Venus begins to transit the face of the sun, on June 8, 2004. The image shows the mysterious black drop effect which can be seen just before the 3rd contact as the planet Venus transits the Sun's disk. A transit occurs when Venus passes in front of the Sun as seen from Earth. This is the first transit since 1882. Venus transits occur in pairs separated by eight years, with alternating intervals of 121.5 and 104.5 years in between pairs. Only Mercury and Venus can transit the Sun as seen from Earth.