The rings around Saturn are considered to be one of the most beautiful things in the solar system. Now a research has revealed that something similar must have existed on Earth too. A paper published last week in Earth and Planetary Science Letters has presented evidence that Earth too must have had a ring. This article published by Andrew Tomkins of Monash University and his colleagues says that the existence of such rings, formed about 466 million years ago and lasting for a few million years, can solve many puzzles of our planet’s history.
Earth with rings
Around 466 million years ago, a lot of meteorites started hitting the Earth. We know this because a lot of craters formed on the Earth in a very short period of time. From the same period, we also find limestone deposits in Europe, Russia and China that contain a lot of debris from a certain type of meteorite. These rocks show signs that they were exposed to space radiation for a much shorter time than meteorites that fall today. There were also a lot of tsunamis at this time. We think all of these events are connected. But what links them together?
a pattern of craters
The research mentions 21 meteorite craters. Using models of the movement of the Earth’s tectonic plates in the past, it has been found where all these craters were when they first formed. It was found that all the craters are on continents that were close to the equator during this period and none are at a place that was close to the pole. This suggests that these craters formed close to the equator. However, is this a fair sample of the impacts that actually occurred?
Under normal circumstances asteroids hitting Earth would have hit anywhere as we see in craters on the Moon, Mars and Mercury. So it is unlikely that all 21 craters from this period would have formed close to the equator and were unrelated to each other. All this evidence led to the conclusion that a large asteroid broke up during its contact with Earth. Over millions of years, debris from the asteroid rained down on Earth, creating the pattern of craters and tsunamis.
how rings are made
You may know that Saturn is not the only planet with rings. Jupiter, Neptune and Uranus also have rings. Some scientists have even suggested that Mars’ tiny moons Phobos and Deimos could be the remnants of a ring. When a small body (such as an asteroid) passes close to a larger body (such as a planet) it is pulled in by gravity. When it gets close enough (within a distance called the Roche limit), the smaller body will break up into lots of small pieces and a few larger pieces. All those pieces hit and roll around and slowly turn into debris orbiting the larger body’s equator. Over time the things in the ring fall onto the larger body where the larger pieces form craters. So it’s possible that Earth too may have had a ring if it smashed into an asteroid about 466 million years ago.
What was the earth like with the rings?
The continents on Earth were in different positions at that time. Much of North America, Europe and Australia were close to the equator, while Africa and South America were at the South Pole. The ring would have been around the equator and since the Earth’s axis is tilted relative to its orbit around the sun, the ring would have shaded parts of the Earth’s surface. This leads us to another interesting puzzle. About 465 million years ago our planet began to cool dramatically. 445 million years ago it was in an ice age, the coldest period in the last half a billion years. This raises the question of whether the ring shading the Earth was responsible for this extreme cold.