Which planet is closest to the Sun?
Mercury is the closest planet to the Sun. the temperature on the side of the planet facing the Sun is as high as 430 degree Celsius. The shaded side of Mercury which faces away from the Sun is bitterly cold at – 180 degree Celsius.
Mercury has almost no atmosphere because it has been burned off by the Sun. The planet consists of bare rock, pitted and scarred by the impact of meteorites. It has extremely steep cliffs that are hundreds of kilometres long. These were formed when the planet cooled from its original molten (liquid) state millions of years ago.
What are the inner planets?
The four planets that are nearest the Sun are called the inner planets. In order from the Sun, they are Mercury, Venus, Earth and Mars. The inner planets are different from the outer planets, which are farther away from the Sun, because they are made of rock. The outer planets are mostly composed of gas. Each of the inner planets has an atmosphere. However, apart from the Earth’s atmosphere, the atmospheres of the inner planets are very thin and would be poisonous to humans.
What are sunspots?
Groups of black blotches appear on the surface of the Sun every 11 years. These blotches are called sunspots. They are areas that are about 1,000 degree Celsius cooler than the rest of the Sun’s surface. Sunspots are caused by changes in the Sun’s magnetic field. When they appear, sunspots cause radiation that often interferes with the radio and television signals on the Earth. Some groups of sunspots can be as much as ten times the size of the Earth.
Could we live on Venus?
Science fiction writers thought that life might exist beneath the thick clouds covering Venus. We now know that conditions there are too extreme for life as we know it. Robot spacecraft have landed on Venus and studied its atmosphere, which is mostly poisonous carbon dioxide and sulphuric acid. We cannot see the planet’s surface through its thick atmosphere, but enough sunlight gets through to raise the surface temperature to 480 degree Celsius. This atmosphere reflects sunlight, making Venus very bright when viewed from Earth.