Our solar system’s icy moons are unlikely to host life, NASA has found

A new study of impact craters on Titan has found bad news in the search for life on the moon, and possibly other icy moons of the solar system.

Titan, Saturn’s largest moon, is often seen as a potential candidate for life. The moon is the only place in the solar system – apart from Earth – that is known to have surface fluids, such as rivers, lakes and seas.

These bodies of water are made of liquid hydrocarbons, most of which is methane. Even more intriguing for scientists searching for life is the gigantic subsurface ocean, thought to be more than 12 times the volume of Earth’s oceans, trapped beneath the planet’s icy crust and extending 55 to 80 kilometers (35 extends up to 50 miles) underground.

“Titan’s rivers, lakes, and seas of liquid methane and ethane could serve as a habitable environment on the moon’s surface, although life there would likely be very different from life on Earth,” NASA explains about the moon. ‘Titan could potentially harbor environments with conditions suitable for life – that is, both life as we know it (in the subsurface ocean) and life as we know it. do not know it (in the hydrocarbon liquid on the surface).”

Liquid water beneath the surface is of course promising for life, but for life to emerge you also need organic substances. It was thought that these ingredients could be carried to the ocean below, where they could swirl and heat and possibly give birth to life via the impacts of space objects. The idea was that the surface – rich in organic matter – would mix with the subsurface ocean as objects hit the surface and pools of water in the ice melt. Because it is denser than the surrounding ice, this would then sink into the subsurface ocean.

However, a study from the University of Western Ontario attempted to estimate how many comets hit the moon each year, and how much organic matter would be released into the subsurface ocean by these impacts. Unfortunately, the team found that the volume of glycine – the simplest amino acid – delivered into the ocean would only be about 7,500 kilograms (16,500 pounds), or about the weight of an adult elephant.

“One elephant per year of glycine in an ocean twelve times the size of Earth’s oceans is not enough to sustain life,” astrobiologist Catherine Neish said in a press release. “In the past, people often assumed that water equaled life, but they ignored the fact that life requires other elements, especially carbon.”

“This work shows that it is very difficult to transfer the carbon on Titan’s surface to the subsurface ocean – in fact, it is difficult to have both the water and carbon needed for life in the same place. Neish added.

Given that Titan has more organic matter on its surface than the other icy moons of Saturn and Jupiter, this puts a bit of a damper on our search for life in the solar system.

“Unfortunately, we will now have to be a little less optimistic in the search for extraterrestrial life forms within our own solar system,” Neish said. “The scientific community is very excited about finding life in the icy worlds of the outer Solar System, and this finding suggests that this may be less likely than we previously thought.”

However, there is still a little wiggle room. For example, life might be possible if there were more organic matter on the surface than previously estimated, if organic matter could come from the core, or if other processes could bring organic matter from the surface to the ocean below.

“It is almost impossible to determine the composition of Titan’s organic-rich surface by viewing it through the organic-rich atmosphere with a telescope,” Neish added. “We need to land there and sample the surface to determine its composition.”

Fortunately, NASA plans to do just that with the Dragonfly mission, which will involve a flying vehicle hopping around the moon’s surface. Neish, who is part of the Dragonfly team, says this research could help identify interesting landing sites.

‘If all the melt produced by impacts sank into the ice crust, we would no longer have samples at the surface where water and organics have mixed. These are areas where Dragonfly could look for the products of those prebiotic reactions and teach us how life can arise on different planets,” Neish said.

“The results of this study are even more pessimistic than I realized regarding the habitability of Titan’s surface ocean, but it also means that more interesting prebiotic environments exist near Titan’s surface where we can sample them with the instruments on Dragonfly.”

The research has been published in Astrobiology.

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