General, Research, Technology

Why does Mars have two satellites and not one?

The planet Mars has two moons.The first of these is Phobos, which has a diameter of 22.5 kilometers. The second satellite of Mars is Deimos with a diameter of 12.4 kilometers. Both satellites are potato-shaped and face the same side to the planet. Like many other celestial bodies in the solar system, they are full of secrets. The main mystery lies in their origin: at the moment there are two theories, and each of them is quite probable. Within the framework of this article, we will find out what the satellites of Mars are, under what strange circumstances they were discovered and how they could have appeared. One theory may explain why Mars has exactly two satellites, and not more or less.

Mars and its moons as seen by the artist


  • 1 Interesting facts about Phobos
  • 2 Interesting Facts About Deimos
  • 3 Discovery of the satellites of Mars
  • 4 How were the satellites of Mars formed?

Interesting facts about Phobos

Phobos is the largest satellite of Mars.It was discovered in 1877 by the American scientist Asaph Hall. The name was given in honor of the ancient Greek god Phobos, who personifies fear. The satellite is located at a distance of about 6 thousand kilometers from the surface of Mars. In the middle of the 20th century, scientists discovered that Phobos was gradually approaching the planet's surface and could eventually fall on it. But this will not happen soon, only after millions of years. During this time, people will already be able to build a colony on Mars and develop to such an extent that they will fly to other galaxies.

Phobos is one of the satellites of Mars. He is big

Interesting facts about Deimos

Satellite Deimos is almost half the size of Phobos.It was also discovered in 1877 by the same American astronomer Asaf Hall. The name was given in honor of the ancient Greek god Deimos, who personifies horror. It is located at a distance of 23.5 thousand kilometers from Mars, then if it is much further than Phobos. The surface of this moon is smooth, but there are two craters on it. The first is called Swift and is 1000 meters in diameter. The second is Voltaire, whose diameter is 1900 meters.

Deimos is the second satellite of Mars. It is smaller

Discovery of the satellites of Mars

For the first time I guessed about the existence of satellites of MarsGerman astronomer Johannes Kepler in 1611. The discovery was made by a happy mistake. In the course of studying the works of Galileo Galilei, he found an anagram, which he deciphered as the Latin expression "Hello, twins, a product of Mars." Subsequently, it turned out that in fact the message was encrypted sentence "The Highest Planet watched in triplets." In such an unusual way, Galileo Galilei described the case when Saturn seemed to him triple due to the presence of rings. In those days, no one knew about the existence of rings.

Moons of Mars - Phobos and Deimos

Also, he spoke about the presence of two satellites on Marswriter Jonathan Swift in his novel Gulliver's Travels. According to the plot, the discovery was made by astronomers of the fictional island of Laputa. The work was written 150 years before the official opening of Phobos and Deimos. The first satellite images were taken in 1909.

Snapshot of the Curiosity apparatus, taken in 2013. Phobos in front, Deimos in back

See also: Where and how could life have originated on Mars?

How were the satellites of Mars formed?

There are two theories of the origin of Phobos andDeimos. The first says that they were once ordinary asteroids. Flying past Mars, they could simply be attracted by the planet and thus become its satellites. This assumption seems to be true, because Phobos and Deimos do not have the perfectly round shape, like natural satellites of other planets. The only catch is that these space objects circle around Mars in an almost perfect circle. And the captured asteroids, according to scientists, would rotate in an elongated orbit.

Phobos and Deimos really look like asteroids

The second version says that once upon a time, Marsthere was one satellite, but for some reason it split into Phobos and Deimos. This assumption has always seemed more plausible, because there are almost no arguments against it. Moreover, research results were recently published in the scientific journal Nature Astronomy that increase the credibility of this version. Scientists from Switzerland have recreated satellites inside a computer model and found that once upon a time they moved in the same orbit.

But, most likely, Phobos and Deimos were once one. They could have been split by an arriving asteroid

If you are interested in the news of science and technology, subscribe to our channel in Yandex. Dzen. There you will find materials that have not been published on the site!

If this theory is correct, approximately 2.7 billion yearsback, an asteroid or other celestial object fell on the only satellite of Mars and split it. And that is why the planet now has two satellites. No more and no less. Of course, this is still just a guess, but the answer to the question "why does Mars have two satellites?" sounds like that. There is also a possibility that Mars could have three moons.