Late in April 2009, astronauts aboard the International Space
Station observed a strange circular area of thinned ice in the southern
end of Lake Baikal in southern Siberia. Siberia is remote and cold; ice
cover can persist into June. The upper image, a detailed astronaut
photograph, shows a circle of thin ice (dark in color, with a diameter
of about 4.4 kilometers); this is the focal point for ice break up in
the very southern end of the lake. A sequence of MODIS images indicates that the feature was first visible on April 5, 2009.
Baikal contained another, very similar circle near the center of the
lake above a submarine ridge that bisects the lake (ice circles are
indicated by arrows in the lower MODIS image from April 20). Both
circles are visible through April 20, 2009. Clouds cover the center of
the lake until April 24,
at which point the circular patch of thin ice was becoming a hole of
open water. Similar circular ice patterns-although not nearly as
distinct-have been documented in the same central area of the lake in
April 1994 (during the STS-59 Shuttle mission) and in 1985 (during the
STS-51B Shuttle mission).
While the origin of the circles is unknown, the peculiar pattern
suggests convection (upwelling) in the lake's water column. Ice cover
changes rapidly at this time of year. Within a day, the ice can melt
almost completely and freeze again overnight. Throughout April, the
circles are persistent: they appear when ice cover forms, and then
disappear as ice melts. The pattern and appearance suggest that the ice
is quite thin. The features were last observed in MODIS images on April
What can cause convection, bringing warmer waters to the surface?
Hydrothermal activity and high heat flow have been observed in other
parts of the lake, but the location of this circle near the southern
tip, over relatively deep water, is puzzling.
Lake Baikal is unique in many regards. It is the largest (by volume)
and deepest (1,637 meters at the deepest point) fresh water lake on
Earth and, as a World Heritage Site, it is considered one of Russia's
environmental jewels. It is also one of the world's oldest lakes (25-30
million years old); sediment deposited on the bottom is up to 7
kilometers deep. The lake's long, thin, and deep shape results from its
location in the Baikal Rift Valley.
As a United Nations World Heritage Site, Lake Baikal is
considered one of Russia's environmental jewels. It is home to an
amazing array of plants and animals, many of them unique to the
ecosystem. The lake's biodiversity includes fresh water seals and
several species of fish that are not found elsewhere on Earth.
- Crane, K., Hecker, B., and Golubev, V. (1991). Hydrothermal vents in Lake Baikal. Nature, 350, 281.
- Evans, C. A., Helfert, M.R., and Helms, D. R. (1992). Ice patterns
and hydrothermal plumes, Lake Baikal, Russia: Insights from Space
Shuttle hand-held photography. International Geoscience and Remote Sensing Symposium, IGARSS 92, 2, 1559-1561.
Astronaut photograph ISS019-E-10556
was acquired on April 25, 2009 with a Nikon 2DXs digital camera fitted
with a 400mm lens, and is provided by the ISS Crew Earth Observations
experiment and Image Science & Analysis Laboratory, Johnson Space
Center. The image in this article has been cropped and enhanced to
improve contrast. The image in this article has been cropped and
enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program
supports the laboratory to help astronauts take pictures of Earth that
will be of the greatest value to scientists and the public, and to make
those images freely available on the Internet. Additional images taken
by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by Cynthia Evans, NASA-JSC.
- ISS - Digital Camera