Using the OSIRIS camera aboard the Rosetta spacecraft, ESA scientists have discovered a strange formation of what appears to be balancing boulders on comet 67P/Churyumov-Gerasimenko.

The three objects are located in the Aker region of the comet. The largest (labelled 3), which measures approximately 100 feet (30 meters) in diameter, appears to be making very little contact with the surface. It also looks like it’s resting on the rim of a small depression.

These features are reminiscent of “balancing rocks” on Earth. They touch the ground with only a tiny fraction of their surface, and they often look very precarious. They can form any number of ways, including the erosion of softer materials in the bedrock, or via glacial melting, i.e. “erratics.”

Balancing rocks in Marble Canyon, Arizona (credit: Arne-kaiser/CC).

“How this apparent balancing rock on Comet 67P/C-G was formed is not clear at this point,” noted OSIRIS Principal Investigator Holger Sierks at the ESA’s Rosetta blog.

It’s possible that cometary activity caused the boulders to move from their original location and migrate to the new site. If confirmed, that would be an exciting observation — an actual example of an evolving exo-geological processes on a cometary surface.

Another possibility is that the rocks are not actually balancing, and that the shadows are playing tricks with the ESA researchers. Further observations will hopefully provide more insight into these unique cometary features.

[ ESA ]