The moon has no atmosphere to hold in moisture. However, that doesn't mean there isn't water there to harvest. By all accounts, the moon is a dry and desolate place, void of color and life. In 2009, though, a sensitive spectrometer on the Indian probe Chandrayaan-1 discovered the presence of water molecules embedded in the lunar soil. Scientists from Brown University have also been able to detect water molecules in regolith, or loose pebbles, retrieved during the Apollo missions. So what does this mean for humanity?
First of all, the water on the moon would need to be mined, then refined. The process of extracting the water is similar to cooking it out of the soil. Scientists have been able to extract two grams of water in the form of ice per minute using a one-kilowatt microwave. At that rate, astronauts would be able to extract about a ton of water per year [source: NASA]. It would take an estimated one ton of lunar dirt to extract one quart or liter of water. While that would make water a scarce commodity, if resourced responsibly, it could be used to grow plants and for drinking and maintaining a moon colony. Mining water would also eliminate the need to transport blocks of ice from Earth, a difficult and costly proposition.
At its closest possible point, the moon is 225,622 miles (384,104 kilometers) away from Earth, and at its furthest point the distance increases to 252,088 miles (405,986 kilometers). That's relatively close compared to Mars. The moon could serve as a hopping point to deeper space exploration. With the technology currently available, any colonization would have to be indoors. But greenhouses and other bio-dome technologies could someday make for a very habitable environment. As it stands, the moon is well within the habitable zone which lies between Venus and just on the inside edge of Mars. Unfortunately, the lack of gravity, which is one-sixth that of Earth's, severely inhibits the moon's ability to ever have an atmosphere. Without an atmosphere, you can forget about creating an outdoor environment capable of sustaining terrestrial life.
Mars, on the other hand, does have an atmosphere. As you'll learn about in the next section, the Red Planet is perhaps more livable than once thought. Does that mean there might actually be Martians gallivanting about? Turn the page to find out.