NASA researchers are searching for water underneath the surface of the arid Kuwaiti desert by utilizing technology similar to that currently being used to search for water on Mars.
There are two radar-emitting instruments orbiting Mars in search for water. One, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) is operated by the European Space Agency, and the other, the Shallow Subsurface Radar (SHARAD) is run by NASA.
Both use radar to detect water and ice below the Martian surface. SHARAD emits radar waves at a frequency of 15-25 MHz to detect water located up to 1 kilometer, or almost 3300 feet below the surface. The radar relies on the electrical reflection caused by rock, sand and water. Water, a highly conductive substance, will reflect more radar waves than the rocks and sand surrounding it. The amount of reflection can then be measured by SHARAD to determine the size of water and ice deposits underneath the surface.
The European MARSIS also uses this technology, but this instrument can detect up to three times the depth of SHARAD using a lower frequency of 1-5 MHz. So far, both have found evidence of ice on Mars, and the search for liquid water continues.
A similar technique was used by an international team led by Essam Heggy of NASA's Jet Propulsion Laboratory to search for water here on Earth.
Using a 40 MHz radar, they made 12 low-altitude passes in helicopters over the course of two weeks to determine the depth of two specific freshwater aquifers, or underground layers of water, in Kuwait's desert. Their radar was able to detect to a depth between 66 and 213 feet to find changes in the water table (the layer below ground containing water) and the locations at which water entered and left the aquifers. By combining the data from each flight, they created a high-resolution, 3-dimensional image of the aquifers.
Several natural characteristics of Kuwait's desert were essential to increasing the penetrating depth of the radar. Drier lower depths are essential to finding water that is deeper under the surface. Also helpful were the flat topography of the desert and the low level of radio "noise," or interference from other sources of electrical and radio wave reflection distorting the noise from the underground water.
The newfound data supplements previous information collected in 1981, 1984 and 1994 which used instruments built by NASA's Jet Propulsion Laboratory (JPL) and flown on space shuttle missions. These instruments were able to find shallow drainage networks and large dry regions in the neighboring Sahara.
The findings of the new research can be used for further mapping of the aquifers of the hyper-arid regions of the world using satellite equipment like that currently employed on Mars. The deserts of North Africa and the Arabian Peninsula are regions for potential exploration. A design concept currently under development at NASA, called the Orbiting Arid Subsurface and Ice Sheet Sounder (OASIS), would put this into effect.
The most direct application of the data is in the field of climate change and global warming. Previous research has focused on the melting of polar ice caps and the increase in deforestation — both of which add to the level of atmospheric greenhouse gases — because of the ease of observing and recording such events.
Expansion of arid regions is also a predicted effect of the current increase in global surface temperatures. A measurable decrease in subsurface water could correlate with other data, examining global warming along with data of changes in ice sheet volume, thickness, basal topography and discharge rates in these areas.
