The Ordovician period, which began approximately 485 million yearshas long intrigued scientists. Tectonic reconstructions of this era revealed a striking anomaly : the presence of 21 impact craters concentrated in a restricted area near the equator. This phenomenon is all the more surprising given that 70% of the Earth’s continental crust is located outside this region.
Professor Andy Tomkins and his team from Monash University used an innovative approach to study this unusual distribution of impacts. They calculated the continental surface area capable of preserving these craters, taking into account specific factors such as:
- The stability of cratons
- The age of rocks
- The absence of tectonic disturbances
- Preservation of geological structures
Their results showed that only 30% of areas suitable for crater preservation were near the equator at that time. Yet, all recorded impacts occurred in this region. The probability of such an occurrence is extremely low, comparable to getting the same result 21 times when tossing a three-sided coin.
The hypothesis of a system of terrestrial rings
To explain this phenomenon, researchers proposed a bold theory: the formation of a ring system around the Earth. According to their hypothesis, a massive asteroid would have approached too close to our planet, crossing the Roche limit. This limit represents the minimum distance a celestial body can approach a planet without being disintegrated by its tidal forces.
The asteroid would then have fragmented, forming a belt of debris orbiting the Earth. Over millions of years, these materials would have gradually fallen back onto the earth’s surface, consequently creating the peak of meteorite impacts observed in the geological record.
This hypothesis is corroborated by the presence of an extraordinary quantity of meteoritic debris in the sedimentary layers dating from this period. Professor Tomkins emphasizes: “We also observe that the sedimentary rock layers from this time contain extraordinary amounts of meteoritic debris. »
Climatic implications of an Earth ring
Beyond its geological interest, this discovery could have major repercussions on our understanding of the Earth’s ancient climate. The researchers hypothesized that the ring system could have cast a shadow on the planet, blocking part of solar radiation. This phenomenon may have contributed to the climatic event known as Glaciation hirnantienne.
This ice age, which occurred near the end of the Ordovician, is recognized as one of the coldest in the last 500 million years of Earth’s history. The following table illustrates the main characteristics of this climatic event:
| Characteristic | Description |
|---|---|
| Period | Late Ordovician (around 445-443 million years ago) |
| Duration | About 2 million years |
| Impact | Global drop in temperatures, expansion of ice caps |
| Consequences | Mass extinction of marine species |
This theory opens new perspectives on the influence of celestial events on the earth’s climate and the evolution of life. It also raises fascinating questions about possible other ring systems that the Earth could have possessed during its history, and their potential impact on the development of biodiversity.
Ultimately, this study reminds us that the history of our planet is intimately linked to cosmic events, and that understanding this distant past can help us better understand current and future climate challenges.
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