Scientists estimate that a whopping 394,178 pounds (178,796 kg) of debris has been left on the Moon, including 73 lunar probes, rovers and satellites that either landed or crashed there. But one artifact, a 3.3-inch (8.5 cm) aluminum sculpture created by Belgian artist Paul Van Hoeydonck, was secretly left by the Apollo 15 crew in 1971 to commemorate 14 astronauts and cosmonauts who had lost their lives in space exploration.
A replica of the "Fallen Astronaut" statuette was given to the Smithsonian Institution on 17 April 1972, the day after CBS anchorman Walter Cronkite described the statuette and an accompanying plaque as the first art on the Moon.
A lunar landfill:
So we already started littering another place in the solar system then.