Terrestrial planets are those that have hard surfaces because they are primarily composed of rock and/or metals. Many planets do not have a hard surface because they are mostly made up of gasses. While terrestrial planets may have some atmospheric gasses, their surfaces are rocky.
An easy way to remember what terrestrial planets are is to remember that these planets are Earth-like planets.
What are the Terrestrial Planets in our Solar System?
Terrestrial planets are also called “inner planets” because they make up the first four and innermost planets our Solar System. Therefore, the terrestrial or inner planets are Mercury, Venus, Earth, and Mars.
What are the Characteristics of Terrestrial Planets?
Aside from their rocky and hard surfaces, terrestrial planets have common characteristics. The core of a terrestrial planet is usually made of a heavy core that primarily contains iron. Part of the core is molten, and the molten metal creates electric currents as the planet rotates.
The sizes of these cores vary between planets; for instance, Mercury’s core takes up most of the planet, which is not true for the other inner planets.
The terrestrial (inner) planets have similar landscapes when looking at their surfaces. Just like Earth, terrestrial planets can have mountains, volcanoes, craters, and canyons. They can also experience erosion. Each planet is shaped by different processes that occur as a result of the planet’s composition.
The features of a planet’s landscape can depend on craters impacting the surface, volcanos erupting, tectonic plates moving, and erosion processing weathering the hard surface. Another significant feature of these planets which also affects their landscapes is their atmospheres.
Mercury has a thin atmosphere that constantly escapes the planet’s gravitation field, so it must constantly replenish its atmosphere. Venus, however, has a very dense atmosphere, which results in severe effects from trapped greenhouse gasses. Earth’s atmosphere is also dense, but not as dense as that of Venus. Mars has a thinner atmosphere, but it is not as thin as Mercury’s atmosphere.
Since Mercury has little air, it does not experience erosion like Venus, Earth, or Mars. Earth has tectonic plates that slowly move and shift, and this movement creates mountains and trenches in the ocean. The thin atmosphere of Mercury also allows for craters to impact its surface and create holes or canyons.
The atmosphere and composition of the planets significantly shape the cosmetic features of their surfaces.
Terrestrial planets can share the following characteristics:
- Heavy molten core
- Atmospheres (thick and thin)
- No rings
- Few Moons (or none)
Terrestrial vs. Jovian planets
Jovian planets are considered the planets beyond Mars; therefore, Jovian planets include Jupiter, Saturn, Uranus, and Neptune. When compared to terrestrial planets, the Jovian planets have significant differences. Just as terrestrial planets are similar to Earth, Jovian planets are similar to Jupiter.
Jovian planets are primarily made of gas, not rock, and they are considered gas or ice giants. Jovian planets are made up of hydrogen, helium, and/or other heavy elements and gasses. Since they are made up of gas, they have no surface. You would not be able to stand on Jovian planets like you would on Earth or Mars.
Whereas terrestrial planets have very few moons, Jovian planets have many moons. They can also have many rings, just like Saturn.
Where Did the Word Terrestrial Come From?
The word terrestrial derives from the Latin word terrestris, where terra means earth. This reinforces the idea that terrestrial planets are Earth-like, which the word illustrates.
Interesting Facts about Terrestrial Planets
- Mars has large volcanoes, which suggests it once had active tectonic plates
- Olympus Mons, a mountain on Mars, is the largest in the Solar System.
- Earth’s tectonic plates give the planet one of the most diverse and unique surfaces in the Solar System
- The atmospheres of terrestrial planets are determined by their distance from the sun, their mass, their radius, their geological processes, and their surface organisms.
- Strange domes can be found on the surface of Venus. Scientists think this is a rock that was pushed upward by lava trying to reach the planet’s surface.
- Venus has acid in its rain clouds which may cause some chemical erosion on its surface.