Once you get beyond the very basic level, astronomy quickly become all about numbers.  It’s both fascinating and a shame.  Fascinating because scientists have been able to send probes millions of miles away, calculating, for example, where the multiple moons of Jupiter and Saturn will be so that they can fly by for an interplanetary peek.  The shame is that many people star-struck by the concepts can’t pursue it as a career.  That’s where books like David A. Rothery’s Moons: A Very Short Introduction come in.  I’ve read a number of books on the moon, but I’ve fallen behind on what we’ve learned about the moons of the outer planets.  This short treatment covers them in just enough detail.  I certainly learned a lot by reading it.

Rothery points out that apart from Earth, in our solar system the likeliest candidates for life are actually some of the moons of Jupiter and Saturn.  Heated by tidal action and volcanism, and having under-surface oceans, conditions may be right for such worlds to spawn life.  Even if microbial, finding life elsewhere would confirm what this dreamer has supposed all along—we’re not alone in the universe.  As Rothery also notes, there are far more moons than planets in our solar system, so that may also apply to other systems as well.  Exoplanets have been discovered for decades now.  If other suns have planets and those planets have moons, who knows what might be out there?  And all this has been happening for billions of years, whether or not we notice it.

For me, it’s concepts such as these that make astronomy so fascinating.  Also, as the book points out, there are all kinds of oddities in our own astronomical back yard.  Asteroids that have their own moons.  Moons that have unusual geological (or lunar) features that haven’t been explained.  Moons that have been torn apart by their host planet.  Moons that have been captured in orbit when passing by.  Probes have been landed on moons other than our own, and the ethics of doing so (since we might transmit microbes unintentionally) are topics of discussion.  There’s a lot crammed into this brief study.  I also can’t help but wonder what amazing things the next generation will discover.  Our knowledge of this universe, impressive as it is, doesn’t even break the crust of ice moons out there, where there is nitrogen ice and methane ice.  Parameters beyond imagination.  It may all come down to numbers in the end, but moons are so much more than that.