Ever since the gargantuan cracks on Plutos moon Charon were first spotted, astronomers have been baffled as to what may have formed them, with explanations ranging from giant impacts to an active, hot mantle.
A new paper, due to be published in the journal Icarus, has come up with an alternative, and arguably more compelling, explanation:Based on a series of computer simulations, it appears that a long history of near-misses by other massive objects, and not plate tectonics, may be responsible for forging mountains and canyons on this distant world.
I was inspired by computer graphics code in how to model the icy moons, Alice Quillen, a professor of physics and astronomy at the University of Rochester and lead author of the study, said in a statement. The inside of the moons is similar to how blood splatter is modeled in games and the outer, icy crust is similar to modeling clothes and how they move.
The computer simulations of the close tidal encounters. Alice Quillen via YouTube
Earth’s Moon may be small, but it’s still sufficiently sizable to be able to generate tides on Earth with its gravitational pull, both at the surface and within the liquid outer core. This mechanism is known as tidal forcing, and the authors of this new study hypothesizedthat this phenomenon may have once acted on the surfaces of icy worlds and moons like Charon when similarlysized worlds drifted close by in the Solar System, although they don’t specify when this would have happened.
The researchers decided to use an N-body simulation, which models objects as having multiple internal regions interconnected by springs. Its commonly used by astrophysicists to model the effect of gravity on planets and stars, but this is the first time it has been applied to a moon.
A massive perturber forming cracks on a Charon-like icy world. Alice Quillen via YouTube
In multiple virtual experiments, simulated icy moons were kept stationary as similar mass objects flew by them, and the team watched as they became deformed.
As it turns out, such close encounters exert enough of a tidal force on the icy moons to cause their surface to fracture in a brittle manner and on surprisingly huge scales. This means that the giant cracks and complex fault structures on the icy moons of Dione and Tethys (of Saturn), Ariel (of Uranus), and Charon (of Pluto) at the very least may be caused by this mechanism.
A close-up of the tectonic belt on Charon. NASA/JHUAPL/SwRI
We know that Earths internal heat escapes through both volcanoes and, significantly, convection currents in the mantle; these move around tectonic plates, which create mountains, faults, canyons, ocean basins, and continents. This process is known as plate tectonics, and its been happening on Earth for at least 3 billion years, but theres little evidence that it has happened anywhere else in the Solar System.
Icy moons like Charon are thought to be too small to still contain any heat left over from their presumably violent formation, so its unlikely that plate tectonics ever managed to effectively operate on them in the same way they did, and still do, on Earth. Perhaps this new study has finally solved the conundrum of where the ginormous alien crevasses come from or, as another recent study suggested, these vast canyons may have instead formed as the icy moon cooled and contracted.
One hundred years ago Albert Einstein in his general theory of relativity predicted the existence of a dark side to the cosmos. He thought there were invisible gravitational waves, ripples in space-time produced by some of the most violent events in the cosmos exploding stars, colliding black holes, perhaps even the Big Bang itself. For decades, astronomers have gathered strong corroborative evidence of the existence of these waves, but they have never been detected directly until now. They were the last part of the general theory still to be verified.
Uncle Albert. Georgios Collidas
Astronomers have used light to study the universe with optical telescopes for hundreds of years. We have expanded that view hugely since the middle of the 20th century, by building detectors and instruments sensitive to all the forms of what physicists mean by light: the electromagnetic spectrum, from gamma rays to radio. Yet the discovery of gravitational waves represents our first steps into studying the universe through the gravitational-wave spectrum, which exists independently from light, probing directly the effects of gravity as it spreads across the cosmos. It is the first page in a whole new chapter for astronomy, and science.
How We Made The Discovery
The discovery dates back to last September, when two giant measuring devices in different parts of the US called LIGO (Laser Interferometer Gravitational-Wave Observatory) caught a passing gravitational wave from the collision of two massive black holes in a faraway galaxy. LIGO is what we call an interferometer, consisting of two 4km arms set at right angles to each other, protected by concrete tubes, and a laser beam which is shone and reflected back and forth by mirrors at each end.
LIGO Washington. Anthony Bolante
When a gravitational wave passes by, the stretching and squashing of space causes these arms alternately to lengthen and shrink, one getting longer while the other gets shorter and then vice versa. As the arms change lengths, the laser beams take a different time to travel through them. This means that the two beams are no longer in step and what we call an interference pattern is produced hence the name interferometer.
The changes in the length of the arms are actually tiny roughly one million millionth the width of a human hair. This is because the signal from a gravitational wave from far out in the cosmos is mind-bogglingly small by the time it reaches us. As if detecting this were not difficult enough, all manner of local disturbances on Earth make it worse, from the ground shaking to power-grid fluctuations; and instrumental noises that could mimic or indeed completely swamp a real signal from the cosmos.
To achieve the astounding sensitivity required, almost every aspect of the LIGO detectors’ design has been upgraded over the past few years. We at the University of Glasgow led a consortium of UK institutions that played a key role developing, constructing and installing the sensitive mirror suspensions at the heart of the LIGO detectors that were crucial to this first detection. The technology was based on our work on the earlier UK/German GEO600 detector. This turned LIGO into Advanced LIGO, arguably the most sensitive scientific instrument ever, to give us our first direct glimpse of the dark universe.
A Long Time Ago…
What a glimpse it was. The two black holes that collided were respectively about 29 times and 36 times the mass of our sun (shown in the computer visualisation below). It is incidentally the first direct evidence that black holes exist, can exist in a pair, and can collide and merge. Comparing our data with Einsteins predictions allowed us to test whether general relativity correctly describes such a collision they passed with flying colours.
The Black-Hole Collision
The merger occurred more than one billion light years from Earth, converting three times the mass of the sun into gravitational wave energy. In a fraction of a second, the power radiated through these waves was more than ten times greater than the combined luminosity of every star and galaxy in the observable universe. This was a truly cataclysmic event a long time ago in a galaxy far, far away. In Star Wars Darth Vader tells us not to underestimate the power of the dark side. This amazing discovery shows how right he was.
Of course our discovery isnt just about checking if Einstein was right. Detecting gravitational waves will help us to probe the most extreme corners of the cosmos the event horizon of a black hole, the innermost heart of a supernova, the internal structure of a neutron star: regions that are completely inaccessible to electromagnetic telescopes.
Could we ever harness gravitational waves for practical applications here on Earth? Could new insights about the dark universe help us, perhaps in the far future, not just to measure gravitational fields but to manipulate them, as imagined in the space colonies and wormholes of Christopher Nolans Interstellar? That is much harder to predict, but the lesson of history is that new phenomena we discover and explore frequently lead to disruptive technologies that come to underpin our everyday lives. It might take a few centuries, but I am confident the same will be true with gravitational waves.
Although many species communicate acoustically, the vast majority of animals use a genetically innate repertoire of sounds to exchange information. But some species, including humans, are capable of imitating sounds and adding it to their own repertoire, a process known as vocal learning. It is thought that the acquisition of this ability may have been a first step in the evolution of human language.
Although this trait is extremely rare, it is not unique to humans and has been discovered in 6 groups of animals: 3 groups of birds and 3 groups of mammals. Now, thanks to new research, we know that killer whales are capable of cross-species vocal learning. When socialized with bottlenose dolphins in captivity, the team discovered that they transitioned from their typical vocalizations and emitted more dolphin-like noises. According to the researchers, this suggests that cetaceans (dolphins, whales and porpoises) may use this trait to facilitate social interactions. The work has been published in The Journal of the Acoustical Society of America.
Killer whales, or orcas, emit three main types of vocalization: clicks, pulsed calls and whistles, with pulsed calls being the dominant form of communication. These are known to vary across social groups in terms of duration and pitch, but killer whales living together tend to produce similar calls that are distinct to that particular group, which is known as a dialect. Researchers had their suspicions that killer whales learn this dialect, but there was no experimental proof. Since dolphins produce similar vocalizations to orcas, and the two are sometimes housed together in captivity, the researchers took this unique opportunity to investigate whether killer whales could learn vocalizations from their cross-species social partners.
For the study, the researchers analyzed recordings of vocalizations produced by 10 captive orcas; three of these lived with bottlenose dolphins for several years, whereas the rest were housed with their own species. They then compared these recordings with the vocalizations produced by the dolphins.
They found that 95% of the 1551 vocalizations made by the seven orcas that were living with members of their own species were the typical pulsed calls that dominate their repertoire. The orcas that were living with dolphins, however, emitted far more whistles and clicks, just like their cross-species social partners. Intriguingly, they found that one of the killer whales even learned how to produce an artificial chirp sequence that a human trainer had taught the dolphins before they were introduced to each other.
According to the researchers, this demonstration of cross-species vocal learning suggests that orcas have substantial vocal plasticity and are highly motivated to match the vocalizations of their social associates. This is important because the fate of orcas in groups disrupted by change, such as oil spills, will be partly dependent on their ability to socialize with new populations and thus their vocal plasticity.
Asteroids might not be what they appear to be. New research suggests some may be coated in material from other objects, providing a form of camouflage that hides their true appearance. The findings were published in the Astronomical Journal.
Led by the Astrophysics Laboratory of Marseilles (LAM), scientists used NASAs Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft to observe the dwarf planet Ceres in the asteroid belt, sometimes also referred to as a large asteroid.
It had been thought that the surface of Ceres was rich in carbon, something common in class C asteroids that Ceres was thought to belong to. Instead, they found a large amount of material that seems to have come from other asteroids, rocky silicates like pyroxene dust, mixed in with wet clays, carbonates, and water ice.
This study resolves a long-time question about whether asteroid surface material accurately reflects the intrinsic composition of the asteroid, said Pierre Vernazza, a research scientist at the LAM, in a statement.Our results show that by extending observations to the mid-infrared, the asteroids underlying composition remains identifiable despite contamination by as much as 20 percent of material from elsewhere.
The study suggests that this dust may have been delivered from interplanetary dust particles (IDPs), created when asteroids collide. And it means Ceres may not have formed in its current position, something that has been hinted at before.
In their paper, the researchers wrote that this finding possibly supports recent results obtained by the Dawn mission [currently in orbit around Ceres] that Ceres may have formed in the very outer Solar System.
And this may not just be limited to Ceres. Its thought that other worlds, like Plutos moon Charon and Saturns moon Iapetus, might also have camouflage coverings that hide their true nature.
You may think the life of a cat is easy, but you’d be dead wrong.
Though they’re much cuter about it, these cats still feel the harrowing reality of the return from a long weekend just as much as any human. Some take out their frustration on a roll of paper towels and some prefer to hide in a brick wall’s crevice.
Let these cats take you to the end of the workday. If they can do it, so can you.
This adorable pet video was published online by Erica Griffith over a year ago, but it has just gone viral, going from zero to over 200,000 views just today.
Erica is a true animal lover, and as a result, has a very unique and diverse pack of pets. She shows them off by calling her five well behaved dogs into the room one at a time and then–the surprise–George, a one year old duck, and Twiggy the kitty.
In an unprecedented decision, a federal appeals court ordered the U.S. government to release a memo detailing the legal justification behind the killing of American citizens by drone strikes overseas.
The 2nd U.S. Circuit Court of Appeals ruled on Monday that the government can’t claim the memo needs to be secret anymore, because various U.S. officials have repeatedly acknowledged the so-called targeted drone strikes program in general and the killings of three American citizens in Yemen in 2011 in particular. This is an addition to a U.S. Department of Justice White Paper, leaked by NBC News and confirmed by DOJ, which explained the legal rationale behind drone strikes.
“Whatever protection the legal analysis might once have had has been lost by virtue of public statements of public officials at the highest levels and official disclosure of the DOJ White Paper,” wrote Judge Jon O. Newman in a decision (embedded below), that was made unanimously by a three judge panel in Manhattan.
Monday’s decision overturns a January 2013 lower court ruling that allowed the Department of Justice to keep secret a memorandum that provided the legal justification for the drone strikes that killed three United States citizens in Yemen: Anwar al-Awlaki, a cleric who allegedly had become a prominent Al-Qaeda spokesperson, his 16-year-old son Abdulrahman, and Samir Khan.
At the time, U.S. District Judge Colleen McMahon ruled in favor of secrecy despite the fact that she found herself in a “paradoxical situation” of letting the government claim it was legal to kill Americans outside of declared war zones, while also claiming it can’t reveal the legal reasoning behind that decision.
“The Alice-in-Wonderland nature of this pronouncement is not lost on me,” she wrote.
The lawsuit in Monday’s decision was filed by The New York Times, which has filed a Freedom of Information Act request to see the legal memo, with the support of the American Civil Liberties Union (ACLU).
It’s unclear whether the DOJ will now appeal the decision, and, for now, there’s no timetable for the release of the documents.
Both the Times and the ACLU, however, celebrated the ruling.
“This is a resounding rejection of the government’s effort to use secrecy and selective disclosure to manipulate public opinion about the targeted killing program,” ACLU Deputy Legal Director Jameel Jaffer said in an emailed statement. “The public has a right to know why the administration believes it can carry out targeted killings of American citizens who are located far away from any conventional battlefield.”
“The court reaffirmed a bedrock principle of democracy: The people do not have to accept blindly the government’s assurances that it is operating within the bounds of the law; they get to see for themselves the legal justification that the government is working from,” David McCraw, the Times‘ lawyer, said in a statement.
Here’s the full ruling from the 2nd U.S. Circuit Court of Appeals.
The echolocation clicks of toothy whales and dolphins typically encounter few obstacles at sea. Amazon river dolphins, on the other hand, live in shallow channels and flooded forests alongside dense vegetation confined environments where sonar operations might result in high levels of clutter and reverberation. According to new findings published in the Journal of Experimental Biology, these dolphins rely on a high-frequency, short-range biosonar.
Previous studies found that body size plays an important role in the evolution of toothed whale echolocation. Aarhus Universitys Michael Ladegaard and colleagues wanted to see if habitat shaped the evolution of their biosonar as well. They recorded the echolocation clicks of wild Amazon river dolphins (Inia geoffrensis, also called botos) in three locations in the Amazon during October of 2013: near So Tom in Brazil, at the confluence of Rio Negro and Rio Solimes, and in the Mamirau Sustainable Development Reserve. The dolphins were recorded from small aluminum-hulled boats, and an array of seven hydrophones were deployed vertically as the team drove slowly ahead of the animals. The researchers recorded almost 35,000 echolocation clicks, of which 268 were recorded head-on and within 21 meters (70feet) of the equipment.
These river dolphins, the researchers discovered, produce soft, high-pitched echolocation clicks that lasted 14.1 microseconds with a brief interval of 35 microseconds between the clicks.
By increasing the frequency of their clicks, these freshwater dolphins could direct their sonar better than their ocean faring cousins. With soft, lower amplitude clicks, echoes only return from nearby objects. That means all of the echoes that they need to interpret return within milliseconds, Inside JEB explains, allowing them to produce high rates of about 30 clicks a second, while limiting reverberations.
Low-amplitude, highly directional biosonar systems, the team argues, are advantageous in riverine habitats because they simplify the auditory scene and help with target detection in cluttered, acoustically complex spaces.