Your vacation to the Rocky Mountains was a time you won't forget. You visited these mountains from a part of the country which is very flat. Seeing tall mountains for the first time was an adventure you truly want to experience again.

Thankfully, you had time to travel southward into Arizona. You thought seeing such tall mountains was cool and amazing - and then you arrived at the Grand Canyon. You quickly saw it was just as cool and amazing as the Rockies! You've now gone from being on mountains towering over two miles high to a canyon a mile deep.

You stay in Arizona that night. Once outdoors, you see more stars in the sky than ever before in your life. One "star" looked like it was glowing "red" and it easily caught your attention. You were told this reddish "star" is Mars. Your natural curiosity caused you to search for more information about this red planet. What you discovered finally caused you to realize that the mountains and canyon you visited are actually small in comparison to similar features found on Mars.

Mars is about one-half the Earth's size but has only one-eighth the volume. Can you figure out why? Some people might assume this statement means that any feature on Mars is also smaller than a similar feature on Earth. The opposite is actually true for Mars features.

There are many large mountains on Mars. They are typically volcanic and are all found in the same region on Mars rather than spread out around the planet as volcanoes are on Earth. These Martian volcanoes are so tall that even Mt. Everest seems short. Anyone who has climbed Mt. Everest's peak has reached an altitude of about 5.5 miles, but that distance is only about one-third of the distance to the peak of Mars' tallest volcano.

This volcano is named Olympus Mons. It is 15 miles high and 340 miles in diameter, which makes it the largest volcano in the entire solar system! Mt. Everest is not a volcano, so it may not be a fair comparison. Hawaii's Mauna Loa (a volcano) is "only" 6 miles high and 75 miles in diameter. Scientists estimate Olympus Mons could contain the volume of about 100 Mauna Loa volcanoes.

Another view is that Olympus Mons is so large that all islands of the Hawaiian Island chain would fit inside its diameter. Olympus Mons could even cover up the entire state of Arizona and its Grand Canyon. Other Martian volcanoes are also 10 to 100 times bigger in diameter than any on Earth. It is interesting to note that volcanoes on Mars were formed much like the Hawaiian volcanoes. These are shield volcanoes, which form almost exclusively from lava, which erupts and builds up the volcano.

Geologists believe volcanoes on Mars have become so large because Mars has less gravity and the volcanoes must have erupted constantly for a longer period of time. Also, Hawaiian volcanoes stop erupting after a period of time because they sit on the Earth's crust, which moves. This movement causes the volcanoes in Hawaii to move away from the magma, which form them. Imagine how large Mauna Loa could have become if it never moved from its magma source. We know this volcano (and the crustal plate on which it sits) has moved, because it does not constantly erupt now. Its last eruption was in 1984 and lasted 21 days.

Volcanoes are not the only feature on Mars much larger than similar features on Earth. Mars has a long canyon system scientists call Valles Marineris - or more commonly, Mariner Valley. It is 4.5 times deeper than our Grand Canyon. This "valley" is as long as the distance on Earth from New York to Los Angeles. The Grand Canyon is 277 miles long - the distance from New York to Washington, DC. Valles Marineris spans one-fifth the distance around Mars and is up to 600 Kilometers (375 miles) wide in some places, while the Grand Canyon averages 32 Kilometers (20 miles) across.

Most geologists still believe the Grand Canyon formed from long-time erosion by the Colorado River in its basin. A few scientists also accept a possibility that an earthquake could have split the crust in the area, which created a "crack" that has grown into the current Grand Canyon (with even more help from erosion by the Colorado River). Most of the Mariner Valley seems to have formed as a "crack" in the crust, which appeared as the planet cooled and the surface settled. Valles Marineris contains some smaller channels that appear to have been formed by water.

There is no doubt future Mars missions will help us better explain how these features formed on Mars. It is equally expected that these missions will discover even more new features, which will only add to the mystery of Mars. Exploring the Martian surface will allow us to understand why Mars can have so many record-breaking features without going through the same tectonic processes as on Earth.