funkyscience.net

My God – Its Full of Moonlets!

 

The world may not literally be getting smaller but our communication networks are getting faster and more interconnected.  And that, my fellow nodes, is changing the nature of planetary discovery.  In early April, days ago as I write this, some of the ubergeeks who hang out on unmannedspaceflight.com noticed something remarkable in some new images from the Cassini Saturn orbiter.  As Saturn approaches equinox in mid-August, sliding toward the part of its orbit where the plane of the rings and satellites will point directly at the sun, the shadows of the moons, long observed as black spots on the clouds of Saturn, are now sliding across the rings, producing lengthening, picturesque shadows.  In one of these pretty pictures, which shows the long sharp shadow of Mimas draped over the rings, some of the aforementioned masternerds saw something delightfully weird:  A rough and chaotic fringe of dark shadow upon the edge of a bright ring just inside of a little ringlet.  This seems to show the actual shadows of objects within the ring itself.  Are we seeing the long sought ring particles here?  Fans of planetary exploration of long watched as the rings have transformed from simple “ears” of Saturn in a telescope to complex structures in spacecraft images twisted, by gravity and interference from various moons, into ringlets and gaps.  We’ve been confident that the smooth looking rings are reallyorbiting collections of billions of tiny moonlets, but when would we actually see these objects?

In Cassini’s stunning closest pictures from July, 2004, the rings appeared strangely perfect, all waves and spirals, serrations and fringes, like computer simulations, like physics laid bare.  We’ve known that at some closer scale the rings must eventually resolve into messy conglomerates of individual objects.  Are we now seeing them?  Not directly, not yet, but as shadows, like projections on the walls of Plato’s cave, hinting at forms beyond our grasp.

After I received an e-mail from an excited colleague, directing me to the Planetary Society blog which linked back to the discovery posts,  I posted the link myself on Facebook and soon saw that others had passed it on.  (I suppose there must have been tweeting about it as well. I myself have not yet twittered but by the time you read this I may well have.  I am allowing myself a last few moments of inner life and continuous attention before I succumb.) Instant analysis ensued.  The geometry and apparent size of the shadows suggests that the objects are several kilometers across – too large for individual ring particles but possibly clumps of smaller moonlets.  This conforms to an idea kicked around for decades, that the rings might be a collection of shifting clumps of smaller objects, weakly bound by gravity.

This discovery was made and publicized by “amateurs”. I use the word in its orginal sense here, meaning motivated by love. Some contributers to this site are “professionals”, but nobody is getting paid.  These lines are being blurred, to positive effect. Many scientists in the field go to this site to learn what’s up and see what people are saying about new images. This fills a niche created by the ready availability of more imagery than the spacecraft teams can possibly look through themselves. Decades ago, in the time of Voyager fly-bys there was a careful hoarding of new images, hierarchical access, and a more controlled release process.  Transgressions were frowned upon and even sometimes punished with professional oppobrium.  Now are in an age of long term reconnaisance with orbiters and rovers.  Missions are no longer simply “encounters”, but commited relationships.  Data rates are much higher, and the web makes it possible to release images instantly. The best examples of this include the Mars Exploration Rovers and the Cassini orbiter. This increases the value of having an army of amateurs go over everything with a loving and obsessive eye. Not only do we have an expanding network of electronic eyes in residence among the planets, and an instant global communications network to spread the riches around, but also a large braintrust of citizen scientists scouring for anything interesting.

This growing unfiltered, democratic branch of science is not without risk.  There are kooky websites where wishful thinking and conspiracy theories reign, finding supressed evidence of fossils and cities in every other image of Mars, and showing that if you try hard enough you can find alien interference anywhere.  You probably cannot have one without the other, and this inevitable looseness preserves an essential role for the standards of peer-reviewed science.  But when something hugely significant is discovered and announced on a site like unmannedspaceflight.com will the informed amateurs get credit for this discovery?  All of us involved in planetary exploration know that the actual individuals who discover things are not always the ones who get the “official” credit in the record of cited papers.  Sometimes that has to do with politics and power games, and sometimes with credit legitimately leaning towards those whose years of effort and commitment made the observation possible.  Perhaps the professional community should give some thought to how to acknowledge this new, self-assembling community of keen-eyed helpers, each themselves nodes in the evolving and complex ring of information and imagination girding our own planet.