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The Young Craters: The Moon's composition is rocky and it has a scarred surface from meteorite impact. Some craters are 240 km/150 mi across. The young craters are surrounded by bright rays of ejected rock.
Not until the historic journey of Mariner 4, which came within 9,660 km (6,000 mi) of Mars on July 14, 1965, and took 21 photographs, did the true nature of the planet's surface become evident. It was found that the surface of Mars is covered with craters and that about the same number of craters appear in these pictures as appear in an equal area of the moon. However, the lunar craters seem better preserved than those on Mars. Windblown dust is probably an important element in shaping the surface features of the red planet, because Mars is known to have extensive storms in its atmosphere.
The Plowshare engineers have long been studying the feasibility of using nuclear explosives near the surface of the ground to create a string of open craters that could form a cut through mountains or a canal across an isthmus. A new Panama Canal is one of the most imaginative of these proposals. Small-scale cratering experiments at the AEC's Nevada test site have shown that 99% of the radiation in these blasts can be confined safely to the bottom of the craters, without ever entering the atmosphere. (See Year in Review: ENGINEERING, Nuclear Engineering, Nuclear Explosives for Peaceful Uses.)
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