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Scientists Are Already Planning the Next Mission to Pluto


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Scientists Are Already Planning the Next Mission to Pluto

Wednesday 12:48pm

Image: NASA

The Pluto-shaped void in our hearts has yet to be filled by Planet 9, copious amounts of Ben & Jerry’s, or anything. Ever since the summer of 2015, when NASA’s New Horizons performed a six-month-long reconnaissance flyby study of Pluto and its moons, fans of the dwarf planet have wondered if or when we’d ever go back. According to New Horizons principal investigator Alan Stern, he and some other planetary scientists are already drawing up the blueprint for a return trip—and this time, it’d be much more than just a flyby.

“The news is not that we have a specific mission design,” Stern told Gizmodo. “The news is that the community is forming around the concept of going back to Pluto with an orbiter mission that would stay and study the planet for years, and do it in ways that we could not have in a simple flyby like New Horizons. It would have much more advanced instrumentation and the ability to map every square inch of the planet, and unravel all the complexity that we found.”

 

New Horizons, which left Earth on January 19th, 2006, was able to provide us with an unprecedented look at some of the mysterious worlds of the Kuiper Belt, including Pluto, its large moon Charon, and four baby moons—Nix, Hydra, Styx and Kerberos—which are very appropriately named for the Greek underworld gods. We discovered that Pluto is an astonishingly dynamic place, with mountains, chasms, a billowy atmosphere, and maybe even a massive subsurface ocean. Best of all, we learned that the icy world has a soft side, with some unforgettable New Horizons images of the dwarf planet’s heart.

Still, many lingering mysteries remain. Pluto might have wind-blown dunes on it, features thought to be impossible before the flyby. Its mountains, which are made of frozen water, could reveal many secrets about geologic activity on the dwarf planet today. With so much left to learn, the only way to get answers is to go back. And unlike the New Horizons flyby, which didn’t spend enough time loitering to even map both of Pluto’s hemispheres at high resolution, much less monitor changes on the surface, an orbiter that remains in the Pluto system for several years would be able to do both.

“Going back to Pluto is becoming, in the scientific community, a real growing concern instead of just scattered conversation,” Stern said. And so, a few days ago, he and 34 scientists gathered in Houston, Texas to start mapping out what an orbiter mission would look like. Some of this new team is comprised of New Horizons members and seasoned pros in the field, in addition to scientists at the start of their careers.

“You won’t see it presented in the next few months, but I’m sure that by next year you’ll see it in many places,” Stern said. He added that this October, he and his team plan to have a workshop on their new mission concept at the49th meeting of the Division of Planetary Sciences.

“We were so surprised by the level of complexity that we found,” Stern said. “If you would have asked me before we got there if I thought there was ever any real chance of going back, I would have said ‘not really.’ And yet, here we are two years later and thinking about all the mysteries we can’t solve except by going back.”

While the plans are still in their infancy, Stern and his team are hopeful that they can get their concept together in time for the next Planetary Science Decadal Survey, a massive report prepared for NASA and Congress by the planetary science community, which helps to set the space agency’s priorities for solar system exploration. The next Decadal Survey will start being compiled around 2020, Stern said.

Gathering enough support within the scientific community is critical to convince the space agency such a trip would be worth it. The good news for Stern and his team is that the public already has their back. As soon as hetweeted the news about the potential orbiter, Stern’s mentions erupted with well-wishers.

 

“Hundreds of people were getting involved and cheering it on,” he said. “It’s like the slightest hope of going back to Pluto…the public interest is amazing.”

 By October, Stern expects that the team involved with the orbiter concept will have grown substantially, maybe with 100 scientists involved. He thinks another trip to Pluto has the potential to gin up public interest in the same way that Enceladus and Europa have. “Just like Ocean Worlds, it’ll catch fire,” he said.
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When the Hell Will We Find Planet Nine?


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When the Hell Will We Find Planet Nine?

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 http://gizmodo.com/when-the-hell-will-we-find-planet-nine-1794681137#_ga=1.17383792.892298330.1450614712
Artist’s concept of Planet 9. (Image: Caltech/R. Hurt)

The hunt for Planet 9—a hypothetical, Neptune-sized object beyond Pluto—has stirred the scientific community since last year year, when a pair of Caltech astronomers argued in favor of the idea. Those intrepid scientists—Mike Brown, best known as the guy who killed Pluto, and Konstantin Batygin—are currently spearheading a search for this elusive giant. Recently, a network of citizen scientists have followed suit. The problem, of course, is we still haven’t found it. So what’s it going to take?

Back in 2016, Brown and Batygin seemed pretty confident that we’d find the mysterious object sometime in the next few years. From the start, their assertion of a new planet was met with some skepticism, since astronomers (and a few quacks) had been peddling the idea of a “Planet X” for years. At a certain point, it kind of became the “fetch” of the solar system. Still, theresearchers’ demonstration that a massive planet could be responsible for the unusual orbits of six known Kuiper Belt Objects motivated the scientific community to take Planet 9 claims more seriously.

“If you say, ‘We have evidence for Planet X,’ almost any astronomer will say, ‘This again? These guys are clearly crazy.’ I would, too,” Brown told Science Magazine in January 2016 shortly after the paper detailing their hypothesis went public. “Why is this different? This is different because this time we’re right.”

Over the past year, Brown and Batgyin have expanded their search team, and are currently gearing up for observations in the fall. According to Brown, the “wrong side of the sky” is up right now, meaning the part of the sky where Planet 9 might be is only visible in the daytime, which is rather inconvenient when you’re trying to make a breakthrough in planetary science.

“What we spent most of the last year doing has been trying to do a combination of computer modeling and looking at the real objects in the solar system and really pinpoint where it is,” Brown told Gizmodo. “We have a modestly precise region where we know to look. It’s about 800 square degrees of sky, which is a pretty large swath of sky, but it’s better than having to look at the whole thing.”

Image: Caltech/R. Hurt (IPAC)

Another boon for the planet hunters is that their support network is huge. In a new project called Backyard World, a network of citizen scientists can look through troves of “flipbook” movies made from images captured by NASA’s Wide-field Infrared Survey Explorer (WISE) mission with the hopes of finding Planet 9, which astronomers say will look a little blue.

“I am very optimistic that we’re going to track this guy down soon because so many people are looking,” Brown said. “And we’ve done a pretty good job of nailing down where to look.”

Still, not everyone is confident that Planet 9 will be found any time soon—or at all. A new study from a team of scientists at Queen’s University in Belfast asserts that the discovery of a minor planet called 2013 SY99—which is, at its closest, 50 AU—might dash our hopes of ever discovering the world. After running computer models of the solar system, the researchers concluded that if Planet 9 did exist, it likely would have altered SY99’s orbit so much we would not be able to view it.

“Computer models do show that a Planet Nine would be an unfriendly neighbor to tiny worlds like SY99: its gravitational influence would starkly change its orbit – throwing it from the solar system entirely, or poking it into an orbit so highly inclined and distant that we wouldn’t be able to see it,” Michele Bannister, an author on the study, wrote in The Conversation. “SY99 would have to be one of an utterly vast throng of small worlds, continuously being sucked in and cast out by the planet.”

Bannister told Gizmodo that while her team’s findings don’t entirely disprove the idea of Planet 9, it calls the hypothetical world’s legitimacy into question.

“The planet 9 idea is a fun idea, it’s exciting, but it’s taking a bit of the oxygen at the moment,” she told Gizmodo. “We have this interesting problem…and the very shiny solution at the moment is called planet 9.”

Brown, on the other hand, read Bannister’s paper and said he and Batgyin had predicted that astronomers would discover objects just like SY99. He said that finding these objects actually reinforces the idea that Planet 9 is out there.

“The reason that we initially thought Planet 9 existed—there are a lot more reasons now—but the initial reasons were that the most distant Kuiper Belt objects were on these very eccentric orbits that are all pointing off in the same direction,” he told Gizmodo. “One of the things we said when we first announced this a year ago was that, ‘We predict that as you continue to find more and more distant Kuiper Belt objects, they too will be pushed off in this one direction. So we’ve been waiting for all these discoveries to come in—this one is exactly where it’s predicted.”

It’s so rare we get planetary drama as delicious as this one with Planet 9. But seriously, if this big guy is out there, it’s only a matter of time until someone finds him. Brown hopes it’ll be one of the citizen scientists.

“I love those,” he said. “Honestly, if I could control the future, I would have one of those citizen science projects find Planet 9. It’d be fun to find it myself…but it’d be cool if we could come up with new ways of finding these things like using the power of citizen scientists and data analysis. I would love that story.”

Celebrate Hubble’s Birthday by Tearfully Reviewing Its Best Photos


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Celebrate Hubble’s Birthday by Tearfully Reviewing Its Best Photos

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

For so many nerds, the Hubble space telescope feels more like a friend than a hunk of metal in the cold vacuum of space—a friend whose job you’re super jealous of. The ‘scope, which launched on the space shuttle Discovery in 1990, has sent back some of the most incredible images from the final frontier—over 1.3 million observations of planets, galaxies and more, all while hurling about our planet at 17,000 miles per hour from its vantage point in low Earth orbit.

Today just so happens to be Hubble’s 27th birthday. This salty ol’ girl, which has outlived NASA’s most optimistic predictions by more than a decade, is finally old enough to vote, gamble, and even rent a car, though she just missed the cutoff for remembering the ‘80s. In lieu of cake, we’ve compiled the telescope’s most timeless pictures, which is really more of a present for us.

Spiral Galaxy Pair NGC 4302 and NGC 4298

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

This stunning close up of a galactic pair was released on April 20th, 2017 (nice), just in time for Hubble’s birthday. These galaxies—called NGC 4302 and NGC 4298—are located roughly 55 million lightyears away, and both are smaller than our own Milky Way. According to Hubble’s site, although the two appear quite different due to the angles at which we see them, the galaxies are actually very similar in composition.

Plume Erupting From Europa

Image: NASA, ESA, W. Sparks (STScI), and the USGS Astrogeology Science Center

It’s hard to believe this image, which looks exactly like an R.E.M. album, is actually real. A composite shot of Europa, overlain on Hubble data taken on March 17th, 2014, the image marks some of the best evidence yet for eruptingplumes of liquid water on Jupiter’s icy moon. This is one of the reasons scientists are currently interested in exploring Europa—and even drilling into it—in order to find biosignatures. Thanks, Hubble!

Veil Nebula Supernova Remnant

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Is there anything more breathtaking than this Lisa Frank-looking nebula? Methinks not. The picture, which was taken in April 2015, shows the beautiful garbage left over from the explosion of a star thought to be 20 times more massive than our Sun. According to Hubble, the Veil Nebula is about 110 lightyears across, though its gorgeousness is infinite.

Pillars of Creation

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

If this picture doesn’t blow your mind, you might be a cyborg, which technically isn’t a bad thing. This revisiting of the 1995 Hubble classic was taken in September 2014, offering a stunning new look at the Eagle Nebula, located 6,500 lightyears from Earth. Within these “fingers” of hydrogen and dust, stars are being born, hence the name “pillars of creation.”

Spiral Galaxy M83

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Acknowledgement: W. Blair (STScI/Johns Hopkins University) and R. O’Connell (University of Virginia)

This M83 is not a French electronic rock group, but it is pretty darn lovely. Located 15 million lightyears away in the constellation Hydra, this galaxy is full of star clusters, which pop in this composite of several exposures taken between August 2009 and September 2012. Its signature pink glow comes from its younger stars (1 to 10 million years-old), which absorb ultraviolet light and give off a hydrogen aura.

You can check out the rest of the telescope’s stunning images here. Happy birthday, Hubble, and here’s to many more!

RIP Cassini: A Look Back At the Doomed Probe’s Most Stunning Saturn Pictures


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RIP Cassini: A Look Back At the Doomed Probe’s Most Stunning Saturn Pictures

4/04/17 10:37am

Photo of Saturn by Cassini, taken on December 18, 2012. (Image: NASA)

Alas, all good things must come to an end. Today, NASA will announce the details regarding its Cassini spacecraft’s Grand Finale—a resplendent ending to its 20-year-long adventure in space, which will begin later this month. From late April to September 15th, Cassini will perform 22 dramatic dives between Saturn and its rings. Then, the brave little orbiter will plunge itself into Saturn’s atmosphere and burn up like a meteor—all while sending information back to Earth.

The orbiter, which launched on October 15th, 1997, reached the Saturn system in 2004. Since then, it’s beamed back countless gigabytes of data and breathtaking photos, enabling the publication of more than 3,000 scientific reports, according to NASA. It’s had a good run, but now, it must die—Cassini is running out of fuel, and scientists fear that if it crashes into one of Saturn’s 62 moons, the orbiter could contaminate them.

To be fair, going out in a blaze of glory (literally) is the most dignified way to go. Before she leaves us forever, let’s take a look back at some of Cassini’s greatest hits:

View of Saturn’s moon, Titan (December 4th, 2015)

Image: NASA

Saturn and its moon, Tethys. Tethys isn’t that small—Saturn’s just huge. (November 26, 2012)

Image: NASA

Spinning vortex on Saturn’s north pole, AKA “The Rose.” (April 29, 2013)

Image: NASA

Saturn and its large son (read: moon), Titan. (August 29th, 2012)

Image: NASA

Saturn and five of its moons. (September 12, 2011)

Image: NASA

Saturn’s tiny moon, Pan, AKA the “dumpling moon.” (March 7th, 2017)

Image: NASA

View from within Saturn’s shadow. (February 3rd, 2016)

Image: NASA

Enceladus’ north pole. (October 15th, 2015)

Image: NASA

Saturn’s moon, Helene. She’s small. (September 17th, 2010)

Saturn’s “Death Star” Moon, Mimas. (October 22nd, 2016)

Of course, some rings. (May 23rd, 2005)

Image: NASA

RIP Cassini (1997-2017)

More Evidence That Aliens Aren’t Trying to Communicate With Us


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More Evidence That Aliens Aren’t Trying to Communicate With Us

Today 11:30am

The “Sombrero Galaxy.” (Image: Hubble)

Some SETI researchers believe the best way to detect aliens is to search the skies for their laser beams. In the largest survey of its kind, astronomers scanned 5,600 stars in search of these optical signals—and they found…absolutely nothing. Nada. Zilch. Here’s what that means to SETI and the ongoing hunt for alien intelligence.

In a new study accepted for publication at the Astronomical Journal, SETI astronomers Nathaniel Tellis and Geoffrey Marcy from the University of California Berkeley report that they were unable to detect optical signatures of advanced extraterrestrials in over 67,000 individual spectra produced by nearly 5,600 stars in the Milky Way Galaxy. Revealingly, around 2,000 of these stars are suspected of hosting warm, Earth-like planets, suggesting that advanced civilizations either don’t get into the habit of transmitting powerful laser beams across the cosmos, or they simply don’t exist. More practically, it means we should look for optical signals elsewhere, and expand our search to include an assortment of other potential alien signatures. Simply put, we’re not done searching for ET.

Listening for radio signals is so old school. All the cool kids are now searching for laser beams. (Image: Contact)

That said, the null result is undeniably discouraging. Laser signals would be an effective, cheap, and easy way for an advanced civilization to get our attention. Using technology similar to what we have today, aliens could deliberately transmit artificial infrared, visible, or ultraviolet emissions at our star. These directed signals could attract our attention by being continuous and abnormally powerful, or by containing tell-tale signs of artificiality, such as unexplained pulsing, or a string of binary data expressing some kind of mathematical phenomena (e.g. prime numbers or pi).

Prior to this study, SETI researchers had evaluated around 20,000 stars in search of optical signals at Harvard’s Oak Ridge Observatory, spending about 10 minutes on each object. Clearly, if the laser blinking frequency is longer than that, or if ET’s laser transmission station is temporarily out of service, we’re out of luck. Not surprisingly, nothing interesting has been detected thus far.

In an effort to conduct a more thorough review of the heavens, Tellis and Marcy analyzed a trove of data collected by the Keck 10-meter telescope and its high resolution spectrometer, HIRES, between 2006 and 2016 as part of the California Planet Search (CPS). The 5,600 stars included in the study, the majority of which are located within a distance of 300 million-light years, produced 67,708 individual stellar spectra, averaging 96 spectral signals per star.

“This study leverages the huge amount of data collected by the Keck telescope over decades, mostly as part of planet-hunting projects,” explained Penn State astronomer Jason Wright, who was not involved in the study, in an interview with Gizmodo. “That makes it sensitive to relatively low laser powers from thousands of the most nearby and interesting stars. It’s a great example of how SETI can ‘piggyback’ off of other science, looking for signals that might have been overlooked or thrown out because they were not expected or they look very similar to known sources of noise.”

Armed with this data, the researchers then set about the task of searching for spectral signatures that, in the words of the authors, “would be expected from extraterrestrial optical lasers.” The power of these lasers ranged from 3 kW to 13 MW, which isn’t extreme by any measure. Unlike radio signals, which dissipate over vast distances, laser light manages to hold its integrity as it travels through space. “We may imagine that beings more technologically advanced than humanity would be capable of constructing…laser launchers with power levels at least as high as those detectable here, for any of the 5,600 star systems we surveyed,” explained the researchers in their study.

An example of a false positive in a signal. This extraterrestrial laser candidate was found in an observation of TW Hydrae. The blip turned out to be heated gas in the protostellar disk around the star. (Image: Tellis and Marcy, 2017).

To analyze this decade’s worth of data, Tellis and Marcy developed an algorithm that was (at least in theory) able to discern a possible alien signal within the natural spectra of a star. If an artificial signal was directed towards Earth,
it would be detectable as an unusually high number of protons compared with the background emissions of the star. The algorithm was configured to flag any occurrence of three consecutive pixels that exceeded the researchers’ thresholds.

“We searched our spectra for ‘brightenings’ of the star, relative to the light it is already emitting, that were both tight in wavelength and in space,” Tellis told Gizmodo. “Finding a signal that matched the instrumental profile of Keck HIRES would have almost unequivocally meant we were seeing laser light, as the normal stellar spectra contain only thermally broadened emission lines. This is one of the key advantages to using Keck, as it has high enough spectral resolution to distinguish the two.”

The thresholds were very liberal, resulting in an initial batch of 5,023 candidates. The researchers manually parsed these results (literally eyeballing the data), pruning the list down further and further as they pinpointed the source of each false positive. The most common sources of these false positives included cosmic rays, gamma rays, radioactivity from the observatory, molecules in Earth’s atmosphere, and emissions from the parent stars. Eventually, Tellis and Marcy had to concede defeat.

“We found no such laser emission coming from the planetary region around any of the 5,600 stars,” conclude the researchers in their study.

This result would seem to strike a blow to the suggestion that advanced civilizations might last for thousands or millions of years, all the while sending hello messages to up-and-coming neighbors. If even a small fraction of the 2,000-or-so systems with potentially Earth-like planets surveyed had technological civilizations who took the time to deliberately beam megawatt-lasers towards us, we should have detected them by now.

“These results put an upper bound on the number of civilizations transmitting lasers at us while we were observing,” said Tellis. “It is only one type of communication, but we believe that for targeted communication, lasers are highly efficient.” That said, he admitted that lasers as a communication medium seem good to us at this time due to our relative youth, and that his team’s strategy relies on serendipity. “We have to ‘catch’ their broadcast,” he said. “Nevertheless, we believe it is a valuable result that the galaxy is apparently not teeming with such bright lasers.”

So either advanced alien civilizations don’t behave in this way (e.g. they hide their presence or engage in other activities), or they don’t exist. It’s also possible that technological civilizations are exceptionally rare in the galaxy (both in time and space), greatly limiting the ability of the researchers to detect a signal. As the authors of the new study admit, “We may begin to wonder if arguments along the lines of the so-called Fermi paradox have some merit.” Indeed, the eerie silence of space is getting louder with each new attempt to detect alien intelligence.

Undaunted, the researchers are planning on an expanded search. As part of the $100 million Breakthrough Listen effort, they will now turn their attention to stars that were overlooked in the study, including brown dwarfs and other odd astronomical phenomena. In addition to optical signals, SETI researchers can look for other potential signs of alien intelligence, such as microwave or neutrino emissions, Dysonian megastructures, industrial waste signatures, transiting space habitats, and so on.

If the aliens are out there, we’ll find them. Eventually.

[The Astronomical Journal (preprint available at arXiv)]

TRAPPIST-1 Has Some Serious New Competition For Best Place to Find Aliens


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TRAPPIST-1 Has Some Serious New Competition For Best Place to Find Aliens

Today 1:00pm

Artist’s rendition of exoplanet LHS 1140b. (Image: ESO/spaceengine.org)

It seems like every week, there’s a new contender for Coolest Planet Where There Are Definitely Aliens. For those of us who want to believe, this is an emotionally exhausting cycle, as we’re built up and let down time and again. At the risk of fucking with our fragile hearts even more, it’s worth mentioning that a recently discovered exoplanet 39 lightyears from Earth might actually give the current favorites—Proxima b and the TRAPPIST-1system—a run for their money.

This rookie, known as LHS 1140b, hails from the constellation Cetus (the sea monster). It was initially discovered in 2014 by Harvard astronomers who are part of The MEarth Project, which hunts for exoplanets. The team first spotted the rocky planet using the transit method, meaning they noticed a dip in the light output of its parent star, a red dwarf called LHS 1140, when it passed in front in our line of sight.

“We originally thought it was just something funny going on in the atmosphere,” Harvard astronomer Jason Dittmann, the study’s lead author, told Gizmodo. “It was only about a year later, when I was going back through our data with a machine learning based algorithm…that I pulled this 2014 transit out and flagged it as possibly real.”

Dittmann and his team of researchers followed up on the observation using the European Southern Observatory (ESO) HARPS instrument, which allowed them to confirm the planet’s orbital period, mass, and density. The group’sresearch will be published in Nature on April 20th (nice).

Though it’s much closer to its sun than Earth is to ours, LHS 1140 is a lot cooler than our life-giving buddy. It just so happens that as a result, LHS 1140b lies squarely in the habitable zone, which means that hypothetically, it could support flowing water. Even though it’s only about 1.4 times the size Earth, it’s about seven times as massive, indicating that it is probably a rocky world with a dense iron core. Naturally, researchers are already pumped about the possibility of life there.

“This is the most exciting exoplanet I’ve seen in the past decade,” Dittmann said in a statement. “We could hardly hope for a better target to perform one of the biggest quests in science—searching for evidence of life beyond Earth.”

It’s not just enough to be excited about this planet, though; there’s a bit of exoplanetary competition going on here. Even the researchers are having some fun encouraging the rivalry between LHS 1140b, Proxima b, a potentially Earth-like exoplanet discovered just five light years away in 2016, and the seven Earth-sized planets recently spotted around the ultracool dwarf star TRAPPIST-1.

“The LHS 1140 system might prove to be an even more important target for the future characterization of planets in the habitable zone than Proxima b or TRAPPIST-1,” researchers Xavier Delfosse and Xavier Bonfils said. “This has been a remarkable year for exoplanet discoveries!”

Still, Dittmann thinks that the TRAPPIST-1 system, also located roughly 40 light years away, stands out as a particularly intriguing.

“I really want to emphasize that both our system and TRAPPIST-1 are exciting and both worthy of intense future study,” he told Gizmodo. “LHS 1140 is brighter at optical wavelengths because it’s slightly bigger than the TRAPPIST-1 star. So, when the future 30 meter optical telescopes are built (the Giant Magellan Telecopes and European Extremely Large Telescope), LHS 1140 can feasibly be studied by these telescopes.”

Indeed, we won’t know much more about any of these planets’ habitability until we can observe their atmospheres, which will require more powerful telescopes than today’s state-of-the-art. There are already concerns about the habitability of Proxima b, which, like LHS 1140b, orbits a red dwarf. Some scientists worry that the frequent solar storms from Proxima b’s host star could strip it of its atmosphere, dashing our chances of finding biosignatures there. It’s possible this could be a concern with LHS 1140b, too.

“There’s definitely a concern that high energy radiation from M dwarfs might ‘spoil’ the habitability of their planets,” Dittmann said. “In the case of Proxima b, the star seems to be very active, flaring quite often. This is also true in the case of TRAPPIST-1. In contrast, LHS 1140 is slowly rotating (130 days), and we haven’t seen any flares from the star. We also expect—and hope to check with future data—that the star is very quiet at high energies as well. So, at least in the present day, LHS 1140b finds itself orbiting a very nice, quiet host star.”

Ultimately, time will tell. NASA’s James Webb Telescope (JWT), which is set to launch in October 2018, could provide some of the answers alien huntersastronomers are desperately seeking. Once it’s completed, JWT will be themost powerful space-based telescope ever deployed—it’ll be used to peer into the atmospheres of all of these planets and more.

When it comes to exoplanetary supremacy, there can only be one. Just kidding, I hope they all have alien babies hiding inside them.

[ESO]

Another One of Saturn’s Moons May Have a Global Ocean


Post 8321

Another One of Saturn’s Moons May Have a Global Ocean

9/30/16 1:10pm

A parting view of Saturn’s moon Dione from Cassini’s final flyby on April 17th, 2015. Image: NASA/JPL-Caltech/Space Science Institute

The evidence is mounting that our solar system is rife with oceans. Last week, scientists reported that Pluto could have an insanely deep liquid water swimming pool beneath its surface, and on Monday, NASA revealed new evidence for geyser activity on icy Europa. Now, another frozen moon is poised to join the club of outer space scuba retreats: Dione.

The fourth largest moon of Saturn, Dione was first imaged by the Voyager space probes in the 1980s, and has been viewed more recently by the Cassini spacecraft, during a series of five close flybys. It’s a beautiful, cratered ball of ice and rock, home to deep canyons and towering cliffs. While early flybys offered hints of geologic activity, there’s never been a smoking gun to prove Dione is alive inside—particularly when compared with its next-door neighbor (and orbital resonance partner) Enceladus, which is spewing seawater out of enormous geysers.

Dione against a backdrop of Saturn’s rings. Image: NASA/JPL-Caltech/Space Science Institute

But a new study, which has been accepted for publication in Geophysical Research Letters, suggests we may have underestimated Dione. The moon could have a liquid water ocean beneath its surface, just like Enceladus. Using a geophysical model that depicts a crust ‘floating’ atop a mantle, Mikael Beuthe of the Royal Observatory of Belgium shows that gravity data collected by Cassini can be explained by a ~100 kilometer (62 mile)-thick shell of ice enveloping a 65 kilometer (40 mile)-deep ocean. Dione’s ocean, in turn, would smother a rocky core.

The first evidence for a subsurface ocean on Enceladus also came from gravity anomalies detected by Cassini, in a series of flybys between 2010 and 2012. As the spacecraft zipped past the moon, its velocity was slightly altered due to variations in Enceladus’ gravitational field. That change in velocity was measured from Earth via the Doppler effect—a shift in the radio frequency of Cassini’s transmissions.

In 2014, researchers at the Jet Propulsion Laboratory concluded that Cassini’s radio transmissions were hinting at a south polar sea beneath Enceladus’ icy shell. But a year later, independent measurements of Enceladus’ “libration”—a slight wobble as it orbits Saturn—revealed that the ocean is probably global.

“For Dione, we did a similar gravity-topography analysis as was done for Enceladus in 2014, but with improved techniques,” Beuthe told Gizmodo. “Thus that’s the best evidence we have now for a present-day ocean on Dione.”

Color map of Dione’s surface, showing ice cliffs and patches of smooth terrain that indicate recent geologic resurfacing. Image: Wikimedia

According to Beuthe, we won’t be able to confirm Dione’s ocean with libration measurements the way we did for Enceladus, both because Dione is more spherical and because its crust is thicker. But there are other reasons to suspect this moon’s ocean is the real deal.

For one, gravity data also tells us Dione has a rocky core, spanning approximately 70 percent of its total radius. As radioactive elements decay within the core, they produce heat, melting the overlying ice. This almost certainly caused a subsurface ocean to form in Dione’s early history—which, by the way, might not have been too long ago.

“We don’t yet know whether the ocean froze or not afterwards,” Beuthe said. “But freezing would cause global expansion which should be seen in a certain type of cracks [which have] not been observed on the surface.”

Icy cliffs and smooth terrains also hint at recent geologic activity, which again, is difficult to explain if Dione is simply a ball of ice frozen to rock. Detection of geysers, similar to those seen on Enceladus and Europa, would really seal the deal for an ocean on Dione. But we haven’t seen geysers yet, and given the estimated thickness of Dione’s crust, Beuthe isn’t so sure we will.

To confirm the ocean, he says, “we need a new mission, which won’t happen for a long time.”

If Beuthe’s hunch about Dione is correct, the astrobiology implications are thrilling. It’s likely the ocean would have been around for the moon’s entire existence, long enough for microbial life to emerge under the right conditions. Another mind boggling thought: perhaps Dione and Enceladus have been exchanging alien microbes for hundreds of millions of years.

If one thing is becoming clear, it’s that oceans are not so unusual or special in our cosmic backyard. Does that mean life isn’t, either? We’ll need to keep exploring to find out.