Earth in the Solar System:

• The Earth is the third planet from the sun in a system that includes the Moon, the sun, seven other planets and their moons, and smaller objects, such as asteroids and comets.

Structure of the Earth System:

• Water, which covers the majority of the Earth's surface, circulates through the crust, oceans, and atmosphere in what is known as the "water cycle." Water evaporates from the Earth's surface, rises and cools as it moves to higher elevations, condenses as rain or snow, and falls to the surface where it collects in lakes, oceans, soil, and in rocks underground.

• Water is a solvent. As it passes through the water cycle it dissolves minerals and gases and carries them to the oceans.

Short Description: This four-slide powerpoint by the Division of Planetary Science includes basic information for college-level introductory courses.

This false-color map created from data taken by NASA's Moon Mineralogy Mapper (M3) on Chandrayaan is shaded blue where trace amounts of water (H2O) and hydroxyl (OH) lie in the top few mm of the surface.

Water Found on the Moon

1. Analysis of lunar rocks collected by Apollo astronauts did not reveal the presence of water on the Moon
   
   
2. Four spacecraft recently reported small amounts of H2O and/or OH at the Moon:
   
   
   • India's Chandrayaan mission
   • NASA's Cassini mission
   • NASA's EPOXI mission
   • NASA's LCROSS mission

   The first three measured the top few mm of the lunar surface. LCROSS measured plumes of lunar gas and soil ejected when a part of the spacecraft was crashed into a crater.

3. How much water? Approximately 1 ton of lunar regolith will yield 1 liter of water

How was Water Detected?

1. Lunar soil emits infrared thermal radiation. The amount of emitted light at each wavelength varies smoothly according to the Moon's temperature.
   
   
2. H₂O or OH molecules in the soil absorb some of the radiation, but only at specific wavelengths
   
   
3. All four infrared spectrographs measure a deficit of thermal radiation at those wavelengths, implying water is present

An infrared spectrum measured by LCROSS (black data points) compared to models (red line).

Discovery of water on the moon may support future activities on the lunar surface and beyond. Artwork from NASA / Pat Rawlings.

The Big Picture

1. Lunar water may come from 'solar wind' hydrogen striking the surface, combining with oxygen in the soil. It may also arrive via meteorite and comet impacts. Both processes are likely.
   
   
2. Lunar water may be 'bounced' by small impacts to polar regions, forming ice in permanently shadowed craters
   
   
3. Similar processes may occur on other airless bodies (e.g., Mercury, asteroids)
   
   
4. Water-laden lunar regolith may be a valuable resource, possibly supporting future lunar exploration activities

For More Information ...

Press Releases

• NASA - 9/24/09 - "NASA Instruments Reveal Water Molecules on Lunar Surface" http://www.nasa.gov/topics/moonmars/features/moon20090924.html

• Space.com - 09/23/09 - "It's Official: Water Found on the Moon" http://www.space.com/scienceastronomy/090923-moon-water-discovery.html

• NASA Ames - 11/13/09 - "LCROSS Impact Data Indicates Water on Moon" http://www.nasa.gov/mission_pages/LCROSS/main/prelim_water_results.html

• Space.com - 11/13/09 - "'Significant Amount' of Water Found on Moon" http://www.space.com/scienceastronomy/091113-lcross-moon-crash-water-discovery.html

Images

• Image from Slide 1 courtesy of [NASA/ISRO/BROWN University/R.N. Clark, USGS] http://www.nasa.gov/topics/moonmars/features/moonm3-images.html

• Images from Slide 2 courtesy NASA http://www.nasa.gov/mission_pages/LCROSS/main/LCROSS_results_images.html

• Image from Slide 3 from NASA / Pat Rawlings http://www.patrawlings.com/

Source Articles (on-campus login may be required to access journals)

• Pieters et al., 'Character and Spatial Distribution of OH/H2O on the Surface of the Moon Seen by M3 on Chandrayaan-1', Science, 326, p. 568, doi: 10.1126/science.1178658, 2009.

• Sunshine et al.., 'Temporal and Spatial Variability of Lunar Hydration as Observed by the Deep Impact Spacecraft', Science, 326, p. 565, doi: 10.1126/science.1179788, 2009.

• Clark R.N., 'Detection of Adsorbed Water and Hydroxyl on the Moon', Science, 326, p. 562, doi: 10.1126/science.1178105, 2009.

All articles available at: http://www.sciencemag.org/content/vol326/issue5952/index.dtl