According to scientists, Venus is known as the Earth’s “twin” because the two planets are so similar in size.
The diameter of Venus is about 7,520 miles (12,100 kilometres), approximately 400 miles (644 kilometres) smaller than that of the Earth. No other planet comes nearer to the Earth than Venus.At its closest approach; it is about 23.7 million miles (38.2 million kilometers) away.
As seen from the Earth, Venus is brighter than any other planet or even any star. At certain time of the year, Venus is the first planet or star like that can be seen in the western sky in the evening.
At other times, it is the last planet or star like that can be seen in the eastern sky in the morning. When Venus is near its brightest point, it can be seen in daylight.
Ancient astronomers called it “the object that appeared in the morning Phosphorus”, and “the object that appeared in the evening Hesperus”. Later, they realized these objects were the same planet. They named Venus in honour of the Roman goddess of love and beauty.
Venus is scorched with a surface temperature of about 482° C (900° F). This high temperature is primarily due to a runaway greenhouse effect caused by the heavy atmosphere of carbon dioxide.
Sunlight passes through the atmosphere to heat the surface of the planet. Heat is radiated out, but is trapped by the dense atmosphere and not allowed to escape into space. This makes Venus hotter than Mercury.
It is this hot because it is the second planet from the sun, and has what scientists call a ‘runaway greenhouse effect (a runaway greenhouse effect occurs when, on a planet with substantial reserves of greenhouse gases in liquid or solid form, some abrupt forcing occurs to begin to gasify them, leading to complete gasification of these reserves).
A thick layer of clouds (mostly sulphuric acid) covers the surface and traps infrared radiation, raising the surface temperature of the planet.
The situation on Earth is very different from that which existed on Venus, as any terrestrial runaway effect is not irreversible on geological timescales. Potential runaway greenhouse effects on Earth may involve the carbon cycle, but unlike Venus will not involve boiling of the oceans to vapour.
A Venusian day or day on Venus is 243 Earth days and is longer than its year of 225 days. Oddly, Venus rotates from east to west.
To an observer on Venus, the Sun would rise in the west and set in the east according to scientists.
Until just recently, Venus’ dense cloud cover has prevented scientists from uncovering the geological nature of the surface. Developments in radar telescopes and radar imaging systems circulating the planet have made it possible to see through the cloud deck to the surface below.
Four of the most successful missions in revealing the Venusian surface are (NASA’s Pioneer Venus mission (1978), the Soviet Union’s Venera 15 and 16 missions (1983-1984), and NASA’s Magellan radar mapping mission (1990-1994). As these spacecraft began mapping the planet a new picture of Venus emerged.
It is believed that Venus’s surface is relatively young geologically speaking. It appears to have been completely resurfaced 300 to 500 million years ago. Scientists debate how and why this occurred.
The Venusian topography consists of vast plains covered by lava flows and mountain or highland regions deformed by geological activity.
Volcanoes and volcanic features are even more numerous. At least 85% of the Venusian surface is covered with volcanic rock. Hugh lava flows, extending for hundreds of kilometres, have flooded the lowlands creating vast plains. More than 100,000 small shield volcanoes dot the surface along with hundreds of large volcanos.
Mariner 10 spacecraft Image of Venus taken on February 5, 1974.
Venus’s atmosphere represents a true puzzle for scientists. Winds are so powerful and fast that they circumnavigate the planet in only four Earth days at the atmospheric super-rotation while the planet itself is very slow in comparison, taking 243 Earth days to perform one full rotation around its axis.
Venus’s atmosphere is composed primarily of carbon dioxide. There are several kilometres of thick layers of clouds composed of sulphuric acid as well.