TIME space

Surprising Discovery From Really Old Moon Rocks

Where boots have tread: The Apollo 17 landing site, photographed by the Lunar Reconnaissance Orbiter, which revisited the moon in 2009. The lunar module descent stage, the lunar rover, scientific equipment and both footprints and tire tracks are visible.
NASA Where boots have tread: The Apollo 17 landing site, photographed by the Lunar Reconnaissance Orbiter, which revisited the moon in 2009. The lunar module descent stage, the lunar rover, scientific equipment and both footprints and tire tracks are visible.

Samples from Apollo 17, the final lunar landing, tell a violent tale of the early solar system

One of the biggest scientific surprises that came out of the rocks hauled back to Earth by the Apollo astronauts of 60’s and 70’s was the discovery that much of the Moon’s trademark cratering came during a single, catastrophic event. Known as the Late Heavy Bombardment, it was an unimaginably violent fusillade of asteroids or comets (or both) that tore through the inner Solar System about 3.8 billion years ago. The cause is still unknown, although theorists think it might have happened when Jupiter and Saturn readjusted their orbits and another giant planet was ejected from the Solar System entirely.

If the bombardment occurred at all, that is. But a paper in the new journal Science Advances suggests that maybe it didn’t—or at least, not all at once. “It’s not a bad theory,” says lead author Cameron Mercer, of Arizona State University, “and in some parts of the planetary science community, it’s accepted as gospel.”

Until now, the only direct evidence challenging the prevailing, single-bombardment theory had been pockets of impact-related melting in lunar rocks that appear to have been formed at different times. The measurements used as evidence, however, are somewhat crude and far from conclusive.

Now, however, Mercer and his co-authors have used ultraviolet lasers to study lunar samples brought back back by the final Apollo landing mission, Apollo 17, more than 42 years ago, and have found evidence of at least three major melting events, presumably caused by powerful impacts, at 3.8, 3.7 and 3.3 billion years ago. All of that evidence was found in just one rock, but another sample, collected a few hundred feet away, showed evidence of yet another bombardment, this one occurring 3.83 billion years ago. “This calls into question just how well we know the chronology of lunar impacts,” Mercer says.

The problem with the earlier estimates, says co-author Kip Hodges, also at Arizona State, is that they were based on samples weighing tens of milligrams—which is actually large when you’re looking for evidence than can be microscopic. Scientists would heat up the bits of rock, then measure the relative amounts of radioactive potassium-40 to argon that emerged. Since potassium decays into argon at a known rate, they could calculate how long it’s been since the rocks last melted.

But if there are pockets within the samples containing ancient, melted rock of different ages, you’d only get their average ages—and that’s what evidently happened, at least in some cases. The new analysis is a lot more precise: it looks at rock fragments a thousand times smaller. “Thirty-five years ago,” says Hodges, “all we could really say ‘there’s been melting,’ but now we can look with much finer resolution.”

The new analysis is based only on rocks from the Taurus-Littrow valley, where Apollo 17 touched down. Now, says Hodges, “we’ve begun work on rocks from Apollo 16, and we’ve got some coming from Apollo 15 as well.” If Taurus-Littrow alone experienced at least four impact events, there’s no telling how many more might be inferred from samples at the other sites.

Still, even if rocks from all six lunar landings are studied, they represent only a tiny fraction of the entire lunar surface. Extrapolating too much from them would be a little like collecting scoops of rock at half a dozen spots in North America and pretending you understand all of Earth’s geology. The lunar sample set remains narrow even if you add material returned by the Soviet Union’s robotic Luna probes and Moon rocks that have fallen to Earth as meteorites.

“If we want to know the real history,” says Hodges, “we need more samples. It’s really time,” he says, “to start thinking about going back.”

TIME space

Best-Ever Photo of Dwarf Planet Ceres

Ready for its close-up: Ceres as you never saw it
JPL/NASA Ready for its close-up: Ceres as you never saw it

An unusual spacecraft closes in on a mysterious world

NASA’s Dawn space probe, which dazzled scientists with its astonishing views of the asteroid Vesta back in 2012, is about to do it again. A little over five weeks from now, the 2.7 ton probe will go into orbit around Ceres—another asteroid-belt object that is so huge, at 590 miles (940 km) across, it was promoted from asteroid to “dwarf planet” at the same time Pluto was being demoted into the same category.

Ceres is also among the strangest objects in the Solar System: unlike most asteroids, which are largely made of rock, this one contains at least 20 percent water, and may even feature geysers, like Saturn’s moon Enceladus. It is, says, Michael Küppers, of the European Space Agency “a very peculiar beast of an asteroid.”

What that beast looks like in detail will have to wait, but with Dawn just 147,000 miles (274,000 km) away from its target—closer than the Moon is to the Earth—NASA has just released the best image of Ceres ever seen. It’s 30 percent sharper than what Hubble can do, even though the Dawn cameras aren’t designed to do their best imaging from this far away.

“We’re seeing things that look like they could be craters,” says Mark Sykes, a Dawn co-investigator from the nonprofit Planetary Science Institute, “We’re also seeing these extended, kind of ribbonlike structures, which could be evidence of the kinds of internal processes you see on larger planets.”

The new images also confirm the existence of a mysterious white spot in the north that was seen in earlier images. (It’s actually very dark—nearly as black as coal, says Sykes, although not as dark as the rest of Ceres; the images are deliberately optically stretched to enhance contrast so surface features will show up). It’s almost certainly not ice, Sykes says: even dirty ice would have vaporized over the ten years since the spot first showed up in Hubble images.

But it could in theory be mineral deposits from under the surface. “If water is gushing out at times, it should leave a signature behind,” Sykes says. Light-colored deposits would darken over time, though, so if that’s what it is, it has to be relatively recent. The answer to this and other questions about Ceres’ structure, surface features and composition won’t come until after Dawn goes into orbit to begin its mission in earnest on March 6.

Astute space cadets might wonder how it could possibly take Dawn five more weeks to travel less than 150,000 miles to its rendezvous with Ceres; after all, the Apollo astronauts rocketed all the way to the Moon, 239,000 miles (384,000 km) from Earth in just three days. The answer is that Dawn was designed from the start to be a super slow spacecraft. Rather than relying on traditional chemical rockets once in space, it uses ion propulsion. The technology is well known to sci-fi fans. In fact, says Marc Rayman, Dawn’s mission director and chief engineer, “I first heard of it on Star Trek, when Captain Kirk says ‘advanced ion propulsion is even beyond our capabilities.'”

Evidently not, though. The idea, first tested on the Deep Space 1 mission back in the 1990’s, is to use electromagnetic fields to shoot charged particles out the back of a spacecraft (in this case, ionized xenon atoms), thrusting the craft itself forward. The acceleration, is much more modest than with a rocket engine. “It’s very gentle,” says Rayman. “It pushes on the spacecraft as hard as a sheet of paper you’re holding pushes down on your hand.” But because ion engines are so efficient, it can maintain that acceleration for far longer.

Once Dawn arrives at Ceres, it will orbit the dwarf planet at an altitude of about 8,000 miles (12,900 km) to start with, then descend to under 3,000 (4,800 km). Ultimately, the probe will image Ceres from less than 250 miles (402 km) up, taking not only photos but also scientific measurements that should finally lay bare the secrets of this most un-asteroidlike body.

Unlike other orbiting probes, however, including Deep Impact, LCROSS and MESSENGER, which visited a comet, the Moon and Mercury, respectively, Dawn won’t be sent in for a crash landing when the mission is over in 2016. “We know Ceres has water,” says Christopher Russell of UCLA, Dawn’s chief scientist. “We don’t know if it has life, but if it does, and if we contaminate the surface, we might mess it up.”

Even as Dawn inches toward Ceres, meanwhile, NASA’s New Horizons probe is speeding at thousands of miles per hour toward its own close encounter with Pluto next July. By mid-May, New Horizons, too, will have taken images of its target that surpass the Hubble. And by early next summer, scientists will be happily drowning in images and data from not one but two dwarf planets—both of which will be revealing their secrets at last.

TIME space

Rings Like Saturn’s, but Supersized

Living large: Artist's conception of the giant ring system
Ron Miller Living large: Artist's conception of the giant ring system

Think you've seen big rings in our own solar system? Not even close.

When the University of Rochester’s Eric Mamajek tells other astronomers about the object he and his colleagues discovered about 430 light-years from Earth, they tend to be skeptical—very skeptical. And no wonder: What he’s found is a giant ring system, sort of like Saturn’s, but some 200 times bigger, circling what may be an exoplanet between ten and 40 times the size of Jupiter. If you put these rings in our own Solar System, they’d stretch all the way from the Earth to the Sun, a distance of 93 million miles (150 km). And what’s more, there’s evidence that the rings are sculpted by at least one exomoon—something that also happens at Saturn, but not remotely on this scale.

MORE These ‘Vintage’ NASA Posters Imagine Travel Beyond the Stars

“It took us a year even to convince ourselves of what we were seeing,” says Mamajek, whose paper is based on a new analysis of observations taken back in 2007 by the SuperWASP planet search project. At the time, the observations seemed to make no sense: when a planet passes in front of a star, you usually see a dip in starlight that lasts for up to a few hours. In this case, the starlight dimmed for two months.

It wasn’t a steady dip, either. The star would fade, then brighten, then fade again, in a way that made no sense at all. When Mamajek and his group stumbled on the data in 2010, he says, “I took a printout of the light curve, put it on the wall, and stared at it for a week.” Crazy as it seemed, the most plausible explanation was a giant ring system with gaps like Saturn’s that let more or less light through at different times during the passage. “It’s the same indirect way the rings of Uranus were discovered in 1977,” he says.

The planet itself doesn’t show up in the observations, but that could be explained if the ring system is slightly off-center as it moves in front of the star. You can see how this works in an animation put together by Mamajek’s collaborator Matthew Kenworthy, of the University of Leiden, in the Netherlands.

The star which the new planet orbits is thought to be very young—about 16 million years, compared with our own Solar System’s 4.6 billion. If the scientists are right about what they’re seeing, the mammoth ring system will get smaller over time as the outer bands condense into moons. “That’s what you see in [our] Solar System,” says Kenworthy. “You have rings tucked in close to the planets and moons further out. So presumably we’re seeing the intermediate step.”

It all seems familiar, except for the ring system’s size, which is unprecedented—and which is the reason other astronomers are waiting to be convinced. “I agree with the authors that it’s appropriate to consider an interpretation based on rings,” says Eric Ford, an expert on exoplanets at Penn State. The idea that the outer parts would condense into moons relatively quickly, however, means that we’re seeing the rings at their full extent during a very narrow window of existence—the sort of coincidence that scientists don’t love to see. “Whenever your explanation involves catching something during a phase that won’t last very long,” Ford says, “it’s a little concerning.”

MORE Cousins of Earth Found Deep in Space

Much of the doubt could be erased if astronomers could see the rings pass by again on another orbit around the star. Unfortunately, that hasn’t happened: they’ve got only the single passage back in 2007, meaning the exoplanet is on a relatively long orbit. “We think it’s at least ten or 15 years,” says Kenworthy.

They don’t know for sure, though, and since it’s tough to keep big telescopes aimed at this one star hoping for another passage, the astronomers have recruited members of the high-end amateur group, the American Association of Variable Star Observers, to monitor the situation. They’re also going back through digitized versions of old images from observatories around the world, looking for evidence of other stars that faded mysteriously for a while without explanation. “Now that we know what we’re looking for,” Mamajek says, “we might find that there are lots of them out there.”

They might, that is, if they’re really seeing rings. “I keep telling people, ‘if you can think of a better explanation, please let me know,'” Mamajek says, and he means it. So far, he has no takers. “The signal is very strong,” says Harvard’s David Kipping, who is doing his own search for exomoons, “and its difficult to believe the instrument could misbehave on such a huge scale. I think many of us find the signal interesting,” he says. That, by itself, is enough to keep the astronomy community looking.

Read next: SpaceX, Boeing on Track to Get Astronauts into Space by 2017

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TIME astronomy

There May Be ‘Super Earths’ at the Edge of Our Solar System

This discovery, if accurate, could completely redraw the map of the Solar System

The reason Pluto was demoted from the ranks of the planets back in 2006 was that astronomers had lately discovered it wasn’t alone out there. A whole assortment of Pluto-like objects is circling out beyond Neptune—too many, said the International Astronomical Union, for schoolchildren to memorize. (Seriously.) So despite a general public outcry that continues today, Pluto was demoted to “dwarf planet,” and the Solar System was left with a tidy eight.

But scientists think planets much bigger than Pluto could be orbiting beyond the reach of our most powerful telescopes. They probably aren’t as big as Saturn and Jupiter—but the unusual orbit of a tiny world called 2012 VP113, discovered last spring, hinted at the presence of something bigger than Earth. And now a pair of papers published in Monthly Notices of the Royal Astronomical Society suggests the evidence is even stronger.

“We have unpublished calculations,” says lead author Carlos de la Fuente Marcos, of the Complutense University of Madrid, “that suggest that there could be two planets with between two and 15 times the mass of the Earth.”

As with last year’s discovery, the evidence for the two planets is indirect. “We would like to emphasize that we have not discovered any new objects,” de la Fuente Marcos says. What they’ve done instead is to look at the orbits of 13 small bodies, including 2012 VP113, that follow elongated orbits in the distant reaches of the solar system.

In particular, they’ve looked at an orbital parameter known, in a quaint throwback to the early days of astronomy, as the “argument of perihelion”—that is, the point at which their tilted orbits cross the plane in which the other planets circle the Sun. What de la Fuente Marcos and his team find is that these points are suspiciously similar for all 13, which implies that the gravity of some massive object or objects, still unseen, is herding them. (It involves the Kozai mechanism, since you’re undoubtedly wondering).

These Super Earths would be located about four times as far away as the outer limit of Pluto’s orbit—and that’s a bit of a problem, since current models of the Solar System’s formation have a tough time putting a big planet out at that distance, especially today. “They may have existed in the past, but at very low probability,” says Ramon Brasser, of the Cote d’Azur Observatory, in France. Brasser also argues that more than half of the objects de la Fuente Marcos and his co-authors cites as evidence come close to Neptune, whose own gravity skews the results.

De la Fuente Marcos disagrees on the second point. “In general,” he says, “these objects are weakly perturbed by Neptune if they are perturbed at all. He agrees on the former, but with a caveat. “If we assume that our models of Solar System formation are correct, the objection is valid. But what if our models are incorrect?”

Even if the models are correct, however and a super Earth can’t be orbiting where de la Fuente Marcos suggests, that doesn’t mean there’s nothing big out there. “It’s possible,” says Brasser, “but the planet would have to be much farther away and much more massive in order to have the same effect. This scenario,” he says, “is currently being investigated.”

But the investigations are still purely indirect. “If large planets do exist,” says de la Fuente Marcos, “these objects must be very dark … and they are very far away from the Sun.” There won’t be a prayer of spotting them until the James Webb Space Telescope, or one of the new giant ground-based telescopes now under construction, is up and running toward the end of this decade.

But for a discovery that could completely redraw the map of the solar system yet again, that’s not too awfully long to wait.

 

 

TIME space travel

These ‘Vintage’ NASA Posters Imagine Travel Beyond the Stars

Designers NASA's Jet Propulsion Laboratory capture the excitement of space exploration

Planet-hunters haven’t found a Mirror Earth orbiting a star beyond the Sun yet, but this week’s discovery of a new batch of exoplanets that come awfully close, plus the announcement that the amazing Kepler probe has topped the 1,000 mark in its search for alien worlds makes it only a matter of time before we find planets where life might be thriving.

Once that happens, of course we’re going to want to go visit.. That’s not going to happen tomorrow: it’s impossible to visit any of these worlds in person with any current technology, so until we build a Star Trek-style warp drive or discover an Interstellar-esque worm hole, a trip to an exoplanet will have to remain a dream.

Fortunately, though, NASA’s Jet Propulsion Laboratory, in Pasadena, has some professional dreamers on staff—artists who try to capture the excitement of space exploration in a way the rest of us can appreciate. Their latest creation: three fanciful posters advertising tourism to three actual exoplanets, done in the gorgeously romantic style of 1930’s-era railway posters.

This being a NASA lab, they didn’t just make stuff up. “There was a lot of back-and-forth with the scientists,” says David Delgado, one of the designers, “figuring out which exoplanets to choose, then noodling on what it would actually like to visit them.” In the case of Kepler 186f, for example, which was discovered last year, the planet orbits a small red star. “Maybe the color of vegetation would be different there,” he says—and on the poster, it is. The second poster shows Kepler 16b, a planet that orbits twin suns. The third depicts HD 40307g, a so-called Super Earth about 1.4 times the size of our home planet and eight times as massive. All three could in principle be habitable, based on how much heat they get from their stars.

“The posters were really designed primarily for use within JPL,” says Joby Harris, another designer on the project. When they were released to the public a few days ago, however, the response was overwhelmingly positive. “We were a little surprised by it,” admits Harris.

He shouldn’t be. One of the reasons JPL has these artists on staff, says Delgado, “is to get people excited about space science, to build their curiosity.” They’re clearly exceptionally good at doing their jobs.

Three more exoplanet posters are in the works, although there’s no word on when they’ll be finished. For those who want to print out their own posters, high-resolution print-optimized versions are on JPL’s Planet Quest website.

 

TIME space

Ka-Boom! Two Black Holes Get Ready to Collide

Don't get too close: A black hole in the galaxy Centaurus A emitting gas jets as it sucks in matter.
NASA NASA; Getty Images/Photo Researchers RM Don't get too close: A black hole in the galaxy Centaurus A emitting gas jets as it sucks in matter.

A dance of death that's never been seen before is slowly unfolding now

For cosmic drama, nothing should beat a supermassive black hole. It weighs millions, or even billions of times as much as the Sun; it eats stars whole with no apparent difficulty (although it does sometimes burp); it heats up surrounding gases to such insane temperatures that you can see the glow halfway across the universe; and perhaps best of all, it gives Stephen Hawking something to theorize and argue about.

For all that, it turns out that something does beat a giant black hole: two giant black holes, especially ones circling each other like wary Sumo wrestlers getting ready to grapple. Such things are by no means unheard of: just about every galaxy has a supermassive black hole lurking at its core, and when two galaxies merge, as they often do, their central black holes orbit each other in an ever-tightening dance, and in many cases they eventually coalesce into one. When that happens, says General Relativity, they should trigger ripples in the fabric of spacetime itself, in the form of so-called gravitational waves that Einstein predicted, but that no one has yet detected directly.

Such a merger hasn’t ever been seen, but astronomers have just announced the discovery of the next best thing: a pair of supermassive black holes orbiting each other more closely than any ever before observed. Other twin black holes won’t merge for another few billion years, but these, says Caltech’s George Djorgovski, co-author of a paper in Nature describing the new discovery, “could merge in a mere million years.”

That still sounds like a long time, but it means the two black holes are virtually on top of each other—on a cosmic scale at least. If one were sitting in the Sun’s position, the other might be as close as the Oort Cloud of comets that sits at the edge of the Solar System. That’s crucial: astrophysicists don’t really know what happens in the last stages of the spiraling-in process—it’s known as the “final parsec problem,” a parsec being a bit over three light-years. And these two are very much in the thick of it.

Djorgovski and his colleagues hasten to say they haven’t seen the black holes as individual objects: instead, they’re looking at the bright spot of light that marks the “accretion disk” of superheated gas that often surrounds black holes. Accretion disks flicker sometimes, as new gas is pulled in, but in the case of this object, known as PG 1302-102, the flicker is periodic, waxing and waning over a period of about five years. That’s the telltale sign that two objects are involved: one of the black holes’ accretion disks may be warped somehow by the gravity of the other, causing a hot spot that flashes us as it rotates into view.

What the astronomers are hoping for now is to find more examples like this. They have some 20 candidates already, and the more twin black holes they can find that are in tight orbits, the better they can understand what’s really going on. We may not be around to see PG 1302-102’s final collision—if it ever takes place—but somewhere out there, two black holes may be even closer to tangling.

Read next: The 20 Most Eye-Catching Booths at CES 2015

TIME space

Cousins of Earth Found Deep in Space

Don't blink: This has been Kepler's field of vision for most of its time aloft as it has searched for tiny flickers around candidate stars
NASA Don't blink: This has been Kepler's field of vision for most of its time aloft as it has searched for tiny flickers around candidate stars

A flock of planets in their suns' habitable zones boost the odds for extraterrestrial life

When NASA scientists declared the planet-hunting Kepler telescope hopelessly crippled in the fall of 2013, the mission’s founding father and principal investigator Bill Borucki pointed out that its useful life wasn’t necessarily over. For one thing, there was reason to believe Kepler could use some clever engineering tricks to keep finding new worlds—which it has. For another, the probe had collected such mountains of data since its 2009 launch that it would take months or even years to plow through it all. There could well be major discoveries to emerge as the backlog was gradually processed.

Turns out he was right. Speaking at the American Astronomical Society’s winter meeting in Seattle today, astronomers announced the discovery of eight planets orbiting in their stars’ “Goldilocks Zone”—the region where temperatures are just right for water to exist in liquid form, a requirement for life as we know it.

“We’re not claiming they’re inhabited,” emphasizes Guillermo Torres, of the Harvard-Smithsonian Center for Astrophysics, lead author of a paper that describes the newly identified worlds. But astronomers do know that if a planet has significant amounts of water on its surface, and if it has a heat-trapping atmosphere like Earth’s, it’s ticked off two very important items on the biology checklist.

That’s the case, at least, if the planet has a surface—and unlike many of the exoplanets discovered so far, at least four of these worlds almost certainly do: they’re small enough to be rocky like Earth, not mammoth gas blobs like Jupiter or Neptune. One of the planets, known as Kepler 182f, was already described by another group last year, so this is more of a rediscovery. At the time, 182f was by far the Earthiest planet ever found, given its size and likely temperature. But two of the brand-new ones, says co-author David Kipping, also of Harvard, known as Kepler 438 and 442, respectively, are even more tantalizing. Kepler 182f is technically in its star’s habitable zone, but is thought to be quite cold nonetheless, at the outer edge of what is considered a good candidate for life.

Kepler 438, however, is just 10 percent larger than Earth and gets about 40 percent more energy from its star than Earth itself does, while 442, which is 20 percent larger than Earth, gets about 30 percent less. Neither is a perfect match, but both are better than 182f.

The bad news is that like the vast majority of Kepler planets, these new ones are too far away to be examined directly for signs of life, even with the next generation of giant Earth and space-based telescopes currently on the drawing boards. They’re also too distant for their existence even to be confirmed with 100 percent certainty. Kepler does its work by looking for a slight dimming of a parent star as a planet passes in front of it. But since other effects can produce a similar dimming (a background star passing in front of another one, for example), the gold standard for confirmation is to measure the gravitational tug a planet exerts on the star it orbits. If the wobble is there, and if its rhythm matches that of the dimming, it’s a slam dunk.

That can’t be done in this case since Kepler was not designed to analyze wobble, but the astronomers were able to accomplish the next best thing: they used software known as “Blender” to simulate all of the ways a planet candidate might be fooling observers and rule them in or out. In this case, says Kipping, the new finds have “been validated with 99.73 percent confidence as true planets.”

There’s one more thing, aside from their slightly larger size and the somewhat different levels of energy they absorb that keeps these planets from being true twins of Earth: they orbit “orange dwarf” stars that are smaller and dimmer than the Sun. But in some ways, that actually makes them more promising. Back in the days of the first exoplanet discoveries in the 1990’s, nobody was thinking much about anything but planets around Sun-like stars as possible places life might exist.

The discovery that a different species of star can be home to at least a distant cousin of Earth only widens the category of worlds on which biology might have taken hold. At the moment, we are still—as far as we know—alone in the universe. But that’s a moment that could be coming to an end soon.

TIME space

This Is How NASA Fixed a Telescope Currently in Orbit

Just a glimpse: 13,000 light years away and 8 billion years old, this patch of the Milky Way represents merely 0.2% of Kepler's original field of vision
NASA Just a glimpse: 13,000 light years away and 8 billion years old, this patch of the Milky Way represents merely 0.2% of Kepler's original field of vision

A vital space telescope recovers after an ingenious long-distance fix

In one sense, the fact that the Kepler space telescope found a new planet last week is pretty unremarkable news. The probe has discovered nearly a thousand exoplanets orbiting stars beyond the Sun since its launch in 2009, and it has another three thousand or so planet candidates waiting for confirmation. At this point, “Kepler Finds Planet” is starting to sound a little like “Dog Bites Man.”

It’s a big deal nevertheless. Back in 2013, Kepler blew out one of the reaction wheels that allows it to focus precisely on its target stars, looking for the silhouette of a planet passing by. It had already lost one wheel, and with just two remaining, the craft couldn’t do its job. “Unfortunately,” said John Grunsfeld, the scientist-astronaut who helped refurbish the Hubble Space Telescope during a 2009 spacewalk, at a NASA press conference just after the Kepler breakdown, “Kepler is not in a place where I can go up and repair it.”

But it turns out he didn’t need to. Thanks to some seriously outside-the-box thinking by a team of scientists and engineers, Kepler has come back to life, its pointing now stabilized by radiation pressure from the Sun, of all things. “It’s working marvelously,” enthuses Kepler Project Manager Charles Sobeck.

The effort to save Kepler began even before that crucial reaction wheel burned out. When the first one failed back in 2012, says project scientist Steve Howell, “we started looking very seriously at the wheel data, and noticed some anomalies.” The reaction wheel that had quit showed a history of excessive friction leading up to the failure. Hoping to head off more problems, the Kepler team and the engineers at Ball Aerospace who built the probe did some detective work on the remaining wheels. “We noticed that another one was showing the same anomalies,” he says, “so we began thinking of what we could do when that one failed.”

But thinking of answers doesn’t mean they actually had one, so when that second wheel did fail, says Howell, “we went into panic mode.” For his part, says Sobeck, “I doubted there was a solution. I thought we’d try to get the wheel working again and then call it quits.”

A Ball Aerospace engineer named Doug Wiemer, however, had already been working on a similar problem for a Navy satellite whose wheels had gone bad and believed he had an answer for Kepler: if radiation pressure from the sun impinged equally on the telescope’s solar panels, that would stabilize it on its roll axis, so the remaining wheels could handle pitch and yaw. The idea worked. “We’ve been operating this way for six or eight months,” says Howell, “and the telescope has been pointing remarkably well.” The aim isn’t quite as precise as it used to be, but, says Howell, “almost.”

The downside: since Kepler has to present its solar panels toward the Sun at all times, the telescope always points more or less directly away from the center of the solar system. In its original mission, Kepler focused on a single patch of sky all the time to let it monitor the same stars continuously for years on end. This required it to shift its gaze constantly as it moved through its orbit in order to keep the target field in its cross hairs. Now its field of view sweeps a band across the entire sky: at most it can monitor a given star for 80 days. That makes it hard to discover a planet with an orbit as long as a year, since it might not pass in front of its star at all during the available window.

But there’s an upside as well. Kepler is now doing observations during the “K2″ phase of the mission that it didn’t have time for before—looking for everything from pulsations in white dwarf stars to giant black holes and supernovas in distant galaxies.

As for the new planet, which is known as HIP 116454b, it’s actually pretty interesting. It’s a so-called Super Earth, about 2.5 times as big as our home planet, orbiting a small, reddish star. The star is much cooler than the Sun, but the planet’s nine-day orbit brings it so close that temperatures are nevertheless too hot for life.

At just 180 light-years from Earth, however, the planet is close enough to make it a prime candidate for intense followup. “HIP 116454b will be a top target for telescopes on the ground and in space,” said Harvard astronomer John Johnson, co-author of a paper to appear in the Astrophysical Journal, in a statement.

And it’s not likely to be the last planet Kepler finds. The mission was shot down four times by NASA before it was finally given the go-ahead. Now, it appears, the satellite has survived yet another near-death experience.

TIME space

Voyager 1 Surfs a Cosmic Tsunami

Wow, Voyager: 12 billion miles from home and still very much in the game
NASA/JPL Wow, Voyager: 12 billion miles from home and still very much in the game

Earth's only Interstellar spacecraft is rocked by a storm from the sun

Planetary scientists have pretty much stopped haggling over whether Voyager 1, the space probe launched in 1977 to explore Jupiter and Saturn, has finally entered interstellar space. The tough little ship is still going strong, but there isn’t exactly a signpost that marks the heliopause—the place where particles streaming from the Sun bang into the thin gas that lies between the stars. As a result, there’s been some confusion about when the spacecraft actually crossed that invisible boundary—though there’s no confusion over the fact that it did. (There’s no confusion either about whether it’s left the Solar System: despite last year’s breathless headlines, it hasn’t. Comets in the Oort Cloud, which are definitely under the Sun’s gravitational influence, are much farther out than the heliopause.)

But the fact that Voyager 1 is now firmly in interstellar space is evident just by the change in its surroundings, says Don Gurnett, of the University of Iowa, whose plasma wave instrument aboard the probe is the final arbiter. “It’s extremely quiet out there,” Gurnett says. “The magnetic fields are constant, the flux of cosmic rays is constant”—a sharp contrast to the turmoil of the so-called termination shock, where particles racing outward at a million m.p.h. (1.6 million k/h) slam into the relatively stationary particles that make up the interstellar medium.

But the comparative quiet of distant space does not mean there’s nothing going on out there. At this very moment, in fact, as Gurnett explained at a talk at the American Geophysical Union’s annual meeting in San Francisco this week, the sparse interstellar gas is reeling from a powerful blast of solar particles that smashed into it last February. The eruption began its life as a coronal mass ejection or CME, a huge burst of hot plasma fired into space during a solar storm. When they hit the Earth, CMEs can disrupt electronic communications and even cause blackouts.

Their impact further away is much greater, causing a kind of cosmic tsunami—huge pressure waves that make the interstellar gas vibrate like a ringing bell. Indeed, a recording the spacecraft made and NASA released reveals that the phenomenon even sounds like a bell. “This shows us how much influence the Sun can have on the surrounding area,” says Caltech physicist Ed Stone, who has been the Voyager project scientist since 1972, “and it’s very likely to be the same with other stars.”

Voyager detected its first cosmic tsunami back in the 1990’s when the impact of a CME colliding with the heliopause created a blast of radio waves. They’re too faint to be picked up from Earth, says Stone. “You need to be out by Saturn, at least, to detect them.” By 2012, the spacecraft was close enough to the heliopause to experience a later tsunami directly, recording a steep increase in the density of the gas it was flying through. It felt another in 2013, and the probe is now in the midst of its third, which was still going nine months later—a period during which Voyager 1 traveled a quarter of a billion miles (.4 billion km). No one knows how far into space the tsunami will travel before it fades out, says Gurnett. “I’m guessing it could be another hundred astronomical units or more.”

That, by the way, is a whole lot. An astronomical unit is the equivalent of the distance between the Earth and the sun—or 93 million mi. (150 million km). A hundred of those is 9.3 billion miles—or 15 billion km. Voyager 1 is currently at 130 A.U., or about 12 billion miles; it will have to reach 21.3 billion just to catch up with the outer reach of the tsunami—a journey that will take decades.

Stone, Gurnett and the other Voyager scientists won’t have to wait that long for another big event, however. The Voyager 2 probe, which lagged behind its sister ship so it could take a look at Uranus and Neptune, is currently at 109 A.U. from the Sun, and approaching its own rendezvous with the heliopause. “We’re hoping it will happen in the next couple of years,” says Stone.

If it’s hard to imagine what it’s like for Stone to watch the Voyager probes continue to make discoveries more than four decades after he took over the project, he offers a single, simple word of explanation: “Wonderful.”

TIME space

Odds For Life on Mars Tick Up—a Little

High-tide: layering in a Mars rock photographed by Curiosity suggests the movement of long-ago water
NASA/JPL High-tide: layering in a Mars rock photographed by Curiosity suggests the movement of long-ago water

New findings about both methane and water boost the chances for biology

September of 2013 was a bad time for those who hope there’s life on Mars. We’ve had evidence for decades that water flowed freely across the surface of the Red Planet billions of years ago, and that evidence has only gotten stronger and stronger the closer we look. Not only was there potentially life-giving water back then: Mars also had the right kind of geology to support mineral-eating microbes. And while all of that was in the distant past, the detection of methane in the Martian atmosphere by Earth-based telescopes and Mars orbiters raised hopes that bacteria might still be thriving below the surface—not unreasonable, both because all manner of Earthly critters do perfectly well below-ground and because the vast majority of methane in our own atmosphere results from biological activity. Mars’s methane might come from a similar source.

But when the Curiosity rover sniffed the Martian air directly last year, it smelled…nothing. At most, there were just three parts per billion (ppb) of methane wafting around, and possibly much less than that. “We kind of thought we’d closed that chapter,” says Christopher Webster of the Jet Propulsion Laboratory, lead scientist for the instrument that did the sniffing. “A lot of people were very disappointed.”

Not any more, though. Just weeks after that dismal reading, Curiosity’s Tunable Laser Spectrometer (TLS) picked up a whiff of methane at a concentration of 5.5 parts per billion. “It took us by surprise,” says Webster, and over the next two months, he says, “every time we looked there was methane. Indeed, the concentrations even rose, to an average of 7.2 ppb over that period, he and his colleagues report in a new paper in Science.

And then, six weeks later, the methane was gone, and hasn’t been sniffed since. “It’s a fascinating episodic increase,” Webster says.

What he and his colleagues can’t say is where the methane is coming from. Because it’s transient, they think it’s probably from a fairly local source. But whether it’s biological or geological in origin, they don’t know. It’s wise to be cautious, however, says Christopher Chyba, a professor of astrophysics and international affairs at Princeton. “Hopes for biology on Mars have had a way of disappearing once Martian chemistry has been better understood. But figuring out what’s responsible for the methane is clearly a key astrobiological objective—whatever the answer turns out to be.”

That’s not the only important Mars-related paper in Science this week, either. Another, also based on Curiosity observations, concerns Mars’s long-lost surface water, and one of the most important points is that there’s a lot more of it left than most people realize—”enough,” says Jet Propulsion Laboratory scientist Paul Mahaffy, lead author of the paper, “to cover the surface to a depth of 50 meters [about 165 ft].” That doesn’t mean it’s accessible: it’s nearly all locked up in ice at the planet’s poles, but some is also entrained in the clay Curiosity dug into when it was prowling the Yellowknife Bay area of Gale Crater.

Some of that water, says Mahaffy, is tightly chemically bound to the clay and is not a big player in Mars’s modern environment. Some is not quite so locked down and has been interacting with the tenuous Martian atmosphere for the past three billion years. The hydrogen in Martian water, as in Earthly water, may contain both a single proton and a single electron, or a proton and electron plus a neutron—so-called heavy hydrogen, or deuterium. As the Martian atmosphere has thinned over the eons, the ratio of hydrogen to deuterium in the water has gradually been dropping, as the lighter version escapes more easily into space. Since the modern water is twice as rich in deuterium as the water from billions of years ago, that suggests that there was about twice as much surface water in total at the earlier time, but its hydrogen residue has vanished.

“That’s a fair bit of water,” says Mahaffy, “but it’s a lower limit. There could be much more beneath the surface today that we haven’t seen. It was a really interesting time. There were a lot of aqueous processes going on, and a lot of flowing water.”

Where there is (or was) water, there could be (or could have been) life. For Mars enthusiasts, that’s why December of 2014 is a lot better than September of 2013.

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