Scientists from Rosetta's OSIRIS team have discovered an extraordinary formation on the larger lobe of comet 67P/Churyumov-Gerasimenko in the Aker region. From a group of three boulders the largest one with a diameter of approximately 30 meters stands out: images obtained on Sept. 16, 2014 from a distance of 29 kilometers with the help of Rosetta's scientific imaging system OSIRIS show it to perch on the rim of a small depression, according to a press release. There seems to be only a very small contact area with the nucleus.
Similar geological formations are found also on Earth. So-called balancing rocks touch the underground with only a tiny fraction of their surface and often look as if they may tilt or topple over any moment. Some can actually be rocked back and forth and are then referred to as "rocking stones." Impressive examples of balancing rocks occur in Australia or the southwest of the USA. Often these boulders travelled to their current location onboard of glaciers. In other cases, wind and water eroded softer material surrounding the rock.
