Francesca DeMeo wanted to know what the asteroid belt looked like. “I thought, everyone else must know this, but not me,” says the Harvard planetary scientist.

As she searched through the literature, she found that an overview of space rocks didn't exist—not one made within the last few decades, at least. So she set out to make a map herself. The result, published in Nature last Thursday, reveals a trend: rogue asteroids—those appearing at a spot different from where they formed—are quite common. Something must have displaced them, which suggests that the Solar System must have once been volatile.

The most recent map DeMeo could find was made in the early 1980s. Composed of just over 1,000 objects, it illustrates a neat arrangement of space rocks within the asteroid belt. Those in the inner part of the main belt, closer to the Sun, are asteroids that, in compositional measurements, appear red. These formed at warm temperatures, where it is too hot for some molecules (like water) to condense and become part of the asteroid. Farther away, closer to Jupiter, were blue-appearing asteroids created in the cold. Here, water can condense to ice. In between the two extremes was a neat gradient. Asteroids were born and stayed put, the story went, and this was repeated for years to come. The Solar System was always pretty calm.

The first clue that the narrative was wrong came in 2000. Magnya, an asteroid discovered in 1937, was revealed to be made of basaltic rock. At 3.15 astronomical units from the Sun in the outer part of the belt, it was unlike anything else nearby. In Science, researchers wondered what the misfit's story was. How had it been ejected, tossed, or propelled to an unexpected location, over one astronomical unit—the distance between the Earth and the Sun—from where it probably formed?

In the years that followed, scientists discovered more rogues. “We'd find a few asteroids, that we think formed close to the Sun, at the outer part of the belt near Jupiter,” says DeMeo. The line of thinking went that each, individually, wandered to a different spot on the red to blue gradient, put there by some unique event.

But the trickle of rogue asteroids became a river, DeMeo writes. She organized the tens of thousands of asteroids that had been discovered since the 1980s. The result: a mish-mash of warm and cold asteroids, all scattered throughout the main belt. “It goes beyond a couple of rogues,” says DeMeo.

The neat gradient, present at the time of the Solar System's formation, does not exist today. DeMeo thinks the gradient was destroyed by movement of planets, shaking the rocks around, “like flakes in a snow globe,” she writes.

A second map—a cartoon—offers an explanation for how the shaking took place. Within the dimensions of time and distance from the Sun, DeMeo traces out the planets in a zig-zag with what are now major bodies Mars, Saturn, Jupiter and Neptune swooping closer to the Sun shortly after the formation of the Solar System. These planets then move back out to where they are today, scattering and flinging rocks along the way. The new image—the asteroid map and the planet-motion cartoon—jives with what theorists have been suspecting, says DeMeo.

Today, astrophysicists are discovering other kinds of “misfit” asteroids, such as the strange six-tailed P 2013/P5, found in August. University of California astrophysicist David Jewitt thinks that this might be an asteroid singing its swan song, spewing trails of dust perhaps until it becomes nothing but dust. Like the misplaced Magnya, P2013/P5 might not be alone in its strangeness: Jewitt thinks this is how small asteroids die, and it might be a process that creates the fine space dust permeating our Solar System.

Each data point, each asteroid, offers a small clue about how our home planetary system formed. As we explore other worlds far away, asteroids will reveal clues about how our own came to look the way it does, how it shifted and shook and broke apart into a place with at least one planet—maybe more—that is home to life. For this, DeMeo has her map.

Nature, 2014. DOI: 10.1038/nature12908 (About DOIs).