Near Earth Object Maps

Below are maps of the inner Solar System for the years 1800, 1850, 1900, 1950, 1990, 2000 and 2007 showing the rate of discovery of the asteroids. Click on the images for the full size versions.

1800 no known asteroids	1850 10 asteroids known and named
1900 hundreds of known objects in the main belt, some even inside the orbit of Mars	1950 almost 2000 known objects with a handfull of Earth crossers
1990 over 9,000 known objects	2000 automated searches bring the total to 86,374
2007 August 379,084 known objects ranging from a few metres up to the dwarf planet Ceres

Legend:
Green dots represent objects which do not approach the Earth at present e.g. Main Belt asteroids
Yellow dots represent objects which approach the Earth but do not cross its orbit e.g. Amor asteroids
Red dots represent objects which cross the Earth's orbit e.g. Aten and Apollo asteroids