2004 EW95: Asteroid Exiled to Cold Edges of Our Solar System Looks Nothing Like Its Neighbors

The edge of our solar system is ringed by a vast cloud of small, icy bodies. But astronomers have always suspected there were a few infiltrators here and there. They thought that as large planets wandered through the solar system during its early days, they kicked a few more traditional rocky asteroids out to this cold, dark exile.

Now, they've finally proven that hunch, according to a new paper published in The Astrophysical Journal Letters. That paper uses new data about an object discovered in 2004—2004 EW95—to identify it as a rocky asteroid like those found in the belt located between Mars and Jupiter.

"It looks fairly convincing to me," Linda French, an astronomer at Illinois Wesleyan University who wasn't affiliated with the new study, told Newsweek. The result suggests that scientists have been on the right track in believing that in the early days of the solar system, Jupiter and Saturn spent some time wandering through the solar system, with their huge masses disturbing everything else in the area. "Basically, all hell broke loose in the solar system and all the small bodies got tossed around," she added.

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The object had seemed a little odd, not quite matching the small, icy look of its neighbors in the Kuiper Belt, the same region where Pluto is found. "It looked enough of a weirdo for us to take a closer look," first author Tom Seccull, a graduate student in physics at Queen's University Belfast in the U.K., said in a press release.

In order to identify what 2004 EW95 was made of, the team studied the light reflected off of it. That showed what the team recognized as the signature of a carbonaceous asteroid, the same kind of carbon-rich asteroid that is typically found in the asteroid belt between Mars and Jupiter.

That's the best evidence to date that the early hubbub sent objects flinging out from the center of the solar system to its edges. Astronomers already had proof that the reverse happened, with some small icy bodies clearly belonging to the far reaches of the solar system wandering in toward its heart.

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An artist's depiction of asteroid 2004 EW95, which looks like none of its neighbors out in the Kuiper Belt. ESO/M. Kornmesser

"It's really nice to see that there's a degree of symmetry," Neyda Abreu, a geoscientist at Penn State DuBois who wasn't involved with the new research, told Newsweek. "That is truly fascinating."

Abreu added that the presence of a type of compound called phyllosilicates on 2004 EW95 is particularly intriguing. Those compounds don't form unless there's water present—and that means that an asteroid like this one could have carried both organic compounds and water out to the borders of the solar system.

From there, because gravity is relatively weak, it's a quick hop out to other solar systems. For Abreu, that raises an exciting possibility: that these exiled asteroids could allow different solar systems to trade the ingredients of life.

It's too early to say precisely how many of these misplaced asteroids may be lurking in the Kuiper Belt—but given how 2004 EW95 looks compared to its neighbors, there's almost certainly at least one.