This is different from the visible light that we see from the planets which is reflected sunlight. The planets in our solar system have temperatures ranging from about 53 to 573 degrees Kelvin. Objects in this temperature range emit most of their light in the mid-infrared. For example, the Earth itself radiates most strongly at about 10 microns. Asteroids also emit most of their light in the mid-infrared making this wavelength band the most efficient for locating dark asteroids.
Infrared data can help to determine the surface composition, and diameter of asteroids.
An example is the zodiacal dust which lies in the plane of our solar system. Silicates emit most of their radiation at about 10 microns. Mapping the distribution of this dust can provide clues about the formation of our own solar system. Another example is the dust from comets which also has strong emission in the mid-infrared. Warm interstellar dust starts to shine as we enter the mid-infrared region.