Researchers say parts of the Moon will be set aside as graveyards for defunct satellites.
Lunar orbit is expected to become crowded as space agencies plan bases and mining projects.
Unlike Earth, the Moon lacks an atmosphere to burn up old spacecraft.
Most dead satellites will eventually be crash-landed on the surface.
Uncontrolled impacts could damage scientific instruments and historic sites.
High-speed crashes also create dust clouds and ground vibrations.
Experts propose designated impact zones far from sensitive areas.
International space agencies are now working to establish disposal rules.
