Each year, the Lunar and Planetary Science Conference condenses more and more people into the Waterway Marriott in The Woodlands, Texas. It’s reaching a critical mass. This year, around 2,046 abstracts were accepted for presentation in talk or poster form. There’s too much to sift through except in your specific field, but I wanted to branch out a bit. So I put out a call on Twitter for a random number between 1001 and 3046 (the numbering system starts at 1001). Lockwood chose 2601, and from that abstract (PDF link) we have the topic of this post: Plumes on Enceladus.
This well-written abstract covers a few interesting points on using satellite photos to infer geological processes. The Cassini spacecraft has a narrow angle camera with broadband filters. These filters allow specific wavelengths of light, ranging from ultraviolet to infrared, to pass through. The wavelengths of light, in turn, are affected by objects they bounce off of. Different minerals reflect or absorb specific wavelengths of light differently, a feature used in many remote observations of planetary bodies to infer (deduce?) surface composition.
Paul Schenk and the other authors of this abstract used surface images filtered using two infrared spectra and one ultraviolet spectrum. One of the main goals of their analysis was to use our observations of Enceladus to use as a comparison to what we are beginning to study on Europa. There are issues to be worked out, with, for example, how the orientation of the spacecraft relative to the surface of a world will affect the observed spectra. If light is uniformly scattered by an object, then we can observe it from any angle and it will look the same. But if there is directionality to the scattering, then the angle we observe will affect what we observe. That will be an issue if we have more limited observations (like at Europa).
The image above was featured in the Astronomy Picture of the Day