Detecting the orbital instability of a Solar System giant planet using enstatite meteorites

Evidence from debris from an obliterated asteroid suggests that a shift in the positions of the giant planets in our solar system billions of years ago occurred between 60-100 million years after the formation of the Solar System and may have been key to the formation of our Moon. .

Astronomers led by the University of Leicester have combined evidence from simulations, observations and analysis of meteorites to reproduce the orbital instability caused by our solar system's giant planets moving to their current locations, which has been well modeled for 20 years.

Findings are Published In the journal Science and presented at the General Assembly of the European Geographical Union in Vienna.

Early in the solar system, the giant planets—Jupiter, Saturn, Uranus, and Neptune—had more circular and more compact orbits than they do today. Previous research has established that orbital instability in the Solar System changed that orbital structure and scattered the smaller planets. As many of these collided with the inner terrestrial planets, scientists called the Late Heavy Bombardment.

Lead author Dr. Chris Avtellido, „The question is, when did this happen? The orbits of these planets were perturbed by some dynamical process and took their final positions that we see today. Each time has different implications, and it's a matter of great debate in society.”

„What we've tried to do in this work is not just do a pure kinematics study, but combine different types of studies, correlations, kinematic simulations, and studies of meteorites.”

They focused on a type of meteorite called enstatite chondrites, which have a very similar composition and isotopic ratios to Earth, meaning they formed in our neighborhood. By making spectroscopic observations using ground-based telescopes, they linked those meteors to their source: a family of fragments in the asteroid belt known as Athor.

This suggests that Athor was originally very large and formed close to the Sun, and that it was affected by a collision from the asteroid belt that reduced its size.

To explain how Athor ended up in the asteroid belt, the scientists tested various scenarios using dynamical simulations, concluding that the most likely explanation was the gravitational instability that moved the giant planets to their current orbits. Analysis of meteorites shows that this occurred 60 million years before the solar system began to form.

Previous evidence from asteroids in Jupiter's orbit has placed constraints on how late this event occurred, with scientists concluding that the gravitational instability must have occurred between 60 and 100 million years after the birth of the Solar System, 4.56 billion years ago.

Previous evidence shows that Earth's Moon formed during this period, with a hypothesis that a planet called Thea collided with Earth, and debris from that collision formed the Moon.

The timing of orbital instability is important because it determines when some familiar features of our solar system will form—and may have influenced our planet's habitability.

Dr. Avtellido added, „It's like you have a puzzle, and you realize that something must have happened, and you try to put the events in the right order to create the picture you see today. The novelty of the study is that we don't. Pure mechanics only do simulations, or only experiments, or telescopes.” Just observations.”

„Our solar system once had five inner planets, not four, so we can have implications for other things, such as creating habitable planets. Questions like when did the objects that sent volatile organics to Earth and Mars arrive on our planet?”

„Time is very important because there were a lot of planets in our solar system to begin with,” said study co-author and research director Marco Delbo of the Nice Observatory in France. You'll have more time to get supplies to Earth and Mars.”