1. Mars is actually pretty small.
You might think that Mars is a near-twin of Earth, but it has a diameter of about half the Earth, measuring only 6,800 km across. With the smaller size comes an even smaller mass. The total mass of Mars is only about 10% the mass of Earth. The surface gravity is only 37% what you would experience on Earth. In other words, you would be able to jump 3 times as high on Mars as you can on Earth.
2. People used to think it had water and canals
Before the first spacecraft arrived at Mars in 1965, nobody had ever seen Mars up close. Dark blotches on the surface of the Red Planet were interpreted as lakes or oceans, and some people even thought they could seen dark lines crisscrossing the surface of the planet. They imagined these might be the irrigation canals of a dying civilization. It turned out these were just an optical illusion, and Mars is a dry dusty desert.
3. But Mars really does have water
Mars might not have oceans, rivers and lakes, but NASA’s Mars Odyssey spacecraft detected huge deposits of water underneath the surface, across the planet – in the form of ice. The Phoenix mission has arrived on Mars to search for ice underneath the soil at the northern polar cap. It has all the tools on board to analyze the water ice to see if has any traces current or ancient life.
4. Mars has the tallest mountain in the Solar System
The tallest mountain in the Solar System is the mighty Olympus Mons on Mars. It rises up 27 kilometers above the surrounding plains. Olympus Mons is a shield volcano, like Hawaii’s Mauna Kea, and formed gradually over billions of years. Some lava flows on the volcano are so young that planetary scientists think that it might still be active.
5. And Mars has the longest, deepest canyon in the Solar System
One of the most distinct features on the surface of Mars is the Valles Marineris canyon. It stretches 4,000 km along the equator of Mars, and can be as deep as 7 km in places. If you could move the Valles Marineris to Earth, it would stretch right across the United States.
6. We have pieces of Mars on Earth
Both Earth and Mars have been slammed by large asteroids in the past. Although most of the debris kicked up by the impact falls back down on to the planet, some of it can be ejected so quickly that it escapes Mars entirely. These ejected meteorites can orbit the Solar System for millions of years before they finally crash down on other worlds. Some have crashed on Earth, and been identified by scientists. Tiny amounts of Mars’ atmosphere were trapped in the meteorites, and this is how scientists were able to study the Martian atmosphere before sending the first spacecraft.
7. One of Mars’ moons is going to crash into it
Mars has two, tiny asteroid-sized moons called Phobos and Deimos. Phobos orbits the planet at such a low altitude that it’s going to eventually be torn apart by the gravity of Mars. It will survive as a ring for a few years, and then the debris will rain down on Mars. Scientists disagree on when this will happen. It could happen as soon as 10 million years from now, and no later than 50 million years.
8. Mars has almost no atmosphere
If you tried to stand out on the surface of Mars without a spacesuit, you would die almost immediately. The freezing cold temperatures would be a problem, but even worse is the thin atmosphere. The air pressure at the surface of Mars is only 1% the pressure we enjoy here on Earth. And the atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon and trace amounts of water and oxygen.
9. Mars is crawling and buzzing with spacecraft
At the time of this writing, there are three spacecraft down on the surface of Mars, NASA’s Spirit and Opportunity rovers, as well as the Phoenix Mars lander. And there are three orbiters watching from orbit: NASA’s Mars Reconnaissance Orbiter, Mars Odyssey and ESA’s Mars Express. No other planet in the Solar System has ever been so well studied.
10. And more spacecraft are on their way to Mars
Every two years, Mars and Earth line up so that missions can be sent with a minimum amount of fuel. NASA has plans to send one of their most ambitious missions to date: the Mars Science Laboratory. This will be an SUV-sized laboratory that can crawl across the surface of Mars for months and months, searching for past and current evidence of life.