Venus has always fascinated scientists. It is the second planet from the Sun, very similar to Earth in size, mass and internal structure. However, unlike our planet, it does not have any natural satellite, which poses a mystery to astronomers. Various hypotheses have been put forward over the years trying to explain this lack. These included a scenario in which Venus never had a moon, or one in which its satellite was destroyed in a massive collision with another celestial body.
However, new research conducted by a team from the University of California, Riverside, indicates a completely different possibility. According to astrophysicist Stephen Kane, lead author of the paper published in The Astrophysical Journal, Venus could have "swallowed" its own moon as a result of natural physical processes taking place in its environment.
At the heart of the new theory is the extremely slow rotation of Venus around its axis. While the Earth completes one revolution in 24 hours, Venus takes 243 Earth days to do so. This specificity of rotation has a huge impact on the fate of the potential moon.
As Stephen Kane explains:
"My research shows that Venus did not need any catastrophe to get to its current situation. It turns out that the planet's gravity, combined with its rotation rate, naturally caused the moon to fall to its surface."
This mechanism is the opposite of what we observe in the case of the Earth and its Moon. The Earth's rotational energy is transferred to the Moon, causing the satellite to gradually move away from the planet - currently at a rate of about 4 centimeters per year. In the case of Venus, the slow rotation means that the hypothetical moon would be unable to maintain a stable orbit and would spiral down towards the planet over time.
To test this hypothesis, scientists created advanced computer models that simulate the gravitational interactions between Venus and the potential satellite. These models took into account different masses of the hypothetical moons - ranging from half to ten times the mass of Earth's Moon - and different rates of rotation of the planet.
The results were clear: in the vast majority of cases, the moon ended its existence by colliding with Venus. The larger the satellite, the faster the collision occurred.
While the research does not conclusively prove that Venus actually once had a moon, it does indicate that if such a satellite did exist, it could not have remained in orbit for billions of years. The collision would have to happen relatively quickly on a cosmic scale - probably within the first billion years of the planet's existence.
Direct evidence of such a cataclysm is difficult to find. The surface of Venus is relatively "young" - about 80 percent. its area was formed as a result of massive geological processes about a billion years ago, which could have destroyed all traces of past collisions. However, future space missions, such as NASA's planned DAVINCI+ and VERITAS, may provide information that will help resolve this issue.
The theory that the moon was "swallowed" by Venus could have far-reaching consequences for understanding the evolution of terrestrial planets. A collision with a large satellite would provide Venus with enormous amounts of energy and angular momentum, which could affect its rotation, climate and geological processes. If Venus had oceans or conditions favorable to life in the past, such a cataclysm could have changed them irreversibly.
The conclusions of this research extend beyond our solar system. Astronomers looking for Earth-like planets in other planetary systems often pay attention to the presence of moons, considering them a potentially important factor in the development of life.
