ALMA Observations Reveal Unusual Behavior Of Organic Material In Titan’s Atmosphere

Chuck Bednar for redOrbit.com – Your Universe Online
Scientists studying the atmosphere of Saturn’s moon Titan have discovered large patches of trace gases shining brightly near the north and south poles, claims research published Wednesday in the Astrophysical Journal Letters.
According to NASA, the regions are strangely shifted to the east or west of the poles, so that dawn is breaking over the southern region of the moon while dusk is falling over the northern one. Those zones are filled with organic molecules that behave counter to perceptions about Titan’s windy atmosphere, the researchers noted.
“This is an unexpected and potentially groundbreaking discovery,” lead author Martin Cordiner, an astrochemist at the Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. “These kinds of east-to-west variations have never been seen before in Titan’s atmospheric gases. Explaining their origin presents us with a fascinating new problem.”
The discovery was made thanks to a series of brief three-minute observations using the Atacama Large Millimeter/submillimeter Array (ALMA), a network of high-precision antennas in Chile. At the wavelengths used by ALMA’s antennas, the gas-rich areas of the moon’s atmosphere glowed brightly, and the sensitivity of the observatory was crucial in obtaining spatial maps that could help them better understand Titan’s chemistry.

Image Above: High in the atmosphere of Titan, large patches of two trace gases glow near the north pole, on the dusk side of the moon, and near the south pole, on the dawn side. Brighter colors indicate stronger signals from the two gases, HNC (left) and HC3N (right); red hues indicate less pronounced signals. Credit: NRAO/AUI/NSF
Scientists have long been interested in Titan’s atmosphere because it acts as a sort of chemical factory, taking energy from the sun and Saturn’s magnetic field and using it to produce an array of carbon-based or organic molecules. Analyzing this complex chemistry could provide new insights into the properties about Earth’s young atmosphere, as NASA said that it might have shared many chemical characteristics with present-day Titan.
As part of their study, the authors focused on the two specific organic molecules formed in the moon’s atmosphere – hydrogen isocyanide (HNC) and cyanoacetylene (HC3N), the US space agency explained. The HC3N appears to be concentrated over the north and south poles at lower altitudes, the researchers said.
“These findings are consistent with observations made by NASA’s Cassini spacecraft, which has found a cloud cap and high concentrations of some gases over whichever pole is experiencing winter on Titan,” NASA said. “The surprise came when the researchers compared the gas concentrations at different levels in the atmosphere.”
At higher altitudes, those gas pockets appeared to be shifted away from the poles, which is unexpected because the fast-moving winds found in Titan’s middle atmosphere move in an east-west direction. That wind results in the formation of zones similar to a less pronounced version of Jupiter’s bands, the researchers said, and for the most part, the atmospheric gases should be thoroughly mixed within each of those zones.
Currently, the researchers said they do not have an explanation for these findings as of yet, but they are considering several possible causes, including thermal effects, previously undiscovered patterns of atmospheric circulation, or the influence of Saturn’s powerful magnetic field. They expect additional observations to improve their understanding of the atmosphere and the ongoing processes on Titan and other objects in the solar system.
“It seems incredible that chemical mechanisms could be operating on rapid enough timescales to cause enhanced ‘pockets’ in the observed molecules,” said co-author Conor Nixon, a planetary scientist at Goddard. “We would expect the molecules to be quickly mixed around the globe by Titan’s winds.”
“These ALMA observations give us new insights into how organic molecules, the building blocks of life, form and evolve in a planet-like environment,” added co-author Anthony Remijan, an astronomer at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia. “It is exciting to imagine the new discoveries ALMA will enable as we look more deeply at other interesting objects in our Solar System.”