Flybys are difficult. A spaceship travels hundreds of millions of miles through the dark void of space, pinpoints a distant planet or moon, and flies past it at 20 to 30 thousand mph, snapping pictures furiously during an achingly brief encounter.
Going into orbit is more difficult. Instead of flying past its target, the approaching spaceship brakes, changing its velocity by just the right amount to circle the planet. One wrong move and the spacecraft bounces off the atmosphere, becoming an unintended meteor.
Landing is ridiculously difficult. Just play NASA's "Seven Minutes of Terror" video. Watching Curiosity parachute, retrorocket, and sky-crane its way to the surface of Mars rarely fails to produce goosebumps. Since the Space Age began, the space agencies of Earth have succeeded in landing on only six bodies: Venus, Mars, the Moon, Titan, and asteroids 433 Eros and Itokawa.
A new ScienceCast video previews the first-ever landing on a comet. Play it
More - Link >>> http://science.nasa.gov/science-news/science-at-nasa/2014/03nov_rosettalanding/
Source: NASA Science News.
2014: 75th Year of Pittsburgh's Buhl Planetarium
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