 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
Study Finds Shuttle Exhaust Is Source Of Mysterious Clouds In Antarctica
Washington DC (SPX) Jul 07, 2005 A new study, funded in part by the Naval Research Laboratory and the NASA reports that exhaust from the space shuttle can create high-altitude clouds over Antarctica mere days following launch, providing valuable insight to global transport processes in the lower thermosphere. The same study also finds that the shuttle's main engine exhaust plume carries small quantities of iron that can be observed from the ground, half a world away. The international team of authors of the study, which appears in the July 6 issue of Geophysical Research Letters, used the STS-107 Shuttle mission as a case study to show that exhaust released in the lower thermosphere, near 110 kilometers altitude, can form Antarctic polar mesospheric clouds (PMCs). The thermosphere is the highest layer in our atmosphere, with the mesosphere (between 50-90 kilometers above the Earth), stratosphere, and troposphere below. New observations presented by the research team from the Global Ultraviolet Imager (GUVI) on NASA's Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite reveal transport of the STS-107 exhaust into the southern hemisphere just two days after the January 2003 launch. Water from the exhaust ultimately led to a significant burst of PMCs during the 2002-2003 southern polar summer, observed by the Solar Backscatter Ultraviolet (SBUV) satellite experiment. The inter-hemispheric transport followed by Antarctic PMC formation were unexpected. PMCs, also known as noctilucent clouds, appear near 83 kilometers altitude and are made up of water ice particles created through microphysical processes of nucleation, condensation, and sedimentation. They typically appear in the frigid polar summer mesosphere where temperatures plummet below 130� Kelvin (-220� F). Little is known about the specific processes that lead to PMC formation. According to the study's lead author, Dr. Michael Stevens, a research physicist at the E.O. Hulburt Center for Space Research at the Naval Research Laboratory, the research produced multiple groundbreaking science results. "This research is exciting in that it extends a new explanation for the formation of these clouds by demonstrating the global effect of a Shuttle exhaust plume in a region of the atmosphere that has traditionally not been well understood," said Stevens. Some believe that the impact of anthropogenic change in the lower atmosphere is reflected in these upper atmospheric clouds. Although historically PMCs have only been seen in the polar region, in recent years PMCs have been spotted at lower latitudes as far south as Colorado and Utah, renewing interest and sparking debate on the implications. However, the findings of this work, "call into question the interpretation of the impact of late 20th century PMC trends solely in terms of global climate change," Stevens said. The team concludes that the water from a space shuttle's exhaust plume can contribute a remarkable 10-20 percent to PMCs observed during one summer season in Antarctica.
|
