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The infrared portion of the spectrum is one of the most useful for identifying what a
surface is made of because both reflected and emitted energy can be studied.
Reflected infrared energy tells us a lot about rocks and minerals. For
example, we can often distinguish clay-bearing minerals from other minerals
(important in gold and silver exploration).
Measuring the differences in ground temperatures by using infrared satellites
shows the distribution of rocks and minerals.
Minerals absorb and emit thermal infrared radiation. The spectra produced
by this infrared radiation acts as fingerprints, identifying minerals and
their proportion in an area.
Thermal infrared data is used to study volcanoes and
predict eruptions by mapping ground
temperatures, the composition of lava flows, and the sulfur dioxide in
volcanic plumes. This data is very useful when monitoring volcanoes
for activity. NASA has developed methods (both from airplanes and spacecraft)
for studying thermal activity from volcanoes from a safe distance.
Infrared detectors onboard satellites and aircraft are used to study the
distribution of vegetation and soil and to detect diseased plants
before problems become visually apparent.
Infrared mapping is also used to evaluate vegetation
soil moisture and
patterns, for irrigation studies, and for detecting diseased fruit and vegetable crops.
For example, thermal infrared imaging is used in forest surveys and in a
NASA project to
help farmers diagnose their fields and determine crop yields.
Infrared imaging is also used to
study plant
freezing.
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