At a time when asteroid 2024 PT5 (often referred to as mini-moon, because it temporarily orbits around the Earth) performs a brief dance around our planet, journalists from National Geographic wondered about the consequences that would have the arrival of a true second Moon in our sky. A hypothesis which, although improbable, would have very significant repercussions on the fragile balance of our terrestrial ecosystem.
The secrets of our only satellite
The Earth-Moon system is characterized by dynamic gravitational interaction. As puny as it is in comparison to the Earth (about four times smaller), its force of attraction subtly deforms our planet, giving it a slightly elongated shape, similar to a rugby ball. Indeed, in accordance with the theory of general relativity, any object endowed with mass or energy curves the metric of space-time, our Moon is no exception. This is why our Earth is not a perfect sphere: the Moon “pulls” it towards itselfalthough it is not the only factor explaining the shape of our planet.
This phenomenon, combined with the Earth’s rotation, generates the tides that have punctuated marine life for millions of years. “ Almost all living beings are influenced, in subtle or profound ways, by lunar cycles. We are therefore deeply linked to the existence of our Moon » explains Thomas Statler, scientific manager at NASA.
Two moons in our sky: a nightmare?
If the Earth had a second moon similar to the current one, the consequences would be spectacular, particularly on the oceans. The stable configuration of two comparable satellites would radically transform the Earth’s tidal system. Not only would the amplitude and frequency of tides be disrupted, but these changes would affect all marine fauna. From the reproduction cycles of aquatic species to the migrations of large marine mammals, including the balance of coastal ecosystems, all marine biodiversity should adapt to this new rhythm.
These two moons, in fact exerting greater tidal forces,seismic and volcanic activity could also increase. More frequent and larger earthquakes, as well as more intense volcanic eruptions, cannot be ruled out.
Human activities would also be affected. Maritime navigation, which relies on precise knowledge of tidal cycles, would require a complete overhaul of its forecasts and itineraries. Ports, coastal infrastructure and fishing and transport activities should be redesigned to adapt to this new ocean reality.
Finally, such a configuration could modify the tilt of the Earth’s axis of rotation. Because this tilt is responsible for the seasons, a change could lead to significant variations in regional climate systems. The consequences would therefore be multiple and would affect all aspects of our environment: geology, climate, biology, etc.
Please note, however, that these scenarios are purely speculative and based on our current understanding of physical phenomena. Earth’s geological history suggests that the appearance of a second moon is highly improbable ; the orbits of planets and celestial objects in our solar system have, in fact, been relatively stable for billions of years. Furthermore, our Moon has always been alone; If the Earth had acquired a second moon of comparable size in the recent geological past, the phenomenon would have left indelible traces in the rocks and sediments. Gold, geologists have found no tangible evidence of such an event. This did not prevent certain science fiction authors from imagining such a scenario, such as Charles Duits in 1997 with his work, The World of Two Moonswhich explores just this subject.
- A second moon would disrupt the tides, strongly impacting marine life and coastal ecosystems.
- Human activities would be disrupted, with consequences for navigation and coastal infrastructure.
- Geological activity could intensify, leading to an increase in earthquakes and volcanic eruptions.
