Deforestation has revealed what could be a giant impact crater in Central Africa, scientists say.
The 36-46km-wide feature, identified in DR Congo, may be one of the largest such structures discovered in the last decade.
Italian researchers considered other origins for the ring, but say these are unlikely.
They presented their findings at the recent Lunar and Planetary Science Conference in Texas, US.
The ring shape is clearly visible in the satellite image by TerraMetrics Inc reproduced on this page.
Only about 25 terrestrial impact craters are of comparable size or larger, according to the web-based Earth Impact Database.
Giovanni Monegato, from the University of Padova, said the feature was revealed only after trees were cleared from the area over the last decade.
The Unia River flows around the ring structure, underlining its round shape. The central part of the Wembo-Nyama feature is irregular and about 550m in elevation.
This is about 50-60m higher than the depression where the river flows. Although this might sound counter-intuitive, experts say that impact craters can sometimes lift up dense rocks. The surrounding rocks may subsequently erode, leaving a dome.
It'll be interesting to see what this turns out to be.