On June 5th, 2012, Venus passed across the face of the sun, producing a silhouette that no one alive today will likely see Transit of Venus again. It rarely happens that Venus passes directly between Earth and Sun. These were used in the passage of the XVIII century. to determine the size of the solar system. Noting the difference in time between the beginning and the end of the passage of the observation from different points of the Earth, astronomers estimated the distance between Earth and Venus.
Transits of Venus are very rare, coming in pairs separated by more than a hundred years. This June’s transit, the bookend of a 2004-2012 pair, won’t be repeated until the year 2117. Fortunately, the event is widely visible. Observers on seven continents, even a sliver of Antarctica, will be in position to see it.
Venus, the second planet in the solar system account. It has the same size as the Earth and its mass is more than 80% of the land mass. Located close to the Sun than our planet, Venus receives from him more than twice as much light and heat than the Earth.
Venus approaches the Earth closer than any other planet. But due to it's thick, cloudy atmosphere we can not directly see its surface. Pictures taken with the radar, showing a very wide variety of craters, volcanoes and mountains. The surface temperature is high enough to melt lead, and once on this planet, perhaps, there were vast oceans. Venus has a nearly circular orbit, which it passes for 225 Earth days at a distance of 108.2 million km from the Sun. Rotation around the axis of Venus is committed to 243 Earth days - the maximum time among all the planets. Around its axis of Venus rotates in the opposite direction, ie in the opposite direction along the orbit. This slow, and, moreover, otherwise, the rotation means that, when viewed from Venus, the sun rises and sets only twice a year, since the Venusian day equal to our 117. Venus approaches the Earth at a distance of 45 million miles - closer than any other planet. For its size Venus is only slightly smaller than Earth, and lots of it is almost the same. For these reasons, Venus is sometimes called the twin or sister of the Earth. However, the surface and atmosphere of these two planets are quite different. On Earth, there are rivers, lakes, oceans and atmosphere that we breathe. Venus - piping hot planet with a dense atmosphere, which would be fatal to humans.
Before the space age, astronomers knew very little about Venus. Thick clouds prevented them from seeing it surface in the telescopes. Spacecraft managed to pass through the atmosphere of Venus is composed mainly of carbon dioxide doped with nitrogen and oxygen. The pale-yellow cloud in the atmosphere contains droplets of sulfuric acid, precipitated on the surface of acid rain. The orbit of Venus is closer to the Sun than the Earth's orbit. When Venus is on the opposite side, illuminated her whole drive, and when it is located between the Earth and the Sun, we see only part of the sunlit hemisphere. For this reason, Venus, like the moon, there are different phases depending on its location in orbit.
The atmosphere of Venus is extremely hot and dry. Surface temperature reaches its maximum in about 480 ° C. The mark In the atmosphere of Venus contains 105 times more gas than in the Earth's atmosphere. The pressure of the atmosphere at the surface is very large, 95 times higher than on Earth. Spaceships have to design so that they withstand the crushing, crush strength of the atmosphere. In 1970, the first spacecraft arrived at Venus, unable to withstand the terrible heat, only about one hour - this is just enough to send data to Earth about conditions at the surface. Russian aircraft, landed on Venus in 1982, sent to Earth color photographs depicting the sharp rocks.
Thanks to the greenhouse effect on Venus is a terrible fever. The atmosphere, which is a dense blanket of carbon dioxide at trapping heat that came from the sun. As a result, accumulated a large amount of thermal energy.
On Earth, where the amount of carbon dioxide in the atmosphere is small, the natural greenhouse effect raises the global temperature at 30 ° C. But on Venus the greenhouse effect raises the temperature even at 400 ° C. By studying the physical effects of the strongest greenhouse effect on Venus, we are well aware of the results, which may result from the accumulation of excess heat on the Earth, caused by rising concentrations of carbon dioxide in the atmosphere due to burning fossil fuels - coal and oil.
To investigate the nature of the surface of Venus under a thick layer of clouds, astronomers use a spaceship, and radio waves. By Venus sent more than 20 U.S. and Russian spacecraft - more than any other planet. The first Russian ship was crushed by the atmosphere. However, in the late 1970s - early 1980s. obtained the first photographs, which show the formation of solid rock - sharp, sloping, crumbling, fine grit and dust - the chemical composition of which was similar to volcanic rocks of the Earth. In 1961, scientists were sent to Venus and the radio was on Earth reflected signal by measuring the velocity of the planet's rotation around its axis. In 1983, in orbit around Venus, the spacecraft went "Venera-15" and "Venera-16". Using radar, they built a map of the northern hemisphere of the planet to the parallel of 30 ". Even more detailed maps of the entire surface with the details of up to 120 m were obtained in 1990 the ship" Magellan. "With the computer turned the radar information in images, like photos, where visible volcanoes, mountains and other parts of the landscape.
"Magellan" sent to Earth the beautiful images of huge Venusian craters. They emerged from the giant meteorite strikes, forced their way through the atmosphere of Venus on its surface. Such collisions release the liquid lava, which is contained within the planet. Some meteors exploding in the lower atmosphere, creating shock waves that formed a dark circular craters. Meteorites, passing through the atmosphere, flying at about 60,000 km / h When a meteorite hits the surface, hard rock instantly turns into hot steam, leaving a crater in the ground. Sometimes the lava after such a blow is way up and out of the crater.
The surface of Venus is covered with hundreds of thousands of volcanoes. There are several very large: a height of 3 km and a width of 500 km. But most of the volcanoes is 2-3 km in diameter and about 100 m in height. The outpouring of lava on Venus is much longer than on Earth. Venus is too hot to ice were there, rain or storm, so there is no significant weathering (weathering). So, volcanoes and craters have changed little since they were formed millions of years ago. The photographs of Venus taken with the "Magellan", we see this ancient landscape, such as never seen on earth - and yet he is younger than many other planets and moons. Apparently, Venus is covered by hard rocks. Under them circulates hot lava, causing the voltage of a thin surface layer. Lava continuously erupts from holes and breaks in the solid rock.
On Earth, geologists are not easy to find out the history of our planet, because under the influence of wind and rain, mountains and valleys are constantly exposed to erosion. Venus is very interested scientists because its surface is like an ancient fossil strata. Details of the landscape discovered "Magellan" are between the ages of hundreds of millions of years. Volcanoes and lava flows are preserved intact in this dry planet, the world is - the closest to ours.