Ancient meteorites reveal clues to how Jupiter formed

Two oxygen isotopic signatures, indicating two different planetary sources, found in single sample

Angrite meteorites on Earth hold clues about the chaotic way Jupiter came into existence. Photo: Nasa

Rare meteorites found in north-west Africa have provided ground-breaking clues into how Jupiter was formed, scientists said on Monday.

The ancient meteorites contained isotopic signatures from two different planetary origins, providing the first physical evidence of collisions between Jupiter and other celestial bodies billions of years ago.

The angrite meteorites help to show how Jupiter formed and settled in its position as the fifth planet from the Sun, according to the findings published in Nature Astronomy.

“The formation and migration of giant gas planets such as Jupiter are crucial to the evolution of planetary systems, and yet the timing of these events in our solar system remains largely unconstrained,” said Ben Rider-Stokes, from the Open University in the UK.

“Angrite meteorites represent some of the oldest materials in the inner solar system, and therefore provide an exclusive window into the processes that occurred during this period.”

It is thought that over millions of years, Jupiter roamed towards the centre of the solar system and back out again, at one point moving in about as close as Mars is now.

“This [Grand Tack] model suggests that upon Jupiter's initial formation it was pulled towards the sun due to gravitational attraction,” Mr Rider-Stokes said.

“However, when Saturn formed, it pulled Jupiter back to its current position in the Solar System.

“This movement of in-and-out is thought to have caused gravitational disruptions to asteroids and other bodies that formed close to Jupiter, causing these bodies to smash into one another.”

Researchers examined angrite meteorites collected by a joint Japanese and Belgian Antarctic research expedition and others found in north-west Africa.

Mr Rider-Stokes said: “Angrite meteorites are ancient meteorites that formed at a similar time period to the proposed formation and migration of Jupiter around 4.5 billion years ago.

“Due to their ancient ages, these meteorites are extremely important in testing this model.”

The international team analysed the chemical composition of the meteorites, focusing on oxygen isotopes — different forms of the same element.

For the first time they found two oxygen isotopic signatures, which indicates two differing planetary origins within a single sample.

“This study indicates these meteorites are a result of asteroids and bodies colliding together and possibly due to the gravitational disruptions of Jupiter's formation and movement,” Mr Rider-Stokes said.

“This, therefore, provides the first empirical evidence for this event, which has only been previously modelled.”

Researchers are next investigating the hydrogen content of the samples to understand more about how water was delivered to the inner solar system.