The Top 10 Science Stories of 2017

Mohamed El-Shahed, AFP/Getty Images
Mohamed El-Shahed, AFP/Getty Images

Scientific breakthroughs of 2017 truly spanned a gamut, manifesting themselves in nearly every discipline—cosmology, biology, and anthropology, to name a few. They ranged from astonishing revelations about Jupiter's famous rings to discovering a new continent on our own planet. Human cellular and embryonic sciences were in the limelight: Researchers fixed a disease-causing gene in human embryos in one experiment and grew human cells in pig embryos in another. Here on Earth, scientists achieved the first ever teleportation (of a particle). Far away, cosmic forces forged an enormous amount of gold, literally of galactic proportions—200 times the mass of our planet. Here are the top 10 most notable science stories of 2017.

1. WE FOUND SEVEN EARTH-LIKE PLANETS ORBITING A DIM STAR.

TRAPPIST-1 planetary system
NASA, Getty Images

We found not one but seven Earth-like planets, out of which three could potentially host life. Orbiting around a cool, dim star 39 light-years from us in the Trappist-1 system, these planets were detected through their eclipses—a brief dimming in their star's brightness when a planet passes in front of it. Although Trappist-1 looks more like Jupiter and its Galilean moons than our own solar system, its seven Earth-sized planets may have "terrestrial" conditions. Three of the planets are located in the habitable zone with their surface temperatures allowing for water oceans and an Earth-like atmosphere to form.

So far, most planet-hunting efforts were focused on brighter stars and bigger planets. Trappist-1 is the first planetary system found to revolve around a smaller, dimmer star—and its discovery holds the potential to uncover many more exoplanets.

2. WE CUT A DISEASE-CAUSING MUTATION FROM HUMAN GENES.

Scientists have successfully used a gene-editing technique, CRISPR-Cas9, to clip out a mutated gene in human embryos, replacing it with a healthy copy. Called MYBPC3, the defective gene causes hypertrophic cardiomyopathy, a heart condition that can lead to sudden death in young people. While this was a stunning medical success, the CRISPR-Cas9 technique remains controversial among doctors, ethicists, and sociologists, who are concerned that attempts to build a better human could lead to dismal medical and social outcomes. When the study was published, an international committee of genetics experts issued a statement advising against editing any embryo intended for implantation into future mothers.

A different group of scientists managed to convert CRISPR into a fast, sensitive, and cheap diagnostic instrument for a range of diseases. Called SHERLOCK (for Specific High Sensitivity Enzymatic Reporter UnLOCKing), this method turns CRISPR into a tool that can sniff out specific genetic information, such as abnormal RNA. Surprisingly inexpensive, SHERLOCK can cost less than a buck per sample, and can hunt down the RNA of disease agents like dengue fever or Zika virus, and even search for mutations that can cause cancer.

3. THE LARSEN C ICE SHELF BROKE, BECOMING ONE OF THE LARGEST ICEBERGS EVER.

Larsen C ice shelf
ESA, Getty Images

A giant piece of ice the size of Delaware broke off the Larsen ice shelf on the Antarctic Peninsula, and is now adrift in the Weddell Sea. Weighting a trillion tons, it's one of the largest icebergs ever recorded.

Over the last few decades, the Larsen ice shelf went through major changes. The sections called Larsen A and B collapsed in 1995 and 2002. More recently, a rift along the Larsen C section was detected, and it grew slowly over two years—until it was hanging by a thread, and then finally split off.

The scientists say that while climate change is responsible for melting sea ice around the world, this particular fracture may have been inevitable. Ice shelves naturally break up as they extend further out into the ocean. Neither will the massive iceberg cause a sea level rise as it melts—the same way ice cubes melting in your gin and tonic do not increase the volume of water in that glass.

4. WE ACHIEVED TELEPORTATION (OF PHOTONS, AT LEAST).

Purely the stuff of science fiction until now, teleportation became possible this year. Although not yet able to teleport an entire human, Chinese scientists said they managed to teleport a photon particle from the ground to a satellite 870 miles away.

How does it work? Teleportation is transmitting the state of a thing rather than the thing itself. It's not unlike a fax machine, which sends information as various marks on a paper sheet rather than the sheet itself.

If you combine this idea with the concept of quantum entanglement, in which two particles are created at the same time and place, so they effectively have the same existence, you can shoot one of the particles far away, but they will remain entangled—meaning if one changes, its remote twin will change too. So it's not a Star Trek–type of teleportation, where you can transfer objects or people from one place to another, but more like having a doppelganger tethered to you far away.

Instead of sending marks on a paper sheet to a receiving-end fax machine, the Chinese scientists transmitted a bunch of photons. The team created 4000 pairs of quantum-entangled photons and fired one photon from each pair in a beam of light towards a satellite that can detect the quantum states of these single photons sent from the ground.

So why all the excitement if we still can't teleport people? For one thing, quantum teleportation offers possibilities of creating un-hackable communications networks. Any attempts to eavesdrop on a quantum system or intercept the info being sent would cause detectable disturbances.

5. WE DISCOVERED A WHOLE NEW CONTINENT.

You'd think Earth was completely mapped out by now, but this year, an international team of scientists discovered an entirely new continent down under. Called Zealandia, this eighth continent broke off Australia millions of years ago, containing New Zealand and New Caledonia, an island further up north. More than 90 percent of Zealandia is underwater, which is why it managed to evade geographers for so long.

The team drilled cores 4000 feet underwater and gathered more than 8000 rock and sediment samples and several hundred fossils. They discovered microscopic remains of organisms that lived in warm, shallow seas as well as spores and pollen from terrestrial plants, revealing that in the past parts of Zealandia used to be above sea level.

Besides their historical importance, these findings will help us understand the planet's future prospects. The fossilized records of Zealandia's past will provide more insight into the movement of Earth's tectonic plates and the global climate system, and contribute to the computer models used to predict future climate flukes.

6. WE FOUND A MYSTERIOUS VOID IN THE GREAT PYRAMID OF GIZA.

Using a new type of tomography that employs subatomic particles called muons, scientists generated 3D images of the ancient Egyptian pyramids, including the Great Pyramid of Giza, the biggest in Egypt. The images, generated as part of the ScanPyramids project, an international endeavor launched in 2015, revealed a surprising void, suggesting an inner structure.

Despite being studied for more than a century, the Great Pyramid of Giza, built more than 4500 years ago as a burial place of pharaoh Khufu (a.k.a. Cheops), is still full of mysteries waiting to be discovered. Muons, which are byproducts of cosmic rays, pass through stones better than x-rays or other similar technology do, so they work very well for peeking inside the inaccessible ancient structures. According to the images, the void is at least 100 feet long and bears a structural resemblance to the section directly below it—the pyramid's Grand Gallery, a long area that feels like a "very big cathedral at the center of the monument," as engineer and ScanPyramids co-founder Mehdi Tayoubi described it. The discovery marks the first time a new inner structure has been located in the pyramid since the 19th century.

7. WE GREW HUMAN CELLS IN PIGS.

baby piglet
iStock

Researchers from the Salk Institute successfully managed to grow human cells inside pig embryos. The goal was to better understand how to develop functional and transplantable tissue or organs.

The project actually consisted of two parts. During the first part, researchers created a cross between a rat and a mouse by implanting rat cells into mouse embryos. During the second part, the team used the same technique with human cells and non-human animal hosts—such as cows or pigs, since their organs are closer in size to our own. The second feat was harder to achieve since people and pigs are further apart from each other than mice and rats are, and pig embryos develop faster than human ones.

While the experiment was successful, the technology remains very controversial, as many experts fear it could potentially lead to human-animal chimeras.

8. WE WERE WRONG ABOUT JUPITER AND SENT CASSINI ON A SUICIDE MISSION TO SATURN.

The Juno mission aimed at exploring Jupiter, which reached the target in 2016, proved that much of what we thought we knew about this planet is wrong. Turns out Jupiter's famous bands do not continue to the north and south poles. Instead, the poles are characterized by chaotic swirls and ovular features, which are Texas-sized ammonia cyclones. Ammonia, which emanates from Jupiter's great depths, plays a role in the planet's atmosphere and weather, but its levels vary greatly between different areas. Scientists still don't know whether Jupiter has a core, but they know that the pressure inside the gas giant is so strong that hydrogen, which normally is a gas, has been squeezed into a metallic fluid. The other mystery Juno may help shed some light on is Jupiter's magnetosphere, which generates spectacular auroras that are different in nature from Earth's Northern Lights.

In September, scientists deliberately sacrificed the Cassini spacecraft, which ran out of fuel after decades-long exploration of our other cosmic neighbor, Saturn. Launched in 1997 and reaching its target seven years later, Cassini tremendously expanded our knowledge about Saturn, its satellites, and our entire solar system. Thanks to Cassini, we assessed the composition of Saturn's rings and discovered that it has six moons. More interestingly, it expanded our assumptions about the habitable planets' range. We learned that a moon named Titan holds methane lakes, which could harbor a different form of life, and may have subsurface water oceans, possibly with hydrothermal vents akin to those in the Earth's undersea crusts. Now that Cassini's mission is over, all eyes are on Juno.

9. WE WATCHED TWO NEURON STARS COLLIDE AND SPEW ENOUGH GOLD TO MAKE 200 EARTHS.

Astronomers watched a never-before-witnessed cosmic phenomenon: two dead stars merging into one. It was a head-on collision of two neutron stars, which are superdense remains of previously exploded stars.

As the two stars smashed into each other in a distant galaxy 130 million light-years from Earth, they emitted gravitational waves which began traveling outward like ripples on a pond. When the waves began their cosmic journey 130 million years ago, Earth was still ruled by dinosaurs, and the complex equipment necessary to observe this phenomenon didn't exist. However, the existence of such waves was predicted by Einstein, so by the time they reached Earth, the scientists were ready with their detectors—two in the United States and one in Italy.

Moments after the detectors noticed the waves, advanced space telescopes registered a high-energy light burst. Hours later, astronomers spotted a bright new point up in the sky, emitting infrared and ultraviolet light, followed by x-rays and radio waves days later. These observations informed scientists about a "kilonova" hypothesis, which postulates that neutron star collisions generate and spew out heavy elements like gold, silver, platinum, and uranium. The blast is believed to have created some 200 Earth-masses of gold, scientists say.

10. WE DISCOVERED HUMANS ARE 100,000 YEARS OLDER THAN WE THOUGHT.

facial reconstruction of 300,000-year-old skull found in Morocco
Gunz et al. in Nature, 2017

Until this year, modern humans were thought to have originated between 150,000 and 200,000 years ago, according to the oldest-known fossils of Homo sapiens found in Ethiopia. But recently unearthed remains of five early H. sapiens were dated at 300,000 years old, making our species 100,000 years older than we thought.

The new fossils were found in Morocco, on the other side of the African continent and further north than Ethiopia. Researchers now think that our ancestors may not have originated in any one specific spot in Africa, but rather evolved across the entire continent.

Before the Sahara became a desert, it sprouted forests and plains, making it possible for early humans to travel across the continent. The early hominids were likely following and hunting herds of gazelles or other animals, evolving new cognitive skills along the way, which enabled them to create more complex tools and develop advanced social behaviors. So as they spread across Africa, these early humans acquired the very traits that later came to define our species.

11 Science-Backed Tips for Winning an Argument

iStock
iStock

For many people, arguing is something to avoid. But arguments can be used for good—they can inform, sharpen thinking, and challenge old ideas in important ways. The expert tips below will help you argue more incisively, which, in turn, will probably make you more likely to win the discussion. (Of course, winning means different things to different people—so not all of these concepts are about making someone else think you’re right.)

1. DETERMINE THE NATURE OF THE ARGUMENT.

According to Mark Porrovecchio, a professor of rhetoric and a debate coach at Oregon State University, understanding the nature of a disagreement will help you determine how best to handle it. “Argument styles vary according to context [and] genre,” he tells Mental Floss. “What might work when arguing with a significant other could backfire when debating with a colleague. The goal is to be mindful of the type of situation you are in … and to be willing to adjust your approach based on a host of situational factors.”

You should adjust your tone—and even the content of your argument—depending on the person with whom you are having it and the place it’s happening. The conversation in a private setting may be a different from one in a public space. This particular tactic, Porrovecchio says, is as old as debate itself: Both the Sophists and Aristotle used it.

2. KNOW YOUR OPPONENT'S PERSONALITY TYPE …

Sometimes you won’t know what your opponent values or what their background is—but sometimes, you will. Use that information.

Most people are either reactive or analytical, says Prince Ghuman, a professor at Hult International Business School and coauthor of the book Allure: the Neuroscience of Consumerism. “Some people tend to be more reactive, so you can convince them using techniques that appeal to them—emotion and empathy," he tells Mental Floss. "Others seem to be more deliberate—you’ll need to provide an analytical support for your argument."

3. … AND MORAL IDENTITY.

In political and ideological arguments, different sides often have fundamentally different ways of looking at the world. According to the moral foundations theory, a framework proposed by a group of social psychologists, most people see society through six different binaries: care/harm, fairness/cheating, loyalty/betrayal, authority/subversion, sanctity/degradation, and liberty/oppression. A politically liberal person, for example, might be more affected by an argument that stresses compassion and fairness, whereas conservatives might find loyalty and authority to be more important. Each person will have a unique idea of which concept in each pair carries more weight, and in an argument, knowing what the other side values can help frame your talking points.

“One reason it’s so hard to reach across the ideological divide is that people tend to present their arguments in a way that appeals to the ethics of their own side, rather than that of their opponents,” journalist Olga Khazan explained in an Atlantic video. Framing your argument to appeal to your opponents' moral code rather than your own can help you win.

4. USE EMOTION—BUT DON'T REST YOUR ENTIRE ARGUMENT ON IT.

Not only is arguing sans emotion almost impossible if you're a human being, it’s also not a great way to succeed. “Every argument, even many seemingly factual arguments, contains an emotional element,” Porrovecchio says.

According to psychologist Sherrie Campbell, author of Success Equations: A Path to Living an Emotionally Wealthy Life, you should include feelings when you make your case, but don’t go too far with an emotional point—especially in professional settings. When it comes to personal disagreements, uncomfortable feelings can sometimes be necessary, and while kindness is important, so is honesty.

“Sometimes emotional arguments that bring about sadness can help people get to the core of where the hurt and frustration is," Campbell says. "As long as the person you're arguing with has empathy and can put caring over being right, then emotional arguments can be effective.”

Ideally, you should try to keep it balanced. “An argument that relies solely on emotion should be treated with suspicion,” Porrovecchio says. Feelings without information or details to back them up fall flat if the other person can’t relate.

5. MAKE YOUR CASE WITH EMPATHY.

“Connect to the listener by conveying your story through one person’s example. Personify, rather than generalize,” Ghuman suggests. He cites research [PDF] by psychologists at the University of Oregon that shows people will donate more money to an individual in need than a group of people. That’s because most of us can empathize with one person but find it harder to relate to groups in the same way. When arguing, use this tactic to your advantage by finding (or imagining) a specific person who might be helped by what you are arguing for.

For instance, if you are arguing that Peggy shouldn’t be fined for parking her car in a tow zone because she was trying to rescue a dog in the street, it would make more sense to describe who she is specifically. Rather than call her “Peggy, a dog owner,” describing her as “Peggy, who has adopted a mutt, a pitbull, and an elderly chihuahua,” would render her more sympathetic. Empathetic details shouldn't be used as replacements for factual information, though; they should be additions to the facts.

6. USE STORYTELLING.

Storytelling works hand-in-hand with empathy and puts data to support your argument in context. Pull all your information together—using empathy, facts, and emotions—to create a compelling story, and your argument will be tougher to beat. When your point seems part of a narrative arc, each aspect of what you're arguing is harder to pick on.

Need a template? Porovecchio recommends the TED format. “I think TED Talks have gained popular cachet because they often manage to balance a degree of detail and fact with a personable, narrative-driven delivery style,” he says.

7. INFLUENCE YOUR ADVERSARY WITH PHYSICAL CUES.

People unconsciously mimic others in social situations, a behavior that psychologists believe is associated with emotional connection. Consciously imitating the posture and movement of your opponent is also a well-known way to bring someone over to your side. Try leaning back if your opponent does so, or cross your arms or legs the way they do. Looking them in the eye when you are listening to them speak is another to reduce their confidence in their own argument—and you’ll look stronger, too. You can even lower your voice a notch to sound more dominant, according to this study.

8. REMAIN CALM.

Whether you are using or responding to an analytic or emotional argument, keep it as relaxed as possible. “The best thing to do when in an argument is to stay calm and talk slowly—you can't yell and talk slowly at the same time,” Campbell says. “Forcing yourself to talk slowly helps to keep the emotions under control and your thoughts rational.” If that sounds like a challenge, it is: “This takes a lot of discipline, but it's a simple thing to focus on.”

9. PRACTICE YOUR DELIVERY.

Like most other skills, spending time arguing will make you better at it. Debate in high school, college, or in a professional-development context “should be viewed as a way to practice the skills of arguing,” Porrovecchio says. “You work to improve your technique, your content, your delivery; then use what you have learned in real world situations.” Porrovecchio says he’s seen his students become not just better debaters over time, but also “better public speakers and critical thinkers.”

10. REFRAME THE DEBATE.

Not all arguments have to be about being right, which some people define as winning. You might consider it a win if your opinion is valued and considered by the person you are disagreeing with—even if you don't change their mind. “Instead of the word argument, replace it with conversation. If you're just having a conversation, then winning is off the table, and a productive discussion can occur,” Campbell says.

11. IF ALL ELSE FAILS, WALK AWAY.

Sometimes it gets ugly, or the argument seems to be going in circles. If you’re not getting anywhere in a discussion, “ask your opponent directly: ‘Is there anything I can do to change your mind?’ If they say that nothing will change their mind, believe them, and walk away,” Ghuman says. Sometimes an argument is a draw—and that’s OK. You’ve won if you’ve learned something, Ghuman adds: “Healthy argument can expand your perspective and open your mind.”

10 Riveting Facts About Mars

Mars's dust storms can be global. In these images taken a month apart in 2001, the dust storm near the southern polar ice cap (left) soon enveloped the entire planet (right).
Mars's dust storms can be global. In these images taken a month apart in 2001, the dust storm near the southern polar ice cap (left) soon enveloped the entire planet (right).
NASA/JPL-CALTECH/MSSS

Few celestial objects have fascinated humankind throughout history more than the Red Planet. For over a century, we've longed to know more about Mars and the beings that we speculated lived there. When NASA dispelled the notion of creatures scurrying along the rusty plains, it raised a more tantalizing prospect: that we might one day be the creatures that call Mars home.

Mental Floss spoke to Kirby Runyon, a researcher at the Johns Hopkins University Applied Physics Laboratory, and Tanya Harrison, the director of research for Arizona State University's NewSpace Initiative, to learn more about the place your kids might live one day.

1. A MARTIAN YEAR LASTS JUST UNDER TWO EARTH YEARS.

It takes 687 Earth days for the Red Planet make its way around the Sun. A Mars day—called a sol—lasts 24.6 hours, which would be a nuisance for the circadian rhythms of astronauts (but not as bad as a day on Venus, which lasts 5832 hours).

2. IT'S NOT AS HOT AS IT MIGHT LOOK.

Mars looks desert-hot—New Mexico with hazy skies, red because of its iron oxide soil—but is actually very cold, with a blistering hot sol being 70°F, and a cold sol a brisk -225°F. Its dust storms can be huge; in 2018, one storm grew so large that it encompassed the entire planet for more than a month. (You can see a similarly huge dust storm in the image above.)

3. MARS IS MUCH SMALLER THAN EARTH ...

Compared to Earth, Mars is a tiny Styrofoam ball, with a diameter just over half of ours and one-tenth of our mass. Its gravity will be an absolute nightmare for future colonists, at .38 that of their native planet. (That means a person weighing 100 pounds here would weigh just 38 pounds on Mars.)

4. ... AND ITS ATMOSPHERE IS MOSTLY CARBON DIOXIDE.

You won't want to get a breath of fresh air on Mars unless you're trying to suffocate: Its atmosphere is 95.32 percent carbon dioxide, with a little nitrogen and argon thrown in. (Earth's atmosphere, by contrast, is mostly nitrogen and oxygen.) When you do try to take that single, hopeless breath, the tears on your eyeballs, saliva in your mouth, and water in your lungs will immediately evaporate. You won't die right away, but you'll probably want to.

5. IT HAS TWO MOONS, BOTH WITH BETTER NAMES THAN OURS.

They're called Phobos and Deimos, which translate to Fear and Dread, respectively. They're shaped like potatoes and don't exactly fill the evening sky: Standing on the Martian surface, Phobos would appear to be about one-third the size of Earth's moon; Deimos would look like a bright star.

Future human Martians will have to enjoy Phobos while they can. The tidal forces of Mars are tearing Phobos apart; in 50 million years, the big potato will disintegrate.

In the meantime, Phobos is one of the stepping stones NASA plans to take on its journey to Mars. No part of human exploration of the Red Planet is easy, and before we land on Mars (and then have to figure out how to launch back into space and somehow get back to Earth), it's vastly easier to land on Phobos, do a little reconnaissance, and then take off and return home. As a bonus, on the journey to Phobos [PDF], astronauts can bring along hardware necessary for eventual Martian settlement, making the ride a lot easier for the next astronauts.

6. MARS IS HOME TO THE TALLEST MOUNTAIN IN THE SOLAR SYSTEM.

The tallest mountain on Earth, Mount Everest, is 29,029 feet tall. Olympus Mons on Mars is over 72,000 feet in height, making it the tallest mountain by far on any planet in the solar system.

Olympus Mons isn't the only extraordinary Mars feature: Mountaineers might also want to check out NASA's trail map for hiking the famous Face on Mars. If canyons are more your speed, you'll want to visit Valles Marineris. It is the size of North America and, at its bottom, four miles deep. (In the solar system, only Earth's Atlantic Ocean is deeper.) Once Earth's ice caps finish melting, you can always visit the ones on Mars. (If you have a telescope, you can easily see them; they are the planet's most distinctive features visible from your backyard.)

7. THE IDEA OF MARTIANS GOES BACK OVER A CENTURY.

That's partially because of popular fiction (War of the Worlds, the 1897 novel by H.G. Wells, sees a Martian invasion force invade England) and partially because of Percival Lowell, the famed astronomer who wrote prolifically on the canals he thought he was observing through his telescope, and why they might be necessary for the survival of the Martian people. (Mars was drying up.)

Though it's easy to dismiss such conclusions today, at the time Lowell not only popularized space science like few others, but left behind the Lowell Observatory in Flagstaff, Arizona—one of the oldest observatories in America and the place where Clyde Tombaugh discovered Pluto.

8. IF THERE ARE MARTIANS, THEY ARE MICROBES.

Today, scientists work tirelessly to unlock the complex geologic history of Mars, to determine whether life exists there today, or did long ago. "We think that Mars was most globally conducive to life around 3.5 to 3.8 billion years ago," Runyon tells Mental Floss. "In the Mars geologic history, that's the end of the Noachian and toward the beginning of the Hesperian epochs." There may once have been a hemispheric ocean on Mars. Later, the world might have alternated between being wet and dry, with an ocean giving way to massive crater lakes. Where there's water, there's a good chance of life.

"If we found life on Mars—either extinct or current—that's really interesting," says Runyon, "but more interesting than that, is whether this life arose independently on Mars, separate from Earth." It is conceivable that meteorite impacts on Earth blasted life-bearing rocks into space and eventually to the Martian surface: "A second life emergence on Mars is not just a geological question. It's a biogeochemical question. We know that Mars is habitable, but we haven't answered the question of whether it had, or has, life."

9. NASA SPENDS A LOT OF TIME OUT THERE.

Mars hasn't hurt for missions in recent years, though scientists now warn of an exploration desert beyond 2020. But that doesn't mean we humans don't have eyes on the planet. Presently in orbit around the planet are the Mars Reconnaissance Orbiter, which images and scans the planet; MAVEN, which studies its atmosphere; Mars Express, the European Space Agency's first Mars mission; MOM, the first Mars mission by the Indian Space Research Organization; the ESA's ExoMars Trace Gas Orbiter, which is searching for methane in the Martian atmosphere; and Odyssey, which studies Mars for water and ice signatures, and acts as a communications relay for vehicles on the ground.

Rolling around on the Martian surface are Curiosity and Opportunity—NASA missions both—which study Martian geology. Though the Russians and Europeans have tried mightily to do so, NASA is the only space agency to successfully land spacecraft on the Martian surface (seven times).

In November 2018, the InSight mission will land on Mars, where it will study the planet's interior. In 2020, NASA will land the Mars 2020 rover; where Curiosity studies Mars for signs of habitability, Mars 2020 will look for inhabitants.

"It is going to collect samples that will hopefully be brought back to Earth," says Runyon. "The three landing sites selected for Mars 2020 are Northeast Syrtis, Jezero Crater, and Columbia Hills within Gusev Crater, which is where the dead rover Spirit is currently sitting. Each of these sites is a hydrothermal environment dating from the Noachian-Hesperian boundary. These are some of the most perfect places to look for past signs of Martian life, and can help answer the question of whether life had a second genesis on Mars."

10. MARS IS CHANGING, BUT NOBODY KNOWS WHY.

"Most people don't realize how active Mars is," Harrison tells Mental Floss. "Other planets aren't just these dead worlds that are frozen in time outside of our own. There are actually things happening there right now." Imagery from the HiRISE and Context Camera instruments on the Mars Reconnaissance Orbiter have revealed such events as avalanches, sand dune erosion [PDF], and recurring slope lineae (flowing Martian saltwater).

Things are moving, but it's not always clear why. "There's a lot of material that has been eroded away," says Harrison. "We have entire provinces of the planet that look like they've been completely buried and then exhumed. And that's a lot of material. The big question is, where did it all go? And what process eroded it all away?" Curiosity might help answer the question, but to really understand the processes and history of the fourth rock from the Sun, we're going to need to send geologists in spacesuits. "You can't replace human intuition with a rover," Harrison says. "Looking at a picture on your computer is not the same as standing there and looking around at the context, stratigraphic columns, being able to pick up the rocks and manipulate them, take a hammer to things. So once humans land on the surface, it'll be kind of like the difference between what we knew about Mars from Viking and Mars Global Surveyor and then the revolution between Mars Global Surveyor and Mars Reconnaissance Orbiter. Our view of what we think happened on Mars is going to completely change, and we'll find out that a lot of what we thought we knew was wrong."

A version of this story ran in 2017.

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