There are four terrestrial planets: Mercury, Venus, Earth and Mars. They are built similarly, mostly from rock and metal, have a solid surface, and few or no moons. In this second instalment of the Solar System Project, I will discuss the two planets closest to the sun, Mercury and Venus.
Don’t know what this project is about? Follow the link at the bottom of this page to get to the introduction of my Solar System Project!
Mercury only weights around 5.5% as much as the Earth, yet its diameter is 38% as long. With a surface temperature of -170 to 430 degrees Celsius, it has very ranging conditions. This planet, because it is closest to the sun, is the most difficult to see. However, scientists have been able to take pictures of the surface. Surprisingly, it looks almost like the moon. There are large craters which arose from meteoric bombardment which occurred early in Mercury’s existence. Since it has no atmosphere, just like the moon, there was no wind or water to damage the craters, and they have remained intact. The last time this bombardment happened was 3.8 million years ago. A 150 km large rock bored a great hole into the planet, causing a bizarre landscape on one side.
Its inside is also quite different to that of Earth. Mercury has an oversized iron core, a mantle, and a crust, while Earth has a small solid core, liquid core, mantle and crust.
Venus on the other hand weighs 81.5% as much as Earth, and its diameter is also 95% as long. Its temperature is steadier, at around 470 degrees Celsius. It is quite easy to observe on the sky, and most people may have seen it as a very bright star. It also has phases like the moon, so that sometimes it is full (like full moon) and half (like half moon). The reason Venus is so bright, is because it has a thick layer of clouds made of sulphuric acid, which reflects light. These clouds also move – very fast at the top, but slower as you get closer to the bottom. The wind is reduced to a breeze at the surface, yet it still carries around a lot of sand and dust.
Peculiar about Venus is the fact that it rotates differently to all other planets. When you look on the solar system from above, you can see all planets rotating anticlockwise. All of them also turn anticlockwise around their own axis – except Venus, which turns clockwise, and very slowly. 2 Venus days are approximately 500 Earth days.
At first, humans thought there might be life on this planet, yet the enormous pressure (90x larger than Earth’s) prevents this. There are merely several volcanoes and some larger volcanic areas, three highland regions, and formations called Coronae (crowns). Coronae are 100-400 km in diameter, and were formed by rising bubbles of magma. That’s why they have high edges and a lower center. It is unsure whether some of the volcanoes on Venus are still active.
Venus’s inside is built up similarly (in proportion) to that of Earth: core, mantle, crust. The crust however is about 1 ½ to 2 times as thick as Earth’s. Also, Venus has no strong magnetic field.
To conclude this article, Mercury and Venus are the planets closest to the sun, and both are in some ways similar to Earth. Look forward to the next article, about Earth and Mars, coming out sometime this week!
If you haven’t read the intro, click here to see what this project is all about.
Wanna know more about the sun? Find the first SSP article here: “Solar System Project: The Sun”