Saturn’s moon Titan is too cold for many types of chemical reactions, but quantum tunnelling could present a loophole that would allow reactions that are crucial for life.
Quantum effects may be key to potential precursors of life on Saturn’s moon Titan. These effects become more important at lower temperatures, so they may enable chemical reactions that would otherwise be impossible on an icy moon like Titan.
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| Titan and Saturn as captured by NASA’s Cassini spacecraft NASA/JPL-Caltech/Space Science Institute |
Titan is the only place other than Earth where liquid oceans and lakes have been observed on the surface – the liquid in question there is ethane and methane, not water, but it is nevertheless intriguing for the possibility of life. It is also known to have complex molecules that make life, or at least the prebiotic chemistry that can lead to life, on Titan even more plausible.
But many chemical reactions require a certain level of warmth, and the average temperature on Titan’s surface is about −179°C (−290°F). Richard Remsing at Rutgers University in New Jersey and his colleagues performed simulations of chemical reactions in Titan-like conditions to try to figure out whether quantum effects could alleviate the problem.
Chemical reactions, such as transferring a proton or electron from one molecule to another, generally need some energy added to set them in motion. It’s like rolling a ball from one valley into the next – the ball needs a boost to get over the hill between the two. At low temperatures, there isn’t enough ambient energy in the environment to push the reaction over that barrier.
That doesn’t mean the barrier is impassable, though. Remsing and his colleagues found that it could be overcome through a phenomenon called quantum tunnelling, in which a particle passes straight through a barrier that it doesn’t have the energy to surmount.
“Lots of people think it’s too cold on the surface of Titan, nothing’s going to happen chemically – but if the particles can tunnel through that energy barrier, it could,” says Remsing. “If you are going to be having prebiotic chemistry in this environment, this might be the only way to have reactions.”
They haven’t simulated specific chemical reactions that we think could occur on Titan yet, but their general simulations have been promising, says Remsing. “We don’t know exactly what would be important for prebiotic and biotic chemistry on Titan, but in general, proton and electron transfer are usually important steps of any multi-step chemical reaction”, including the interactions that happen inside living organisms, he says. And on Titan and other icy worlds, quantum tunnelling could be the only thing enabling this crucial chemistry.
The researchers presented the work on 15 March at the Lunar and Planetary Science Conference in Houston, Texas.
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