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Shuttle's last flight formed clouds over Antarctica
A burst of mesospheric cloud activity over Antarctica in January 2003 was caused by the exhaust plume of the space shuttle Columbia during its final flight, reports a team of scientists who studied satellite and ground-based data from three different experiments. The data also call into question the role these clouds may play in monitoring global climate change.
On Jan. 16, 2003, the Columbia lifted from Kennedy Space Center on its final flight before the loss of the crew and orbiter 16 days later. As with previous shuttle launches, the orbiter released about 400 tons of water -- the primary product of the liquid hydrogen and liquid oxygen fuel -- while flying nearly horizontally at an altitude of 68 miles. The resulting plume was about 2 miles in diameter and about 650 miles long.
"The plume was detected and tracked by the Global Ultraviolet Imager on NASA's Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics satellite," Stevens said. "The GUVI images reveal rapid movement of the shuttle plume toward the South Pole."
"Within the next two weeks we measured almost all of the polar mesospheric clouds we were to see that season," Chu said. "Only four hours of cloud observations were recorded before mid-January. From January 19-26, however, 18 hours of cloud observations were recorded." The increase in polar mesospheric clouds was also observed with the Solar Backscatter Ultraviolet instrument on the NOAA-16 satellite. Additional evidence that the shuttle plume was responsible for the burst of cloud activity can be found in the mesopause temperature, inferred from the iron observations near an altitude of 56 miles, the researchers report. At Rothera, the mesopause temperature was minus 120 degrees Celsius, which is too warm for polar mesospheric clouds to form under typical water vapor concentrations. By dumping so much water vapor into the mesosphere, the shuttle raised the concentration enough to allow the clouds to form.
"Our data will force scientists to rethink the role of polar mesospheric clouds in monitoring global climate change," Stevens said. "Any interpretation of recent trends in cloud activity must consider the potential influence of the space shuttle program."