Conventional wisdom holds that the moon is a barren, hostile place different in every way from the planet it orbits, Earth. However, the United States National Aeronautics and Space Administration (NASA) reports that water has been discovered on the moon, rendering this closest neighbor to Earth a little less eccentric than had been suspected.
How Did NASA Find Water on the Moon?
Anthony Colaprete, principal investigator of the NASA lunar study project LCROSS, states that "multiple lines of evidence show water [is] present" in the lunar soil in a crater on the moon's surface that is permanently shaded from the sun ("LCROSS Impact Data Indicates Water on Moon", NASA website, November 13, 2009).
But, how exactly did NASA discover water on Earth's moon? The Lunar CRater Observation and Sensing Satellite (LCROSS) remotely observed the controlled impact of a small rocket and probe with the surface of a sheltered lunar crater. The dust and vapor plume kicked up by these impacts was formed by substances that have been locked away in the moon's soil for billions of years. Near-infrafred and UV spectroscopy of the debris plume indicates that water vapor was present in the plume. That is, the way that the debris plume interacted with light is characteristic of water plus some other compounds.
The LCROSS research team is "ecstatic" and is eagerly continuing to analyze the data resulting from the lunar impacts to determine just how much water was present in the plume, and the identity of the other substances in the crater's soil.
Is Water on the Moon Liquid, Ice, or Vapor?
All sunlit parts of the moon are too warm – up to 250 degrees Fahrenheit (121 degrees Celsius) – for liquid water to be stable. Any liquid water on the moon's surface would immediately evaporate, forming water vapor. However, water vapor cannot be contained by the moon's thin atmosphere, so when it forms it is lost into space. This means that water cannot persist as a liquid or as a gas on the moon for any length of time.
What about ice? Water ice can only exist on the moon's surface in areas that are never exposed to sunlight, such as the "dark side" of the moon or the bottom of lunar craters near the moon's north or south poles. Therefore, it makes sense that the origin of the water NASA observed is water ice within the moon's soil.
Implications for Human Exploration of the Moon
Water is absolutely essential for all forms of life, including humans. The presence of water on the moon is not only of purely scientific interest, but also of practical significance for further lunar exploration by astronauts. A native, abundant source of water that could be exploited by astronauts would make longer lunar missions possible, which may help shed further light on the nature of Earth's closest neighbor, the moon.
Discovery of Water on the Moon and Its Implications
NASA reports that water ice is present in the soil of sheltered lunar craters, judging from spectroscopic data gathered from observations of an impact plume containing lunar debris and gases. If water is indeed fairly abundant in the moon's soil, this water may facilitate further exploration of the lunar surface by human space programs.
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