The solar system consists of 8 planets that most of us can quickly identify in the night sky using our naked eyes or a telescope, in the case of Neptune and Uranus.
However, comparing the masses of these planets by eyeballing them and comparing their sizes is a bit complicated since they are composed of different materials, which greatly influence their final mass.
Mercury, Venus, Earth, and Mars, the four closest planets to the Sun, have a solid surface and are thus called rocky or terrestrial planets.
In contrast, the remaining four, Jupiter, Saturn, Uranus, and Neptune, are called gaseous planets. They are mostly made of gas, although they have a solid core.
Gaseous planets tend to be huge and occupy large spaces, yet are made of lighter materials. Rocky planets are relatively small but are made of heavy rocks, which have a lot of mass per unit area.
The following is a list of the planets in order of mass, from smallest to largest.
Table of Contents
Mercury
Mercury is the smallest planet in the solar system by size and mass.
With a radius of 2,439.7 km, Mercury’s size translates to only 0.38 that of planet Earth while its mass of 3.30 x 1023 kg is 0.055 that of our home.
It is the most iron-rich planet in our solar system, with iron forming 70% of the planet’s total weight.
However, since Mercury’s atmosphere is weak, it can not effectively prevent meteors from hitting it regularly.
This makes it the planet with the highest number of craters in the solar system.
Mars
Mars is also referred to as the red planet because of the brownish-red color of its surface.
It has a radius of 3,389.5 km, which is almost half that of Earth.
However, despite being half the size, the red planet’s mass is significantly lower at only 6.42 x 1023 kg or 0.1 of our planet’s mass.
Mars and Earth have many similarities, including a day in the red planet being only 41 minutes longer than Earth.
In addition, Earth and Mars both have tilted rotation axis at very similar angles. The tilt on Earth is at 23.4 degrees, while that of Mars is 25.2 degrees.
This tilting of the axis also makes the red planet experience seasons just like planet Earth.
However, the lengths of these seasons are longer on Mars since the planet takes a long time to go round the Sun.
Venus
Even though it’s not the closest planet to the Sun, Venus is still the hottest planet in the Solar System.
This is because the planet has a thick atmosphere filled with carbon dioxide and yellowish clouds of sulphuric acid that trap the planet’s heat, causing the temperatures to soar up to 475 degrees Celsius.
Venus’ radius at 6,051.8 km puts the planet’s size at 0.9 that of Earth. The similarity between the two planets’ sizes is why Venus is also referred to as Earth’s twin.
Since the planet is also composed of materials similar to Earth’s, Venus’ mass at 4.87 x 1024 kg translates to 0.8 that of our blue planet.
Earth
Next up in the hierarchy is our planet, with a mass of 5.97 x 1024 kg.
Earth remains the only planet known to support life in the entire universe. However, scientists are carrying out numerous studies to find life on other planets and moons.
Water covers around 70% of Earth’s surface, while the atmosphere consists of 78% nitrogen and 21% oxygen.
The availability of water and oxygen is what essentially separates Earth from the other planets in the solar system.
Uranus
Uranus has the smallest mass among the gaseous planets in our solar system, but it is still bigger than the rocky planets.
At 8.68 x 1025 kg, Uranus has 14.5 times the mass of Earth, while its radius of 25,362 km makes the planet’s size four times larger than Earth.
Despite Neptune being further away from the Sun than Uranus, Uranus still manages to hold the title of the coldest planet in our solar system because it gives off much less heat than it absorbs from the Sun.
Unlike all the other planets in our solar system, which rotate on their axis, Uranus turns on its side.
This hints that it once collided with a planet-size body soon after it was formed billions of years ago.
Its mass consists of hot dense fluids such as water, methane, and ammonia. The core of the planet can heat up to 4,982 degrees Celsius.
On the other hand, the atmosphere is mostly hydrogen and helium, with a small amount of methane and traces of water and ammonia.
Neptune
Neptune, the furthest planet from the Sun, also has a radius four times that of the Earth at 24,622 km.
However, despite being smaller than Uranus, Neptune has a bigger mass because it consists of denser materials. Its mass at 1.02 x 1026 km is 17.1 times bigger than that of Earth.
Like Uranus, Neptune’s atmosphere consists of hydrogen, helium, and methane, while its core is composed of iron, nickel, and silicates.
With winds that can hit 2,100 km/hour, Neptune has the strongest winds in the Solar System.
Saturn
The scale starts to get big when you get to Saturn. Its radius of 58,232 km is nine times bigger than that of Earth, while its mass at 5.68 x 1026 kg is 95.2 times that of Earth.
Saturn, popularly known for its ring system, is also the furthest planet from Earth that can be seen with the naked eye. The rings consist of chunks of ice and small amounts of carbonaceous dust.
Its atmosphere is made up of hydrogen and helium, with slight traces of other gases like methane and ammonia.
Because the core of the planet is so hot, the hydrogen in this region becomes metallic.
Jupiter
The last planet on our list and one with the biggest mass is Jupiter.
At 11 times the size of Earth, Jupiter’s radius is 69,911 km with a mass of 1.90 x 1027 kg, which is 318 times that of Earth.
To put this in perspective, when the masses of all the other planets are combined, Jupiter remains 2.5 times more massive.
Like Saturn, this planet primarily consists of hydrogen and helium with rocks and a dense ice core.
The liquid metallic hydrogen present in Jupiter, just like in Saturn, is responsible for the planet’s massive magnetic field, which is 14 times stronger than that of Earth.