18 September 2009

Broken Land: Touring Conamara Chaos, Europa

At last we move on (or back) to Europa.  I will be posting a series of Europa views as I work through my Galileo image and data archives.  These data are on the order of 10 years old, and I have started to combine some of my new color mosaics (generated for the forthcoming Atlas of the Galilean Satellites, which I will describe later this month), with the stereo and photoclinometry based Digital Elevation Models (DEM) or topographic maps I have been generating over that same time.  I start with one of the best of Galileo's data sites, Conamara Chaos, a type example of this broken and jumbled terrain. 

Over the next days and weeks I will post more of these, interspersed with an odd Ganymede or Callisto set.  These satellites did not get as good coverage from Galileo.  Io will not be forgotten, but requires additional processing.   The key difference for Galileo was the antenna failure, which crippled communications and limited mapping and stereo coverage to small mosaics.  These limited areas require tight turns and makes video production more challenging.  I might get an Academy Award yet!



Broken Land: Conamara Chaos

These perspective views show parts of the interior of Conamara Chaos, a region where the ridged crust of Europa has been disrupted into smaller plates set amidst a crazed and rugged terrain, termed matrix, that is in reality crushed ice.  Although some areas look like frozen over liquid water, it is as likely, if not more so, that these are the result of diapirs, rising blobs of warm ice from below that have broken through to the surface.  The total relief across Conamara Chaos is only 500 meters, so don't expect towering mountains.  Individual ridges and blocks can be 100 to 200 meters high.  The color shown here is actual surface color, enhanced to bring out contrasts.  Galileo's camera was sensitive to infrared and ultraviolet radiation and so these colors are a little stronger than what we would see.  The original images have a basic resolution of about 55 meters.  The large blocks are typically 5 to 10 kilometers across.


Broken Land: Conamara Flight
The video can be seen on Facebook (at least thats what I'm trying to link to here). 

Credit: Paul Schenk/Lunar and Planetary Institute, Houston

10 September 2009

Miranda's Warning

Miranda, always taking the spotlight. Nobody cared much about this small world, about the size of Louisiana, until January 24, 1986, when a (relatively) primitive but stout robot Voyager 2 sailed past - just 4 days before Challenger. (I had the opportunity to return to JPL to witness the encounter but as my doctoral exams were not going well, it was "suggested" I stay at Wash U and study.)  Expectations were not especially high, and Miranda was expected to look a bit like Saturn's lumpy moon Mimas, although given Voyager's history, anything was possible. Voyager's path to Neptune took it closest to Miranda of Uranus' five larger classical moons. Resolutions as high as 250 meters were possible, among the best of the entire Voyager mission. Happily, most of these images came back unsmeared and sharp. They revealed a complex and evolved landscape. Half of Miranda looked indeed a bit like cratered Mimas, but the other half was paved over if you will by lanes of ridges and grooves vaguely (and misleadingly) reminiscent of grooved terrain on Ganymede, all concentrated in three ovoid or retangular regions called coronae. This tiny moon with the multiple personalities has fascinated researchers ever since. Most now agree that Miranda attempted to turn itself inside out due to residual formation or forced tidal heating. Soft warm ice oozed up in three (or more) convective cells, forming the ovoid coronae on he surface where some of this ice breached the surface. Alas, only 45-50% of the surface was visible in sunlight at the time due to the fact Uranus and its moons being at southern solstice in 1986. Efforts to return to Uranus and Neptune have so far met with frustration. Perhaps the images shown here of Miranda, Ariel and Triton will relight the fires of interest in these planets and their active moons.


Flyover of Miranda, Uranian moon.
Imaging data acquired January 1986 by Voyager 2, topography derived by P. Schenk. The total topographic relief shown here is roughly 10 kilometers. Note that we are seeing roughly half of the entire moon here (which is roughly 500 km across), but the data are shown in flat map projection (the renderer cannot as yet handle a true sphere).
The movie begins with an approach toward Elsinore Corona, one of the ovoid regions of ridges and grooves. It then turns toward and over Inverness Corona, a smaller region of resurfacing very close to the south pole. We end with a "landing" along the edge of the 10 km deep Verona Rupes fault canyon system.


Elsinore Corona
The first two views of Elsinore Corona, an ovoid shaped region resurfaced by ridges composed of water and possibly other ices.  These ridges stand up to 2 kilometers high in some locations.  The rugged terrain nearby is ancient cratered highlands, which has relief of 5 kilometers or more.


Inverness Corona
The next two views show the border between Inverness Corona and the more rugged cratered highlands.  Inverness, like Elsinore, has been resurfaced by viscous ices that flowed onto the surface, forming ridges several hundred meters to a kilometer or so high.  The cratered highlands have relief of several kilometers.
Verona Rupes and Inverness Corona
 This area is the most rugged terrain known on Miranda.  Up to 10 kilometers of relief has been mapped here, a complex area formed by the intersection of multiple tectonic features.


New Global Image Mosaic and Topographic Map of Miranda
These maps (image mosaic on top, topography on bottom) are in lambertian equal area projection, centered on the south pole.  They have been reduced in size by a factor of 2 for the web.

All images may be used with permission.
Credit: NASA/JPL and Paul Schenk/Lunar and Planetary Institute, Houston

03 September 2009

The Turn of Enceladus

When we think of Saturn, its tiny icy moon Enceladus is right there on the list of fun stuff. The south polar region is where the current action is, so naturally I am curious about its topography. The August 2008 Cassini pass produced a set of high resolution images with resolutions from 12 to 30 meters, and synoptic coverage at 50 to 200 meters resolution. Using my magic topo maker TOPO, I have produced the first high resolution map of this terrain based on this image set. A more complete map is in progress, but it will improve this one only by degrees. Like Europa and Triton, relief is not very high, rarely exceeding a few hundred meters locally (the story on Europa is much more complex, but that is a future blog). For now I present these fun images and movies of three of the "tiger stripe" tectonic ridges that scar this terrain.
I will be editing this post with more pix and details over the weekend!  I have added the Bagdhdad Sulcus movie today (Sunday).  Higher resolution versions of the movies can be made available for special needs. Uncompressed versions of the videos are available on Facebook under my name http://www.facebook.com/paul.schenk?ref=profile

Please advise me when any of these are used! I like to keep track of where this stuff ends up.

All images and videos credit: NASA/JPL and Paul Schenk/Lunar and Planetary Institute, Houston

Looking Down the Throat of Damascus Sulcus
This double ridge is a site for one of the source jets for the south polar plumes. The ridges are 100 to 150 meters high, and the medial trough is 200 to 250 meters deep. The small elongate blocks at the base of the trough formed when blocks slid off the wall scarps or were thrust up from the interior along the central fault. The numerous parallel ridges within the plains formed by crumpling of the icy surface. These smaller ridges stand tens of meters high.

Baghdad Sulcus
This view shows a deformed area between two branches of this tiger strip. These ridges stand is 80 to 100 meters high. Like Damascus Sulcu, numerous small elongate blocks have formed at the base of the medial troughs, which are 200 to 250 meters deep. The second view below shows an area extending into the ridged plains.


Cairo Sulcus

The ridges of Cairo stand 150 to 200 meters high. This view shows the steep wall scarp of the medial trough that splits the feature into two ridges. Vertical striations and large boulders 10s of meters can be seen. The rolling fractured ridges in the foreground most likely formed due to buckling of the icy surface. The largest of these ridges are nearly 50 meters high.