Mars, the red planet: Facts and information
Once upon a time, though, wind and water flowed across the red planet. Robotic rovers have found clear evidence that billions of years ago, lakes and rivers of liquid water coursed across the red planet’s surface. This means that at some point in the distant past, Mars’s atmosphere was sufficiently dense and retained enough heat for water to remain liquid on the red planet’s surface. Not so today: Though water ice abounds under the Martian surface and in its polar ice caps, there are no large bodies of liquid water on the surface there today.
Mars also lacks an active plate tectonic system, the geologic engine that drives our active Earth and is also missing a planetary magnetic field. The absence of this protective barrier makes it easier for the sun’s high-energy particles to strip away the red planet’s atmosphere, which may help explain why Mars’s atmosphere is now so thin. But in the ancient past—up until about 4.12 to 4.14 billion years ago—Mars seems to have had an inner dynamo powering a planet-wide magnetic field. What shut down the Martian dynamo? Scientists are still trying to figure out.
High highs and low lows
Like Earth and Venus, Mars has mountains, valleys, and volcanoes, but the red planet’s are by far the biggest and most dramatic. Olympus Mons, the solar system’s largest volcano, towers some 16 miles above the Martian surface, making it three times taller than Everest. But the base of Olympus Mons is so wide—some 374 miles across—that the volcano’s average slope is only slightly steeper than a wheelchair ramp. The peak is so massive, it curves with the surface of Mars. If you stood at the outer edge of Olympus Mons, its summit would lie beyond the horizon.
Mars has not only the highest highs but also some of the solar system’s lowest lows. Southeast of Olympus Mons lies Valles Marineris, the red planet’s iconic canyon system. The gorges span about 2,500 miles and cut up to 4.3 miles into the red planet’s surface. The network of chasms is four times deeper—and five times longer—than Earth’s Grand Canyon, and at its widest, it’s a staggering 200 miles across. The valleys get their name from Mariner 9, which became the first spacecraft to orbit another planet when it arrived at Mars in 1971.
And the exploration continues …
