Date: August 30, 2009

Title: The Environments of Jupiter’s Moons

Podcaster: Amy Bowen

Link: Amy Bowen’s website
http://amybowen.wordpress.com/

Description: The moons of Jupiter are home to some of the most fascinating extraterrestrial environments known to science. They’re so fascinating, in fact, that this podcaster decided to set one of her earliest science-fiction stories there. In this episode, we’ll learn about what facts the podcaster got right and wrong in her story, and about some of the new facts we’ve learned about the moons of Jupiter in the past 25 years.

Bio: Amy Bowen is an aspiring science-fiction and fantasy writer and podcast novelist who has made guest appearances on several podcasts about sci-fi, fantasy, and entertainment. She recently moved back to Southern California after completing a year of national service in Florida.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Joseph Brimacombe.

Transcript:

Hello, everyone. I’m Amy Bowen, and this is the 365 Days of Astronomy Podcast for August 30th, 2009. In my last episode, back on July 24th, I talked about three astronomy-inspired arts and crafts projects that I’ve done. Two of them were inspired by the book Sky Above and Worlds Beyond by Judith Herbst. Today’s topic is another creative project I did that was inspired by that same book.

In Chapter 5 of her book, Herbst takes her readers on a tour of the solar system in an imaginary rocket ship. The section of the chapter that inspired me to get creative was the section that described the objects whose discovery 400 years ago we’re celebrating this year: the Galilean moons of Jupiter. I think I first learned that these moons existed when I read Sky Above and Worlds Beyond for the first time at age ten or eleven. I thought they were just so unbelievably cool, especially Io, because it had active volcanoes, and Callisto, because it had ice on it. I was fascinated by the idea that there were moons out there whose surface features were more similar to some features on the surface of the Earth than they were to the surface of our moon. Not long afterward, I got an idea for a sci-fi story that was set among the moons of Jupiter. That was my very first sci-fi story that I can remember writing.

The story involved a group of people building a rocket and flying to Io to start a colony there. My reasoning went like this: “Space is cold, so if we’re going to build a colony in space, the obvious choice for a location is Io, because its volcano would provide a reliable source of warmth and energy for the colony.” Yes, I did say “volcano.” In that early story, I wrote that the protagonists chose Io for the location of their colony because it has a volcano. Strange, because Sky Above and Worlds Beyond itself makes it clear that Io has many volcanoes, all over its surface. I must have forgotten that while I was writing the story. Io’s volcanoes were known to science even in 1984, when the book was published. They were one of the discoveries made by the Voyager 1 space probe in 1979. Today, thanks to the Galileo orbiter, we have much more information about Io (as well as the other Galilean moons,) including more and better pictures.

So, in light of what we know now, was I right? Would Io be a good environment for a space colony? Well, there are indeed lots of volcanoes there – more than 400, in fact. Many of its more prominent volcanoes are named after gods of fire and thunder from various mythologies of the world, such as Pele, Masubi, and Loki. The visible and infrared light emitted by its many volcanic hot spots testify that there is plenty of energy there, so my youthful imagination was right about that. Something I didn’t know when I was first writing my story was that Io is so hot and volcanically active because of tidal friction caused by the intense tidal forces that Jupiter exerts on Io. (I actually learned that just this year from fellow 365 Days of Astronomy podcasters Mr. Jason Perry and Mr. Robert Morehead. Thanks, guys!) The gravitational pull of Jupiter’s other moons, especially Europa and Ganymede, exerts still more force on Io, but in the opposite direction. All these forces give Io a constantly-changing landscape of erupting volcanoes, rising mountains, and plains flowing with lava. While Io is primarily composed of silicate rock, and there are certainly flat plains where one could conceivably build a structure, those plains are covered with either lava flows, or frost made of sulfur or sulfur dioxide. Not only that, but its thin atmosphere is composed mostly of sulfur dioxide, and it has radiation and magnetic fields originating from Jupiter, which any structure on Io would have to be built to withstand. In short, no, Io would not be a very easy or hospitable place to build a space colony.

When I was in elementary school, I started writing that first science-fiction story, but didn’t finish it. Four or five years later, at the end of eighth grade, I wrote a longer, revised version of the story, which I did finish. This new version was based on the same premise as the original, but both my writing and my reasoning skills had matured. At age fourteen, I reasoned that if we were going to start a colony in space, an even more important resource than a reliable source of energy was a reliable source of water. Therefore, this time around, I had my pioneers of the Jupiter system building their colony, not on Io, but on Callisto, because I knew that the surface of Callisto had water ice on it. The Galileo Orbiter gave us a closer look at this surface ice. While passing above Callisto, it took a picture that shows spires of ice jutting out from the surface in a particular area. The other main feature of Callisto’s surface is craters. Lots and lots of craters. Callisto is, in fact, the most cratered object in our solar system. The many bright spots of white that we see in pictures of Callisto are places where water ice has frozen over impact craters. Callisto also has oxygen trapped in its rock and ice, as well as a very thin exosphere of carbon dioxide gas hovering around it. All in all, I think my colonists made a smart move. Callisto would be a much more comfortable place for a space colony than Io. It would be cold, but at least there would be water, and there wouldn’t be quite as much sulfur and radiation there.

Little did I know when I wrote that story that Callisto, Europa, and Ganymede all have ice on their crusts. In fact, my fictional colonists might find Europa almost as appealing as Callisto, due to the possibility that Europa might have liquid water under its crust, which appears to be a thick layer of ice. On the other hand, even if there were liquid water on Europa and they could get to it through all that ice, they would probably still have to desalinate it. Salty water would be more likely to stay liquid at a lower temperature, so any liquid ocean on Europa would probably have to be salty. The surface of Europa also has frozen sulfuric acid, which happens to be an oxidant that provides energy. Callisto still stands out as the most likely place in the Jupiter system to build a space colony, at least in this sci-fi writer’s opinion.

However, if Europa really does have a liquid sea, then it has the environment with the strongest potential for supporting, or having once supported, its own native life out of all the other worlds in the solar system. It’s a fascinating and inspiring thought, and certainly something to think about if I ever decide to rewrite that story again for publication. I still think Jupiter’s moons are so unbelievably cool, so rewriting and publishing that story is certainly within the realm of possibility for me. Of course, now that I know so much more than I used to about the environments of Jupiter’s moons, any future version of the story will have much more real science in it than the earlier versions.

It has been my pleasure to share with you, over the course of my three episodes, how astronomy has helped to shape my creative life. You can find me on the Web at amybowen.wordpress.com. Thank you for listening, and maybe, just maybe, someday I’ll see you in the bookstores.

End of podcast:

365 Days of Astronomy
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