An important building block of life has been discovered in the hazy upper atmosphere of Saturn's largest moon, Titan.
In 2015, Cornell University researchers tackled the question of whether any organic molecules likely to be on Titan could, under such inhospitable conditions, form structures similar to the lipid bilayers of living cells on Earth.
Acrylonitrile, also known as vinyl cyanide, is a chemical found on Earth which is useful for manufacturing plastics.
In this new study, data collected by the Atacama Large Millimeter/submillimeter Array (ALMA) detected large amounts of vinyl cyanide. But while it doesn't have liquid water, Titan does have lakes of liquid methane, which along with vinyl cyanide, could foster the development of those essential cell membranes.
On Earth, cell membranes are made up of lipids, fatty molecules that require liquid water.
"It's definitely a rough estimate because there are just so many things we don't know about Titan", lead author Maureen Palmer of NASA's Goddard Space Flight Center said.
Previous research determined that vinyl cyanide, or acrylonitrile, could come together to create a sheet like a cell membrane. But they did find them, in data from the Cassini spacecraft, which is now in its final year in orbit around Saturn. If that's hard to imagine, think of the vinyl cyanide membrane as something similar to the human skin which keeps all the parts that make us human - and alive - inside our bodies and protects them from the outside world.
'The ability to form a stable membrane to separate the internal environment from the external one is important because it provides a means to contain chemicals long enough to allow them to interact, ' said Michael Mumma, director of the Goddard Center for Astrobiology.
Cassini's plasma spectrometer, called CAPS, as Cassini flew through Titan's upper atmosphere, 950-1300 km above the surface. "If there was going to be life in Titan's oceans, then it's plausible vinyl cyanide could be a component of that". From there, it makes its way down to the lower atmosphere and condenses, before raining onto the surface below.
The team also calculated how much material could be deposited in Ligeia Mare.
In the span of Titan's lifetime, it could have accumulated enough acrylonitrile to firm roughly 10 million azotosomes in every millimeter, or quarter-teaspoon, of liquid. In contrast, Earth's coastal seas contain only about 1 million bacteria per cubic centimeter of water.
"These inspiring results from Cassini show the importance of tracing the journey from small to large chemical species in order to understand how complex organic molecules are produced in an early Earth-like atmosphere", Nicolas Altobelli of the European Space Agency said.
The team that made this discovery included researchers from University College London in the United Kingdom, the University of Colorado, the University of Grenoble, the Southwest Research Institute, Swedish Institute of Space Physics, Uppsala University, and NASA's Goddard Space Flight Center.
This largest moon of Saturn boasts a thick atmosphere made up of methane and nitrogen, thus presenting a good example of exciting chemistry in our solar system.