The Rings in the Ice of Baikal
From space, astronauts saw huge dark rings, several kilometres wide, in the ice of the world's deepest lake.
What was reported
In April 2009, photographs from the International Space Station and satellites showed giant dark rings in the ice of Lake Baikal in Siberia, each about 4 to 7 km across. Similar rings have since been spotted in other years.
The images went around the world, and speculation ranged from gas eruptions to something landing on the ice.
Explanations offered
A study led by scientists in France and Russia found that the rings form above slow, swirling eddies of warmer water beneath the ice. The warmer water thins the ice in a ring, making it darker. The eddies can be predicted, which matters for people who drive across the ice in winter.
- When
- Seen from space since 2009
- Where
- Lake Baikal, Russia
- Witnesses
- Astronauts and satellite images
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.