Venus

Venus, known for its beauty, is the second nearest planet to the Sun. It is the brightest celestial object in the Earth's sky after the Sun and the Moon. The terrestrial planet is the sixth in the row of massiveness and size. But what makes it more interesting is that Venus is similar to Earth in many contexts, yet it doesn't support life. And this is what interests scientists to learn and understand to get a proper understanding of habitable planets and explore life beyond Earth. 

Venus and Earth are similar in size, mass, closeness to the Sun, and internal surface that Venus is known as a 'twin sister' of Earth. If you slice both the planets from pole to pole in halves and join one side of Venus with the other side of Earth, you would barely notice differences. Yes, the two planets have the same iron core enveloped by a hot-rock mantle and a thin crust. 

And because of several similarities, scientists believe that the planets must have had similar reasons for existence. Venus must have formed from clouds of gas and dust that cooled down slowly a billion years ago. 

Its surface has a large number of evenly distributed comet impacts. About 85% of the comets are still in their natural state. Venus also has several volcanoes, and about 167 of them are 100 kilometres apart. These craters, along with high volcanic activities, have shaped the present-day surface of the planet. 

Not only a heavily crated surface to make conditions worse, but the planet also has the densest atmosphere of all the four terrestrial planets in the Solar System. The atmospheric pressure of the planet's surface is 92 times the sea level pressure of the Earth, which is equal to the pressure you will feel if you go 900 metres underwater on Earth. Its atmosphere has more than 96% of Carbon dioxide, about 3.5% is Nitrogen, and then there are traces of sulphur and sulphuric acid. We all know these are greenhouse gases, and they trap ultraviolet radiations in themselves increasing the environment temperature. And this is the reason for Venus being the hottest planet in the Solar System, with a surface temperature of 480 degrees Celsius, though it is twice as far away from Sun as Mercury. 

The planet has a diameter of 12100 kilometres and a mass of 4.8673 x 1024 kilograms. It has a density of 5.24 g/cm3 while Earth has a density of 5.51 g/cm3. The terrestrial planet has no natural satellites revolving around itself and it doesn't have any magnetic fields either. 

Scientists believe that Venus must have had water a billion years ago, but all of the water would have been vaporized, because of the presence of greenhouses gases rising the temperature. Also, scientists think that the water must be photo-dissociated, meaning break down into atoms on interaction with light particles. They believe the elemental hydrogen atoms from water molecules must have gone into interplanetary space because of the absence of magnetic fields. 

Also, one of the interesting facts to know about Venus is that it rotates opposite to Earth, meaning on Venus, the Sun rises in West and sets in East. Moreover, One day on Venus is longer than a year! 

Surprised? This means you got older by a year before the day completes. Strange. Yes, because the planet has low angular momentum, and therefore it takes 243 Earth days to rotate on its axis compared to 225 Earth day period to revolve around the Sun. 

Interesting, the first interplanetary mission was to Venus by the Soviet Union. The Venera program was launched in 1961, though it lost contact in the middle of its journey. The first successful mission to Venus was Mariner 2 by the United States to collect data about and understand the surface and atmosphere of the planet. In 1967, the Soviet Venera 4 successfully entered as the first to probe the atmosphere of Venus and deployed science experiments. It showed the surface temperature was hotter at almost 500 °C, determined the atmosphere was 95% carbon dioxide and discovered Venus's atmosphere was considerably denser than thought.

Scientists believe that they would sooner unfold the mysteries behind the twin sister of Earth, known as Venus. 

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