Understanding these numbers allows us to prepare meticulously for space travel, especially missions to deep space and planetary landings.
Gravity is one of the four fundamental forces of physics. After billions of years of formation, Earth has a gravitational force of about 9.8 m/s², creating conditions for humans and various other organisms to evolve and thrive. Humans, with their intelligence and science, refer to this gravitational force as 1 g. However, on different planets within the Solar System, their gravitational forces vary significantly.
In essence, gravitational force depends on the mass of an object. Everything, from stars and planets to galaxies and subatomic particles, exerts gravitational attraction on other objects. Depending on size, mass, and material density, the resulting gravitational forces differ.
For example, Earth’s current gravitational force is approximately 9.80665 m/s². This means that if an object is on Earth’s surface and thrown upwards, it will fall back with a velocity increasing at 9.8 meters per second.
According to Isaac Newton’s Universal Law of Gravitation, the magnitude of the gravitational force between two objects is calculated by the formula F = G (m1m2/r²). Here, F is the magnitude of the force, m1 and m2 are the masses of the two objects, r is the distance between them, and G is the gravitational constant (6.674×10^-11 Nm²/kg²).
Based on the size and mass of each planet, their gravitational forces can be expressed in terms of g units, as well as the rate at which objects accelerate when free-falling towards their surface. So, the results of these calculations are as follows:
Mercury
With an average radius of about 2,440 km and a mass of 3.30 x 10^23 kg, Mercury’s size is approximately 0.383 times that of Earth, and its gravity is only about 0.055 g. This makes Mercury the smallest and lightest planet in the Solar System.
However, due to its high material density of around 5.427 g/cm³ compared to Earth’s 5.514 g/cm³, Mercury has a surface gravity of 3.7 m/s², equivalent to 0.38 g.
Venus
Venus is similar in size to Earth, often referred to as our “sister planet.” With a surface area of 4.6032 x 10^8 km², a mass of 4.8675 x 10^24 kg, and a density of 5.243 g/cm³, Venus is about 0.9499 times the size of Earth, with a mass of 0.815 times and a density of approximately 0.95 times. Therefore, it’s not surprising that Venus’s surface gravity is very close to Earth’s: 9.87 m/s² or 0.904 g.
The Moon
The Moon is the only celestial body outside of Earth that humans have experienced gravitational force on its surface, during the Apollo missions. Calculated based on a radius of 1,737 km, a mass of 7.347 x 10^22 kg, and a density of 3.3464 g/cm³, the Moon’s gravity is 1.62 m/s² or 0.16 g.
Mars
Mars is the largest and heaviest planet in the Solar System after Earth. Its average radius is 69,911 ± 6 km, which is about 10.97 times that of Earth, and it has a mass of 1.8986 x 10^27 kg, equivalent to 317.8 times Earth’s mass. However, being a terrestrial planet with a thin atmosphere, it has a material density of approximately 1.326 g/cm³. As a result, the surface gravity on Mars (defined at the top of its atmosphere) is approximately 3.72076 m/s² or 0.379 g.
Jupiter
Jupiter is a gas giant and much larger than Earth. With a radius of about 58,232 ± 6 km (9.13 times that of Earth) and a mass of around 5.846 x 10^26 kg (95.15 times that of Earth), Jupiter has a material density of 0.687 g/cm³. Consequently, the surface gravity on its cloud tops is approximately 24.79 m/s² or 2.528 g.
Saturn
Saturn’s average radius is 25,360 km, and its mass is 8.68 x 10^25 kg. Saturn is about four times the size of Earth and over 14,536 times its mass. However, being a gas giant, it has a much lower material density, approximately 1.27 g/cm³. The surface gravity on Saturn’s gaseous surface is approximately 8.69 m/s² or 0.886 g.
Uranus
With an average radius of 24,622 ± 19 km and a mass of 1.0243 x 10^26 kg, Uranus is the fourth-largest planet in the Solar System. These figures indicate that it is about 3.86 times the size of Earth and over 17 times its mass. With a low material density of approximately 1.638 g/cm³, characteristic of gas giants, the surface gravity on Uranus’s cloud tops is around 11.15 m/s² or 1.14 g.
Neptune
Neptune’s average radius is 24,622 ± 19 km, with a mass of 1.0243 x 10^26 kg. It is the fourth-largest planet in the Solar System. These dimensions mean it’s approximately 3.86 times the size of Earth and over 17 times its mass. However, due to its low material density, approximately 1.638 g/cm³, characteristic of gas giants, the surface gravity on Neptune’s cloud tops is around 11.15 m/s² or 1.14 g.
In conclusion, it can be seen that the gravitational forces of the planets in the Solar System range from 0.38 g on Mercury and Mars to 2.528 g on Jupiter. The lower gravity on the Moon, at 0.16 g, allows for interesting experiments in a low-gravity environment.
Our ancestors and humanity as a whole have lived for millions of years in a 1 g gravitational environment. Understanding these numbers and the effects of different gravitational environments enables us to prepare meticulously for space travel, especially missions to deep space and planetary landings.