Gravitation is one of the fundamental forces of nature, along with the weak nuclear force, the strong nuclear force, and the electromagnetic force. Gravity is typical of bodies that have mass. Since Mars has it, obviously there is gravity there.
The force of gravity between two bodies causes them to attract each other. It is proportional to the mass of the two bodies, the proportionality constant being the universal gravitational constant, G, and it is inversely proportional to the square of the distance that separates them. In the case of the Earth, as it has a mass of six quadrillion kilos, for a person with a mass of 70 kilos, the gravitational force would be slightly more than 380 newtons, which would be his weight. Colloquially, we tend to use the unit of mass (kilogram) to refer to weight, which is not strictly correct.
On Mars, as its mass is considerably less than that of Earth, its gravity is also less, about a third of that of our planet. Something similar happens with the Moon, whose gravity is 16% of Earth’s.
Surely you remember the images of the astronauts who reached the Moon, in which they made very big jumps. These jumps are possible due to the difference in mass between the satellite and the planet. That is, on the Moon or on Mars we weigh much less than on Earth. On the Moon, a sixteenth part, and on Mars, a third part.
The Solar System is composed, in its area closest to the Sun, by the planets we call rocky: Mercury, Venus, Earth and Mars. And in the farthest zone, by the gas giants: Jupiter, Saturn, Uranus and Neptune. Among the rocky ones, Mercury has a gravity similar to that of Mars and Venus more similar to that of Earth. And in the giants, Jupiter has a little more than twice the Earth’s gravity, Saturn has more or less Earth’s, Uranus a little less and Neptune a little more. As I explained to you at the beginning, gravity is related to mass. These planets are much larger than Earth, but since they are gaseous, their density is much lower than that of rocky ones and therefore their gravity is also much lower.
The Sun is the most massive element in the Solar System. Its mass is more than 300,000 times that of the Earth. Therefore, its gravity is the greatest and causes the rest of the bodies in the system to orbit around it.
If we go back to Mars, it is a planet very similar to Earth, and yet it has aged much more rapidly. It is about 227 million kilometers from the Sun, while the Earth is only 150 million kilometers away. That additional distance, and the fact that it is a little smaller than ours, caused it to lose its atmosphere and its magnetic field, which is essential for life because it serves as a screen for solar radiation. Those characteristics have left the planet as we know it, with that desert aspect. But it is also very interesting because it has, for example, the most impressive volcanic fields in the Solar System. Mount Olympus, which is a volcano and the highest mountain on Mars, and in the entire Solar System, is 25 kilometers high, much higher than Everest.
As for the two satellites of Mars, Phobos is 6,000 kilometers from the planet and Deimos 20,000 kilometers. They are much smaller than the Moon, which is more than 3,000 km in diameter. Phobos is about 27 kilometers and Deimos, 15 kilometers. As a little challenge, can you calculate what your weight would be on Deimos?
Marina Diaz Michelena She is head of the Space Magnetism Area of the National Institute of Aerospace Technology (INTA).
Question sent via email byManuel Hernandez
Coordination and drafting:victory bull
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