International Space Station photographs a massive ice circle
by Scott Carmichael on May 28th 2009 at 2:00PM

Earlier this year we wrote about a strange phenomenon causing circles of ice to
break free and start rotating on their own. Those circles were obviously man-
made, and clearly the work of someone looking for something more entertaining
than boring crop circles.

Last April, NASA found something far more interesting, and too big to be man-
made. The photo above shows a massive ice circle in Lake Baikal, Russia. The
circle is over 4 kilometers wide, and the scientific explanation for its occurrence
is described in easy to understand language on their site (see NASA release
below).

While you are there, be sure to check out some of the other amazing imagery of
our planet published by NASA on their Earth Observatory site.

http://
www.gadling.com/2009/05/28/international-space-station-photographs-a-
massive-ice-circle/

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Issued by NASA - International Space Station.
Circles in Thin Ice, Lake Baikal, Russia
Posted May 25, 2009

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 27, 2009.

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. 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.

References
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.

Instrument: ISS - Digital Camera

http://
earthobservatory.nasa.gov/IOTD/view.php?id=38721
See second image below. Copyright: NASA International Space Station. 2009.