What does the abundance of water in the solar system mean for life?

This illustration shows Cassini diving through geyser plumes on Saturn’s the ocean world moon of Enceladus. Credit: NASA/JPL-Caltech

There was much excitement when NASA recently revealed new details about the oceans that lurk beneath the surface of Saturn’s tiny moon Enceladus and Jupiter’s Europa.

Why the excitement? Well, here on Earth, where you have water, energy and nutrients, you have life. So why not life on these other worlds?

Thanks to measurements made by the Cassini spacecraft, we already knew that Enceladus has an ocean buried deep beneath its surface.

From the new research, published in Science this month, it now seems highly likely that at the base of that ocean, hydrothermal vents are actively spewing nutrients and energy into the dark ocean depths.

The vented material drives chemical reactions, deep in the ocean, releasing molecular hydrogen that is eventually carried away from the moon in the giant geysers we observe.

Jupiter’s icy moon Europa has also long been known to host a sub-surface ocean that contains more liquid water than is present on the entire planet Earth.

Like Enceladus, it is thought that the base of Europa’s ocean might feature hydrothermal activity, and hence that it might be a suitable place for life to develop and thrive.

This month’s results tie Europa and Enceladus more closely together than ever. Observations of Europa with the Hubble Space Telescope revealed two episodes of geyser-like eruptions showed water being ejected to an altitude of 50km above the moon’s surface in 2014, and 100km in 2016.

Enceladus, just 500km across, is now known to host a buried ocean of liquid water. Credit: NASA/JPL/Space Science Institute

Water, water everywhere

When we look at other planets we see no oceans, no lakes and no rivers.

In the past we tended to imagine that water was a scarce and precious resource. But as we learn more about our place in the Universe, we are becoming ever more aware that water is everywhere.

Around 75% of all atoms in our galaxy are hydrogen, and it is the most common element in the Universe. Oxygen is the third most common element in space, albeit making up only about 1% of the total sum of all the atoms that are out there.

Water (H2O) is made of two hydrogen atoms and one oxygen atom. So it should be no surprise that water is everywhere, nor that it played a key role in the formation and evolution of our planetary system.

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