Mars is one of the most studied planets in the Solar System. We’ve learned a lot about it from telescopic observations and experiments that date back thousands of years.
In 1659, Dutch scientist Christiaan Huygens made the first crude map of Mars. He discovered that it rotated about once every 24 hours, and he also measured its atmosphere’s thinness.
1. It has a thin atmosphere
Mars has a thin atmosphere that exerts less than one percent of the Earth’s atmospheric pressure at the surface. The air is mostly carbon dioxide, with small fractions of nitrogen and argon. This is because the planet’s gravity isn’t strong enough to keep atmospheric gases from escaping into space.
The air on Earth is a bit thicker because the gravity there is stronger and we have more oxygen than Mars does. But the atmosphere on both of these planets is gradually being leaked out into space.
Unlike Earth, however, the Martian atmosphere is going through the loss of its air much faster. This is because the planet’s light gravity has left it vulnerable to the constant flow of particles coming from the sun, known as the solar wind. Over millions of years, this pressure stripped the lighter molecules from Mars’s atmosphere, thinning it considerably.
In order to understand the thin atmosphere of Mars, scientists have to look at the planet’s past. During the early years of Mars’ history, it had a very dense atmosphere.
Scientists are not exactly sure why the atmosphere was so thick early in its history. They think that water could have accumulated in the upper layers of the atmosphere. This would have formed a layer of water ice only about 10 micrometres (0.0004 inch) thick. Then, it may have been vaporized or percolated into the crust over time.
It may also have been ejected from the atmosphere into space during an impact. This change in the planet’s atmosphere could have radically altered the water cycles and climate on Mars.
This is why Mars’s climate and water systems are more complicated than Earth’s. Currently, the amount of water on Mars is very low and it exists mainly in icy dirt and in thin clouds on the planet’s surface.
Another reason for the thin air on Mars is because it has no ozone layer like ours. Our ozone layer protects us from harmful ultraviolet radiation that is radiated by the sun and astronomical sources. The lack of this protective layer means that ultraviolet radiation reaches the planet’s surface unhindered and can damage organic compounds.
2. It has a volcano
Mars, the second smallest planet in the Solar System, has an extensive history of volcanic activity. The most famous is Olympus Mons, which may be the largest volcano in the solar system.
Volcanoes are formed by the movement of lithospheric plates across a stationary mantle plume that emits heat and creates lava. This is the same process that formed Hawaii on Earth, where the Pacific Plate moved over a stationary hotspot, causing volcanoes to form on top of the plume.
This kind of volcanic activity doesn’t occur on the surface of Mars, because the crust doesn’t move. It instead sits on top of the mantle, and so if there was an eruption on the surface, it would be concentrated in a single point.
The most spectacular volcanic features are the giant shield volcanoes of Tharsis, located along the crest of the planet’s massive uplifted region called the Tharsis bulge. These enormous basaltic mountain-like volcanoes dwarf the Mauna Loa shield volcano on Earth.
These huge shield volcanoes are also the source of the Martian’s biggest impact craters, which are found in the slopes of Tharsis. These craters aren’t old enough to be evidence of ancient lava flows, but they are so large that they can tower above the seasonal dust storms on Mars.
But, the volcanoes in Tharsis aren’t the only ones on Mars that are still active today. Other major volcanic centers on the planet include Elysium Planitia, Syrtis Major, and a cluster of low-profile volcanoes near the Hellas impact basin.
Until recently, it was believed that the volcanoes on Mars had stopped erupting. But new findings from a team of scientists suggests that the red planet may still be experiencing some type of volcanism.
Researchers have analyzed data from multiple probes that spent decades analyzing the Red Planet. The results suggest that a mantle plume could be responsible for the unusual amount of seismic and volcanic activity detected on Mars.
This is the first time a single plume has been shown to have caused this unusual seismic activity. The plume could be a remnant of the mantle hotspot that once emitted heat and created giant volcanoes on Mars.
3. It has a ring system
A ring system has been proposed to explain how the Red Planet has two moons. It was first proposed by Purdue University professor David Minton and graduate student Andrew Hesselbrock in 2017.
For billions of years, Mars may have had a cycle of rings that formed and then shattered into new, smaller moons. Then those moons — and the resulting debris — spiraled back onto Mars, forming rings again. Then the cycle was repeated and each time the debris was pulled apart, it reformed into another moon.
The moons clumped together again over millions of years and then formed rings again. This cycle lasted several dynasties.
What’s more, the researchers suggest that some of that reformed material still exists on Mars today. It could form piles of rocks and dust on the surface, similar to what you find on Earth in the case of asteroid or comet impacts.
It’s also possible that some of the materials on the planet’s surface are from past planetary moon explosions. That’s because Martian tides could have swept up these reformed materials, too.
Cuk’s team has analyzed the movements of one of Mars’ moons, Phobos, which is slowly spiraling inward toward the planet. It’s getting so close to Mars that tidal forces will eventually tear it apart.
In about 50 million years, Phobos will reach a point where the gravity of Mars is strong enough to pull it into pieces. It will probably break into rubble pile-like pieces that will spread out in orbit around Mars.
This could happen to a large chunk of a moon called Deimos, too. It’s not quite at the point where Mars’ tidal forces will pull it in, but it might drift further and further away from the planet as its mass gets less massive over time.
Then it’s likely that the tidal forces of Mars will tear it up into pieces once again, this time creating a ring system. Once again, this would be a big change for the Red Planet.
The ring system around Mars would block sunlight, which could be a problem for space flights and human settlements on the surface of the planet. So it’s not a good idea to try to make your way to the planet, especially in a future where the rings have formed.
4. It has water
Mars is a rocky planet with a thin atmosphere that can’t support liquid water. Although there are signs that ancient floods once covered the surface, today most of the red planet’s water is found in icy dirt or thin clouds, or on the surfaces of some hillsides.
Researchers have long wondered what happened to the water that once covered Mars’s surface. Several flybys, orbiters, and rovers have confirmed the planet had water once, but that water escaped into space rather than staying on its surface.
But now, a new study published in Science suggests the Martian water might have been trapped for billions of years within the planet’s crust, locked up in special rocks known as hydrous minerals. It could explain how Mars has been dry for so long – and also help scientists understand the planet’s past habitability.
A team led by Caltech and JPL scientists say that up to 99% of the water on Mars is still there – not in liquid form, but locked up in mineral deposits deep in the planet’s crust. This is contrary to the current theory that water escaped into space and that only 30% or so remains on the surface.
The team looked at 20 meteorites, ranging in age from 200 million years old to 4 billion years old. In each meteorite, they measured the ratio of two isotopes of a chemical element – potassium-39 and potassium-41 – that change when subjected to varying levels of gravity. In lower-gravity environments, such as Mars, water is easier to lose to space, leaving a greater ratio of the heavier isotope.
This is why many meteorites contain water, but they have very little of it on their surfaces. But the team’s new research indicates that, during the early days of the planet’s formation, water was probably very abundant on Mars’s surface, but then escaped into space.
“Mars’s geological history shows that water once flowed on the planet and flooded canyons and river beds, making it an ideal habitat for life,” said Caltech PhD candidate Eva Scheller (MS ’20). In fact, the first evidence of water on the planet dates back more than 4020 km (2500 mi) to the Valles Marineris canyon system.