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An artist's rendering of the Europa mission's spacecraft. Main Image: NASA/JPL-Caltech Banner Image: NASA/JPL-Caltech

How Will the Europa Lander Search for Life?

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An artist's rendering of the Europa mission's spacecraft. Main Image: NASA/JPL-Caltech Banner Image: NASA/JPL-Caltech

Water, chemistry, energy: three key components for life. We only have confirmation of life on Earth so far, but we're always looking elsewhere. One of the biggest targets in the solar system is Europa, one of Jupiter's moons. We're aiming for that target with the Europa lander, which will launch for the Jovian moon around 2024. The mission will be the first on-site search for evidence of life on another world since Viking 1 and Viking 2 landed on Mars in 1976.

Last month, the team behind the Europa Lander released the mission’s scientific objectives [PDF], and at the recent 48th Lunar and Planetary Science Conference in The Woodlands, Texas, scientists answered questions and led a discussion about the trip with the wider planetary science community.

They explained that the Europa lander is not like the spacecraft Cassini or the Mars rovers—expeditions with big initial objectives, but quiet hope for decades of continued operation and science experiments. In contrast, this mission will live hard and die young. It will have to: The radiation environment at Europa is punishing, so the communications relay orbiter that will act as go-between for the lander and Earth won’t last more than a month or two. The lander will have enough power to run for just 20 days on the surface and will run on batteries; nuclear power was considered but discarded as being too expensive and challenging to launch. Batteries also have the advantage of being “quieter,” providing less vibration, magnetic, and electromagnetic disruption to sensitive instruments.

The lander will launch on a Space Launch System rocket and will spend years traveling to Europa. Upon arrival, the relay orbiter―which during the cruise phase to Jupiter acts as a carrier―will release the lander to Europa’s surface. As the communications satellite establishes its Europan orbit, the lander will use a mini sky crane system to land, looking and acting much like the rover Curiosity on Mars.

But notably, the scientists don’t call this process “Entry, Descent, and Landing” (EDL), but rather DDL, for Deorbit, Descent, and Landing—there’s no atmosphere around Europa for a lander to “enter.” This makes the job of landing much easier than on Mars, whose tenuous atmosphere is insufficient for parachutes alone, and yet enough that it makes a pure supersonic retropropulsive landing a challenge.

WHAT’S ON THE LANDER?

This artist's rendering illustrates a conceptual design for a potential future mission to land a robotic probe on the surface of Europa. Image Credit: NASA/JPL-Caltech

The lander is a square about the size of a large riding lawnmower with four long, articulated cricket-like legs that will each compress independently on landing, allowing it to touch down on an uncertain or jagged surface and still remain level. (If it landed on a ledge, for example, one leg might remain fully extended along the drop, and three legs might compress fully, bringing the belly of the robot even and near the ground.) A communications antenna will then deploy and establish communications with the relay orbiter.

The lander will host a payload of science instruments weighing nearly 94 pounds. “That is a considerable mass for getting science done on any world,” Kevin Hand of the Jet Propulsion Laboratory, co-chair of the science definition team, said. To get the science done, the lander will carry five instruments: a gas chromatograph mass spectrometer and a Raman spectrometer, which can identify the contents of a sample; a context camera, which should return some spectacular images, including a giant Jupiter hanging in the black sky over the ice world; and a geophone, used for seismometry, the study of seismic activity. Except for the camera, these instruments will live inside of the lander, which will protect them from the worst of the radiation.

The most crucial tool for gathering material is a sample collection arm: essentially an angled, twin-bladed boring instrument that will carve strips of granite-hard Europan surface at a depth of 4 inches or deeper. (Regolith at such a depth is not radiation-processed, increasing the likelihood of observing indicators of life.) The collected material will be loaded into a dock in the lander’s side, and the instruments within will begin their analyses. Over the course of the mission, the lander will collect and analyze a minimum of five samples with a minimum volume of .4 cubic inches from five different regions within the lander “workspace”―that is, the radial reach of the collector arm.

WHAT WILL WORKING ON EUROPA BE LIKE?

Two views of the trailing hemisphere of the ice-covered Europa. Image Credit: NASA/JPL/DLR

An Earth day is called a “day.” A Mars day is called a “sol.” A Europan day is called a “tal.” The carrier relay will orbit Europa every 24 hours―this is a happy coincidence with Earth, but wasn’t planned that way―and return three to four gigabits of data per orbit. Mission operations are therefore planned in 24-hour intervals.

At the start of a tal―00:00—the carrier relay will receive its commands from Earth to determine that period’s working schedule. The lander receives those instructions at 01:00, when the carrier is in view of the lander in its orbit. On an ordinary tal, the lander will start collecting samples for the next five hours. At 06:00, the lander will upload engineering data to the relay, which will, in turn, send that data to Earth.

The lander will then get to work on sample analysis, and at 11:00, upload its findings, and go to sleep. At this point, the carrier relay orbiter will be out of range of the lander. Two hours later, it will have a clear shot at Earth, and will send the data back here for analysis. Humans will use this data to plan the science and engineering for the next day, and will generate commands to that effect. At 23:00, those commands and instructions will be sent to the relay orbiter, and the cycle will repeat itself.

The baseline science mission will be achieved in 10 days. Depending on what the lander finds, the team might decide to prioritize different things—for example, focusing on collecting samples or image acquisition.

HOW WILL IT FIND LIFE?

Reddish spots and shallow pits pepper the ridged surface of Europa. Image Credit: NASA/JPL/University of Arizona/University of Colorado

There is no such thing as a “life detector.” Instead of a single magic reading, the lander will look for many organic biosignatures that, taken together, reveal life. Instruments will look for signs and abundance of organic material, cell-like structures, chirality (molecular properties, like those found in amino acids), and biominerals (minerals produced by living things)—among many other things.

Individually, none of these biosignatures can reveal life, but if found collectively, the evidence will be all but irrefutable. A biosignature matrix of positive and negative results is, in essence, plotted on a spreadsheet. Hand called this “biosignature bingo.” Not all of the biosignatures are necessary, but some combination of them are; finding, for example, an abundance of organics, cell patterns, chirality, and microscopic evidence but no signs of biominerals would still conclude life with certainty. On the other hand, if none of these features were found but biominerals and cell patterns were, we wouldn't call that evidence of life.

Sampling will be done in triplicate to confirm life findings. Three samples will have to confirm the biosignatures. The lander team is confident about this process. “It would be very hard to have a false positive, especially after replicating it three times,” Hand told mental_floss. “We use life on Earth as a guide, and so applying that matrix to life on Earth, both past and present, we would have a hard time leading to a false positive.”

The lander, of course, will not be the first spacecraft to arrive at the Jovian moon. The Europa Clipper spacecraft will have arrived and studied Europa years earlier, and will have ably characterized the habitability of that world. What Clipper finds, Lander will build upon. The Clipper’s work will determine one of four possible outcomes: Europa is not habitable, in which case the lander will figure out why (for example: geological activity); Europa is maybe habitable, in which case the lander will resolve the ambiguity of the finding; Europa is habitable, in which case the lander will try to find life; and Europa is inhabited―Clipper outright finds life on Europa, in which case the lander will confirm the finding and set the stage for future exploration. In addition, Clipper will act as a backup plan for the lander should the relay orbiter fail. The lander can talk to Clipper, which will in turn send the information back to Earth.

Despite the recent White House budget request that notably failed to earmark money for the Europa lander, these missions are realistically in no danger. Congressional appropriators have made it clear that the Europa lander is going to happen, and, just as in the case of Clipper (which the Office of Management and Budget ignored for years), it is still expected to receive billions of dollars over the next decade.

HOW DOES THIS COMPARE TO VIKING?

Images from the Viking mission on Mars. Image Credit: NASA

NASA undertook its last true life-finding mission—Viking’s mission to Mars—decades ago. There’s a reason for this time gap: Viking didn’t find life. Scientists had previously held out hope that animals might be scurrying about on the Martian surface. When the red planet was found to be creature-less, interest was quickly lost in the Mars program. Viking is thus sometimes criticized as being a failure. But Hand disagreed. “Viking is vindicated by Europa,” he said. “If Pathfinder had gone back and found a golf course on Mars, someone could say Viking made mistakes. Viking worked beautifully. Mars did not cooperate. Life detection experiments should provide valuable information, regardless of the biology results.”

Even in the absence of life, scientists will learn a lot about Europa as an ocean world, and as a world with liquid water recycling through the sea floor. In the absence of biology, they will still advance the sciences of geochemistry and oceanography.

“As exciting as a positive result for biosignatures would be, a negative result is equally profound. It gets to the question of what does it take for the origin of life to occur,” Hand said. Today, for example, hydrothermal vents are thought to have been critical to the birth of life on Earth. If Europa—which also has hydrothermal vents—is dead, perhaps hydrothermal vents are not that important after all.

Science has marched rapidly since the Viking missions, which means if life exists on Europa, we’re more likely to find it now than Viking scientists on Mars were. When the Viking landers set down in the mid-1970s, the structure of DNA had only been known for about 20 years. In the years since Viking, hydrothermal vents were discovered on Earth, and a whole new domain of life was discovered in the microbial realm, like cryptoendoliths in Antarctica—not to mention the “polymerase chain reaction” was developed, allowing the human genome to be sequenced. Last year, a new tree of life was created based on this research. So going into the lander mission, Hand and his team are cautiously optimistic.

“We don’t know if biology works beyond Earth,” Hand said. “We have every reason to believe it should and could, but we have yet to do that experiment.” The Europa lander team hopes to change that.

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Astronomers Observe a New Kind of Massive Cosmic Collision for the First Time
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NSF/LIGO/Sonoma State University/A. Simonnet

For the first time, astronomers have detected the colossal blast produced by the merger of two neutron stars—and they've recorded it both via the gravitational waves the event produced, as well as the flash of light it emitted.

Physicists believe that the pair of neutron stars—ultra-dense stars formed when a massive star collapses, following a supernova explosion—had been locked in a death spiral just before their final collision and merger. As they spiraled inward, a burst of gravitational waves was released; when they finally smashed together, high-energy electromagnetic radiation known as gamma rays were emitted. In the days that followed, electromagnetic radiation at many other wavelengths—X-rays, ultraviolet, optical, infrared, and radio waves—were released. (Imagine all the instruments in an orchestra, from the lowest bassoons to the highest piccolos, playing a short, loud note all at once.)

This is the first time such a collision has been observed, as well as the first time that both kinds of observations—gravitational waves and electromagnetic radiation—have been recorded from the same event, a feat that required co-operation among some 70 different observatories around the world, including ground-based observatories, orbiting telescopes, the U.S. LIGO (Laser Interferometer Gravitational-Wave Observatory), and European Virgo gravitational wave detectors.

"For me, it feels like the dawning of a next era in astrophysics," Julie McEnery, project scientist for NASA's Fermi Gamma-ray Space Telescope, one of the first instruments to record the burst of energy from the cosmic collision, tells Mental Floss. "With this observation, we've connected these new gravitational wave observations to the rest of the observations that we've been doing in astrophysics for a very long time."

A BREAKTHROUGH ON SEVERAL FRONTS

The observations represent a breakthrough on several fronts. Until now, the only events detected via gravitational waves have been mergers of black holes; with these new results, it seems likely that gravitational wave technology—which is still in its infancy—will open many new phenomena to scientific scrutiny. At the same time, very little was known about the physics of neutron stars—especially their violent, final moments—until now. The observations are also shedding new light on the origin of gamma-ray bursts (GRBs)—extremely energetic explosions seen in distant galaxies. As well, the research may offer clues as to how the heavier elements, such as gold, platinum, and uranium, formed.

Astronomers around the world are thrilled by the latest findings, as today's flurry of excitement attests. The LIGO-Virgo results are being published today in the journal Physical Review Letters; further articles are due to be published in other journals, including Nature and Science, in the weeks ahead. Scientists also described the findings today at press briefings hosted by the National Science Foundation (the agency that funds LIGO) in Washington, and at the headquarters of the European Southern Observatory in Garching, Germany.

(Rumors of the breakthrough had been swirling for weeks; in August, astronomer J. Craig Wheeler of the University of Texas at Austin tweeted, "New LIGO. Source with optical counterpart. Blow your sox off!" He and another scientist who tweeted have since apologized for doing so prematurely, but this morning, minutes after the news officially broke, Wheeler tweeted, "Socks off!") 

The neutron star merger happened in a galaxy known as NGC 4993, located some 130 million light years from our own Milky Way, in the direction of the southern constellation Hydra.

Gravitational wave astronomy is barely a year and a half old. The first detection of gravitational waves—physicists describe them as ripples in space-time—came in fall 2015, when the signal from a pair of merging black holes was recorded by the LIGO detectors. The discovery was announced in February 2016 to great fanfare, and was honored with this year's Nobel Prize in Physics. Virgo, a European gravitational wave detector, went online in 2007 and was upgraded last year; together, they allow astronomers to accurately pin down the location of gravitational wave sources for the first time. The addition of Virgo also allows for a greater sensitivity than LIGO could achieve on its own.

LIGO previously recorded four different instances of colliding black holes—objects with masses between seven times the mass of the Sun and a bit less than 40 times the mass of the Sun. This new signal was weaker than that produced by the black holes, but also lasted longer, persisting for about 100 seconds; the data suggested the objects were too small to be black holes, but instead were neutron stars, with masses of about 1.1 and 1.6 times the Sun's mass. (In spite of their heft, neutron stars are tiny, with diameters of only a dozen or so miles.) Another key difference is that while black hole collisions can be detected only via gravitational waves—black holes are black, after all—neutron star collisions can actually be seen.

"EXACTLY WHAT WE'D HOPE TO SEE"

When the gravitational wave signal was recorded, on the morning of August 17, observatories around the world were notified and began scanning the sky in search of an optical counterpart. Even before the LIGO bulletin went out, however, the orbiting Fermi telescope, which can receive high-energy gamma rays from all directions in the sky at once, had caught something, receiving a signal less than two seconds after the gravitational wave signal tripped the LIGO detectors. This was presumed to be a gamma-ray burst, an explosion of gamma rays seen in deep space. Astronomers had recorded such bursts sporadically since the 1960s; however, their physical cause was never certain. Merging neutron stars had been a suggested culprit for at least some of these explosions.

"This is exactly what we'd hoped to see," says McEnery. "A gamma ray burst requires a colossal release of energy, and one of the hypotheses for what powers at least some of them—the ones that have durations of less than two seconds—was the merger of two neutron stars … We had hoped that we would see a gamma ray burst and a gravitational wave signal together, so it's fantastic to finally actually do this."

With preliminary data from LIGO and Virgo, combined with the Fermi data, scientists could tell with reasonable precision what direction in the sky the signal had come from—and dozens of telescopes at observatories around the world, including the U.S. Gemini telescopes, the European Very Large Telescope, and the Hubble Space Telescope, were quickly re-aimed toward Hydra, in the direction of reported signal.

The telescopes at the Las Campanas Observatory in Chile were well-placed for getting a first look—because the bulletin arrived in the morning, however, they had to wait until the sun dropped below the horizon.

"We had about eight to 10 hours, until sunset in Chile, to prepare for this," Maria Drout, an astronomer at the Carnegie Observatories in in Pasadena, California, which runs the Las Campanas telescopes, tells Mental Floss. She was connected by Skype to the astronomers in the control rooms of three different telescopes at Las Campanas, as they prepared to train their telescopes at the target region. "Usually you prepare a month in advance for an observing run on these telescopes, but this was all happening in a few hours," Drout says. She and her colleagues prepared a target list of about 100 galaxies, but less than one-tenth of the way through the list, by luck, they found it: a tiny blip of light in NGC 4993 that wasn't visible on archival images of the same galaxy. (It was the 1-meter Swope telescope that snagged the first images.)

A NEW ERA OF ASTROPHYSICS

When a new star-like object in a distant galaxy is spotted, a typical first guess is that it's a supernova (an exploding star). But this new object was changing very rapidly, growing 100 times dimmer over just a few days while also quickly becoming redder—which supernovae don't do, explains Drout, who is cross-appointed at the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto. "We ended up following it for three weeks or so, and by the end, it was very clear that this [neutron star merger] was what we were looking at," she says.

The researchers say they can't be sure if the resulting object was another, larger neutron star, or whether it would have been so massive that it would have collapsed into a black hole.

As exciting as the original detection of gravitational waves last year was, Drout is looking forward to a new era in which both gravitational waves and traditional telescopes can be used to study the same objects. "We can learn a lot more about these types of extreme systems that exist in the universe, by coupling the two together," she says.

The detection shows that "gravitational wave science is moving from being a physics experiment to being a tool for astronomers," Marcia Rieke, an astronomer at the University of Arizona who is not involved in the current research, tells Mental Floss. "So I think it's a pretty big deal."

Physicists are also learning something new about the origin of the heaviest elements in the periodic table. For many years, these were thought to arise from supernova explosions, but spectroscopic data from the newly observed neutron star merger (in which light is broken up into its component colors) suggests that such explosion produce enormous quantities of heavy elements—including enough gold to put Fort Knox to shame. (The blast is believed to have created some 200 Earth-masses of gold, the scientists say.) "It's telling us that most of the gold that we know about is produced in these mergers, and not in supernovae," McEnery says.

Editor's note: This post has been updated.

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11 Out-of-This-World Facts About Carl Sagan
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Hulton Archive/Getty Images

Carl Sagan was perhaps America’s most beloved scientific visionary since Albert Einstein. Both a gifted astronomy researcher and an incredible communicator, he brought the wonders of the universe to the masses with his popular TV series Cosmos and books like the Pulitzer Prize–winning Dragons of Eden and Pale Blue Dot. His only novel, Contact, later became a sci-fi movie starring Jodie Foster and Matthew McConaughey. Here are a few things you might not know about the scientist, TV star, and amateur turtleneck model.

1. HARVARD PASSED ON HIRING HIM.

After Sagan served five years at the esteemed university as an assistant professor, Harvard denied him tenure in 1967, in part because one of his mentors at the University of Chicago derided his work as needlessly wordy and useless. He took a job at Cornell instead, where he stayed on as a professor until his death in 1996.

2. HE DICTATED ALL OF HIS WRITING TO AN AUDIO RECORDER.

Carl Sagan standing with a model of the Viking Lander.
JPL via Wikimedia Commons // Public Domain

Sagan was an avid self-editor. A total of 20 drafts of Sagan’s 1994 book Pale Blue Dot exist today in the Library of Congress, each filled with handwritten edits, annotations, and revisions by the author. However, he drafted all of his writing—even grant proposals—by dictating his ideas onto a cassette. The contents were then transcribed for him and returned for editing.

3. HE CONSIDERED WRITING A CHILDREN’S BOOK CALLED HOW DO BIRDS FLY?

In 1993, Sagan brainstormed a long list of possible children’s books for a series structured around the theme of “why?” Other potential ideas included Why Is It Warm In Summer?, Why Are There Lakes?, and What Is Air?

4. HE DIDN’T LIKE THE SPACE SHUTTLE PROGRAM.

Sagan argued against funding NASA’s Space Shuttle program in favor of more robotic exploration of the farther reaches of space. “That’s not space exploration,” he said in an interview about the space shuttle program’s week-long orbits. “Space exploration is going to other worlds.” A space station would only be worth it, he argued, if it was preparing humans for long-term journeys to space, he told Charlie Rose in 1995.

5. HE WAS AN EARLY CRUSADER AGAINST CLIMATE CHANGE.

Carl Sagan with the other founders of the Planetary Society in the 1970s.
JPL via Wikimedia Commons // Public Domain

Sagan’s 1960 Ph.D. thesis concerned the atmosphere of Venus. His theoretical model showed that the planet’s extremely high surface temperatures were due to the greenhouse effect of an atmosphere filled with carbon dioxide and water vapor. In his book Cosmos, he wrote, “The surface environment of Venus is a warning: something disastrous can happen to a planet rather like our own.”

6. HE HAS AN ARCHIVE IN THE LIBRARY OF CONGRESS ENDOWED BY THE CREATOR OF FAMILY GUY.

Part of the Carl Sagan Papers in the Library of Congress.
Paul Morigi/Getty Images

Family Guy creator Seth McFarlane put up an undisclosed sum to help the Library of Congress buy more than a thousand boxes of material kept by the late scientist and his wife and collaborator, Ann Druyan. The papers in The Seth MacFarlane Collection of Carl Sagan and Ann Druyan Archive, which opened in 2013, include some of Sagan’s earliest notebooks and report cards.

7. HE BECAME FAMOUS FOR A PHRASE HE NEVER SAID.

After Sagan appeared in several successful spots on the Tonight Show Starring Johnny Carson, Carson saw fit to send up the scientist’s signature style (turtleneck included) in a parody sketch.

Carson’s exaggerated use of “billions and billions” would later become associated with the astronomer, though he didn’t use it himself. However, Sagan did talk about large numbers quite a lot, as this supercut shows.

8. HE AND ANN DRUYAN DATED FOR ONE PHONE CALL—AND WERE ENGAGED BEFORE HANGING UP.

Sagan and Druyan, who would create the TV show Cosmos together, fell in love while working on the Voyager message. The courtship was exceedingly brief, as NPR's Radiolab describes:

“After searching endlessly for a piece of Chinese music to put on the record, Druyan had finally found a 2500-year-old song called ‘Flowing Stream.’ In her excitement, she called Sagan and left a message at his hotel. At that point, Druyan and Sagan had been professional acquaintances and friends, but nothing more. But an hour later, when Sagan called back, something happened. By the end of that call, Druyan and Sagan were engaged to be married."

9. HE WANTED TO LEGALIZE POT.

Under the pseudonym “Mr. X,” Sagan wrote a 1969 essay for Time magazine about the personal benefits he’d seen from cannabis use. Then in his mid-30s, he admitted to smoking throughout the prior decade. “I find that today a single joint is enough to get me high,” he wrote, going on to observe that marijuana had enhanced his appreciation for art and music. He concluded that “the illegality of cannabis is outrageous, an impediment to full utilization of a drug which helps produce the serenity and insight, sensitivity and fellowship so desperately needed in this increasingly mad and dangerous world.”

10. HE THOUGHT STAR TREK WAS TOO WHITE.

“In a global terrestrial society centuries in the future, the ship’s officers are embarrassingly Anglo-American. In fact, only two of 12 or 14 interstellar vessels are given non-English names, Kongo and Potemkin,” he wrote in a piece about the impact of science fiction on his life in The New York Times in 1978.

11. HE WANTED US TO LEAVE MARS ALONE.

Despite his passion for exploring space, Sagan argued for the preservation of Mars even if it meant limiting our exploration of the planet. In Cosmos, Sagan declared:

“If there is life on Mars, I believe we should do nothing with Mars. Mars then belongs to the Martians, even if the Martians are only microbes. The existence of an independent biology on a nearby planet is a treasure beyond assessing, and the preservation of that life must, I think, supersede any other possible use of Mars.”

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