Large spirals on Mars, as seen by an orbiting spacecraft. / Image courtesy U. Arizona/NASA
for National Geographic News
Published April 26, 2012
Hundreds of large spirals have been discovered on Mars, and scientists think the coiled features are evidence of a type of lava flow never before seen on the red planet.
If so, the spirals would suggest that volcanoes—not ice floes, as other experts believe—shaped an unusual area near the red planet’s equator.
Athabasca Valles is a region of flow channels and valleys covered with terrain plates, structures that show clear evidence of something fracturing and drifting across the planet’s surface millions of years ago.
Scientists have been divided, however, as to whether the plates were made by the hardening of a massive lava flow or by icy “rafts”—much like Arctic pack ice—from an ancient inland sea.
Now, high-resolution pictures of Athabasca Valles from NASA’s Mars Reconnaissance Orbiter have revealed 269 coils up to a hundred feet (30 meters) wide.
"There are no known mechanisms to naturally produce spiral patterns in ice-rich environments on the scale and frequency observed in our study area," study authors Andrew Ryan and Philip Christensen write in a new paper in this week’s issue of the journal Science.
Instead Ryan and Christensen, of Arizona State University, think the coils are most similar to features seen in smooth, slow-moving Hawaiian lava flows.
"Everything that we have observed in Athabasca Valles can be formed by lava. Although you could attribute certain features to ice, the lava coils indicate that this is not the case," Ryan told National Geographic News in an email.
Valley Shaped by Ice or Fire?
On Earth, so-called pahoehoe lava flows can move past each other in different directions or at different speeds. The resulting shear produces a twisting motion, which coils the rubbery crust atop the flows into a distinctive shape—one that closely resembles the newfound Martian spirals.
On Earth similar spirals are found underwater on a mid-ocean ridge, where two “conveyor belts” of spreading crust move outward in opposite directions, causing the upwelling lava between them to swirl.
As with many things Martian, however, the new data remain open to interpretation.
John Murray, with the Department of Earth Sciences at the Open University in the U.K., said Ryan’s paper is interesting and that the spiral features are quite curious. But Murray still believes that the surface near Athabasca Valles shows the lingering effects of an ancient frozen sea.
"I think there are so many features here that it’s difficult to explain them other than [the theory] that this was essentially water that froze and has since sublimated away," he said. Sublimation is when a solid turns directly into a gas.
"There is no lava that behaves in so many different ways."
The appearance of the plates themselves, not the spirals in between, remains a main sticking point for Murray.
"You do get plates in lava, but on the scale of a few meters," he said. "Here you’re talking about things which are kilometers long, and the only way you can do that really is to have a liquid that’s extremely mobile and fluid—water or something like water.
"If you freeze the top of that, as in the Arctic, you do get ice floes that are several kilometers or more, which is what you get on Mars in this region. You never see anything like that in a lava flow."
A Place to Look for Life?
The debate pitting lava against ice is more than purely geological. If Athabasca Valles does show clear evidence of water ice, the region could become an important target for future Mars astrobiology missions.
"If this really is the remains of a large inland sea, that’s where you’re going to find life, if there is any there," Murray said.
"Even if the sea was five million years old, there may still be subsurface remains of the ice, and … microfossil traces could perhaps be found there."
Study author Ryan, meanwhile, is confident the odd features of Athabasca Valles can be explained by volcanism alone.
"I don’t believe it would be a very good place to search for life," he said. "However, it is a very interesting place to study the volcanic and geologic history of Mars."
(Source: National Geographic)
National Geographic News
Published September 29, 2011
Holy bat buzz, Batman—a new study shows the night flyers are the first known mammals with superfast muscles.
Found in some songbirds and snakes, superfast muscles in bats occur in the throat and enable a crucial hunting behavior: echolocation, in which the bat sends out sound waves and listens for echoes bouncing off prey.
As a bat closes in on an insect, the mammal emits more than 160 calls a second, a phenomenon called terminal buzz.
The discovery explains how bats release such rapid calls. “It’s really cool, because the muscles belong to this rare group, superfast muscles,” said study leader Coen Elemans, a biologist at the University of Southern Denmark.
But “at the same time, they also limit the bats.”
Though fast, the specialized muscles allow only a finite number of calls per second, Elemans pointed out. With even faster muscles, bats would benefit by making more calls per second, since each sound wave gives them more information about prey.
For the study, Elemans and colleague released individuals of a species called Daubenton’s bats in a large cage, where they flew toward mealworms that the researchers had hung on a string. The bats’ echolocation calls were recorded with a sophisticated microphone array.
The scientists measured when the bats were issuing calls, as well as when the echoes of those calls reached the bats’ ears.
The team had suspected that bat call rates may be limited by the need to process the calls’ echoes. That is: If a bat calls too soon, it won’t be able to hear the previous call’s echo and therefore will lose track of prey.
Each echo, though, hit the caller within about 2.5 milliseconds, yet the bats waited 6 milliseconds, on average, before making the next call—”a sea of time,” Elemans noted.
That means that the bats are physically incapable of making more calls per second, not because they’re deliberately waiting for echoes.
Next, the scientists removed superfast muscle fibers from some of the bats’ larynxes and measured the tissue’s mechanical performance by stimulating it with electricity.
The team found the bats’ laryngeal muscles—which determine call frequency by tensing the bats’ vocal folds—could power movements up to, but not beyond, 180 times a second. That’s exactly the rate at which bats call during terminal buzz.
Superfast-Muscle Evolution Still a Mystery
The discovery of superfast muscles in mammals may also help scientists disentangle the muscles’ evolution overall, Elemans said.
For instance, researchers will now be able to compare the bat genome with other genomes of superfast-muscled animals—such as songbirds and snakes—to figure out when and how the muscles evolved.
What’s more, Elemans suggests that the tracking boost afforded by terminal buzz helped bats flourish when they first evolved 50 million years ago.
"You need these buzzes to catch stuff," Elemans said. In addition to flight and "regular" echolocation, terminal buzz is "the third reason why they’ve been successful evolutionarily."
(Source: National Geographic)
By David Dobbs
Photograph by Kitra Cahana
Although you know your teenager takes some chances, it can be a shock to hear about them.
One fine May morning not long ago my oldest son, 17 at the time, phoned to tell me that he had just spent a couple hours at the state police barracks. Apparently he had been driving “a little fast.” What, I asked, was “a little fast”? Turns out this product of my genes and loving care, the boy-man I had swaddled, coddled, cooed at, and then pushed and pulled to the brink of manhood, had been flying down the highway at 113 miles an hour.
"That’s more than a little fast," I said.
He agreed. In fact, he sounded somber and contrite. He did not object when I told him he’d have to pay the fines and probably for a lawyer. He did not argue when I pointed out that if anything happens at that speed—a dog in the road, a blown tire, a sneeze—he dies. He was in fact almost irritatingly reasonable. He even proffered that the cop did the right thing in stopping him, for, as he put it, “We can’t all go around doing 113.”
He did, however, object to one thing. He didn’t like it that one of the several citations he received was for reckless driving.
"Well," I huffed, sensing an opportunity to finally yell at him, "what would you call it?"
"It’s just not accurate," he said calmly. " ’Reckless’ sounds like you’re not paying attention. But I was. I made a deliberate point of doing this on an empty stretch of dry interstate, in broad daylight, with good sight lines and no traffic. I mean, I wasn’t just gunning the thing. I was driving.
"I guess that’s what I want you to know. If it makes you feel any better, I was really focused."
Actually, it did make me feel better. That bothered me, for I didn’t understand why. Now I do.
My son’s high-speed adventure raised the question long asked by people who have pondered the class of humans we call teenagers: What on Earth was he doing? Parents often phrase this question more colorfully. Scientists put it more coolly. They ask, What can explain this behavior? But even that is just another way of wondering, What is wrong with these kids? Why do they act this way? The question passes judgment even as it inquires.
Through the ages, most answers have cited dark forces that uniquely affect the teen. Aristotle concluded more than 2,300 years ago that “the young are heated by Nature as drunken men by wine.” A shepherd in William Shakespeare’s The Winter’s Tale wishes “there were no age between ten and three-and-twenty, or that youth would sleep out the rest; for there is nothing in the between but getting wenches with child, wronging the ancientry, stealing, fighting.” His lament colors most modern scientific inquiries as well. G. Stanley Hall, who formalized adolescent studies with his 1904 Adolescence: Its Psychology and Its Relations to Physiology, Anthropology, Sociology, Sex, Crime, Religion and Education, believed this period of “storm and stress” replicated earlier, less civilized stages of human development. Freud saw adolescence as an expression of torturous psychosexual conflict; Erik Erikson, as the most tumultuous of life’s several identity crises. Adolescence: always a problem.
Such thinking carried into the late 20th century, when researchers developed brain-imaging technology that enabled them to see the teen brain in enough detail to track both its physical development and its patterns of activity. These imaging tools offered a new way to ask the same question—What’s wrong with these kids?—and revealed an answer that surprised almost everyone. Our brains, it turned out, take much longer to develop than we had thought. This revelation suggested both a simplistic, unflattering explanation for teens’ maddening behavior—and a more complex, affirmative explanation as well.
for National Geographic News
Published September 15, 2011
Like the imaginary Star Wars world Tatooine, a new planet found 200 light-years away has two suns, astronomers announced today.
NASA’s Kepler spacecraft uncovered the new planet, dubbed Kepler 16b, as it transited—or crossed in front of—both its parent stars, causing the brightness of each star to dim periodically.
Kepler data first allowed scientists to see that the stars are what’s known as an eclipsing binary system—a pair of stars that orbit in such a way that they eclipse each other, causing them to dim, as seen from Earth.
Based on the eclipses, the team calculates that the binary stars are just 20 percent and 69 percent the mass of our sun.
Sometimes, however, the system’s overall brightness dipped even when the stars were not eclipsing each other—hinting at the presence of a third body orbiting the binary pair.
"By timing the stellar eclipses, we could determine how much the third body was perturbing the two inner stars," said study leader Laurance Doyle, an astronomer at the SETI Institute in Mountain View, California.
The extra, irregular dimming “turned out to be no stronger than a planetary gravitational pull would be.”
Next: An Earthlike Planet With Two Suns?
Kepler’s data suggest that the new planet is a Saturn-like gas giant without a solid surface.
Traveling on a nearly circular, 229-day orbit around both host stars, the planet lies outside the system’s habitable zone—the region where liquid water, and thus life as we know it, could exist.
In fact, the new planet likely receives about the same amount of sunshine as Mars, which means that, even if it had a solid surface, the world would be far too cold to support life.
Still, as on Tatooine, “from Kepler 16b one would see a double sunset, but with the stars shifting position [and moving in relation to each other] while setting.”
And while Kepler 16b may not have any sand dunes, it’s theoretically possible for Earthlike planets to exist in similar binary star systems—an arrangement that Doyle says may be quite common.
"I estimate that there may be about two million such systems in our galaxy," he said.
The new planet with two suns is described in this week’s issue of the journal Science.
(Source: National Geographic)
By Nancy Shute
Photograph by Fabrice Coffrini, AFP/Getty Images
Perched on the edge of a cold, windswept dune in North Carolina, I was about to fulfill a dream I shared with Leonardo da Vinci: To fly. The Renaissance genius spent years deciphering the flight of birds and devising personal flying machines. On his deathbed in 1519, Leonardo said one of his regrets was that he had never flown. Five hundred years of innovation since then had produced the hang glider I held above my head, simple and safe enough to be offered as a tourist entertainment. But despite those centuries of adventure and experimentation, personal flight—the ability to bound from Earth like a skylark, swoop like a falcon, and dart as blithely as a hummingbird—remains elusive.
That’s not for lack of trying. Many lives have been lost and fortunes squandered pursuing the dream of flight, and even today scientists, inventors, and adventurers persist in the quest.
Leonardo drew hundreds of images of birds on the wing, trying to decode their secrets, and drafted meticulous plans for flying machines not unlike today’s gliders and helicopters. But he never figured out the physics of flight. It took more than 300 years and many more failed experiments until Sir George Cayley, a British engineer, determined that flight required lift, propulsion, and control. He built a glider with a curved wing to generate lift. Then he ordered his coachman into it and had farmworkers pull it down a slope until it gained enough speed to fly. Control, alas, was lacking. The craft crashed after flying a few hundred yards. The coachman survived, but reportedly was not amused.
My student hang glider was almost as low concept as Cayley’s, and though I knew it could fly, control clearly remains an issue. The instructors at Kitty Hawk Kites, at Kill Devil Hills a couple of miles from where the Wright brothers flew the first powered aircraft in 1903, explained that piloting requires just five simple motions: lean left or right to turn; push the control bar up or down for speed; push the bar up to land. But students in my class still augered into the sand. One fell hard enough to break the glider’s sturdy aluminum strut. That made me more determined to succeed.
I have always loved to fly, even in lumbering jumbo jets. When the Kitty Hawk Kites school quoted Leonardo as saying, “For once you have tasted flight, you will walk the Earth with your eyes turned skywards,” I sighed in recognition.