhole -- a tunnel through space-time that is thought to be held together by gravity. The idea seemed to suggest that, in the case of wormholes, gravity emerges from the more fundamental phenomenon of entangled black holes.

Following up on work by Jensen and Karch, Sonner has sought to tackle this idea at the level of quarks -- subatomic building blocks of matter. To see what emerges from two entangled quarks, he first generated quarks using the Schwinger effect -- a concept in quantum theory that enables one to create particles out of nothing. More precisely, the effect, also called "pair creation," allows two particles to emerge from a vacuum, or soup of transient particles. Under an electric field, one can, as Sonner puts it, "catch a pair of particles" before they disappear back into the vacuum. Once extracted, these particles are considered entangled.

Sonner mapped the entangled quarks onto a four-dimensional space, considered a representation of space-time. In contrast, gravity is thought to exist in the next dimension as, according to Einstein's laws, it acts to "bend" and shape space-time, thereby existing in the fifth dimension.

To see what geometry may emerge in the fifth dimension from entangled quarks in the fourth, Sonner employed holographic duality, a concept in string theory. While a hologram is a two-dimensional object, it contains all the information necessary to represent a three-dimensional view. Essentially, holographic duality is a way to derive a more complex dimension from the next lowest dimension.

Using holographic duality, Sonner derived the entangled quarks, and found that what emerged was a wormhole connecting the two, implying that the creation of quarks simultaneously creates a wormhole. More fundamentally, the results suggest that gravity may, in fact, emerge from entanglement. What's more, the geometry, or bending, of the universe as described by classical gravity, may be a consequence of entanglement, such as that between pairs of particles strung together by tunneling wormholes.

"It's the most basic representation yet that we have where entanglement gives rise to some sort of geometry," Sonner says. "What happens if some of this entanglement is lost, and what happens to the geometry? There are many roads that can be pursued, and in that sense, this work can turn out to be very helpful."

Source of Article: ScienceDaily.com

Did Volcano on Mercury Erupt for a Billion Years? (Op-Ed)

Extra-terrestrial volcanism is every bit as stellar as its sounds. The Earth puts on its fair share of spectacular eruptions — but it's Earth's distant cousins who win the awards. 

Lava-scarred Venus has more volcanoes than any other planet we know; Olympus Mons, a treble Everest soaring above Mars' Northern Hemisphere, is the largest active peak in the solar system; while Saturn's frozen moon, Enceladus, where cryovolcanoes shoot towering streams of water through a crust of solid ice, must surely rank as the strangest.

But what about the one place where you'd expect the ground to melt? Sitting just 36 million miles in front of our star, sun-baked Mercury receives a colossal dose of solar radiation with almost no atmosphere to soften the blast. It's perhaps not surprising, then, that alongside its thick coating of meteor scars, the gray, scorched crust also shows signs of damage from within. Since Mariner 10 first revealed its surface in the 1970s, conspicuously smooth plains — reminiscent of the lunar mare—suggestedthat in places, the impact craters had once been resurfaced by giant lava flows.

And now, NASA's latest mission to the inner solar system — the MESSENGER satellite, currently in orbit around Mercury — has begun to shed new light on its volcanic past; and it could be about to join the record breakers.

When MESSENGER performed its first flyby of Mercury in early 2008, it sent back a hazy image of a feature, from somewhere in the planet's Northern hemisphere, showing what its discoverers called a "kidney-shaped depression." This strange formation was clearly very different from the ubiquitous, uniform impact craters. What's more, it was surrounded by an unusually bright, reflective material, which the satellite's instruments later identified as pyroclastic debris; the scientists were looking at an alien volcano.

And, as it transpired, alien in more ways than one. It soon became apparent that the "crater" in the flyby image was actually several — a collection of distinct, individual depressions, rather than the single summit vent typically associated with a volcano. Intriguingly, this formation was strikingly similar to a type of volcano found on Earth, called a compound volcano. These rare features are caused when the location of volcanic activity "migrates" over time, and their occurrence on Mercury was something completely new. 

Frustratingly, the images from the flyby were too coarse to allow a more detailed interpretation; but when MESSENGER returned, three frustrating years later, the kidney was back in its sights.

In 2011, now in full orbit, the stabilizing influence of Mercury's gravity allowed the satellite to map its target in unprecedented detail; and with this boost in clarity, the enigmatic volcano quite literally took on new dimensions. Several new craters, invisible during the flyby, emerged on the sharpened images — the volcano lost its organic resemblance, and grew by 30 percent.

With this increased resolution, even more subtle features rose into view. While the floors of the volcanic depressions had previously appeared smooth, they were now found to contain tiny impact craters. And it was this find which gave planetary geologists the chance to do something incredible.

Most of Earth's ancient scars have been erased by erosion or subduction of the planet's crust. But with no plate tectonics to recycle Mercury's crust, its meagre atmosphere, and not even wind to reshape its surface, the countless meteors which have etched themselves into the planet's landscape over time remain there as an ancient record — one which is particularly useful for scientists. The density of impact craters in a given area can be used to estimate its age; roughly speaking, the more meteors which have hit, the older it is.

Interestingly, this 'crater-age' can also be used to reconstruct ancient volcanic activity. The density of impact craters within a volcanic crater can be related to the timing of its last eruption — that is, the last time it was 'resurfaced' by ash or lava. And in freshly published research, a team of researchers from the UK and France — writing in the journal Earth and Planetary Science Letters — have applied this technique to the volcano found by MESSENGER, to estimate when its various craters were active.

Their findings showed that, despite being so close together, the clustered craters of the volcano had very different histories. The largest depression, in the far West of the formation, was peppered with meteor scars, suggesting that activity there had dwindled a relatively long time ago. The Easternmost craters, however, were almost pristine; it seemed that here, activity had persisted until much more recently. All this added up to an astonishing conclusion: According to the researchers, the impact pattern suggested that activity in the volcanic complex could have lasted for billions of years.

A terrestrial volcano which endures for a million years is considered ancient. But here, next to the sun, was a single volcanic structure which had conceivably remained active for as long as there has been complex life on our planet.

There are volcanoes on the Tharsis plateau on Mars that may have been active over similarly huge timescales; and it will take much more interpretation — perhaps even repeat visits — before Mercury is awarded a record of its own. But this incredible view of Earth's still-mysterious neighbor has raised an enticing question: Have scientists just found the longest-lived volcano our solar system?

Source of Article: Space.com

Giant Plasma Spirals Found on the Sun

Colossal spiral-shaped flows of super-hot plasma have been discovered on the sun, completing a nearly 50-year quest to confirm their existence, scientists say.

These giant solar plasma spirals — each of which is at least 60,000 miles (100,000 kilometers) wide — could help spark the formation of strongly magnetic regions on the sun that have been linked with solar flares and other sun eruptions, researchers added.

The sun's internal heat causes matter to rise to its surface, where the material cools when near the cold of space, and then sinks back downward. This cycle of motion is altogether known as convection, and zones where it takes place are known as convection cells.

The rotation of the sun on its axis causes the largest convection cells to form circular, spiraling patterns.

"These are a lot like weather patterns seen on Earth — vortices that spiral and turn all over the place," study author Lisa Upton, a solar scientist at Vanderbilt University in Nashville, told SPACE.com. Convection in Earth's atmosphere is ultimately driven by heat from the sun; the rotation of the Earth then makes convecting air on Earth spiral.

Super cells on the sun

Convection was already evident on the surface of the sun in two kinds of structures — granules, which are about 600 miles (1,000 kilometers) wide, and supergranules, which are about 18,000 miles (30,000 km) across. Granules last about 10 minutes, and matter flows in them at speeds of about 6,700 mph (10,800 km/h); supergranules endure longer, surviving about 24 hours, but matter flows in them slower, at speeds of about 1,100 mph (1,800 km/h).

Scientists have suggested the sun might possess even larger convective cells for nearly five decades. These giant cells were expected to be about 120,000 miles (200,000 km) deep and wide, spanning the entire convection zone of the sun, the outermost third of the star's interior.

"You have to have something like these giant cells to help explain why the sun's equator rotates so rapidly,"study lead author David Hathaway, an astrophysicist at NASA Marshall Space Flight Center in Huntsville, Ala., told SPACE.com.

These giant cells are expected to each last months, helping transport incredible amounts of heat generated in the sun's core to its surface.

"They ultimately help drive the sun's 11-year sunspotcycle, and should also help active regions — highly magnetic areas — form," Hathaway said. These violently active regions underlie activity such as sunspots and explosions such as solar flares and coronal mass ejections, which drives space weather that can damage electronics on Earth and in orbit.

The hunt for giant sun cells

The problem in finding these giant cells is how slow they were expected to flow, making it difficult to identify their influence on the surface of the sun. Now, by using NASA's Solar Dynamics Laboratory, researchers detected these humongous structures.

The researchers followed the motions of supergranules for days. This helped them identify the patterns of flow caused by the giant cells.

"People have been looking for these cells for 45 years," Upton said. "A combination of having the right data and the right techniques ultimately led us to observe these features on the sun."

Matter flows in these cells at speeds of about 18 mph (30 km/h). The spirals are at least 60,000 miles (100,000 km) across, and can last for at least three months. As expected from the effects of the sun's rotation, these cells flow clockwise in the north and counterclockwise in the south — in both cases, around high-pressure regions.

"Now we have to figure out how big an effect these giant cells have on the emergence of active regions on the sun's surface, and what that means for space weather," Hathaway said.

Hathaway, Upton and their colleague Owen Colegrove detailed their findings in the Dec. 6 issue of the journal Science.

Source of Article: Space.com