Across the Universe: Europa

This column first ran in The Tablet in February, 2009

This copy of Galileo's text for his first book includes his hand-drawn diagram of Jupiter and its moons

This copy of Galileo's text for his first book includes his hand-drawn diagram of Jupiter and its moons

Under the dim light of a distant sun, a cold white ball smaller than our Moon orbits a huge gas planet, garishly striped with colored clouds. Galileo first saw this jovian moon – to be named “Europa” by his rival, Simon Marius – on January 7, 1610.

In 1805, Laplace had worked out Europa’s mass (using an elaborate theory of the moons’ orbits), and other 19th century astronomers timed the way the Jupiter moons shadowed each other to estimate their sizes. By the end of that century clever instruments allowed Pickering to estimate its brightness.

All the information was there. From these data, any schoolchild could have calculated that Europa was less dense than rock, more dense than ice, and brilliantly white. But no one actually put all that information together until 1908, when Pickering finally noted the low density and bright surface... and speculated that this Jupiter moon was a ball of white sand!

The first published description of it as an icy body came in the 1923. Jeffreys was arguing that the giant planets Jupiter and Saturn must be rich in ice, and noted in passing that this was supported by the obvious icy nature of their moons. Obvious; but no one had ever actually said so before.

That’s where Europan science stood in the mid 1970s, when I wrote a student thesis using a computer model to predict the evolution of these icy moons. The density suggested a mixture of rock and ice (indeed, for Europa, more rock than ice); rock contains radioactive elements that give of a tiny amount of heat as they decay, enough to melt the ice. Following the suggestion of my thesis advisor, my models showed that Europa should have a large rocky core, a thin icy crust, and a liquid ocean between the two. An ocean rich in dissolved minerals… and maybe…

My real passion then was not science, but science fiction. I imagined a world where intelligent tuna swam between a rocky floor and an icy ceiling, never knowing that there was a whole universe of planets and galaxies over their heads… until the day a colliding asteroid poked a hole through the crust and sent my dolphin hero flying out to discover: it was full of stars!

(And what opaque ceilings hide most of the universe from us?)

Indeed, similar moons (as yet undiscovered) around the giant planets already detected orbiting hundreds of nearby stars may have similar environments, similar havens for life.

A few years after my thesis was published, the first NASA spacecraft flew past Europa. Snapshots taken then, and during subsequent fast flybys, have shown that that surface of Europa is covered with fractured ice like the sheets over the arctic oceans, and Europa  deflects Jupiter’s magnetic field the way you’d expect if it contained a salty, electrically conducting ocean. My thesis wasn’t completely crazy.

But is there life inside Europa? As of yet, we don’t even know for sure if the ocean is really there, or how thick the crust is between it (should it exist) and the surface. [Actually, the interaction of Europa with Jupiter's magnetic field is pretty strong evidence that there is salty liquid water below its crust. And some evidence of water appearing intermittently above Europa was also found in 2013. But we haven't seen the kinds of plumes that have been spotted over the surface of Enceladus.] We don’t know enough about Europa to know how to go about looking for life.

And so, [in February, 2009] NASA and ESA announced plans for a three billion dollar mission to orbit Europa. Its job is to find out what we need to know, to find out what we want to know.

Will my dream be confirmed? The proposed mission won’t launch until 2020, and won’t orbit Europa until 2028... more than 50 years after I wrote my thesis. Should I still be around, I’ll be 75 years old by then. Any follow up mission to drill through the crust and look for my dolphins, probably won’t happen before I reach 100. Meanwhile, I’ll just have to dream.

As of 2016, the ESA's JUpiter ICy moons Explorer (JUICE) mission announced in 2009 is now set for a 2022 launch for a 2030 arrival; the contract to build the spacecraft was signed in December 2015. NASA is still on board with a particles and field experiment and the radar that they hope will peek below the surface. In 2015 NASA announced plans for its own mission to Europa. to be launched in the 2020s...

Br. Guy Consolmagno

About Br. Guy Consolmagno

Brother Guy Consolmagno SJ is Director of the the Vatican Observatory and President of the Vatican Observatory Foundation. A native of Detroit, Michigan, he earned undergraduate and masters' degrees from MIT, and a Ph. D. in Planetary Science from the University of Arizona; he was a postdoctoral research fellow at Harvard and MIT, served in the US Peace Corps (Kenya), and taught university physics at Lafayette College before entering the Jesuits in 1989.

At the Vatican Observatory since 1993, his research explores connections between meteorites, asteroids, and the evolution of small solar system bodies, observing Kuiper Belt comets with the Vatican's 1.8 meter telescope in Arizona, and applying his measure of meteorite physical properties to understanding asteroid origins and structure. Along with more than 200 scientific publications, he is the author of a number of popular books including Turn Left at Orion (with Dan Davis), and most recently Would You Baptize an Extraterrestial? (with Father Paul Mueller, SJ). He also has hosted science programs for BBC Radio 4, been interviewed in numerous documentary films, appeared on The Colbert Report, and for more than ten years he has written a monthly science column for the British Catholic magazine, The Tablet.

Dr. Consolmagno's work has taken him to every continent on Earth; for example, in 1996 he spent six weeks collecting meteorites with a NASA team on the blue ice regions of East Antarctica. He has served on the governing boards of the Meteoritical Society; the American Astronomical Society Division for Planetary Sciences (of which he was chair in 2006-2007); and IAU Commission 16 (Planets and Satellites). In 2000, the small bodies nomenclature committee of the IAU named an asteroid, 4597 Consolmagno, in recognition of his work. In 2014 he received the Carl Sagan Medal from the American Astronomical Society Division for Planetary Sciences for excellence in public communication in planetary sciences.

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