Ice Moon Seismology Could Accelerate Search for Life Beyond Earth

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>

 Millions of miles from our planet, extraterrestrial life could reside in salty seas encased by hard spheres of ice. Lacking close proximity to the sun, as well as the proper evolutionary advantages to glean energy from sunlight, life on these so-called “icy ocean moons” might harness chemical energy instead. Either bacteria or archaea—bacteria’s primitive counterparts—would be the most likely candidates, said Peter Girguis, a professor of organismic and evolutionary biology at Harvard University. “That said, until we have the appropriate technology to send really sophisticated instruments directly to these planets, we’re simply left to make inferences,” he said.
 

 Today, scientists can roughly estimate the thickness of the ice shells on distant ocean moons (like Jupiter’s Europa) using orbiting spacecraft or detect salinity via changes in planetary magnetic fields. But what’s transpiring at the seafloor remains anyone’s guess.
 
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/europa-jupiter_1024x576.width-990_SAmPNjm.jpg"/>
<figcaption>Jupiter’s icy ocean moon, Europa
 
 </figcaption>
</figure>

 Researchers centered at Caltech’s Jet Propulsion Laboratory (JPL) advocate using a familiar method to assess habitability—the same technology employed to understand what lies beneath our feet here on Earth. In a recent
 <a href="https://arxiv.org/abs/1610.10067">
 article
 </a>
 submitted to Astrobiology, the team proposed landing seismology experiments on the ice shells to determine their moon’s internal structure and potential for life. However, the mission’s first challenge begins on Earth—convincing NASA that bringing seismology instruments to icy ocean moons is a worthwhile endeavor.
 

 Most of what we know about the inside of our own planet stems from data collected by seismometers—sensitive devices that record the waves of energy released by subterranean tremors. As they spread underground, these seismic waves bounce off formations inside the planet (which, in the case of an ocean moon, include a rocky core engulfed by an icy sea). Just as we map the interior of the human body by tracking X-rays, recording seismic waves as they reach the surface of a planet reflects internal structure.
 

 This could reveal alternative sources of life-sustaining energy (like ice volcanoes or hydrothermal vents), and indicate potential nutrient cycling through the ice shell as well as the presence of liquid water near the surface. So far, seismometers have been positioned on the Moon and Mars, but not on any icy moons.
 

 “Interest in these icy moons is at an all-time high,” said Jennifer Wiseman, the Hubble Space Telescope senior project scientist. “Seismic activity will certainly contribute to our understanding of whether habitability is likely in these places.”
 

 Based on signs of surface geological activity, like fractures, scientists are relatively certain the icy moons are seismically-active. However, seismometers could verify this immediately upon landing. According Steve Vance, first author of the paper, seismology should be used in tandem with preexisting techniques that examine planetary interiors.
 

 The JPL paper is the first to offer a holistic approach to assessing internal structure of five such icy moons in the context of potential life. Girguis, who was not affiliated with the paper, said it “comprehensively reviews” the advantages and limitations to applying this technology to questions of habitability.
 

 Ralph Lorenz, an author of the paper, hopes the piece will spur researchers to explore these moons in new ways. “Many seismologists have not considered the potential for making measurements on worlds like these,” he said. “Perhaps the prospect of implementing one of these investigations is close at hand.”
 

 There are two main icy worlds that could be well-suited to test the technology—Jupiter’s moon Europa and Saturn’s moon Enceladus. “The activity at the surface of these moons suggests they are really dynamic places,” said Alyssa Rhoden, another author of the paper. If recent observations on Europa are confirmed, these will also be the only two icy moons known to harbor geyser-like water vapor “plumes.” These bursts signify seismic activity and would permit sampling the oceans without drilling through miles of ice.
 

 Delivering a seismometer to Europa or Enceladus would require a lander—a spacecraft that makes direct contact with the ground. However, NASA has only initiated flyby missions thus far: The Voyager mission launched in 1977, Galileo in 1989, and New Horizons in 2006. Cassini also collected images of Europa on its way to Saturn, where it has remained since 2004, snapping photos of Enceladus and Saturn’s other moons. According to Rhoden, there has yet to be a mission solely devoted to either Enceladus or Europa.
 

 That may change as NASA is currently developing the Europa Multiple-Flyby Mission, nicknamed the Europa Clipper. The orbiter is slated for lift off in the early 2020s, performing approximately 42 passes at 16 to 1700 miles above Europa’s surface. It will capture high-resolution images, as well as samples from the erupting plumes. Analyzing the chemical make-up of these plumes, which might spew from the frothing sea below, could provide insight into the potential for life.
 

 NASA is also considering the possibility of a Europa lander as a future mission post-Clipper, which would be the first of its kind to touch down on an icy ocean moon. However, these plans are far from concrete.
 

 “To put it in perspective, we spent about fifteen years working on the Europa Clipper mission before NASA gave us the go-ahead,” said Curt Niebur, lead program scientist of the mission. “We still have to come up with a design for the lander that’s possible and scientifically worthwhile.”
 

 The NASA team began their preliminary studies a mere six months ago. “We are considering including instruments that could help detect life, as well as instruments like a seismometer that could tell us about Europa’s interior structure,” Niebur added.
 

 Mark Panning, a collaborating author on the JPL paper, is optimistic. “There’s a very good chance that the Europa lander could include some sort of seismic instrument,” he said. “We want [NASA] to look at this paper and start thinking about what kinds of science they could do with a proposed seismic instrument.” He said the group’s follow-up studies, which will incorporate more precise numbers and models, could be even more informative.
 

 Neibur emphasized that they would need to ensure the seismometer could be securely coupled to Europa’s surface. “Unless you can do that, you’ve just spent a lot of money accomplishing nothing,” he said.
 

 Jay Melosh, professor of earth, atmospheric, and planetary sciences at Purdue University, agreed. He also said landing a spacecraft on Europa would be extremely challenging due to the moon’s powerful gravitational field. A lander would require extra fuel to have enough power to reach the surface. And, unlike Mars or the Moon, Europa lacks an atmosphere—making a “soft” parachute landing to avoid damage to the delicate seismometer quite difficult. Plus, without this layer of insulation, intense radiation from Jupiter constantly bombards Europa’s surface. Coupled with the frigid temperatures, this makes for an extremely hostile environment.
 

 “I would actually think that a seismometer to Titan, Saturn’s largest moon, would fly earlier,” Melosh said. “Titan has a very substantial atmosphere, and it doesn’t suffer from the horrendous radiation problem that Europa does.”
 

 Consensus here, too, is split. NASA planetary scientist Terry Hurford noted that an atmosphere means wind can disrupt the sensitive seismology instruments. (This was the case with one of the 1976 Viking probes to Mars.)
 

 But both Melosh and Hurford agreed that, in order for an icy moon seismology experiment to succeed, there must be planetary quakes large enough to detect.
 

 Vance recognized there is much to learn before seismometers can probe our solar system’s icy ocean moons. “This paper is a jumping off point for more detailed studies,” he said.
 

 “The fervor is certainly there,” Wiseman said.
 
</section>

 Image credit: Public Domain

An artist’s impression of the expected distribution of dark matter around the Milky Way galaxy

Galaxy's Disk of Dark Matter Could Trigger Mass Extinctions on Earth

<div class="related"></div>

 Approximately every 35 million years, a comet careens from outer space and lays waste to the Earth. For nearly two decades, researchers at Harvard have attempted to understand this “periodicity” of mass extinction. Now, in a
 <a href="https://arxiv.org/abs/1610.04239">
 paper
 </a>
 recently submitted to Astrophysical Journal Letters, two Harvard graduate students used the 250 million-year-old crater record to show how a disk of dark matter suffusing the galaxy could spark mass extinctions.


 Most scientists agree that the observable stuff in our galaxy, concentrated in a disk, is surrounded by a diffuse halo of dark matter. But some maintain that a portion of dark matter exists in a separate, condensed form—a “dark disk” located both on top of and within our own flat galaxy. It’s the relative movements of our galaxy and this disk that may trigger events that lead to mass die-offs.


 “There’s a cycle in our galaxy; the solar system bobs up and down through the plane of the disk-shaped galaxy—we’re pulled towards the plane, we go through it, we overshoot, we go back,” said Michael Rampino, professor of biology at New York University. “The folks at Harvard are proposing that there is a thin disk of concentrated dark matter, and the solar system moves through it every 35 million years or so.”


 Since this timeline matches the interval between comet impacts, the idea is that dark matter exudes powerful gravitational forces, disrupting the comet cloud around our solar system as we pass through the dark disk. Dislodged meteorites can then tumble towards Earth with dire repercussions.

<div class="ad"></div>

 The researchers’ analyses were unique in that they incorporated three important measurements related to our galaxy: specific estimations of its mass components, its rotating spiral arm pattern, and the radial bobbing motion of the solar system as it revolves around the galactic center. In fact, this was the first study to include either of the latter two features. Taking such factors into account, co-author Michael Rowan said the model accurately predicted the date 66 million years ago when the Chicxulub crater was created by the impact that annihilated the dinosaurs.


 Harvard physics professor Lisa Randall, who served as an advisor for the paper, was largely responsible for revitalizing the dark disk theory in the early 2013 after its decline in the 1990s. “The dark disk is controversial because the data weren’t always correctly interpreted or understood,” Randall said. “The idea is re-emerging with a growing consensus that we don’t know the nature of dark matter well enough to rule out interesting candidates.”


 Both Rampino and Manoj Kaplinghat, a professor of physics and astronomy at UC Irvine, are sympathetic to this view “If the normal stuff, which is just 20% of the matter in the universe by mass, is so complicated, then why should the rest of the 80%, which is dark, be simple?” Kaplinghat said. But, he added, as it currently stands, the theory requires additional data to back it up.


 According to Kaplinghat, this model is novel because it includes a dark disk possibly thick enough to be stable, yet thin enough to match the periodicity in the crater record. He also said this was the first model to account for the motion of the solar system through the spiral arms of our galaxy. The gravitational forces exerted by the spiral arms impede the solar system as it bobs through the plane of the galaxy—which could explain why the periods between comet impacts are not always exactly 35 million years.


 To test the effects of these adjustments, the researchers asked their model to predict the dates of multiple crater impacts already noted on the record. Rowan’s collaborator, Eric Kramer, said the Chicxulub prediction stuck out in particular. “Previously, it appeared the comet that killed the dinosaurs was a few million years off from the time the sun crossed the galactic plane,” he said. “But when you take spiral arm passages into account, the data line up quite well.”


 Rowan said, in theory, the model could be used to anticipate future comet impacts. Kramer affirmed that we’re currently passing through the dark disk, which suggests a higher probability of comet impact. “Of course, these showers happen over timescales of millions of years, so hopefully we’re safe,” he said. “All it takes is one comet to have disastrous consequences.”

<div class="newsletter"></div>

 Image credit:
 <a href="https://commons.wikimedia.org/wiki/File:Artist's_impression_of_the_expected_dark_matter_distribution_around_the_Milky_Way.jpg">
 ESO/L. Calçada / Wikimedia Commons (CC BY 4.0)
 </a>

A new model of dark matter disk theory has accurately predicted the date of the Chicxulub crater impact, which annihilated the dinosaurs.

Fusion Reactor Breaks Record on the Day It's Shut Down by Budget Cuts

<div class="related"></div>



 On Albany Street in Cambridge, Massachusetts, there is a device that confines the power of the stars, generating energy at over 180 million degrees F. Known as the Alcator C-Mod, MIT’s plasma fusion experiment has operated for more than 20 years. Yet as of Friday, September 30, it was terminated by federal decree.


 Four years ago, without warning, the Department of Energy (DOE) announced its controversial decision to cut funding. Although the closure date was originally slated for October 2012, after some negotiation this timeline was ultimately pushed to the end of the 2016 federal fiscal year. “To this day, C-Mod is still a highly productive and unique plasma fusion experiment run by a number of outstanding scientists,” said Michael Mauel, professor of applied physics at Columbia University, who runs his own fusion experiment.

<div class="ad"></div>

 While it may sound like the stuff of fiction, plasma is simply a state of matter composed of charged particles. At temperatures as hot as the sun, the positively charged particles collide and fuse together, releasing energy in the form of heat. The particles move extremely quickly—so quickly they could travel around the Earth several times in a single second.


 Scientists hope to one day construct fusion reactors capable of supplying nearly unlimited electricity. It would be the holy grail of energy production, since nuclear fusion generates very little radioactive waste and no greenhouse gasses. But first, scientists must learn how to trap the plasma in a container with magnetic fields for long periods of time, using less energy than the fusion process creates.


 C-Mod is a container called a tokamak, which resembles a donut. The circular machine confines the plasma using immense magnetic forces, holding the whizzing particles in a ring for several seconds at a time. C-Mod boasts the highest magnetic field of any tokamak—40,000 times more powerful than the Earth’s own magnetic field—even though the device is fairly compact compared to the 200 others in existence. The donut’s radius is only about 67 cm.


 Some attribute the DOE’s decision to C-Mod’s diminutive size. “It’s not as large or as new as many other machines, which do novel things with plasma C-Mod can no longer do,” said Dr. Weston Stacey, professor of nuclear engineering at Georgia Tech. “Its time has come.” Stacey said there are advantages to being big, because anything remotely resembling a reactor must be relatively large. “You don’t want to light a lightbulb, you want to light a city,” he said.


 Others disagree. “I wouldn’t say small isn’t as good,” Mauel said. “Fusion requires a large product of magnetic strength and physical size. Because C-Mod has very high magnetic strength, it can operate at smaller size,” he added.


 The DOE’s decision to shut down a working experiment was intended to shift funding to international efforts to achieve a self-heated plasma. “At the moment, that’s ITER,” Mauel said.


 Started in 2006, ITER, the International Thermonuclear Experimental Reactor, is a 35-country collaboration that’s assembling the world’s largest fusion experiment in the south of France.


 “ITER will weigh almost a thousand times as much as C-Mod and cost about a thousand times more to build,” said head of the C-Mod project, Dr. Earl Marmar. “When ITER was proposed, it was going to cost the U.S.—a 9% partner in the project—about $1.1 billion. Now, a recent DOE review suggests it’s between $3-6 billion.”


 At MIT, C-Mod had been producing plasma for over 20 years. Marmar claims the DOE’s choice to cut funding was a political one. “ITER is promising to do something we were never designed to do because we would need a bigger facility,” he said.


 To emulate a power plant, the MIT facility would need to be large enough to reach 360 million degrees F. “We think we can do that in the future,” Marmar said.


 Since the DOE announced its decision in 2012, he’s had plenty of time to plan his next steps. His team at MIT hopes to eventually develop superior superconducting magnets for their next tokamak that will more effectively confine and heat the plasma.

<div class="newsletter"></div>

 On the C-Mod’s final day of operation, Marmar and his colleagues gave the tokamak one last hurrah, cranking up the pressure inside its powerful magnetic fields. At 9:25 pm, they had squeezed the 63 million degree F plasma to 2.05 atmospheres, twice as dense as air pressure at sea level, breaking their own record set back in 2005.


 “We think we could make something not much more than twice as big as C-Mod that could put more power out than we would need to run the facility,” Marmar said. “At the moment though, we still don’t have funding.”


 Photo credit:
 <a href="https://commons.wikimedia.org/wiki/File:Alcator_C-Mod_interior_from_A-Port.jpg">
 Bob Mumgaard/Wikimedia Commons (CC BY-SA)
 </a>

Funding for MIT&#x27;s C-Mod tokamak was cut by the Department of Energy, but not before it could break its own record for highest pressure plasma.

Cyber Security AI Can Find Threats Hiding in Plain Sight

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>

 If you’re planning a cyber-attack on the federal government, don’t discuss it on social media. Seems like common sense, but experienced hackers keen on exploiting software vulnerabilities often use online forums to exchange strategies and define targets.
 

 Despite advancements in modern technology, analysts today still rely on cumbersome manual searches to sift through Internet content and pinpoint cyber threats. Researchers at the Lincoln Laboratory outlined a simple, automated method to streamline this process—“simple” being nearly as significant as “automated”—which was recently published in the Laboratory’s own
 <a href="http://www.ll.mit.edu/publications/journal/pdf/vol22_no1/22_1_4_Campbell.pdf">
 journal
 </a>
 .
 

 Although automated techniques and cyber security have been well-studied in their respective research spheres, this paper is among the first works to marry the two, said Yuheng Hu, assistant professor of Information and Decision Sciences at the University of Illinois at Chicago.
 
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/hacking_2048x1152.width-990_XgGHt4d.jpg"/>
<figcaption>Although automated techniques and cyber security have been well-studied in their respective research spheres, this paper is among the first works to marry the two.
 
 </figcaption>
</figure>

 The Lincoln Lab team devised and tested an automated computer program, called a classifier, which separates content into pre-defined categories. They trained the classifier to recognize key words within sample social media texts and then asked it to use this knowledge to categorize the documents as either suspicious or benign. The authors drew their example texts from Twitter, Reddit, and Stack Exchange, because these forums represent the three most common types of Internet discourse.
 

 On its own, a classifier doesn’t understand the content of the conversations. That’s why the Lincoln Lab researchers chose to create a tool that incorporated a human language technology (HLT) component in addition to a traditional classifier. HLT takes advantage of the contextual content that classifiers do not, breaking down sentences into simpler pieces—for instance, reducing “hacks,” “hacker,” or “hacking” to “hack”—which are then fed to the classifier.
 

 HLT comes into play once again after the documents have been grouped by the classifier to help interpret the results, and it assigns each a numerical value according to its potential threat. For instance, “infection” is far less suspicious in the context of bacterial infections than it is in terms of software vulnerabilities. If a ranking above 0.7 is considered problematic, then this medical reference would fall somewhere below that benchmark.
 

 “Once the classifier has been trained, it knows the key words that are representative of a specific type of document,” said David Weller-Fahy, a member of the research team. The classifier essentially learns what social media discussions will be of interest to an analyst without being told exactly what to look for.
 

 Hu recommended expanding the classifier’s dictionary, however, since Twitter lexicon is ever-changing and oftentimes unconventional. “Twitter is very dynamic, so that makes it hard to maintain a static dictionary,” he said.
 

 Weller-Fahy explained he’s received similar suggestions to increase the classifier’s complexity, because in academia more is often better. But Weller-Fahy is catering to a different client; he’s targeting industry and the objectives of his sponsor.
 

 “These are people looking to solve a particular set of problems,” he said. “If I provide them with something that’s simple, fast, and solves their problems, then they’re going to be happy.” Simple technologies can do impressive things with very little computing power if you start with the right data, he added.
 

 In this case, he said less is more because the classifier is not limited to just one type of data. It purposefully ignores certain aspects of social media posts—like usernames, up and down votes, etc.—and scours only the text. It’s also possible to condense the classifier and email it directly to analysts, although Weller-Fahy hopes that once it’s officially released it will be automatically incorporated into software packages.
 

 That said, the classifier is still far from polished. Eduard Hovy, professor at the Language Technologies Institute of Carnegie Mellon, urges the authors to address the accuracy of their classifier, which was absent from their paper. “No system works 100%,” he said. “But if the classifier read, say, 400 social media messages and found three bad ones, we don’t know if it missed two or found them all.” Hu echoed this concern.
 

 Weller-Fahy affirmed that, while the paper did report a “miss rate,” it didn’t specifically disclose accuracy. “We only focused on those performance metrics that were important to our sponsor,” he said—who, of course, is highly classified.
 
</section>

 Photo credit:
 <a href="https://www.pexels.com/photo/technology-computer-desktop-source-code-113850/">
 Markus Spiske raumrot.com / (CC0)
 </a>

Raleigh McElvery

Articles

Ice Moon Seismology Could Accelerate Search for Life Beyond Earth

Galaxy's Disk of Dark Matter Could Trigger Mass Extinctions on Earth

Fusion Reactor Breaks Record on the Day It's Shut Down by Budget Cuts

Cyber Security AI Can Find Threats Hiding in Plain Sight

Support Provided By