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How Will We Find Life on Ocean Worlds?

Ocean worlds might be more hospitable to life.

How Will We Find Life on Ocean Worlds?
An image of the moon Enceladus. Igor_Filonenko / iStock

NASA's Perseverance has several mission goals, but one of its most important was established long before it landed on Mars on Feb. 18, 2021: to seek out new signs of ancient life on the surface of the Red Planet.

However, the techniques used by one of the science instruments on the Perseverance rover might have crucial roles on Saturn's moons Titan and Enceladus, in addition to Jupiter's mysterious moon: Europa, according to an initial study published in the journal Astrobiology.

Future missions to water worlds could examine life signs in ice layers

"Perseverance is going to look for a shopping list of minerals, organics, and other chemical compounds that may reveal microbial life once thrived on Mars," said Principal Investigator Luther Beegle of the Mars 2020 Scanning Habitable Environments, using the Raman & Luminescence for Organics & Chemicals (SHERLOC) instrument. "But the technology behind SHERLOC that will look for past life in Martian rocks is highly adaptive and can also be used to seek out living microbes and the chemical building blocks for life in the deep ice of the moons of Saturn and Jupiter."

Scientists think Europa, Enceladus, and Saturn's hazy moon Titan might contain vast oceans of liquid water, with chemical compounds conventionally linked to biological processes of life beneath their thick icy shells. Obviously, these environments break drastically with the monotonous, dusty, and arid environment encountered on Mars. But if microbial life subsists in underground oceans, scientists might discover evidence of life in the ice, too. And to find it, we're going to have to dig.

NASA is developing a 3.9-foot-long (1.2-meter-long) tube-like prototype device — called the Wireline Analysis Tool for the Subsurface Observation of Northern ice sheets (WATSON) — in its Jet Propulsion Laboratory in Southern California, to probe the icy layers of distant moons. The WATSON has been paired with the Planetary Deep Drill of Honeybee Robotics, and was tested in the extremely cold environs of Greenland's ice layer.

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A smaller, more compact model of WATSON might hitch a ride on a future robotic mission to explore potentially habitable locations on one of these promising moons. The instrument could survey the depths of the icy layers to identify biosignatures — organic molecules produced by biological entities. If any show up, the future mini-WATSON might also collect ice from the borehole wall, and collect live samples for additional studies.

Water worlds might be more hospitable than Earth

And, with deep-ultraviolet laser Raman spectroscopy, the potentially organic materials may be studied where they lie, instead of only after retrieval and extraction to the moons' surfaces. This would add scientific value to discoveries, since the analysis can go forward within the samples' natural environment.

"It would be great if we first studied what these samples actually looked like in their natural environment before scooping and blending them up into a slurry for testing," said JPL Astrobiologist Mike Malaska, who is also lead scientist for WATSON, according to a NASA blog post. "That's why we're developing this non-invasive instrument for use in icy environments: to get a deep look into the ice and identify clusters of organic compounds — maybe even microbes — so they can be studied before we analyze them further and lose their native context or modify their structure."

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Every year we're inching closer to exploring the enigmatic moons of Jupiter and Saturn. And, recently, a study found that ocean worlds might be far more hospitable to life than planets like Earth — which means there may be a far greater chance of finding signs of life on Europa, Enceladus, or Titan than Venus or Mars. There's no certainty around what life evolving in such alien environments might look like, but the knowledge alone could transform our understanding of life in the universe more drastically than ever since Charles Darwin published his theory of evolution.

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