Mars was named for the Roman god of war.
Ares is what the ancient Greeks called the god Mars. He always went into battle with his sons Phobos (panic) and Deimos (terror). When American astronomer Asaph Hall discovered the two small Martian moons in 1877, he named them after the sons of Ares.

Mars is red.
For a god of war, a planet the color of blood sounds just right. But Mars isn't bloody, it's rusty. The color comes from iron oxide, the chemical name for rust.

Mars is over one and a half times further away from the Sun than the Earth is.
The Martian year is long. It takes 687 Earth days to orbit the Sun. But a day on Mars is only 41 minutes longer than a day on Earth – a Martian day is called a sol.

Mars has a thin atmosphere that's mostly carbon dioxide.
The air at the top of Mount Everest is about 200 times thicker than it is on Mars. If there were oxygen in the Martian atmosphere, instead of carbon dioxide, it would still be too thin for us to breathe.

Mars doesn't have liquid water on the surface.
There isn't enough air pressure from the thin atmosphere for bodies of water to exist on the planet's surface. Long ago Mars had a thicker atmosphere, and the planet flowed with water. There is still lots of water frozen on Mars. If the southern polar icecap melted, there could be enough water to cover the whole planet with 11 meters (36 feet) of water.

Mars is much smaller than the Earth.
It has only half Earth's diameter, and the pull of gravity is just 38% of what we're used to. So a person weighing 100 lbs (46 kg) on Earth would weigh 38 lbs (17 kg) on Mars.

The highest volcano in the Solar System is on Mars.
Olympus Mons is 27 km (17 miles) high, which is more than three times the height of Mount Everest. People used to think Olympus Mons was also the highest mountain in the Solar System. But in 2011 NASA's Dawn mission arrived at the asteroid Vesta for a 14-month visit. It discovered Vesta's mountain Rheasilvia which is slightly higher than Olympus Mons.

The largest known canyon in the Solar System is on Mars.
Valles Marineris is about 4000 km (2500 miles) long. It's deeper than the Grand Canyon and over three times as long.

There are enormous dust storms on Mars.
The storms can be local and last a few days, but others cover the whole planet for months. The Martian Rovers Spirit and Opportunity survived a major storm in 2007. A few years later Spirit broke down, but Opportunity explored until 2018 when the mission was ended by the biggest dust storm ever seen on Mars.

There were never any canals on Mars.
In the 19th century Italian astronomer Giovanni Schiaparelli thought he saw long channels (canali in Italian) on Mars. The word sounded like the English “canals”, which are always man-made. A prominent American, Percival Lowell, was enchanted by the idea of a great Martian civilization of canal builders. He built Lowell Observatory in Arizona to observe them. As telescopes got better, it was obvious to other astronomers that the canals were an illusion. However, Clyde Tombaugh did discover Pluto at Lowell Observatory. We lost a Martian civilization, but we gained an interesting dwarf planet.

We haven't found any life on Mars yet.
Many people still hope to find life on Mars, even though ultraviolet radiation from the Sun would be fatal to living things on the planet's surface. Earth is protected from dangerous radiation by a thick atmosphere and a magnetic field, but Mars isn't. Future missions are being designed dig deeply into the soil to take samples. If there is still bacterial life – or evidence of past bacterial life – we'll be most likely to find it underground.

The “stone face” in Cydonia is a natural rock formation.
In 1976 the Viking orbiter took a low-resolution picture of the Cydonia area of Mars that included something that looked like a giant face. This was a trick of the light and shadows. You can see a more recent high-resolution picture of the same rock formation, along with the original Viking photograph.