Craters Only Ever Seen on Other Planets and Moons Discovered in Wyoming

Impact craters that have only ever been seen on other planets and moons have been discovered in Wyoming.

In a study published in the Geological Society of America Bulletin, scientists have announced the finding of secondary impact craters clustered in a field unlike anything else found on Earth before. The findings raise the possibility of a much larger impact crater yet to be discovered in the region.

Secondary impact craters are formed by debris from the larger initial impacts made by material crashing into a planet or moon from space. When such impacts occur at a high enough speed, the destruction they cause can eject material that cuts the secondary craters, which appear as elongated scars, into the surrounding land.

The paper compared the Wyoming craters to formations found not on Earth but elsewhere in the solar system. These included planets and moons that have thinner atmospheres than Earth, like Mars, Mercury and Ganymede—a moon orbiting the distant gas giant planet Jupiter.

Researchers said their work had uncovered a large number of craters—31 in total—in what they have called the Wyoming Crater Field, while more than 60 other structures that could be other impact craters await confirmation. They found the craters in a triangular area between the cities of Laramie, Douglas and Casper.

Images that accompanied the research showed the strange, stretched structures of the craters that appeared like close-ups of the moon or Mars.

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"The trajectories indicate a single source and show that the craters were formed by ejected blocks from a large primary crater," project leader Thomas Kenkmann, professor of geology at the University of Freiburg, Germany, said in a statement. "Secondary craters around larger craters are well known from other planets and moons but have never been found on Earth."

The speed at which these impacts occurred was incredibly fast—researchers said ballistics modeling indicated the impacts happened at between 700 and 1,000 meters per second (1,500 to 2,200 miles per hour), as fast as a speeding bullet.

Such high-speed impacts also ejected materials far out from where they occurred according to the scientist's modeling. The paper said that material thrown out from the impact sites could travel between six and 430 miles away.

The paper said that despite the clear evidence of secondary impact craters, the site of the initial larger impact which created them was still unknown. Its modeling proposed a site somewhere on the border between Wyoming and Nebraska.

They said the findings represented a rare phenomenon on Earth because our planet's thicker atmosphere typically breaks meteors up into smaller fragments prior to collision.

"Here, for the first time, evidence is provided that secondary cratering has been possible on Earth," the study said.