How Many Moons Does Mercury Have?

How many moons does mercury have
Credit: NASA

There’s something strange about the planets in our solar system. While some planets boast dozens of planets, some have none. Today we’re going to learn how many moons does mercury have. So stay put!

During the 1970s, the astronomers believed that even mercury had a moon when the instruments on the Mariner 10 spacecraft of NASA found huge amounts of ultraviolet radiation around the planet. The scientists were quite convinced that the radiation was not coming from Mercury and was probably from a nearby moon. However, the radiation disappeared the next day and was later found to be coming from a distant star. But what about Mercury? Does it have a moon?

How Many Moons Does Mercury Have?

You’ll be surprised to know that mercury does not have a moon. Wondering why? That’s because Mercury lies very close to the sun and its gravity would make it impossible to hold on to its own moon. If Mercury even had a moon, it would probably crash into the planet itself. And if it survived the crash, it would probably get into orbit around the Sun and get pulled into it eventually. Either way, the moon wouldn’t survive on planet Mercury.

Now, this was a simple answer to your question. Let’s get into detail about why planet Mercury doesn’t have any moon?

Why Is There No Moon On Mercury?

To answer this question of yours, we’d have to examine the process through which the other 7 planets acquired their moons. Why seven? Because even Venus has no moon! A celestial body acquires a natural satellite in three ways. Firstly, satellite forms from a circumplanetary disk orbiting a planet. In this case, the disk coalesces to form larger bodies, which may or may not be huge enough to become spherical. That’s how Neptune, Uranus, Jupiter, and Saturn got most of their satellites.

Secondly, satellites are acquired when a small body is captured by the virtue of the gravity of a larger body. That’s how Phobos and Deimos, the moons of Mars, and the small, irregular moons of Saturn, Neptune, Uranus, and Jupiter were formed.

Thirdly, moons can also be a result of massive collisions that made the planet throw out some of their material into space, which amalgamated to form a satellite in orbit. This is how Earth’s Moon was formed when a Mars-sized object collided with it 4.5 billion years ago.

Now, let’s come to Hill Sphere, a region around an astronomical body that attracts the satellites. The outer edge of the Hill Sphere has a zero-velocity surface, referring to a body surface that energy cannot cross because of the zero velocity on it. So to orbit a planet, a moon must have an orbit lying within the Hill Sphere of the same planet. Take the Earth for example, which holds the Moon in its orbit, despite the gravity of the Sun. And how is it possible? It’s because it orbits within the Hill Sphere of the Earth. And this is why Mercury does not have a moon of its own. But this isn’t just the only reason why Mercury doesn’t have anyone. There are various other reasons, which we’re going to discuss below!

  1. The Size And Orbit:

As mentioned above, the small size of this planet and its close proximity to the Sun make its gravity too weak to retain a natural satellite. So if a large object approaches Mercury and tries to enter its Hill Sphere, it would be snatched by Sun’s gravity.

  1. Scarcity Of Material:

The scarcity of material in its orbit could also be the reason for the lack of a moon in Mercury. During the formation of Mercury, trace substances like methane and hydrogen remained in gaseous form and were later swept away, leaving only nickel and iron in solid form. All these merged to form Mercury and other planets.

To conclude, planets that are closer to the sun, such as Venus and Mercury will always be without natural satellites and the moon. If you’ve anything else to ask, leave us a question below.


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