May 26, 2020

Review: Unmasking Europa by Richard Greenberg

Out from Springer Books!

Something interesting is going on underneath the icy surface of Jupiterís Moon, Europa. This week, Astroguyz takes a look at Unmasking Europa by Richard Greenberg out from Springer Books. Dr. Greenberg is a professor of Planetary Sciences at the Lunar and Planetary Laboratory at the University of Arizona in Tucson. Orbital mechanics are a specialty of his, and Europa has fascinated him from the start. The adventure he takes us on in Unmasking Europa is nothing short of a true tale of how modern science gets done and a look at the labyrinth of bandwagons, pursuits of tenure and personality conflicts that often occur behind closed doors. In 1979, the Voyager spacecraft gave us the first good look at the moons of Jupiter since Galileo spied them in 1610; immediately, the blue-white world of Europa captivated researchers. Here was a place that was unlike most of the other rocky worlds in the solar system, with its grooved ice covered surface and relative lack of craters, here is a place that things are happening. To this end, Europa was targeted by the Galileo spacecraft for several close flybys of the enigmatic moon when it arrived at Jupiter in 1995. The story of the problems that Galileo itself endured to get to the launch pad, let alone spaceborne also regale the reader; the 1986 Challenger accident pushed back the launch by several years, and the very fact that the payload had to make several instrument-jarring crisscross trips over the United States before even reaching space is suspected to be the ultimate cause of the failure of the high gain antenna. Some innovative engineering had to be performed to retrieve data exclusively from the low-gain transmitter, but even then, scientists on the ground were stuck with an agonizing pre-modem data speed of 160 bits (no megas or kilos attached) per second!

Galileo on Earth. (All images courtesy of NASA/JPL).

Never the less, Galileo re-wrote the book on Europa, and posed more questions that are still debated to this day. Is that surface active, or relatively stable? Is there an†under-surface ocean, and is it worldwide? Is that ice thick or thin? Dr. Greenberg is firmly in the thin ice camp, and argues convincingly for such in the book. Itís also interesting to see the interpretation of imagery play out, as something as simple as a change in shadow angle and even just spinning an image 180į degrees can suddenly make mounds look like pits. Folks who interpret satellite imagery for the military and backyard lunar observers have long known of this phenomenon, but itís interesting to see it applied in a new environment.

A Europa mosaic as seen from Voyager 2.

The book is also very timely, as the Decadal Survey for planetary exploration just came out earlier this year. Unfortunately, the Juno spacecraft headed towards Jupiter wonít target the inner moons, but the overall Jovian environment. Still, a dedicated Jovian Icy moons mission would provide a through survey of these worlds. What Dr. Greenberg and those of us who run with the ďEuropa mafiaĒ would really like to see is a dedicated Europa orbiter, preferably with a lander/submersible explorer attached.

But itís the look at how modern science gets done thatís especially compelling. While scientists hotly debated the minutiae of the Galileo mission, Europa quietly sat in wait, being simply what it is rather than what we wanted it to be. Dr. Greenberg gives us a fly-on-the-wall view to some of these sessions, much like an anthropologist watching the displays of virility by great apes as male scientists duke it out. (Ultimately it is the female scientists that get the cooperative ball rolling again!)

Pwyll crater, one of the few large crater formations on Europa.

But of course, the big question on everyoneís mind is; is there life under that icy exterior? A thin layer may open up such prospects for interchange of material and energy with the surface, while still protecting said hypothetical life from the hail of radiation bombardment from Jupiter. A relatively thin layer would also open up prospects for an undersea explorer. A thick layer would mean that any prospects for life would be restricted to energy produced by the hydrothermal vents powered by the warping of the moonís core by the planet Jupiter, an area of exploration that would probably be forever hidden from our reach.

A close up look at Europa’s chaotic terrain courtesy of Galileo.

Do give Unmasking Europa a read for both a look at one of the most intriguing places in our solar system and a snapshot of how modern science gets done. Will we reach out and touch this icy moon in our life time? Now is a time of both crisis and opportunity in planetary science; watch this space as the next decade of planetary science unfolds!

An artist’s conception of a dedicated Europa orbiter.

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