Tag Archives: Europa

Across the Universe: Europa

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This entry is part 54 of 180 in the series Across the Universe

This column first ran in The Tablet in February, 2009; we ran it here for the first time in 2016. 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 … Continue reading →

Does Studying the Universe Change Your Perspective of the Environment Around You?

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An 8th grader doing a research project on astronomy recently emailed the Warren Astronomical Society asking “Does studying the universe change your perspective of the environment around you?” In this post, I expand upon the response I wrote back to that student.   Absolutely it does! Astronomy and cosmology are enormously wide fields of study, encompassing everything from quantum mechanics down at the sub-atomic level, to the interactions of (as of yet) unseen dark matter on the large-scale structure of the universe. Climate studies Studying how gases in Earth’s atmosphere and liquid in the oceans reflect and adsorb light, and radiate heat is but a small part of understanding how Earth’s climate functions and can change over time. The same principles used to study the Earth’s atmosphere can be applied to the atmospheres of other worlds; Venus is an example of a “runaway greenhouse effect,” and should be viewed as a cautionary tale for Earth’s ever increasing CO2 level (410.31 parts per … Continue reading →

Across the Universe: Leaving the neighborhood

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This entry is part 136 of 180 in the series Across the Universe

This column first ran in The Tablet in September 2013 At the annual European Planetary Science Congress [held in September 2013] in London, I was chatting with some postgraduate students about their studies of Jupiter’s icy moon, Europa. It’s the target of the Jupiter Icy Moon Explorer mission that the European Space Agency hopes to launch in 2022. Europa’s subcrustal oceans may be the best place in our solar system to look for non-terrestrial life forms – an idea that I can claim credit for first proposing in print in 1975, based not so much on my computer models as on all the science fiction I’d been reading.           It’s exciting to see a crazy idea of mine (and, to be honest, of many other folk) turned into a space mission. But it’s sobering to realize I will be 78 years old in 2030, when it arrives. Indeed, not only were those postgraduate students not yet … Continue reading →

Across the Universe: Asking the right questions

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This entry is part 40 of 180 in the series Across the Universe

This column first ran in The Tablet in October, 2007 My first scientific paper, more than thirty years ago, was a review of the icy moons of Jupiter. Knowing only the mass and volume of the moon Europa and the evidence of its bright surface, I calculated that Europa’s density matched a mixture of rock and ice, with enough rock (90%) that its natural trace radioactivity would, over the age of the solar system, melt the ice. Europa, I asserted, should have a shiny thin ice crust, a moon-like rocky center, and a liquid ocean water between the two. I even speculated about creatures swimming in that ocean. Then the Voyager and Galileo spacecraft arrived and mapped that moon, showing the kinds of cracks expected for ice overlaying an ocean. And Europa deflected Jupiter’s magnetic field just like a salty, electrically conductive ocean might do. Now I’ve been invited to co-author the lead chapter on a new book about Europa. … Continue reading →

Enceladus, Ocean World

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NASA’s Cassini mission scientists have determined that the slight wobble observed in Saturn’s moon Enceladus, as it orbits the ringed giant planet, is too large for the moon to be entirely frozen to its core. This wobble, referred to as a libration, reveals that the icy crust of Enceladus is disconnected from its rocky interior. In other words: Enceladus’ icy crust is sliding around on top of a global ocean of liquid water, and where there’s water, life may follow. This graphic (above) is an update to Enceladus: Possible Hydrothermal Activity (left), which showed only a regional sea beneath the south polar region of Enceladus. As Enceladus orbits Saturn, it is subject to tidal forces due to gravitation. These forces stretch the moon, causing friction, which heat up the moon’s interior. This is a process is called tidal heating. Jupiter’s moon Io is the most volcanically active body in the solar system, as a result of tidal heating. It was … Continue reading →