Remotely Sensed Data
The module contains a number of remotely-sensed images. These images were taken by a satellite that senses electromagnetic energy (light) in different wavelengths. The images are not "photos," even though they appear to be very much like photos except for their color. Typically, the color of the images is a "false" color that enhances some feature.

Remember that film in a camera captures electromagnetic wavelengths we call visible light. These are the same wavelengths that your eyes sense. Other wavelengths also can be sensed. Landsat and other satellites have instruments that can sense these other wavelengths. Remote sensing is more than an extension of our five senses. It provides us with information that is ordinarily invisible to us because it cannot be sensed by our eyes or because it is hidden from our view or would be dangerous for us to acquire.

Remote sensing from space is particularly important in helping us find ancient impact sites, where Earth was hit by asteroid/comet-like bodies. When we stand on Earth, we don't have the vantage point necessary for seeing these very large and usually highly eroded, craters. By analogy, if we put our hands over our eyes, we cannot see that they are hands, but if we get a more remote view by moving our hands 4 or 5 inches away from our face, we can tell their shape.

Remote sensing on Earth, through the use of seismic (sound vibrations) waves, has enabled us to find older craters that lie buried under layers of younger sedimentary rocks. The most famous example of this kind is the Mexican (Yucatan Peninsula) crater called Chixulub, which may have been made at the time of the last dinosaurs.

Remote sensing also helps us to know our present situation in the Solar System. A small group of individuals have devoted themselves to searching the sky for Near Earth Objects (NEOs). These objects may be like those that have cratered Earth. Sometimes these objects are detected as they pass by us. They travel at high speeds and would cause devastation if they were to hit Earth.

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