Using radar aboard NASAs Cassini spacecraft, Hofgartner and his colleagues peered through Titans thick, hazy atmosphere to analyze Ligeia Mare, the second-largest sea on Titan. Ligeia Mare is named after one of the Sirens from Greek mythology, and is about 48,650 square miles (126,000 square kilometers) in size, making it larger than North Americas Lake Superior. Titans seas and lakes are usually pretty dark, Hofgartner said. The way the radar system works is by transmitting radio beams at Titan, which scatter off its surface and back at the radar system. The seas are normally so flat; all the radar energy is scattered away and doesnt come back to the spacecraft, so the seas appear perfectly dark, he explained. However, in July 2013, Cassini detected features that are essentially as bright as the surrounding terrain. The anomaly disappeared after subsequent observations. The bright anomaly occupies an area of about 6.2 by 12.4 miles (10 by 20 km), Hofgartner said. Now that Titans northern hemisphere is entering its summer season, its probably receiving enough solar energy to drive winds and power other phenomena, Hofgartner said. The seas are normally very smooth on Titan, with features no taller than 1 to 3 millimeters (.04 to 0.12 inches), making them smoother than any natural surface on Earth, Hofgartner said. This is because the winds on Titan have likely not been strong enough to create waves. Now, however, the winds might be getting stronger, and we might be seeing waves, he added. Another possibility is that the bright anomaly could represent gases pushing up from the seafloor and rising as bubbles. It could also represent solids becoming buoyant with the onset of warmer temperatures and floating on the surface, or solids that are neither sunken nor floating, but rather suspended in the sea like silt in a delta on Earth. As summer comes on Titan, we hope to learn more about the seas there, Hofgartner said. One plan is to put a boat or raft on Titans seas to study it in more detail, and understanding what processes are happening there now can tell us what instrumentation to bring and also how to improve the safety of the craft as well, he said.
Posted on: Tue, 24 Jun 2014 06:03:09 +0000
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