Program "Маriner":research of  Venus

Ayr of automatic space probes began from 1962 when American vehicle " Маriner-2 " has passed near to Venus and has transmitted the information which has confirmed, that its surface is very hot. It was established also, that the period of rotation of Venus around axis - long, about 243 earth day is, more, than cycle time around of the Sun (224,7 day), therefore on Venus "day" is longer than year and the calendar is completely unusual.

"Маriner-10" has come nearer to Venus in February, 1974 and has transmitted the first pictures of the upper layer of clouds. This vehicle has only once passed about Venus. It was  the main purpose.. However pictures were high quality and have shown striped structure of clouds. They also have confirmed, that the period of rotation of the upper layer of clouds only 4 day, so a structure of a Venus atmosphere not similar on earth.

  Atmospheric conditions in an equatorial zone of a planet are distinct from those in polar areas.