Venus: Earth’s Sister Planet
Discover just how similar this planet actually is to Earth.
Venus has often been called Earth’s sister planet because of their similarities. Both planets are terrestrial (meaning that they are made up of silicate rocks) and close in size, mass and gravity. Venus probably has a similar structure to Earth, with a crust, mantle and core. It has a diameter of around 12,000 kilometres, 650 kilometres smaller than Earth. Its mass is about 80 per cent of Earth’s mass, and its gravity 90 per cent of Earth’s gravity.
However, there are also many differences between Venus and Earth. Venus is about 108 million kilometres from the Sun and has an almost perfectly circular orbit, while all of the other planets have elliptical orbits. Venus completes one orbit every 225 days and has one of the slowest rotations of any planet, with one every 243 days. Venus’s consistently high temperature means that it has no surface water. The planet also has more than 1,500 volcanoes, many of which are more than 100 kilometres across.
Most of the volcanoes are extinct, but some believe that there has been recent volcanic activity. Because Venus doesn’t have rainfall, lightning could have been caused by ashy fallout from a volcanic eruption. These eruptions have created a rocky, barren surface of plains, mountains and valleys. Venus is also covered with more than 1,000 impact craters. While Earth and other planets also have craters, Venus’s are unusual because most of them are in perfect condition. They haven’t degraded from erosion or other impacts.
Venus may have experienced a massive event as much as 500 billion years ago that resurfaced the planet and changed its atmosphere completely. Now bodies entering its atmosphere either burn up or are slowed down enough to avoid making a crater. It has proven difficult to learn more about Venus, in part due to its dense atmosphere. Although probes first visited the planet in the early Sixties, it was not fully mapped by radar until the 1989 NASA Magellan probe. The Venus Express, launched by the European Space Agency in 2005, is a long-term exploration probe currently orbiting the planet and sending back data about its atmosphere.
Venus’s atmospheric pressure is greater than that of any other planet – more than 90 times that of Earth’s. This pressure is equivalent to being almost one kilometre below the surface of Earth’s oceans. The atmosphere is also very dense and mostly carbon dioxide, with tiny amounts of water vapour and nitrogen. It has lots of sulphur dioxide on the surface. This creates a Greenhouse Effect and makes Venus the hottest planet in the solar system. Its surface temperature is 461 degrees Celsius across the entire planet, while Mercury (the closest planet to the Sun) heats up to 426 Celsius only on the side facing the Sun.
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