Help Shape the Future of Space Exploration

Join The Planetary Society Now Join Now!

Join our eNewsletter for updates & action alerts

   Please leave this field empty
Blogs

Headshot of Emily Lakdawalla

Door 28 in the 2010 advent calendar

Posted by Emily Lakdawalla

28-12-2010 20:37 CST

Topics:

Time to open the twenty-eighth door in the advent calendar. Until the New Year, I'll be opening a door onto a different landscape from somewhere in the solar system. Where in the solar system is this cratered and streaked surface?

Door 28

NASA / JPL / SSI / color composite by Gordan Ugarkovic

Door 28
Resolution is about 280 meters per pixel, and the image covers an area about 280 kilometers square.
It's Dione, but I'd give partial credit for guesses of Tethys or Rhea, since those three moons of Saturn look quite similar, especially from this close. All are solid worlds of cratered ice, with leading hemispheres discolored a yellowish-greenish color (in this enhanced-color view, which is composed of images taken by Cassini through infrared, green, and ultraviolet filters) by deposition of something that came from outside the moons. Their surfaces are seamed by sharp, relatively fresh fractures. Dione's fractures have especially bright walls, and from Voyager's point of view it looked like wispy deposits overlaid on the surface. From Cassini's sharper eyes and more recent images (this one was taken on September 30, 2007 from a distance of 47,000 kilometers) it's clear that the "wispy terrain" was actually systems of parallel fractures that cut right across the craters, and which may have formed when an internal ocean solidified, causing the crust of the moon to expand and crack.

But there's other neat stuff besides the wispy terrain. There's a very straight but discontinuous crack running across the image from the upper left corner to the center. Near it, there's an especially fresh, rayed impact crater. Underneath it, running from left to right, is a curious pattern of parallel grooves (these are easier to see if you enlarge the image). I honestly have no idea what could have caused those grooves that would be distinct from what caused the formation of the wispy terrain. Maybe Paul Schenk knows!The Planetary Society Blog 2010 Advent Calendar


 
See other posts from December 2010

 

Or read more blog entries about:

Comments:

Leave a Comment:

You must be logged in to submit a comment. Log in now.
Facebook Twitter Email RSS AddThis

Blog Search

LightSail - Flight by Light

Support LightSail!

In 2016, The Planetary Society’s LightSail program will take the technology a step further.

I want to help!

Featured Images

Hayabusa 2's ion power

Hayabusa 2 and DCAM3
Hayabusa 2 at Gate Position
Hayabusa 2 in flight
More Images

Featured Video

View Larger »

Space in Images

Pretty pictures and
awe-inspiring science.

See More

Join the New Millennium Committee

Let’s invent the future together!

Become a Member

Connect With Us

Facebook! Twitter! Google+ and more…
Continue the conversation with our online community!