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Cassini’s Legacy September 11, 2017

Posted by aquillam in Astronomy, MichiganAstro, Science.
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As the Cassini mission comes to an end, NASA and JPL ponder what its legacy will be.

When the mission started, I had just recently started working as the outreach coordinator for Michigan Astronomy, and the presentations I did about it were some of the first of my career here.

My how the time flies.

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Discovery of Enceladus August 28, 2013

Posted by aquillam in Astronomy, Science.
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On August 28 in 1789, William Herschel turn his mammoth 48-inch telescope on the planet Saturn, and identified a new moon, latter to be called Enceladus.

Just a month earlier, he had begun a systematic series of observations in order to determine the number and orbits of Saturn’s moons. His data for that year were published in the  Philosophical Transactions of the  Royal Society of London,  1 January 1790 vol. 80 pp. 427-495. You can read his paper online (if you have access) at http://rstl.royalsocietypublishing.org/content/80/427.full.pdf+html

Enceladus - Voyager 2

19th and early 20th century spectroscopic observations identified water on or near the surface of the moon, but very little else wan know about it until the Voyager and Pioneer 11 flybys on the mid 1980s. These showed a bright, icy surface with a mix of moderate cratering and almost no cratering, showing the moon was still geologically active in some regions. At that time, there was no known mechanism for geologic activity on such a cold object. The Voyager I observations also lead to the hypothesis that Saturn’s E ring was actually formed of material vented by this moon, but the Voyager II observations were not good enough to confirm this.

Skip forward 20 years to 2005, and NASA’s Cassini mission’s first encounter with the moon. A lot of questions were answered in those first few flybys, and a whole lot more raised. Titan may be the largest moon, and the only one with an atmosphere, but is some planetary scientist’s books, Enceladus is the most interesting!

Enceladus

Enceladus (Photo credit: Wikipedia)

Cassini quickly confirmed the E ring material was ejected from some very active geysers on the younger, southern side (yep, it has a young side and an old side, like a lot of moons, and even Mars).  The southern hemisphere is lined with “tiger stripes” (the blue lines in the image at left) that are much warmer, hinting at cryovolcanism. They also appear to contain organic material, leading some scientists to speculate on the potential habitability of the moon.

Cassini is still orbiting Saturn, and still looking for more answers, though where Enceladus is concerned, every answer seems to raise at least three new questions.  http://saturn.jpl.nasa.gov/science/moons/enceladus/

If you’d like to observe Enceladus yourself, you’ll need a small telescope (48″ is nice, but 6″ will do). The Saturn’s moons javascript app from Sky&Tel will show you where to look relative to the planet.

Pale Blue Dot: Distant Spacecraft Photograph Earth – NASA Science July 23, 2013

Posted by aquillam in Astronomy, Science.
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Pale Blue Dot: Distant Spacecraft Photograph Earth – NASA Science.

Last Friday, many people all over the world took a moment to stop and wave at Saturn while the Cassini spacecraft snapped our picture. And what a great picture it is too!

You might also want to check out, or submit your own photos to, the Saturn Masaic Project, http://www.astronomerswithoutborders.org/tdtes-saturn-mosaic-project.html.

In case you aren’t familiar with the Pale Blue Dot reference, it comes from Carl Sagan, from a commencement speech “Reflections on a Mote of Dust” and his Book, the Pale Blue Dot. As Voyager 1 was headed out of the solar system, Sagan asked the team to turn the spacecraft to face each planet and take a picture, creating a Solar System Family Portrait. There’s a lovely poster with the Family Portrait and an excerpt from Sagan’s speech at http://arnett.us.com/psc/guest/SaganPoster1.pdf.