Why are there no moons that orbit Mercury and Venus?

Question:

Why are there no moons that orbit Mercury and Venus?

Our Solar System:

Our solar system consists primarily of the Sun at its center, and eight planets orbiting around it. These planets are broken up into two different groups. The first four, Mercury, Venus, Earth, and Mars, are the rocky worlds known as the terrestrial planets. The next four planets, Jupiter, Saturn, Uranus, and Neptune, are the gas giants known as the Jovian planets. Along with the planets there are also their many moons, the asteroid belt between Mars and Jupiter, and finally the Kuiper belt out beyond Neptune.

Answer and Explanation:

Scientists don't know for certain, but there are probably no moons that orbit Mercury and Venus because they are too close to the Sun.

For a planet to have a moon, that moon has to be able to form over many billions of years in a stable orbital region of space around the planet. This means that the moon must form at just the right spot that the material the moon is made is neither too close nor too far away from the planet. At a spot too close the material would just be brought down to the planet by its gravity, and if too far away it would drift away into space.

The problem with Venus and Mercury is that they are so close to the Sun that the Sun would try to pull the material needed to create their moons into it instead. This probably resulted in such a small stable region of space where a moon could form that either not enough material was there to form one, or the region was so small as to be too unstable to allow a moon to form over billions of years it would be necessary to do so.


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What is a Solar System? - Planets & Model

from General Studies Earth & Space Science: Help & Review

Chapter 1 / Lesson 2
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