Mars - Earth Sidereal Proximity
For about 17,000 UFO sightings with known dates, the Heliocentric Longitude of Earth and Mars are compared.The DIFFERENCE between these longitudes is divided into 24 "zones" of 15 degrees each. In "zone 12" Earth and Mars are on the same side of the Sun, the closest they get for any given orbit. In late August 2005, due to an eccentric orbit, Mars came much closer to Earth than is usual.
Zone zero UFOs occur when Mars and Earth are on opposite sides of the sun. While Venus is often blamed for UFO sightings, It seems Mars correlates better using a filtered database.
Since the Martian year lasts 687 Earth-days, Earth passes Mars from behind on each approach, on an inside track closer to the Sun. All planets orbit counter clockwise as seen from the North Star.