HANKSVILLE, Utah (AP) — The Mars Society chose the American Southwest for its training facility because the soil and lack of vegetation resemble the landscape of the red planet, but that's where the similarities end.

Most of the simulations in Utah require participants to imagine the conditions of Mars, suspending the reality around them. A look at some of the main differences between Mars and the Earth:

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DANGEROUS RADIATION

Astronauts venturing into deep space on their way to Mars would face radiation from high-energy galactic cosmic rays spewed by distant supernova explosions and sporadic bursts of charged particles hurled by the sun. Earth's magnetic field helps to deflect much of that radiation. Astronauts would be bombarded with as much radiation as getting a full-body CT scan about once a week for a year, according to researchers who reviewed data from a radiation sensor aboard a rover during the journey to Mars. In some cases, that dose would exceed NASA's standards and be enough to raise an astronaut's cancer risk by 3 percent.

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NO RUNNING WATER

There is no liquid water on the current surface of Mars, though scientists believe that the planet had running water long ago. That belief comes from the fact that Mars has river beds and canyons that were probably formed by water. Mars does have frozen water on its polar cap, which is a mixture of carbon dioxide ice and water ice.

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NO OXYGEN

On earth, 21 percent of the atmosphere is oxygen and less than 1 percent carbon dioxide. But on Mars, 96 percent of the atmosphere is carbon dioxide and less than 1 percent is oxygen. That means astronauts must wear spacesuits at all times.

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FREEZING TEMPERATURE

The Earth has some cold places, but they pale in comparison to freezing Mars. The average temperature on Mars is minus 81 degrees, with lows reaching minus 284. Earth's average temperature is 57 degrees, with the coldest temperature ever on record being minus 126.

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GRAVITY

Mars has 63 percent less gravity. A person who weighs 100 pounds on earth would weigh only 38 pounds on Mars.