6 Fascinating Facts About Mars

Mars Isn’t Really Red

“The red planet” is a slight misnomer. Martian rocks are filled with iron, and much like on Earth, if you leave iron outside in the elements it’ll eventually rust. The dust from these oxidized rocks gets kicked up into the atmosphere, creating the red hue stargazing humans see. But over the millennia, we’ve crept closer to our planetary neighbor for a better look — even dropping a few robotic rovers to do some poking around — and scientists have discovered that the surface of Mars is more yellowy-brown, sort of like butterscotch. In fact, Mars is a vibrant palette of gold, tan, brown, and even some green. NASA’s Curiosity rover also discovered in 2015 that if you dig only a few inches beneath the oxidized outer layer of the Martian surface, the soil is actually bluish-gray — not red at all.

Mars’ Moons Are Nothing Like Earth’s Moon

Ever since their discovery in 1877, the moons Phobos and Deimos — named after the Greek gods of fear and dread, respectively — have been something of a curiosity. Phobos orbits only 3,700 miles above Mars (compared to our moon’s 238,855 miles). Deimos, meanwhile, is relatively tiny at some 6.8 miles in diameter, making it one of the smallest moons in the solar system.

However, the biggest mystery about Mars’ moons is where they came from. One theory suggests that the two moons could have been formed from asteroids impacting the Martian surface, much like our moon. Alternatively, they could possibly be asteroids themselves, captured in orbit by Mars’ gravitational pull. Unfortunately, neither moon will be around forever. Phobos is slowly being pulled toward Mars and will eventually (in 50 million years or so) break apart, either forming a ring around Mars or impacting the surface. Deimos, on the other hand, is slowly escaping Mars’ gravitational clutches and will one day be flung into space.

Mars Also Has Four Seasons

Seasons might seem like a feature exclusive to planet Earth, but Mars also experiences four distinct seasons. Because the Martian year is twice as long as Earth’s, its seasons are also double in length — stretching from 142 days in autumn to nearly 200 days in spring in its Northern Hemisphere. (Days on Mars are 24 hours, 39 minutes, 35.244 seconds.)

Mars’ ice caps grow during its winter period and recede, almost disappearing entirely, when spring turns to summer. Summer on Mars can be tumultuous: Because the Red Planet is closest to the sun when the Southern Hemisphere is tilted toward it, Martian summers in the Southern Hemisphere are much hotter than summers in the Northern Hemisphere, and this temperature difference creates strong storms. Martian summers are also far from hospitable, as lows reach -284 degrees Fahrenheit. However, summer highs can reach a balmy 68 degrees if you’re willing to brave those chilly nights.

Mars Has Liquid Water

Earth is a water planet — 71% of its surface is covered with the stuff. Mars, on the other hand, has more in common with the Mojave Desert, but that doesn’t mean it isn’t sporting some H2O of its own.

Scientists have known for a while that water flowed on Mars in its distant past, but until recently, many believed that any water on the planet was currently locked up in its frozen ice caps or in Martian rocks. But in 2018, the European Space Agency’s Mars Express mission used ground-penetrating radar to explore Mars’ southern ice cap, and scientists were astounded to find that liquid water flowed a mile beneath the surface of a subglacial lake. Although temperatures there are far below water’s typical freezing point, salt deposits keep the water in liquid form. These pools beneath the icy surface are similar to Lake Vostok in Antarctica, and their discovery opens up an exciting new area for exploration.

Mars’ Soil Is Poisonous

With a nearly nonexistent atmosphere, freezing temperatures, and scarce water, Mars isn’t a place you want to stay if you’re a living, breathing organism. Even microbes can’t survive on the surface, because Mars’ soil is poisonous.

For more than 20 years, Mars rovers have analyzed soil samples in different parts of the planet and have found a ubiquitous compound known as perchlorate, a substance toxic to humans. Usually, microbes love perchlorates, but Mars’ particular conditions — especially its high abundance of UV light — turn the perchlorates into a toxic cocktail. In 2017, scientists recreated Martian conditions in a lab and found that UV rays broke down perchlorates into hypochlorite and chlorite, a mixture that’s fatal to bacteria. Within 30 seconds, all microbes exposed to this Martian soil facsimile were sterilized.

Mars Is the Only Planet Entirely Inhabited by Robots

Scientists haven’t found life on Mars (yet), but that doesn’t mean Mars is a boring place. On July 4, 1997, NASA’s Pathfinder rover landed on the red planet, and in the quarter-decade since, NASA has sent four more rovers — Spirit, Opportunity, Curiosity, and its latest robotic addition, Perseverance (2020-2021) — to follow in its footsteps (or in this case, treads). The European Space Agency also hopes to send its rover, the Rosalind Franklin, to Mars by 2028. In addition to these rovers, Mars is also populated by robotic landers such as NASA’s InSight, several orbiters from space agencies around the world, and even a pint-sized robot helicopter. Mars might be void of life, but until humans put boots on Martian soil, the planet will continue to be a playground for one thing: robots.