Organic 'building blocks' discovered in Titan's atmosphere

Saturn's moon Titan is the second largest in the solar system -- and the only one with a dense atmosphere. The atmosphere, nitrogen and methane, resembles that of the early Earth. NASA's Cassini spacecraft peered through the atmosphere, imaged the haze layers -- and ESA's Huygens probe landed on the surface. UCL-built equipment on the orbiter detects an unexpected component in Titan's high atmosphere -- extremely heavy hydrocarbon-based negative ions. Their mass is at least 10,000 times that of a hydrogen atom, detected at 953 km above the surface; about the distance from London to Milan. The image shows Titan's haze and the heavy ions. These are part of the haze in the atmosphere, and may fall towards Titan's surface as organic gunk. They are Carl Sagan's tholins; a brown residue appearing in the Miller-Urey experiment, where a spark excites a mixture of gases resembling that of Earth's early atmosphere. The right hand side of the image shows the negative ion signature at 4 different encounters, including T16 where we see the 10,000 amu ions. The vertical stripes show the ions seen as the instrument is scanned through Cassini's direction of travel and increasing numbers of ions are seen as they ram into our sensor. Credit: Titan image courtesy NASA/JPL/Space Science Institute

Scientists analysing data gathered by the Cassini spacecraft have confirmed the presence of heavy negative ions in the upper regions of Titan’s atmosphere. These particles may act as organic building blocks for even more complicated molecules and their discovery was completely unexpected because of the chemical composition of the atmosphere (which lacks oxygen and mainly consists of nitrogen and methane).