Cosmic camouflage? How oceans could conceal extraterrestrial life

By Stephen Beech

Alien lifeforms living in oceans on other planets could remain hidden from spacecraft, suggests new research.

Searching for life in extraterrestrial seas may be more difficult than previously thought - even when we can sample the waters directly, say scientists.

The new study focused on Enceladus, a moon of Saturn that sprays its ocean water into space through cracks in its icy surface.

Using computer models similar to those used to study Earth's oceans, researchers say their findings have important implications for the search for life in the solar system and beyond.

The study suggests that the physics of alien oceans could prevent evidence of deep-sea life from reaching places where it can be detected.

The findings, published in the journal Communications Earth and Environment, show how Enceladus's ocean forms distinct layers that "dramatically slow" the movement of material from the ocean floor to the surface.

Chemical traces, microbes, and organic material - tell-tale signatures of life that scientists look for - could break down or transform as they travel through the ocean's distinct layers.

Scientists say the biological signatures might become unrecognizable by the time they reach the surface where spacecraft can sample them, even if life thrives in the deep ocean below.

Study lead author Flynn Ames said: "Imagine trying to detect life at the depths of Earth's oceans by only sampling water from the surface.

"That's the challenge we face with Enceladus, except we're also dealing with an ocean whose physics we do not fully understand.

Ames, a doctoral student in the Department of Meteorology at the University of Reading, said: “We’ve found that Enceladus’ ocean should behave like oil and water in a jar, with layers that resist vertical mixing.

"These natural barriers could trap particles and chemical traces of life in the depths below for hundreds to hundreds of thousands of years.

"Previously, it was thought that these things could make their way efficiently to the ocean top within several months."

He added: "As the search for life continues, future space missions will need to be extra careful when sampling Enceladus’s surface waters."