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.