Mars' striking red color and prominent features have fascinated sky-watchers for centuries, and as telescope resolutions increased in the 19th century, our fascination with the planet grew. Since then, we’ve learned a lot more about this blood-red planet, so here are five facts you might not know.
5Mars Is Earth-Like in Many Ways
Despite only being around half the diameter of Earth, Mars is probably the most Earth-like of all the planets in the Solar System. In fact, Mars and Earth were likely formed from the same materials when the Solar System came to be over 4.5 billion years ago.
Like Earth, Mars has a discernible rocky crust, mantle, and core, though their properties differ. What’s more, many of the features on the Martian surface—such as mountains, volcanoes, and canyons—look similar to what we have here on Earth. It also has polar ice caps that grow and shrink with the seasons, and there is evidence of Martian water channels similar to Earth’s.
Martian days (also known as sols) are currently 39 minutes and 35 seconds longer than Earth days. I say “currently” because Mars' rotation is very gradually speeding up (by about three-quarters of a millisecond each year), and Earth’s rotation is very gradually slowing down (by about 1.8 milliseconds per century).
4Mars Has the Highest Mountain in the Solar System
All four rocky planets have standalone mountains, mountain ranges, or a combination of both, and they all have signs of past volcanic activity. Scientists believe Mercury’s volcanoes stopped erupting 3.5 billion years ago, while a 2024 analysis of data obtained during the Magellan mission during the late 1980s and early 1990s found that two volcanoes erupted on Venus around 1991.
Where Mars wins, however, is in the sheer size of its largest mountain and volcano, Olympus Mons. Although it hasn’t been active for millions of years, it stands proud as the tallest known volcano in the Solar System. Standing at around 14 miles high, it’s about two-and-a-half to three times the elevation of Mount Everest. It’s also about 400 miles across, a distance that would take you six to seven hours to travel at a speed of 60mph!
3It Can Take Months for Dust From Storms to Settle
The images above, taken by NASA’s Curiosity rover, show just how murky Mars really gets during a storm. The image on the right was captured only three days after the image on the left, which shows how quickly visibility can drop in Mars' thin atmosphere.
This murkiness is caused by strong winds whipping up the red dust from the rocks rich in iron oxides. Sometimes, the storms are strong enough to affect the whole planet, visibly changing how it appears from Earth through a telescope. This dust can sometimes take months to settle, re-sculpturing Mars' landscape in the process.
When NASA sent the Opportunity rover on its Martian mission, they thought that thick layers of dust would quickly descend on the craft, covering up its solar panels and limiting its operational length to 90 Martian days. However, experts didn’t realize that thestrong gusts from the powerful storms would clear the debris from the panels, contributing significantly to Opportunity’s extended 15-year life.
2Mars Has Two Moons
Mars' two moons, Phobos and Deimos, were discovered in 1877 by American astronomer Asaph Hall.
Phobos and Deimos are among the smallest moons in the solar system. Phobos is about 14 miles across, while Deimos has a diameter of just 7.7 miles. They may be made ofcarbon-rich rock mixed with ice, and scientists believe they are asteroids captured by Mars' gravity.
Phobos orbits only 3,700 miles above the planet’s surface, the closest lunar orbit of all known moons in the Solar System. For comparison, the average distance between the Earth and our moon is around 239,000 miles. What’s more, Phobos is getting 1.8 meters closer to Mars every century, meaning that, within 50 million years, it will either crash into the planet or break up to form a Martian ring.
1Mars Has Water (Lots of It)
Mars' aquatic history has been known to humankind since 1971, when Mariner 9 returned the first images of the planet’s dry rivers. However, we only discovered water still exists on Mars only quite recently, and this raises exciting questions about whether there is, after all, life on Mars.
In August 2024, data from NASA’s InSight Mars Lander revealed the presence of a reservoir of liquid water deep underneath the Martian surface. This followed many other discoveries of liquid and ice water since the turn of the millennium.
In 2008, NASA’s Phoenix lander found water ice in the Martian soil. Seven years later, in 2015, NASA discovered hydrated salts on Mars' surface, suggesting the possibility of the presence of trickling or flowing liquid water. In 2020, researchers from Roma Tre University in Italy discovered saltwater lakes under Mars' southern-pole ice, and NASA released new images of the planet’s winter frost at the end of 2022.
Billions of years ago, as Mars lost the residual heat from its formation, its magnetic field grew weaker, and solar winds and storms stripped away most of its atmosphere. Consequently, much of Mars' water evaporated into space. However, some water (literally) got through the cracks, forming what scientists believe to be large reservoirs of liquid water.
The presence of water on Mars is crucial if the dream of inhabiting the planet remains alive. As well as using the water for consumption, we can also split it into its components to form hydrogen and—importantly—oxygen.
However, the water is believed to be six to 12 miles beneath the Martian crust. This means that, at their deepest points, Mars' subterranean oceans could be up to five miles deeper than we’ve ever dug below Earth’s surface and up to five miles deeper than the Mariana Trench (the deepest part of Earth’s oceans). Ironically, six miles is quite far to drill when you don’t have cooling water to stop the drill from overheating!
Mars has been central to the debate aboutwhether space tourism is realistic in our lifetime. Maybe one day, tourists will be able to walk on the red planet’s surface, though this is still only speculation—it could be many, many decades before visits to Mars become a regular occurrence.
