Jupiter-ho!

“...to explore strange, new worlds; to seek out new life...”

I think that the most exciting news of this week was the European Space Agency (ESA) announcing a new robotic mission to explore three of Jupiter’s largest moons: Ganymede, Callisto, and Europa. Named JUICE (for Jupiter Icy Moon Explorer), the probe is scheduled to launch in 2022, and after a 7½-year journey, will spend 3½ years studying these distant worlds.

Artist’s impression of JUICE.
The design of the probe is not
yet finalised.
Image copyright: ESA, used
here for educational and
informational purposes, in
agreement with their terms.

In particular, JUICE will examine Jupiter’s moons from the perspective of determining whether such worlds are capable of supporting life—or perhaps already do. Data returned by previous space probes that visited Jupiter (the two Voyager probes, and Galileo) suggests that these moons have large amounts of liquid water under their frozen surfaces: vast subterranean oceans. Although they are far from the Sun’s light and heat, Jupiter’s immense gravity and radiation belts provide energy for these worldlets.

Could life exist in such places? Might it already? A better understanding of these three moons will help us answer these questions: questions that are more compelling today than ever, for two reasons.

First, the discovery of deep-sea ecosystems in 1977 has forced us to think more broadly about what conditions might support life. Clustered around volcanic vents on the ocean floor, intricate communities of life forms exist in a completely sunless realm. It turns out that forms of energy other than sunlight can power even complex organisms.

Second, in 1988, the only planets that we knew to exist were those of our own solar system. Since then, nearly 800 worlds have been discovered around other stars, many of them “gas giants” like Jupiter. So far, we know for absolutely certain that life might exist on rocky worlds with large amounts of liquid water on their surfaces. Knowing whether the conditions are right for life on Jupiter’s icy moons would provide us with another environment in which to search for life around other stars.

If the recent probe into Lake Vostok—3.7 km under Antarctica—reveals life there too, the questions become more compelling still. Lake Vostok is perhaps the environment on Earth most like these moons of Jupiter.

When the Voyager probes departed, the existence of deep-sea ecologies was brand-new knowledge. When Galileo departed, the existence of planets around other stars was brand-new knowledge. Human understanding of life is deepening and broadening significantly, even within our own lifetimes. Learning is building on learning.

In the meantime, science-fiction authors have wasted no time in speculating about what kinds of life might inhabit these moons. Arthur C. Clarke’s 2010: Odyssey Two portrays primitive life on Europa, and I recently enjoyed a novella called “The Frozen Sky” by Jeff Carlson with quite a different portrayal. Such tales only make me more excited to learn what the truth might eventually be determined to be.

Wonder awaits us!

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Author’s note:
I wrote this piece in part as a reply to a comment I read on Twitter this week:

The European Space Agency has approved a mission to Jupiter's moons to check for fish there. Which will give us something else to kill.

I find this kind of cynicism and pessimism really disappointing and frustrating. We are living in one of the most exciting periods of human history: the generation in which we have learned that our solar system is far from unique in the cosmos. The best is truly yet to come, and don’t let anyone tell you otherwise!

If you feel the same way, you might enjoy Annalee Newitz’s article about Neal Stephenson’s Heiroglyph project, “Dear Science Fiction Writers: Stop Being So Pessimistic!” in the April 2012 edition of the Smithsonian magazine.