Of the six outer planets, Mars, commonly called the Red Planet, is the closest to Earth. M
ars, 4,200 miles in diameter and 55% of the size of the Earth, is 34,600,000 miles from the Earth, and 141,000,000 miles from the Sun. It takes this planet, along 0with its two moons, Phoboes and Deimos, 1.88 years to circle, the Sun, compared to 365 days from the Earth.
For many years, Mars had been thought of as the planet with the man made canals, supposedly discovered by an Italian astronomer, Schiaparelli, in 1877. With the United States spacecraft Viking I's landing on 'Mars in 1976, the man-made canal theory was proven to be only a myth.
Viking I, after landing on the soil of Mars, performed many scientific experiments and took numerous pictures. The pictures showed that the red color of the planet is due to the reddish, rocky Martian soil. No biological life was found, though it had been speculated by many scientists. The Viking al so monitored many weather changes including violent dust storms. Some water vapor, polar ice and permafrost were found, indicating that at one time there were significant quantities of water on this distant planet. Evidence collected by the spacecraft shows some present volcanic action, though the volcanoes are believed to be dormant, if not extinct.
Which of the following is true？
A．Mars is larger than the Earth.
B．Mars had Viking as its moon.
C．Martian soil is brownish rod.
D．It takes longer for Mars to circle the Sun than it takes the Earth.
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