Titan is Saturn’s largest moon, enshrouded by a smog-like haze.
Work by a University of Arizona (UA) research team has simulated that haze, finding amino acids and nucleotide bases – the most important ingredients of life on Earth.
“Our team is the first to be able to do this in an atmosphere without liquid water. Our results show that it is possible to make very complex molecules in the outer parts of an atmosphere,” says Sarah Hörst, a graduate student in the UA’s Lunar and Planetary Lab, who led the international research effort together with her adviser, planetary science professor Roger Yelle.
According to Hörst, their results suggest not only that Titan’s atmosphere could be a reservoir of prebiotic molecules that serve as the springboard to life, but they offer a new perspective on the emergence of terrestrial life as well.
That is, instead of coalescing in a primordial soup, the first ingredients of life on Earth may have rained down from a primordial haze high in the atmosphere.
Titan’s atmosphere is more similar to ours than any other atmosphere in the solar system, Hörst adds. “In fact, Titan has been called ‘Earth frozen in time’ because some believe this is what Earth could have looked like early in time.”
Outer fringes
Hörst and her collaborators mixed the gases found in Titan’s atmosphere in a stainless-steel reaction chamber and subjected the mixture to microwaves causing a gas discharge – the same process that makes neon signs glow – to simulate the energy hitting the outer fringes of Titan’s atmosphere.
Thousands of complex organic molecules accumulated on the bottom of the chamber during this experiment.
Along with creating nucleotides, the elements of the genetic code of all life on Earth, Hörst identified more than half of the molecular formulas for the 22 amino acids that life uses to make proteins.
“There are a lot of reasons why life on Titan would probably be based on completely different chemistry than life on Earth,” Hörst points out, “one of them being that there is liquid water on Earth. The interesting part for us is that we now know you can make pretty much anything you want in an atmosphere. Who knows this kind of chemistry isn’t happening on planets outside our solar system?”
The work is funded through NASA’s Planetary Atmospheres Research Program.
This research was a collaborative effort of an international team including scientists at the Lunar and Planetary Laboratory and department of chemistry at the UA, the Laboratoire de Génie de Procédés et Matériaux of Ecole Central Paris, France, the Laboratoire Atmosphères, Milieux, Observations Spatiales at the Université Versailles St-Quentin, Guyancourt, France, and the Laboratoire de Planétologie de Grenoble of the Université Joseph Fourier, Grenoble, France.
By LD/CSE