Is there life on Europa?

Europa. Credit: NASA

Jupiter’s moon Europa is one of the most intriguing places in the solar system – with a global ocean of water thought to exist beneath its ice crust, speculation has grown that it may harbour life of some kind.

Studies have shown the water is likely quite similar to ocean water on Earth, with abundant oxygen available. If there are heat sources like hydrothermal vents, as on Earth, and chemical nutrients, the Europan ocean would seem an ideal place to search for life of some kind. Even with no sunlight due to the perpetual ice cover, life could still thrive; various organisms and marine life have been found here on Earth, in similar environments below the ice of Antarctica for example.

A new study is putting a damper on those hopes however. It contends that the water on Europa may be too acidic to support life, at least more complex forms.

According to the report, oxygen in Europa’s crust, formed by bombardment from cosmic radiation, reacts with sulphur and other material coming from rocks at the bottom of the ocean, creating sulfuric acid. The scientists involved used the same computer models used to predict the chemistry of groundwater or the chemistry of water at phosphate mines here on Earth.

As explained by Assistant Professor of Geology Matthew Pasek at the University of South Florida, “When the two meet, they generate acid – sulfuric acid in this case. That would produce water with a pH of about 2.6, about the same as your average soft drink. Just as soft drinks are bad for your teeth as they are quite acidic, fish, corals, whales, or other large animals would find it difficult to live within the ocean of Europa.”

If true, it would make the environment more challenging for life to have started or evolved beyond simple microorganisms. Does it mean life would be impossible there? No, as there are microbes on Earth which do just fine in similar and even more extreme conditions, like the acid mines of Rio Tinto. The microbes actually use the iron and sulfide as energy sources. There is also the fascinating ecosystem, in dark subterranean caves in Mexico, where a wide variety of life forms, including small fish, also thrive in highly acidic conditions.

We will probably have to wait for a return mission to Europa before the life question can be addressed more directly. Until then, the debate will certainly continue.

The paper is available here.

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