What Caused this Mysterious Ring in Antarctica?Ever since its discovery was announced earlier this year, the 3 km-wide ring structure discovered on the of Antarctica has been a source of significant interest and speculation. Initially, the discovery was seen as little more than a happy accident that occurred during a survey of East Antarctica by a WEGAS (West-East Gondwana Amalgamation and its Separation) team from the Alfred Wegener Institute.

However, after the team was interviewed by the Brussels-based International Polar Foundation, news of the find and its possible implication spread like wildfire. Initial theories for the possible origin of the ring indicated that it could be the result of the impact of a large meteor. However, since the news broke, team leader Olaf Eisen has offered an alternative explanation: that the ring structure is in fact the result of other ice-shelf processes.

As Eisen indicated in a new entry on the AWI Ice Blog: “Doug MacAyeal, glaciologist from the University of Chicago, put forward the suggestion that the ring structure could be an ice doline.” Ice dolines are round sinkholes that are caused by a pool of melt water formed within the shelf ice. They are formed by the caving in of ice sheets or glaciers, much in the same way that sinkholes form over caves.

“If the melt water drains suddenly,” he wrote, “like it often does, the surface of the glacier is destabilised and does collapse, forming a round crater. Ice depressions like this have been observed in Greenland and on ice shelves of the Antarctic Peninsula since the 1930s.”

However, in glaciers, these cavities form much more rapidly, as the meltwater created by temperature variations causes englacial lakes or water pockets to from which then drains through the ice sheet. Such dolines have been observed for decades, particularly in Greenland and the Antarctic Peninsula where the ice melts during the summertime.

Initial analysis of satellite images appear to confirm this, as they indicate that the feature could have been present before the supposed impact took place around 25 years ago. In addition, relying on data from Google Maps and Google Earth, the WEGAS (West-East Gondwana Amalgamation and its Separation) team observed that the 3 km ring is accompanied by other, smaller rings. More