TIME space

What’s That Thing on Saturn’s Biggest Moon?

What in the world? The mystery formation as seen over time
What in the world? The mystery formation as seen over time JPL/NASA

Something strange is happening on the cloud-shrouded world known as Titan—and a NASA orbiter is trying to figure it out

It’s not the first time a formation has appeared, seemingly out of nowhere, on a world beyond Earth. Usually, it’s Mars: this year alone the Mars Reconnaissance Observer spotted a brand-new crater that wasn’t there last time NASA looked, while the Opportunity Rover discovered the amazing Ghost Rock that also didn’t exist—and then it did.

Now it’s Titan’s turn. Saturn and its moons have been under close scrutiny by the Cassini probe ever since the spacecraft arrived in the neighborhood back in 2004, discovering such oddities as geysers and a subsurface ocean on the ice moon Enceladus; a mysterious hexagon-shaped storm on Saturn itself; and a hydrocarbon cycle on Titan that mirrors Earth’s water cycle, complete with rainstorms, rivers and lakes.

But in July, 2012, Cassini spotted something that hadn’t been there anytime in the previous seven years: a bright spot, covering about 30 square miles (78 sq. km), in the lake known as Ligeia Mare, which is bigger than Lake Superior. NASA called it a “transient feature,” while the Internet dubbed it the “Magic Island.” And as of August 21 of this year, the space agency has just announced, it was still visible—and in fact, it had doubled in size.

“The fact that it’s still there shows that it isn’t just some artifact of the imaging system,” says Jason Hofgartner, the Cornell grad student who’s in charge of figuring out what the darned thing is. “Something is really happening on Titan.”

Hofgartner and his colleagues have narrowed the “something” down to four possibilities. “It could be waves,” he says. “It could be bubbles rising up from the bottom. It could be solids of some kind floating on the surface—or solids suspended below the surface. All of these,” he says, “are equally viable at this point.”

The scientists are convinced, however, that the mystery island almost certainly has to do with the changing of seasons on Titan. Riding along in its orbit around Saturn, Titan takes 30 years to circle the Sun, and the northern hemisphere, where Ligeia Mare is located, is just at the start of its 7 1/2-year summer. It’s bathed in solar energy, and, says Hofgartner, “any of those [features] could be powered by the seasonal change.”

If so, it wouldn’t be the first time scientists have seen seasonal effects on Titan: when Cassini first arrived in the Saturnian system, the moon’s southern hemisphere was edging into the end of summer, and observations suggested at the time that evaporation had shrunk the lakes in the region from their maximum extent—the same thing that happens to lakes and reservoirs on Earth.

In fact, the search for evidence of seasonal changes on Titan was a primary objective of the Cassini mission, and the space probe should get at least another look at the mystery island before the mission ends.

That won’t remotely solve all of the mysteries about this extraordinary moon, however. It’s nothing less than a Bizarro version of Earth, with methane and other hydrocarbons taking the place of water. “It has all kinds of processes we can learn about,” says Hofgartner, “which could help us understand processes on Earth better.”

That could call for a return visit one day by a successor of Cassini. “There are lots of reasons,” Hofgartner says, “to go back.”

TIME Biology

Meet the Fish That Can’t Get Jet-Lagged

Who cares about the time? A blind fish needs no internal clock
Who cares about the time? A blind fish needs no internal clock Reinhard Dirscherl; Getty Images/WaterFrame RM

There's a reason you get sleepy at night: because it's dark out. Now a little blind fish helps explain all that

Birds have ‘em. Bees have ‘em. Even bacteria have circadian rhythms, the ramping up and slowing down of internal functions that signals organisms to be more or less active, depending on the time of day. Humans have circadian rhythms too—and when they’re disrupted by time-zone changes, lack of sleep or working the night shift, the result can be an increased risk of heart attacks, depression, diabetes, weight gain and more.

For eyeless Mexican cave fish, however, no problem, says a new study in the journal PLOS ONE reports. “Some organisms have stronger circadian rhythms, and some weaker,” says lead author Damian Moran, of the private company Plant and Food Research, based in New Zealand. “But these fish have none at all.”

The finding, says Moran, “just fell into our laps.” He and his colleagues were actually studying the energy costs of vision—that is, how much of the body’s resources evolution thinks it’s worth devoting to having the advantage of being able to see. The Mexican tetra fish is especially useful for such studies because it comes in both a surface-dwelling subspecies and several versions that live in caves, in perpetual darkness (the latter, says Moran, “look a little like Gollum“).

In order to measure the energy cost of having vision, the scientists put both versions of tetra into a kind of fish treadmill, where they could swim constantly upstream while instruments measured their oxygen intake, a gauge of their energy use. To cover all their bases, the scientists tested both types of fish under their most familiar conditions—with a day-night cycle, and in total darkness.

The scientists were looking to measure the differences in energy use between the fish with eyes and those without—but they noticed something else as well. “The surface-dwellers,” says Moran, “had a typical increase of oxygen use during the day, and a decrease during the night. Whereas the cave fish showed a flat line day and night.”

It makes sense: an animal that lives in changing conditions of light and darkness needs to be more active when its food sources are more active, whereas a creature that never sees the light of day probably doesn’t care. Even so, since many organisms that live in utter darkness are descended from surface-dwellers, they maintain at least a weak circadian rhythm. But the cave-dwelling tetra have none, and because they don’t have to ramp their metabolism up and down, they use 27% less energy overall than their daytime-nighttime cousins.

While this is the first such animal ever found, says Moran, the eyeless tetra might actually be just the tip of a gigantic biological iceberg. “Most of the Earth’s biomass lives in areas that never see light at all. I suspect that when we look in the deepest part of the sea or deep underground,” he continues, “we’ll find many organisms that have no circadian rhythms.”

Because after all, what’s the point?

TIME space

The People Have Voted: Pluto is a Planet!

Sure looks like a planet: An artist's rendering of Pluto
Sure looks like a planet: An artist's rendering of Pluto NASA

A populist uprising restores a space favorite to the planetary ranks. Will the astronomers listen?

When Pluto was hurled from the pantheon of planets back in 2006, it could simply have slinked away, accepting its new title of “dwarf planet” without a fuss. But thanks to the undying support of its millions of fans—not just schoolchildren, but many astronomers as well—the little planet that could is still a contender.

The latest evidence: a debate at the Harvard-Smithsonian Center for Astrophysics, in which three astronomers squared off to present both sides of the question: “Is Pluto a Planet?” And when the dust settled, the audience, made up mostly of ordinary citizens, declared once again that the answer is “duh, obviously.”

Three may seem like one side too many, but David Aguilar, the Center’s director of public affairs, who set up the debate, wanted to look at the question not just from a scientific perspective, but also through the lens of history. The first speaker, therefore, was the eminent Harvard astronomer and historian of science Owen Gingerich. “Planet,” he pointed out, “is a culturally defined word that has changed its meaning over the ages.”

In fact, the word itself comes from an ancient Greek word meaning “wanderer.” Unlike the stars, which seem fixed in place, the planets are objects that wander from one constellation to another in the sky—and since the Sun and the Moon do that too, they were originally considered planets as well.

That designation didn’t last, of course, but when astronomers began finding asteroids in the early 1800’s, they were also counted as planets, at least as first, (The fact that astronomer William Herschel had recently discovered the new planet Uranus had evidently given the scientists’ a taste for more.) Within a few decades, though, astronomers found so many asteroids that things were getting confusing. Objects like Ceres and Vesta, the largest asteroids in the asteroid belt, were demoted from “planet” to “minor planet,” in a foreshadowing of Pluto’s fate a century and a half later—and it had nothing to do with any sort of scientific definition of the word.

And neither did the International Astronomical Union’s decision to downgrade Pluto in 2006. Just as with the asteroids, astronomers began finding additional Pluto-like objects starting in the 1990s, including Eris, which turns out to be essentially the same size as Pluto. If Pluto is a planet, so is Eris, and so are several other objects at the edge of the Solar System.

That would be just too confusing, argued the second debater, astronomer Gareth Williams, associate director of the IAU’s Minor Planet Center. If you let Pluto stay, he said, you logically have to let the number of planets rise to 24 or 25, “with the possibility of 50 or 100 within the next decade” as more objects are found. “Do we want schoolchildren to have to remember so many? No, we want to keep the numbers low.”

This isn’t exactly a rigorous scientific argument—so to give its decision the flavor of science, the IAU came up with a definition of “planet” so convoluted it seemed entirely arbitrary. To qualify as a planet, a body must orbit the sun and be large enough to be at least roughly spherical—two rules that make sense. But it must also have gravitationally “cleared its neighborhood” of other bodies, meaning it has its orbital traffic lane all to itself, which Pluto doesn’t—at least during the most remote portion of its journey around the sun. The rule seemed carefully crafted so that “dwarf planets” like Pluto, Eres and the asteroid Ceres didn’t make the cut.

“It didn’t make sense at all,” said Center for Astrophysics communications director David Aguilar, who set up the debate. “Isn’t a dwarf fruit tree also a fruit tree? Isn’t a dwarf rabbit a rabbit?” But in the end, the resolution was approved by IAU members, and in 2006 the number of planets was pared from 9 to 8—the ones known to science pre-Pluto.

The last debater was astronomer Dimitar Sasselov, director of Harvard’s Planets and Life initiative. His argument, he explained in a conversation after the debate, was that the word “planet” does need a scientific definition, but that we don’t know enough yet to create one. The reason: we’ve discovered thousands of planets orbiting stars beyond the Sun, and until we can understand how they formed and what they’re really like, any definition is premature. Pluto may be a planet based on scientific reasoning, or it may not be. “For now,” he said, “we should keep Pluto as a planet by default.”

In the end, the Harvard audience voted in favor of Pluto’s reinstatement by a landslide. Planetary scientist Alan Stern, whose new New Horizons probe will reach Pluto next summer for a first-ever close encounter, wasn’t there. But when he heard about the vote, he said, “every time there’s a poll it turns out this way. The IAU have become largely irrelevant in this.”

The organization may seem to count even less when you consider something Gingerich revealed during his arguments. He was there for the 2006 IAU vote, which came when most of the attendees had already gone home. Just 424 of the organization’s nearly 10,000 members were present, and when the organizers offered the gathering the chance to reconsider Pluto’s demotion, Gingerich said, “they voted not to vote again because they wanted to go to lunch, so that was the end of it.”

TIME Paleontology

Meet the Dinosaur With the Biggest Nose

"This dinosaur has a huge nose"

It’s easy to get excited about the biggest dinosaur ever found, or the baddest, or some other impressive superlative. But the one with the biggest nose? Somehow, it just doesn’t have the same impact.

Yet that’s what a team of paleontologists are reporting in the Journal of Systematic Palaeontology. The newly described dino is a hadrosaur, the group that includes the so-called duck-billed dinosaurs. Many of these plant-eating creatures sported huge bony crests atop their heads.

Not this one. “…instead,” reads a press release announcing the discovery, and calling a spade a spade, “this dinosaur has a huge nose.” What else to call it but Rhinorex, or “King Nose.” It was, says the release, the “Jimmy Durante of dinosaurs.” (If you’re under 50 or so, you’ll have to lo0k it up.)

The obvious question is: why would a dinosaur need a gigantic nose? We know why T. Rex sported long, dagger-like teeth and velociraptors needed razor-sharp claws. It’s clear why apatosaurus—better known to many, including Fred Flintstone, as brontosaurus—had such a long neck (like the giraffe’s, it was for more effective browsing).

But paleontologists Terry Gates of North Carolina State University and Rodney Sheetz of Brigham Young, who found the fossil embedded in sandstone in a Brigham Young Museum of Paleontology storage area, haven’t got a clue. It probably wasn’t for smell, but more likely for easy recognition by others of its species, or for knocking down edible plants, or—strange though it might sound—attracting mates.

“We are already sniffing out answers to these questions,” Gates said in a statement. He’s probably already regretting it.

TIME astronomy

The Mystery of the Solar System’s Weirdest Moon, Explained

Miranda
High-resolution image of the surface of Miranda, one of Uranus' largest moons, taken from the Voyager 2 spacecraft NASA

We already knew Miranda, one of Uranus' five major moons, has "one of the strangest and most varied landscapes among extraterrestrial bodies." Now, we (probably) know why

The first and only space probe ever to visit the planet Uranus timed its encounter very badly from a public-relations perspective. Voyager 2 zipped past the solar system’s seventh planet on Jan. 24, 1986; four days later, the shuttle Challenger exploded in flames. And suddenly, far-off Uranus and its retinue of moons didn’t seem so important anymore.

Yet the images Voyager took during that overshadowed encounter have continued to intrigue planetary scientists ever since — and that’s especially true when it comes to Miranda, one of the planet’s five main moons. Its surface, U.S. Geological Survey astrogeologist Laurence Soderblom told TIME shortly after the encounter, “is a bizarre hybrid,” while NASA describes Miranda as having “one of the strangest and most varied landscapes among extraterrestrial bodies.”

Perhaps the strangest features of all are Miranda’s three visible “coronae” — relatively crater-free regions marked by ridges and valleys and slapped onto the surface “like mismatched patches on a moth-eaten coat,” in NASA’s words. But now, nearly three decades after they were found, Miranda’s coronae may have an explanation at last. Writing in the journal Geology, Brown University planetary scientists Noah Hammond and Amy Barr argue that these odd scraps of terrain come from ancient hot spots in the moon’s 100-mile-thick crust of ice. “Despite being incredible cold,” says Hammond, ” there’s a lot of geologic activity on this moon.”

Geology on the frigid moons of the outer solar system itself isn’t such big news these days. Scientists have spotted volcanoes on Jupiter’s moon Io, ice geysers on Saturn’s moon Enceladus, lakes on Titan, plate tectonics on Europa and more. But to have geology, you need some source of heat, and there just doesn’t seem to be one for Miranda, which is deep-frozen to about –350°F.

There’s no heat source now, anyway. But Miranda’s orbit is unusually tilted with respect to Uranus’ equator — its “inclination,” as astronomers call it, is about 10 times greater than that of the planet’s other major moons. One way that could have come about is if Miranda’s orbit was originally very eccentric, or elongated. That would have brought it into close encounters with other moons, which could have relocated into a tilted orbit.

If Miranda’s orbit really was elongated, the moon would have been squeezed and stretched by the tidal effect of Uranus’ gravity, and, just like a rubber ball squeezed in your hand, it would have heated up a bit. And that rising heat would have made the ice itself flow very, very slowly upward — a process physicists call convection. Hammond and Barr created a computer model of that flow, and sure enough, he says, “we were able to show that if shell is convecting, it naturally produces four upwellings.” Since it’s just a model, it can’t simulate the actual moon precisely, but it’s definitely in the ballpark of what Voyager saw.

Each upwelling of ice would have tried to spread as it reached the surface, and crinkled, accordion-fashion, into the ridges and valleys that characterize the coronae. The fact that these regions are relatively crater-free fits right in: new ice flowing out from the interior would have to sit on the surface for a long time to match the cratering of the surrounding areas.

The coronae can’t be more than a few hundred million years old — peanuts compared with the rest of the surface, which dates back billions of years, and consistent, Hammond says, with the fact that Miranda probably gained its tilt and lost its heat generation about that long ago.

It all hangs together — but since it’s based on a handful of images taken nearly 29 years ago that only show Miranda’s southern hemisphere, it may be hard to be proved definitively. Planetary scientists have a far richer set of observations for the moons of Jupiter and Saturn, where the Galileo and Cassini probes respectively stuck around snapping photos for years rather than flying by (and Cassini is still going strong).

Unfortunately, while scientists are contemplating return missions to Jupiter and Saturn, nobody’s got plans to revisit Uranus. Which leaves Hammond and Barr’s theory of where the coronae came from in the “convincing but not definitive” realm.

Hammond is absolutely definitive about one thing, however. “Miranda,” he says, “is a really cool moon.”

TIME Research

Chin-Powered Energy Is Now Possible, Say Scientists

Can’t you just see the infomercial?

“Darn it, that hearing-aid battery went out again!”

“Never happens to me, Fred. Because I have this.” (Pulls out strap, buckles around top of head and under chin. Pops a stick of gum in mouth. Starts chewing.) “Yep, I have all the power I need, right here.” (Points to chin. Fred looks on with a mix of awe and envy.)

It sounds like an Onion piece but it’s real—and it’s really, really peculiar. A new report in the journal Smart Materials and Structures lays it out: engineers at Montreal’s École de Technologie Supérieure have created a prototype of the energy-generating chin strap and proven that it works in the lab, putting out 18 microwatts of electricity.

“Given that the average power available from chewing is around seven milliwatts, we still have a long way to go before we perfect the performance of the device,” writes study co-author Aidin Delnavaz, in a press release—which is a bit of an understatement, since that would be about a thousandfold increase in performance.

The technology behind the chinstrap power source isn’t new, mind you: it involves piezoelectric materials, which generate electricity simply by being squeezed or flexed. They’ve been used to create energy-producing kneepads (“not that pleasant” to wear, says its inventor) and boots (not that fashionable).

But the chinstrap is evidently the new state of the art. Once the engineers get the kinks out, which could take a few years, it could become commercially available, at which point, said Delnavaz, “the device could substantially decrease the environmental impact of batteries and bring more comfort to users.”

This depends on your definition of “comfort,” though. If you think strapping a contraption around your head every time you sit down to dinner and chewing against resistance is likely to be comfortable, either physically or socially, this item is for you.

 

TIME Dinosaur

The Biggest, Baddest Dinosaur Ever Has Been Discovered

Spinosaurus at National Geographic
Pedestrians walk past the newly erected replica of the Spinosaurus, the largest predatory dinosaur to ever roam the Earth, in front of the National geographic Society in Washington on Sept. 8, 2014. Bill Clark—CQ-Roll Call

Most of North Africa is no more than a sun-scorched desert today, but 95 million years ago the landscape was crisscrossed by rivers, dotted with marshes and populated with all sorts of reptilian monsters. The German paleontologist Ernst Stromer stumbled on this lost world back in 1912. Among the fossils he brought back to Munich were a few bones from a strange-looking predator he called Spinosaurus aegyptiacus—notably a long, thin jawbone studded with sharp teeth and a backbone festooned with enormous spines. The animal was clearly a predator, and the bones were so huge that this new creature could, he thought, be even bigger than T. Rex.

Unfortunately, most of Stromer’s fossil collection was destroyed in an Allied bombing raid during World War II, leaving just his drawings and descriptions. That record has obsessed University of Chicago paleontologist Nizar Ibrahim since he read about them as a child, and, says Nizar, “I always wanted to go back to do the same thing Stromer did a century ago.”

A few years ago, he did. The results have just appeared in a new report in Science. And it turns out that Spinosaurus was even stranger than Stromer realized. “There are so many ways it was unusual,” says Ibrahim, “that it’s hard to come up with my top three favorites.” At nearly 50 ft. long, he says the creature was in fact bigger than T. Rex—the biggest predatory dinosaur ever found, by about nine feet. “It had a long snout like a crocodile,” he says. “It had a big sail on its back.”

And perhaps most important from a scientific perspective, Spinosaurus is the first swimming dinosaur ever discovered (ichthyosaurs weren’t dinosaurs, so they don’t count). “It had relatively puny hind legs,” says Ibrahim’s University of Chicago colleague Paul Sereno, who co-authored the new paper, “with wide feet and flat claws that are ideal for paddling.”

Its tail, unlike that of T. Rex, was flexible, which would have helped propel it through the water, and its nostrils were high up on its head, allowing it to breathe as it searched for its underwater prey—freshwater sharks, among other things. “The skull,” says Ibrahim, “resembles the skull of fish-eating crocodiles, and the tip of the snout, with its slanted, interlocking teeth, is like a fish-catching trap.” The sail—the biggest ever found on a dinosaur—was almost certainly used to attract females, since it didn’t have a rich system of blood vessels that would have marked it as an adaptation for getting rid of excess heat. For that reason, says, Sereno, “It was probably brightly colored.”

If Spinosaurus is the biggest, weirdest predatory dino ever found, and the tale of its discovery a mystery story lasting nearly a century, the way it was reconstructed was almost equally unusual: the scientists digitized Stromer’s old drawings of the bones he’d found, digitized images of the bones they’d found, and merged them with a computer to figure out what the whole creature must have looked like—a process you’ll see, along with the story of Spinosaurus’ discovery and rediscovery, on a National Geographic/NOVA special airing on PBS on Nov. 5 at 9 p.m. You can see Spinosaurus itself, meanwhile, at the National Geographic Museum in Washington, D.C., starting September 12.

And if Spinosaurus itself isn’t strange enough to grab you, there’s plenty more to come. “We’ve collected an entire menagerie of strange predators,” says “Ibrahim, “and we’ll be publishing more papers. I’m interested in Spinosaurus, but also in the world it lived in. Spinosaurus had bizarre adaptations,” he says, “but they make sense once you understand the bizarre river system it ruled.”

 

 

 

 

TIME Evolution

The Remarkable, Movable Whale Penis: It’s Just Science, People

No snickering please: A humpback whale on the prowl
No snickering please: A humpback whale on the prowl Gerard Soury; Getty Images

A new study of cetacean pelvic bones reveals how pleasing the ladies gave some male ocean mammals a reproductive edge

It’s hard to imagine what a dolphin or a whale needs a pelvic bone for. Sure, the structure was important 40 million years ago, when the ancestors of these seagoing mammals were walking around on land and had actual legs attached to actual hips. But for a legless swimmer, there doesn’t seem to be any point. No wonder evolutionary biologists have long considered these small, apparently useless bones purely vestigial, destined eventually to vanish.

“Apparently” is the key word here, however. A team of biologists has figured out what the pelvic bones of dolphins and whales are good for—and it’s a lot more fun than walking. The bones anchor muscles that control the animals’ penises, and far from fading away, they appear to be evolving to give the animal even more, well, finesse.

“We’ll never be able to ask a female whale, ‘was it good for you?'” says Jim Dines of the Natural History Museum of Los Angeles County, co-author of a new study in the journal Evolution. “But it’s plausible that if you can maneuver the penis in a slightly different way, there could be an evolutionary advantage.”

The advantage, in case it’s not obvious, is that keeping a female cetacean happy (“cetacean” being the umbrella term that covers both whales and dolphins) would give a particularly expert lover a better chance of getting his sperm to its destination. That in turn would give him more descendants with the ideal, pelvis-anchored musculature to keep their partners happy, producing even more descendants, and so on. The triumph of the agile penis.

That’s the theory, anyway, and while it’s not quite a slam-dunk, there’s plenty of circumstantial evidence to support it. To start with, Dines and his co-authors examined the pelvic bones of 130 whales and dolphins from 29 different species—not just superficially, but using a laser scanner that made exquisitely detailed 3-D models of the bones that could be digitally compared for similarities and differences.

It turned out that the animals with the largest pelvic bones in relation to overall body size also had larger testicles than the other species. That’s important, says co-author Matthew Dean, of the University of Southern California: “Species that are the most promiscuous tend to have the largest testes.” The reason: the animals’ strategy for providing their sperm to as many receptive females as possible is to make a whole lot of it. For example, he says, “chimpanzees have gigantic testes—they’re almost as big as their brains.” Now that this image is forever lodged in your head, the more important point is that there’s a direct line from larger, more evolved pelvic bones to larger testicles to more sperm to more babies—which is the entire point.

When it comes to whales and dolphins particularly, things are more complex still. Consider that cetacean penises are, for want of a better word, prehensile. “The penis of a whale or a dolphin is very dextrous,” says Dean. “It has a mind of its own.” Specifically, it’s controlled by two strong muscles that pull with differing tension to let the organ change shape. “I think of it like a trick kite, controlled by two strings and capable of complex motion. That’s a whale’s penis to me.” And now, surely, to all of us.

To make sure the authors weren’t kidding themselves, they also looked at the ribs of big-testicled cetaceans to rule out the possibility that the relationship between large gonads and large pelvic bones was a coincidence—that all of the bones in the skeletons of these species were oversized and the pelvis bones were just going along for the ride. But nope, a bigger pelvic bone didn’t correspond with bigger rib bones. Improved sexual performance remained the leading theory.

The pelvic structures that make certain cetacean species such sexual virtuosos probably evolved very rapidly. “Male genitalia evolve much faster than other parts of the body,” says Dean, because even the slightest mating advantage can give an individual more offspring. Still, in the case of the cetaceans’ maneuverable penises, Dean concedes, “It’s a speculation. We don’t know for sure.”

Here’s hoping they prove it soon; it’s too good a story not to be true.

TIME space

Jupiter’s Moon Europa Just Got Even Cooler

Look familiar? Europa (in natural color, left, and enhanced-contrast color, right) is more like Earth than we ever knew.
Look familiar? Europa (in natural color, left, and enhanced-contrast color, right) is more like Earth than we ever knew. NASA/JPL/DLR

There is no moon in the solar system like Jupiter's Europa, with an icy surface and a salty sea that may harbor life. Now, it appears that the moon has plate tectonics too—just like Earth

The more they look at other worlds in the Solar System, the more scientists discover that Earth isn’t as special as we earthlings like to think. Our planet has active volcanoes—but so does Jupiter’s moon Io. We have geysers—and so does Saturn’s moon Enceladus. We have lakes, rivers and rain, and so does Titan, another moon of Saturn’s.

Now a paper in the journal Nature Geoscience argues that one more geological feature thought to be unique to Earth may not be after all. Using images from the Galileo spacecraft, planetary scientists think they’ve found evidence of plate tectonics on Jupiter’s ice-covered moon Europa—a world that’s already on astrobiologists’ radar because the ocean that lies beneath the moon’s thick rind of ice could conceivably host life of some sort.

Plate tectonics is the same process that causes continents to drift slowly around on the surface of the Earth, and, says Michelle Selvans, a research geophysicist at the Smithsonian’s National Air and Space Museum, who wrote a commentary on the new research for the same journal, “we’ve never seen this anywhere else.”

If plates are indeed shifting on the Jovian moon, it explains a longstanding mystery. Europa’s surface is crisscrossed with cracks where the thick ice has spread apart and the resulting gaps have been filled in by new slushy ice oozing up from the water deep below. “The fundamental question,” says the paper’s lead author, University of Idaho planetary scientist Simon Kattenhorn, “is how you can keep adding new surface without getting rid of old surface?

That’s wouldn’t be a problem if Europa were simply growing in size, but, writes Selvans, that is “unlikely.” (She admits privately that this is really science understatement-speak for “ridiculous.”) It also wouldn’t be a problem if the old surface simply folded like an accordion, as it was pushed aside. “We’ve looked for that,” she says, “and haven’t seen it.”

On Earth, however, the creation of new surface that spreads from places like the submerged Mid-Atlantic ridge is balanced by tectonic plates of crustal rock plunging back down to melt in the sea of magma below. It’s these sinking, melting plates in Earth’s so-called subduction zones that give rise to volcanoes in the “Ring of Fire” surrounding the Pacific Ocean.

And now Kattenhorn and his co-author, Louise Prockter, of Johns Hopkins, seem to have found evidence that Europa gets rid of its excess crust via subduction as well. One clue: they looked at surface ice features on Europa that have been scrambled by repeated cracking and shuffling, then manipulated the imagery to move the pieces around and reassemble them as they must have been when they were intact. Some of the puzzle pieces, they discovered, had clearly disappeared. “We looked at an area about the size of Louisiana,” says Kattenhorn, “and there was a missing piece the size of Massachusetts.”

Another telltale sign: along the boundaries where the scientists think some of the crust plunged back under the adjoining ice, there was evidence of “cryolava”—that is, partially melted, slushy ice—on one side of the divide but not the other. That’s similar to what happens on Earth, where volcanoes happen on one side of a subduction boundary but not the other.

Finally, the existence of plate tectonics and subduction on Europa would answer another longstanding question about the frigid moon. Its surface is remarkably deficient in craters considering the number of comets and asteroids zipping around the neighborhood.

This suggests that Europa was completely resurfaced no more than 90 million years ago. It could have happened just that once, but that, says Selvans, feels like “special pleading”—that we’re looking at the moon at a unique time in its four-billion-year-plus history. It’s much more palatable to scientists to think they’re looking at an ongoing process, which plate tectonics certainly is.

Selvans emphasizes that the evidence so far isn’t a slam-dunk, and Kattenhorn is quick to agree. Galileo took high-resolution images of only a small part of Europa’s surface. “Our paper can’t answer the question of whether this is a global process,” he says. Since melting ice and melting rock behave differently in terms of buoyancy and density, moreover, it’s not clear that what’s going on at Europa is an exact analogy for what’s happening on Earth.

The only way to figure it out for sure is to get more imagery, and Galileo went out of service back in 2003. Unfortunately, the only probe scheduled to visit Europa (and two of Jupiter’s other moons too) is a European Space Agency mission, which won’t arrive until 2030. NASA’s own Europa mission, meanwhile, known as the Europa Clipper, is still only a concept.

TIME anthropology

The Lost Hobbits of the Eastern Arctic

Wooden dolls were used both in ceremonies and as children's toys by the lost Paleo-Eskimos
Wooden dolls were used both in ceremonies and as children's toys by the lost Paleo-Eskimos University of Aberdeen/Qantiruuq, Inc

Scientists never understood what became of the Paleo-Eskimos who once peopled the north. Now they know—and there's new reason to miss them

Every indigenous group European explorers found when they first reached the Americas, from the Aztecs to the Inca to the Maya to the obscure Taino people were descended from a hardy bunch of immigrants who trekked over from Siberia more than 12,000 years ago, then spread east and south from there.

But when the Vikings began visiting Greenland and Baffin Island they bumped up against an indigenous group with a very different heritage—the Arctic dwelling people formerly known as Eskimos and now mostly called the Inuit. Based on archaeological evidence, scientists had established that they first came over from Siberia about 6,000 years ago and spread eastward across the very northernmost reaches of Canada, on the margins of the Arctic Ocean.

Then about 700 years ago, these so-called Paleo-Eskimos, gave way to a newer group known as the Thule culture. They displaced the earlier arrivals, just as our own invading ancestors had displaced the Neanderthals in Europe some 40,000 years earlier. What wasn’t clear, however, was whether the Paleo-Eskimos (or the Dorset, the name given to the last stage of Paleo-Eskimo cultural evolution) were simply absorbed into this new, more modern culture or whether, they vanished from the Earth, as the Neanderthals did.

But now it is, thanks to new paper in Science. Based on genetic analysis of 169 ancient human remains from Siberia, Alaska, Canada and Greenland, along with genome analyses of modern indigenous people, the authors can say definitively that the Paleo-Eskimos did indeed vanish; that the Inuit people who live in the North American Arctic today are the direct descendants of the Thule invaders; and that neither group is related to the Native American tribes that came to inhabit the rest of the Americas.

Exactly how the Dorset people were overwhelmed is unclear. Unlike the Neanderthals, they evidently didn’t mate with the invaders. “In other places,” said co-author Eske Willerslev of the Center for GeoGenetics at the University of Copenhagen’s National Museum of Natural History, at a press briefing, “we see people meeting, maybe fighting, but also having sex with each other.”

But the Paleo-Eskimos were genetically distinct. “There is some genetic admixture with the Thule,” said lead author Maanasa Raghavan, also at the Center for GeoGenetics “but it happened thousands of years earlier, most likely in the Old World.”

Instead, argued co-author William Fitzhugh, of the Smithsonian’s National Museum of Natural History, in Washington, “they were probably just overwhelmed.” The Thule, he explained, had bows and arrows, dogsleds and large whaling crews he calls “almost military” in their organization. The Dorset, by contrast, had much simpler tools, and lived in small, isolated villages.

“Socially and technologically,” he said, “they were no match for this Thule machine that spread across their territory in less than 100 years.” They were either pushed out into fringes where couldn’t survive, or they were annihilated, he said.

Until that happened, however, the Paleo-Eskimos were an astonishing success story, given that they endured in the harshest of climates, without major disruption for a staggering 5,000 years. It’s extraordinary, said Fitzhugh, that they maintained genomic and cultural continuity over such a long period, while other world cultures were going through radical changes.

“One might almost say,” said Fitzhugh,”that they were the Hobbits of the eastern Arctic—a strange, isolated, conservative people whose history we’re just starting to get to know.”

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