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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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Space
8 Useful Facts About Uranus
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Uranus as seen by the human eye (left) and with colored filters (right).
NASA/JPL

The first planet to be discovered by telescope, Uranus is the nearest of the two "ice giants" in the solar system. Because we've not visited in over 30 years, much of the planet and its inner workings remain unknown. What scientists do know, however, suggests a mind-blowing world of diamond rain and mysterious moons. Here is what you need to know about Uranus.

1. ITS MOONS ARE NAMED AFTER CHARACTERS FROM LITERATURE.

Uranus is the seventh planet from the Sun, the fourth largest by size, and ranks seventh by density. (Saturn wins as least-dense.) It has 27 known moons, each named for characters from the works of William Shakespeare and Alexander Pope. It is about 1784 million miles from the Sun (we're 93 million miles away from the Sun, or 1 astronomical unit), and is four times wider than Earth. Planning a trip? Bring a jacket, as the effective temperature of its upper atmosphere is -357°F. One Uranian year last 84 Earth years, which seems pretty long, until you consider one Uranian day, which lasts 42 Earth years. Why?

2. IT ROTATES UNIQUELY.

Most planets, as they orbit the Sun, rotate upright, spinning like tops—some faster, some slower, but top-spinning all the same. Not Uranus! As it circles the Sun, its motion is more like a ball rolling along its orbit. This means that for each hemisphere of the planet to go from day to night, you need to complete half an orbit: 42 Earth years. (Note that this is not the length of a complete rotation, which takes about 17.25 hours.) While nobody knows for sure what caused this 98-degree tilt, the prevailing hypothesis involves a major planetary collision early in its history. And unlike Earth (but like Venus!), it rotates east to west.

3. SO ABOUT THAT NAME …

You might have noticed that every non-Earth planet in the solar system is named for a Roman deity. (Earth didn't make the cut because when it was named, nobody knew it was a planet. It was just … everything.) There is an exception to the Roman-god rule: Uranus. Moving outward from Earth, Mars is (sometimes) the son of Jupiter, and Jupiter is the son of Saturn. So who is Saturn's father? Good question! In Greek mythology, it is Ouranos, who has no precise equivalent in Roman mythology (Caelus is close), though his name was on occasion Latinized by poets as—you guessed it!—Uranus. So to keep things nice and tidy, Uranus it was when finally naming this newly discovered world. Little did astronomers realize how greatly they would disrupt science classrooms evermore.

Incidentally, it is not pronounced "your anus," but rather, "urine us" … which is hardly an improvement.

4. IT IS ONE OF ONLY TWO ICE GIANTS.

Uranus and Neptune comprise the solar system's ice giants. (Other classes of planets include the terrestrial planets, the gas giants, and the dwarf planets.) Ice giants are not giant chunks of ice in space. Rather, the name refers to their formation in the interstellar medium. Hydrogen and helium, which only exist as gases in interstellar space, formed planets like Jupiter and Saturn. Silicates and irons, meanwhile, formed places like Earth. In the interstellar medium, molecules like water, methane, and ammonia comprise an in-between state, able to exist as gases or ices depending on the local conditions. When those molecules were found by Voyager to have an extensive presence in Uranus and Neptune, scientists called them "ice giants."

5. IT'S A HOT MYSTERY.

Planets form hot. A small planet can cool off and radiate away heat over the age of the solar system. A large planet cannot. It hasn't cooled enough entirely on the inside after formation, and thus radiates heat. Jupiter, Saturn, and Neptune all give off significantly more heat than they receive from the Sun. Puzzlingly, Uranus is different.

"Uranus is the only giant planet that is not giving off significantly more heat than it is receiving from the Sun, and we don't know why that is," says Mark Hofstadter, a planetary scientist at NASA's Jet Propulsion Laboratory. He tells Mental Floss that Uranus and Neptune are thought to be similar in terms of where and how they formed.

So why is Uranus the only planet not giving off heat? "The big question is whether that heat is trapped on the inside, and so the interior is much hotter than we expect, right now," Hofstadter says. "Or did something happen in its history that let all the internal heat get released much more quickly than expected?"

The planet's extreme tilt might be related. If it were caused by an impact event, it is possible that the collision overturned the innards of the planet and helped it cool more rapidly. "The bottom line," says Hofstadter, "is that we don't know."

6. IT RAINS DIAMONDS BIGGER THAN GRIZZLY BEARS.

Although it's really cold in the Uranian upper atmosphere, it gets really hot, really fast as you reach deeper. Couple that with the tremendous pressure in the Uranian interior, and you get the conditions for literal diamond rain. And not just little rain diamondlets, either, but diamonds that are millions of carats each—bigger than your average grizzly bear. Note also that this heat means the ice giants contain relatively little ice. Surrounding a rocky core is what is thought to be a massive ocean—though one unlike you might find on Earth. Down there, the heat and pressure keep the ocean in an "in between" state that is highly reactive and ionic.

7. IT HAS A BAKER'S DOZEN OF BABY RINGS.

Unlike Saturn's preening hoops, the 13 rings of Uranus are dark and foreboding, likely comprised of ice and radiation-processed organic material. The rings are made more of chunks than of dust, and are probably very young indeed: something on the order of 600 million years old. (For comparison, the oldest known dinosaurs roamed the Earth 240 million years ago.)

8. WE'VE BEEN THERE BEFORE AND WILL BE BACK.

The only spacecraft to ever visit Uranus was NASA's Voyager 2 in 1986, which discovered 10 new moons and two new rings during its single pass from 50,000 miles up. Because of the sheer weirdness and wonder of the planet, scientists have been itching to return ever since. Some questions can only be answered with a new spacecraft mission. Key among them: What is the composition of the planet? What are the interactions of the solar wind with the magnetic field? (That's important for understanding various processes such as the heating of the upper atmosphere and the planet's energy deposition.) What are the geological details of its satellites, and the structure of the rings?

The Voyager spacecraft gave scientists a peek at the two ice giants, and now it's time to study them up close and in depth. Hofstadter compares the need for an ice-giants mission to what happened after the Voyagers visited Jupiter and Saturn. NASA launched Galileo to Jupiter in 1989 and Cassini to Saturn in 1997. (Cassini was recently sent on a suicide mission into Saturn.) Those missions arrived at their respective systems and proved transformative to the field of planetary science.

"Just as we had to get a closer look at Europa and Enceladus to realize that there are potentially habitable oceans there, the Uranus and Neptune systems can have similar things," says Hofstadter. "We'd like to go there and see them up close. We need to go into the system." 

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Astronomers Discover Another Earth-Like Planet Near Our Solar System
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ESO / M. Kornmesser

Astronomers with the European Southern Observatory (ESO) have discovered an exoplanet orbiting a star just 11 light-years from our own Sun. It's roughly the size of Earth and is predicted to have a temperate climate, making it the second-nearest Earth-like planet known to exist.

As reported in the journal Astronomy & Astrophysics [PDF], the planet, dubbed Ross 128 b, circles the inactive red dwarf star Ross 128. Its orbit is 20 times closer to its star than Earth's is to the Sun, but the exoplanet receives only 1.38 times more radiation than we do. Ross 128 is much cooler than our Sun, and calmer than typical red dwarfs. Researchers estimate the planet's equilibrium temperature to be between -76°F and 68°F, making it temperate like our home planet.

The discovery was made by an international team of astronomers working with the ESO's High Accuracy Radial Velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile. Popular Mechanics reports that instead of waiting for the exoplanet's shadow to pass across its star (what's known as the transit method), the scientists monitored the star's radial velocity. The gravitational pull of orbiting planets can cause their stars to wobble slightly, and by measuring these disturbances, researchers can estimate everything from a planet's mass to its location.

At just 11 light-years away, Ross 128 b is close, though not close enough to make it our nearest Earth-like neighbor. That title belongs to Proxima b, a planet similar in size, mass, and temperature to Earth that orbits the star Proxima Centauri. But Ross 128 is creeping closer to Earth, and in just 79,000 years, it could occupy the No. 1 slot. In the meantime, scientists will study Ross 128 b along with other close exoplanets to determine if they can support life.

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