Frontiers of Science:
Valles Marineris:
The Grand Canyons of Mars

By Dr. Sherwood B. Idso

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    Imagine yourself on a trip to Mars. You have been traveling for several months and the red planet now looms before you. Peering out of your spaceship through the pane of glass that protects you from the cold vacuum of space, a fantastic drama unfolds before your eyes as the great sphere rotates on its axis and new features of its surface emerge from the dark of night into the light of day.

    To the north or top of the disc, with bright clouds trailing from its summit, stands Ascreaus Mons, one of the giant Martian volcanos. To the south or bottom of the disc, with a thin layer of gray white frost glimmering in the morning sun, lies the great Argyre meteor crater. Suddenly, however, your attention is drawn to a third feature midway between the two, a giant scar upon the land that stands out in stark relief against the red terrain. Rubbing your eyes in disbelief, you look again. Yes, it’s still there—and growing bigger! As it moves into the full light of day, you see that it is a giant system of canyons that stretches more than a quarter of the way around the globe. Then you remember. It is the Valles Marineris, the Grand Canyons of Mars.

    Named in honor of the Mariner spacecraft that first brought them to our attention, the Valles Marineris or Mariner valleys are perhaps the most magnificent such features in the entire solar system. But how can their greatness be truly comprehended? There is only one comparison that can even come close; and that, of course, is the Grand Canyon of Earth.

    Running from the head of Marble Gorge near the northern boundary of Arizona to Grand Wash Cliffs near the Nevada state line, the “awesome abyss,” as Earth’s Grand Canyon has often been called, extends for 217 miles and ranges in width from 4 to 18 miles. The world’s most complex system of canyons, gorges, and ravines, it was created over a long period of time by the Colorado River. As the surrounding land slowly rose over 5,000 feet in elevation, the river resolutely cut its way deeper and deeper between its ever-widening banks. First sighted by the Coronado expedition of 1540, it was formally recognized as being discovered by two other Spanish explorers in 1776. Today it is a center of worldwide fame, to which travelers flock by the millions.

    Consider, then, the fame that must surely come to the Valles Marineris. Long enough to span the entire United States, this great system of canyons and gorges is as much as 400 miles wide in places, plunging to depths of over 20,000 feet. Standing at the top of one of its rims and gazing toward the other, a visitor from Earth could not even see a hint of its end. It would truly seem like the “edge of the world.”

    Besides the great difference in size between the Grand Canyons of Earth and Mars, there are also differences in the processes by which they are thought to have been created. Earth’s Grand Canyon appears to have been formed by the cutting action of river water, but the Martian system is believed to have been formed by great stresses in the surface crust of the planet that caused the ground to literally split apart in these places. Such valleys are called rift valleys, and the most notable such feature here on Earth is the Great Rift Valley of Africa. Scientists believe that the cause of the great stresses on Mars that tore the land apart may have been a tremendous upward bulge at the western end of the valleys, where the huge Martian volcanos are located.

    Because the great rift system of Mars is so long, it is warmed by the sun at one end while it is still dark at the other. Thus, large temperature differences are set up each day along the floors of the valleys, and these temperature differences are thought by some scientists to create violent winds that roar back and forth through the canyons. If these blasts are as strong as suspected, they have undoubtedly had a large influence in shaping the steep canyon walls.

    Think again, now, about your imaginary spaceflight. If you were really on a trip to Mars, what would you take along to help you remember the journey? A camera? Right! And that is just what scientists do whenever they send a spacecraft to another planet. Their snapshots are one of the ways that we are expanding our knowledge of the great variety of God’s creations. In the Valles Marineris we have one more example of His magnificent handiwork.

    The impressive view from Viking II orbiter as it approached the dawn side of Mars in early August 1976. (NASA photo.)

    The Grand Canyon of Earth. Although it is one of the wonders of the world, it is only the size of one of the smaller side canyons of the great Valles Marineris of Mars. (Arizona Office of Tourism photo.)

    A view of the East Central Troughs of the Valles Marineris taken by Viking I orbiter on October 1, 1976. The area photographed (1,120 x 1,250 miles) is a little more than twice the size of Alaska. The great valley at the bottom of the picture is known as the Coprates Chasma. (NASA photo.)

    A full view of the Valles Marineris, stretching over a distance that would span the entire United States from coast to coast. (NASA photo.)