Saturn is well known for its ring system and many recognise that the planets Jupiter, Uranus and Neptune also have rings. Did Earth ever have rings though? A team of researchers suggests that a worldwide collection of impact craters points to the existence of a ring around Earth millions of years ago. It’s possible that Earth captured and destroyed an asteroid that passed too close 466 million years ago. The asteroids torn up debris orbited the Earth as a ring and then the individual chunks entered the atmosphere, landed on the surface and produced the craters observed today. 

Seeing the rings of Saturn against an inky black sky are the very things that grabbed my attention as a ten year old boy. Since then I have been fascinated by all things space. The rings of Saturn, and Jupiter, Uranus and Neptune are made up of a collection of lumps of ice and rock all orbiting around the host planet in the same way our Moon orbits around the Earth. Collectively, and from a distance, they look like a complex system of rings. 

The origin of the rings of the giant gas planets has been the cause of many debates over the decades. The most likely explanation is that the rings formed from the remains of moons or other celestial bodies that wondered a  little too close. The intense gravitational force from the planets tore the objects apart in a process known as tidal disruption. 

In a paper published by Andrew G. Tomkins and a team of researchers they suggest Earth too may have had its own rings in the past. Interactions between Earth and material from within our Solar System has been clearly evident. The Arizona crater and the Chicxulub impact event have left their scars on our planet but in the last 540 million years there was an increase in cratering events. Recorded in limestone deposits around the world are higher levels of chondrite (stony) meteorites and micrometeorite debris. At the same time there seems to have been an increase in seismic and tsunami activity although the correlation between the two is not confirmed. 

The increase in meteoric material in limestone has been suggested as being caused by a general increase in asteroid dust across the inner Solar System but an interesting alternative theory has been suggested by Tomkins and his team. They propose instead that a large chondrite asteroid experienced a near-miss with Earth around 466 million years ago. If the object passed within the Roche limit of Earth, then Earth’s gravitational field will be strong enough to stop any smaller object from being held together by gravity. It would therefore break-up and lead to the formation of a debris ring.

The team investigated the impact sites of the 21 meteorite impacts known to coincide with the increase in meteorite activity in the Ordovician period. They then calculated the probability that the identified impact points resulted from randomly distributed impact events. This would be the likely cause of all the impactors came from the asteroid belt scenario. Instead the team concluded that the impact structure were located near to the equator as would be the case if they came from a single body that broke up in orbit. The resultant decay of the ring particles would have lasted several tens of millions of years before finally settling in the limestone records for future researchers to unearth. 

Source : Evidence suggesting that earth had a ring in the Ordovician