Gravity on Other Planets
Today, we’ll be talking about gravity on other planets. Gravity is a fundamental force in physics, and it’s one we often take for granted on Earth. Having only lived on this planet, humans are accustomed to Earth’s environment, where gravity is a steady 1 g, or 9.81 m/s². We rarely think about it, and many assume gravity is the same everywhere in the universe. However, if you ventured into space or set foot on the Moon, the gravity would be quite different—something earthlings aren’t accustomed to.
In simple terms, gravity depends on mass. It arises from stars, planets, galaxies, and even subatomic particles and seems to rely primarily on just one thing: mass. Mass itself can be categorised in three ways: size, mass, and density. These factors determine the gravity of an object. In our solar system, planets vary widely in size, density, and mass, which means the gravitational strength on each of their surfaces can vary dramatically.
Earth’s Gravity
To discuss today’s topic, gravity on other planets, let’s start off with the Earth’s gravity. As noted before, it was 9.8 m/s2. This means that if you helped hold an object and let go of it, it would accelerate towards the surface at a speed of 9.8 m/s every second from the freefall. This is a standard measurement to know the gravitational pole of a planet, and we express this in what’s known as a single ‘g’. Isaac Newton’s Universal Gravitational Law states that two bodies can be expressed mathematically as a formula of a force, where f is the force, M1 and M2 are the masses of the objects interacting, and R is the distance between the centres of the object. There is also a gravitational constant, so now that we know how to mathematically figure it out and use experimentation to prove this, let’s compare gravity on other planets in the solar system.
Gravity on Mercury
So, let’s start off with Mercury. It has a mean radius of 2,440 km and a mass of 3.3 X 1023 kg. Mercury is only about 1/3 the size of Earth, making it the smallest and least massive planet in the solar system. However, it does have a high density, which is just slightly lower than the density of Earth. Mercury has a surface gravity of 3.7 m/s2, so if you do the calculation, that’s the equivalent of 0.38 g.
Gravity on Venus
So, what’s the gravity like on Venus? Venus is a very similar planet to Earth, and it’s often known as the Earth’s twin. Venus has a radius of just over 6,000 km and has a mass of 4.87 X 1024 kg, and as you can see, it’s pretty much the same size as Earth but just a tiny bit smaller. It again has around about the same density, but because of the lower density, the gravity changes. This comes out at 8.87 m/s2, which means that the gravity on Venus is just lower than Earth’s at 0.91 g.
Gravity on Moon
So, what’s the gravity on the moon? The Moon is the only astronomical body where human beings are being able to test out gravity in person. So, the Moon is a very small object at around 1700 km in radius; its mass is 7.35 X 1022 kg, and the surface area is the same as the United States. Because of its size and mass, it also has a low density, which means that the gravity is only 1.62 m/s2, so the gravity is very low at 0.17 g. This gives a great reason why the astronauts on the Apollo missions were jumping around like they were on a trampoline; it also gave them a great excuse to experiment with the gravity of the moon. You can do certain things on the surface of the moon that you could never do on the surface of the earth.
Gravity on Mars
So, what about Mars? Its size, mass, and density are very small compared to our home planet. It has a radius of over 3,000 km and a mass of 6.42 X 1023 kg, but of course it’s a lot smaller than Earth. With this, it comes with a lower density, and therefore its gravity is lower as well, at 3.72 m/s2. So, if you calculate, it comes out to 0.38 g, which again is actually closer to the gravity on the moon than it is to Earth.
Gravity on Jupiter
What about the king of the planets, Jupiter? Well, Jupiter has just under 70,000 km in radius and has a mass of 1.9 X 1027 kg. Because it’s the giant of the solar system, it completely dwarfs the Earth and all of the inner planets. But because it’s mainly made out of gas, it has a much lower density, and therefore, because of its considerable size, it doesn’t have a higher ‘g’ than you’d expect; it only comes out at 24.75 m/s2. This means that Jupiter’s gravity is only 2.53; that’s only 2.5 times the strength of Earth, even though Jupiter’s mass is over 317 times that of the earth.
Gravity on Saturn
So, what’s the gravity like on Saturn, well, like Jupiter? Saturn is a very similar planet at just under 60,000 km. This is the second biggest planet in the solar system after Jupiter and has a mass of 5.69 X 1026 kg, and of course it dwarfs all of the inner planets put together. But again, it falls short like Jupiter because of its composition. This means that its gravity is only 10.44 m/s2, and surprisingly, it has near enough the same ‘g’ as Earth does at 1.07.
Gravity on Uranus
So, now we come to the outer solar system. This is the realm of the icy giants, so let’s start with Uranus. Uranus is the third-largest planet in the solar system, at just over 25,000 km. It has a mass of 8.68 X 1025 kg, and of course it’s just over four times the size of Earth. So again, this is still a very large planet, but like the other gas giant, Uranus falls short on density. So, this means that it’s only 8.69 m/s2, so therefore it comes out lower than 1 g at 0.87.
Gravity on Neptune
And finally, we come to the furthest planet from the sun, Neptune. Neptune is just under 25,000 km, making it the fourth largest planet. It has a mass of 1.03 X 1026 kg, and again, it’s a very similar size to Uranus, not only in mass and size but also in density. But it does have a higher gravity at 11.15 m/s2, which means that it actually goes higher than Earth at 1.14 g.
So, it doesn’t quite matter if you’re on the surface of Mercury, the surface of Mars, or the clouds of Jupiter. Gravity on other planets and Sun basically depends on the size, mass, and density; it also seems to figure out the formation of our solar system and the orbits of the planets. Understanding the effect of gravity, or 0 g, on the human body is essential for space travel, especially when you’re going on long-duration missions like to the International Space Station, the moon, or possibly even Mars. Knowing how strong the gravity is on other planets could help us understand more about gravity itself because understanding the gravity on other planets basically relies on three things: its mass, its size, and its density, so I hope that’s given you a great insight into the gravity on other planets.