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Poking up through the dust clouds:

The Mountains of Mars

Mars Olympus Mons mountain photo by Viking1
Mars Olympus Mons photographed by Viking 1
click to enlarge 260k NASA image
What's the advantage of having a probe orbiting another planet? The orbiter can map the entire surface of the planet, repeatedly, to look for seasonal and long-term changes in features.

For instance, a global dust storm was sweeping the Red Planet as the first Mars orbiter from Earth, Mariner 9, arrived in 1971. The spacecraft had to wait three months to send back to Earth pictures of some important discoveries.

What were they? Poking through the top of the slowly settling cloud of dust were the tops of four immense volcanic mountains. The largest of these so-called "shield volcanoes" was named Olympus Mons (Mount Olympus).

Olympus Mons dwarfs the largest such feature on Earth, which is the largest of the Hawaiian Islands.

Shield volcanoes. On both Earth and Mars, shield volcanoes have been produced by out-pourings of fluid molten rock. Over a long time, that builds slowly into a huge mountain. There are no shield volcanoes on the Moon.

Olympus Mons is over 310 miles (500 kilometers) across at the base and stands 15 miles (24 kilometers) above a smooth plain. By contrast, the largest of the Hawaiian Islands is 75 miles (120 kilometers) across and 5.6 miles (9 kilometers) above the ocean floor.

Why the difference? The plate motion of Earth's surface produces a string of volcanoes along the ocean floor, while lack of plate motion on Mars piles up the volcanic material in one place, producing one immense volcano.

Four huge shield volcanoes have been seen on Mars, plus many smaller ones like those on the Earth. Most of Mars' major volcanic structures are in two regions where the crust has swelled upward. These crustal uplifts also are found on Earth, but not on the Moon.

Learn more:
Human Exploration of Mars:
There have been three stages of exploration so far
Sand dunes: Dust Storms: Air: Carbon Dioxide: Outflow Channels: Valley Networks: Rift Valley: Ice: Ice caps: Frost: Water: Artesian Water: Mars Weather: Mars Photo Galleries: Planet features: Canals: Rocks: Mountains: Dating and aging: Seasons:
Exploring Mars
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Mars Orbiter 2005
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Rover Spirit 2003
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Express 2003
Odyssey 2001
Polar Lander 1999
Climate Orbiter 1998
Deep Space 2 1999
Global Surveyor 1996
Pathfinder Lander 1996
Rover Sojourner 1996
Pathfinder Mission 1996
Viking-1 Lander 1975
Viking-2 Orbiter 1975
Viking-1 Lander 1975
Viking-1 Orbiter 1975
Mariner 9 Orbiter 1971
Mars 3 Lander 1971
Mariner 4 Flyby 1964
Viking Mission 1975
Mars Meteorites - JPL
2003 & Beyond - Goddard
2005 & Beyond - JPL
Mars Exploration - JPL
Plans to Explore Planets

Solar System - JPL
Welcome to the Planets - JPL
Planetary Photojournal - JPL
Mars - Athena - NASA Ames
Solar System Tour - BBC
Mars - New York Times
Windows...Universe - UMich
Mars - Apollo Society
Planetary Society
Mars Society
The Nine Planets
Planet Mars Company
Solar System - STO
Solar System Tour
Artist conception of Mars with water four billion years ago
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