We calculate the \gamma -ray albedo flux from cosmic-ray ( CR ) interactions with the solid rock and ice in Main Belt asteroids ( MBAs ) , Jovian and Neptunian Trojan asteroids , and Kuiper Belt objects ( KBOs ) using the Moon as a template .
We show that the \gamma -ray albedo for the Main Belt , Trojans , and Kuiper Belt strongly depends on the small-body size distribution of each system .
Based on an analysis of the Energetic Gamma Ray Experiment Telescope ( EGRET ) data we infer that the diffuse emission from the MBAs , Trojans , and KBOs has an integrated flux of less than \sim 6 \times 10 ^ { -6 } cm ^ { -2 } s ^ { -1 } ( 100–500 MeV ) , which corresponds to \sim 12 times the Lunar albedo , and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope ( GLAST ) .
If detected by GLAST , it can provide unique direct information about the number of small bodies in each system that is difficult to assess by any other method .
Additionally , the KBO albedo flux can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions .
The orbits of MBAs , Trojans , and KBOs are distributed near the ecliptic , which passes through the Galactic center and high Galactic latitudes .
Therefore , the asteroid \gamma -ray albedo has to be taken into account when analyzing weak \gamma -ray sources close to the ecliptic , especially near the Galactic center and for signals at high Galactic latitudes , such as the extragalactic \gamma -ray emission .
The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock .
This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory ( INTEGRAL ) observations of the Galactic 511 keV line emission including the direction of the Galactic center .