Now you see it. Now you don't. Titan's Mystery Island has lit up news feeds around the world and I have followed many of them with a keen, vested interest (more to follow). The original article, Transient features in a Titan sea, in Nature Geoscience, is the scholarly report on a transient feature that the news feeds are calling "Titan's Mystery Island". The free news feeds are numerous. My favorite article is contained in Sci-News.com. It is entitled Planetary Scientists Discover Mysterious Geologic Object on Titan. The article is well written and contains interesting images which help to clarify this interplanetary phenomenon.
First, let's give you some of my involvement with Titan's methane seas. On February 23, 2008, while visiting with my son's family, I made a map of an unnamed methane sea located on Titan, a moon of Saturn. Using Cassini derived PIA100008 imagery as my base image, I created a vector map entitled, "Titan's Unnamed Methane Sea".
My EVS Precision map of Ligeia Mare (formal name)
This map turned out to be one of my most popular. I even had a call from Spin wanting to write up the scientist behind this first map of an interplanetary liquid sea. After a brief phone interview, they weren't impressed that an ordinary "Joe" could make a quality map. It was fun none the less.
Back to my day job, teaching, and Titan's Unnamed Methane Sea was just a pleasant memory. Two days ago the "Transient Geologic Object" hit the news. As I read more and studied the image that displayed the transient object, I realized that it was a portion of the shoreline of my 2008 map.
Before (left) and After (right) and After, After (left)
This is not an insignificant portion of the shoreline. It covers an area of approximately 5600 sq kms (75 x 75 km). The sea, Ligeia Mare, is comparable in size to Lake Superior.
Just for the heck of it, I decided to study the phenomenon in more detail. I loaded the Before and After image into Global Mapper and began inspecting the image. The After portion seemed fatter than the Before. That would be my study question, just how much fatter is the After image then the Before image? I decided to divide the Before and After image into smaller panels to work with.
Before and After (Panel's Left, Middle Right)
The first panel seemed less complicated and allowed me to see how much fatter the After is compared to the Before.
Before and After, Panel Left
Since I love working with vector files, I figured that would be a good beginning. Right off, I didn't like the color differentiation. The various shades of brown did not, in my opinion, give me the comparison accuracy I desired. Global Mapper allows one to use color blend modes that can be applied to images. One of my favorites is Color Burn. With the proper background interesting color differentiation takes place. First I tried a white background.
Before and After, Panel Left with white (255,255,255) background
Yeah, it didn't work. Just a white image. Can't work with a blank canvas to accomplish what I wanted to do. I tried a number of other background colors. The best was a light blue (218,240,253) which made features on the image clearly definable.
Special Study Panel 1, Color Burn and light blue background
After studying the color burn, light blue background image, I decided to create a vector file that traced the green outlines of the pale blue area within the limits of the dark blue areas. The light blue areas appeared to define and match the lighter browns in the original image.
Digitizing the areas within the green outline and dark blue areas
I digitized my areas of interest. It took a couple of hours and lots of zooming to ensure the vectors were reasonably aligned with the green outlines. I digitized both Before and After creating polygons.
Special Study Panel 1, Color Burn and light blue background with digitized polygons
Special Study Panel 1, Color Burn and white background with digitized polygons
Special Study Panel 1, Original image with digitized polygons
The Before image contained 49 polygons with an area of 5.9633. Since my base image was not georectified, I wasn't concerned with the units of measurement, just the final figure that I would compare against the After image figure. The After image contained 40 polygons with an area of 7.2873. I divided 7.2873 by 5.9633 and arrived at 1.2220. Yes, the Before image is only 88% of the After image in areas within the green outlines. Seeing how the polygons line up on the original image, I'll go out on a limb (no peer review, please) and state that the After image geologic features on Panel 1 are approximately 22% larger than the geologic features in the Before image.
Is 22% significant? I think so. I intend to create polygons, using the same mapping processes, for Panels 2 and 3. At that time I will give my final results and I suspect they will read something like this, "After is Fatter than Before".
Until then, Enjoy!
Labels: Color Burn, Ligeia Mare, Saturn's Moons, Titan, Titan's Mystery Island