11// terrestrial planets in our solar system

hey guys :D

There are 4 terrestrial planets in our solar system, so let's talk about each one!

The first one, closest to the Sun is Mercury.

Mercury is the smallest planet, with a diameter of 4 480km. It's approx. 60 million km away from the Sun, and it is too hot to have an atmosphere.

With a lack of a proper atmosphere, Mercury is the hottest and the coldest planet in our solar system (simultaneously). The temperature on the surface can go from 100K (at night) to 700K (day)

Mercury makes a full orbit around the Sun in 88 (earth) days and rotates around its axis in 59 days. Mercury rotates around its axis 3 times in two Mercurian years. A solar day on Mercury is 176 days on Earth. 

Mercury has an elliptical orbit - it goes faster at its perihelion (closest to the Sun) and slows down at its aphelion (farthest from the Sun)

Because of the Sun's gravity, Mercury changes its location a bit, we can see this change well on Mercury's aphelion. We call this perihelion precession, and it is explained by the general theory of relativity.

One thing we could sometimes see happen on Mercury is a returning sun. Because Mercury has a 3:2 spin-orbital resonance, the sun could be seen rising from the east, stopping and setting on the east, and then rising again.

Mercury doesn't have a strong magnetic field. 

The planet's core takes up 55% of Mercury's mass. It is made out of iron and nickel, and the surface is mostly made of silicates. Mercury's surface is covered with craters, similar to the moon.

The second planet from the Sun is Venus.

Venus is 108 million km away from the Sun, and the closest to the Earth. It's similar to the Earth in terms of size and mass, but very different in climate.

Venus has a very thick atmosphere, mainly from carbon dioxide. Because of that, there's a 100x bigger atmospheric pressure than on Earth.

Carbon dioxide is very good at trapping heat, and the temperature on the planet's surface is 735K. This makes Venus hotter than Mercury, even tho it's farther away from the Sun.

Venus has very thick clouds made of sulfuric acid, that make it impossible to see the planet's surface. These clouds reflect light really well - this is why Venus is so bright in the sky.

Thanks to the Magellan spacecraft, we have a map of what the surface of Venus looks like. The surface is relatively flat, with only 2 elevated regions, similar to continents on Earth. One of the continents is named Ishtar Terra and it's as big as Greenland, the second one is named Aphrodite Terra and it's as big as South America. There are also (probably active) volcanoes on Venus.

Venus probably has an iron core.

An interesting thing about Venus is that it rotates the opposite way to the other planets. This means that the sun rises in the west and sets in the east.

Venus rotates around its axis in 243 days. A solar day is 117 days on Earth.

The third planet is Earth. It's the only known planet where life exists.

The Earth was a very hot planet at first, but after collisions with other objects happened less and less, it cooled down. Water was brought to the Earth by comets and gases inside rocks were released in collisions, creating an atmosphere.

The atmosphere is made mainly out of nitrogen, oxygen, and a tiny bit of argon, water vapor, and other stuff. Hydrogen and helium can escape our atmosphere because they're very light.

Earth has an iron core, a silicate mantle, and a rocky crust. Movements in the core cause electrons to align, creating a strong magnetic field.

Earth's magnetic field shields us from solar winds. Solar winds colliding with the atmosphere create north lights.

Earth has one natural satellite - the Moon.

A natural satellite is an object that orbits around a planet, not a star.

The Moon was created due to a collision of the Earth with a Mars-sized object. Dust and rocks were ejected into space where they then grouped together creating the Moon. 

The Moon is created from the same materials as Earth's mantle (the collision that resulted in the creation of the Moon happened when the Earth's mantle was being made)

The Moon doesn't have an atmosphere, and it's covered in craters. 

It rotates around its axis at the same time as it orbits around the Earth (27 days). That's the reason we only see one side of the Moon.

Because the Moon has a gravitational influence on Earth, we can see tides happen. The water basically shifts towards the Moon. Tides were probably very important for life to exist on land.

The fourth planet is Mars. It's the last terrestrial planet.

People thought Mars could have life on it (which is why Martian aliens are so common in sci-fi), but it is a dead planet.

Mars has a similar surface as the Earth, but it's much smaller, having only half of Earth's diameter.

Temperatures on Mars are around -125 to 20 degrees Celsius

Mars has a really thin atmosphere, and it's too cold for liquid water to be there. It does have polar ice caps with water tho, but there's a lot of carbon dioxide along with it.

The atmosphere is mainly out of carbon dioxide, and it's only 1% as thick as Earth's atmosphere.

Even tho the atmosphere is so thin, there are huge dust storms that create a pink hue.

There is a huge canyon on Mars called Valles Marineris. It's 5000km long and 10km deep. There's also the highest peak in the solar system, a volcano called Olympus Mons, which is 25km tall.

Mars has an iron core, which is solid due to the size of Mars. It has a mantle and a core, like the Earth. It doesn't have a big magnetic field.

It doesn't rain on Mars, but there probably was water a few million years ago. We know this because of the visible erosion on the surface of Mars.

Mars has two natural satellites: Phobos and Deimos.

Both of these moons are only 20 km in size and are probably asteroids from the asteroid belt.

that's all of the terrestrial planets! 

add stuff or correct me if I made a mistake somewhere :3

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