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 LCROSS - Lunar CRater Observation and Sensing Spacecraft
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Lunar CRater Observation and Sensing Satellite (LCROSS)

lunar surfaceThe Moon is the brightest object in the night sky and the most easily noticed. Like all major heavenly bodies, the Moon played a significant part in ancient mythology. Most ancient religions had a Moon god or goddess. The ancient Greeks had many Moon goddesses, the most notable being Selene and Artemis. In Roman mythology, which is based on the Greek's, Artemis became Diana. The other Roman Moon goddess was named Luna—this is why many modern words associated with the Moon have "Luna" as their root.

In more recent history, the Moon has been significant as well. Using his telescope, Galileo was able to look at the Moon and see that it was not a perfect sphere as previously believed, but instead had mountains and other imperfections, much like the Earth. In the late 1800s the Moon became the subject of science fiction. Most notable are Jules Verne's "Moon Ship" and "Round the Moon." Although trips to the Moon were once considered science fiction, in the 1960s, the Apollo program accomplished just that. In July 1969, Michael Collins, Neil Armstrong, and Buzz Aldrin rocketed to the Moon aboard Apollo 11. On July 20, 1969, Neil Armstrong and Buzz Aldrin were the first humans to set foot upon the surface of another world.

Click here for a lunar exploration timeline.

Apollo 17 Astronauts explore the Moon

The Moon is not a very hospitable place for humans. There is no atmosphere to speak of, making it a very hostile environment. The lack of atmospheric pressure means that without protection, a person's blood would boil instantly on the Moon. The surface gravity is 0.17 Earth's, making normal walking nearly impossible. Anyone who has seen footage of Apollo astronauts is familiar with the way they had to take small hops to get around. Compared to the environment on Mars, which has more gravity and a denser atmosphere, the Moon is a very harsh world.

The Moon is much closer to Earth than any other body in the solar system. The average distance to the Moon is only 347,467 km from the Earth. Compared to Mars, with a closest distance of 55,746,199 km, it is clear to see that the Moon is much easier to reach. The Apollo astronauts took only a few short days to make the trip to the Moon. By comparison, just getting to Mars could take more than six months. According to Franco Ogaro of the European Space Agency’s Aurora project, "If space is an ocean, then the Moon is our nearest island."

(To compare Earth, Mars, and the Moon, you can use What’s the Difference from NASA Quest. What’s the Difference is an interactive software program that allows for side-by-side comparisons. For more information and to download the software, visit Go to the Download section and download the Solar System Explorer version.)

A point of interest on the Moon is the possibility of water ice at its poles. In December 1996, the Clementine probe flew by the Moon and reported possible evidence of water ice at the bottom of a crater at the South Pole. In March 1998, the Lunar Prospector probe reported possible evidence of water in craters at both poles. The ice is most likely fragments from comets and other space debris that collided with the Moon and scattered icy material across the Moon, including into these polar craters where there is no sunlight to vaporize it. Although the probes gave hints that water might be present, the only way to know for sure is to actually go to one of these permanently shadowed polar pockmarks and look. This is where LCROSS comes in!

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Editor: Brian Day
NASA Official: Daniel Andrews
Last Updated: August 2010