Chaotic Terrain on Europa: My upcoming research

Okay, you may or may not know that I have been doing observational research on Helheim Glacier. That’s coming to a close and I’m moving on to studying Europa. GA Tech has this program called PURA where you could get funding for doing research for a semester. My professor suggested I apply, and I did. I submitted it yesterday, so I haven’t heard back about it yet. I figured I could make another blog post, after long last, of what I wrote. It isn’t too technical, and I think it should be pretty easy to follow. Plus, I’ll threw in pretty pictures. so….

The Effect of Existing Geologic Features on the Formation of Europa’s Chaotic Terrains

Josh Hedgepeth

Related Work and Background Information:

Icy satellites are of particular interest to planetary scientists with their potential to harbor life. Where there is water, there is likely life. Enceladus has been considered a good candidate for life. It is significantly smaller than Earth and was believed to only have a small localized ocean near its Southern pole. It wasn’t until recently that we discovered these seas actually spanned the entire moon in the form of a global ocean (Thomas et al., 2016). This discovery has profound implications and raises many interesting questions. Except, these questions aren’t new. The Galilean moon of Jupiter, Europa, has long been suspected to have a global ocean (Cassen et al., 1979; Squyres et al., 1983; Carr et al., 1998; Kivelson et al., 2000). It has a radius 6 times larger than Enceladus, and its surface is arguably far more interesting.

It was thought that Enceladus, moon of Saturn, had only a small ocean near it's south pole, where large plumes of water has been observed to shoot out.
It was thought that Enceladus, moon of Saturn, had only a small ocean near it’s south pole, where large plumes of water has been observed to shoot out.
Enceladus_cross-section_2134x1200
We recently found out there is a global ocean, not just one near the southern pole.
europe-mole-3-100430-02
Europa, moon of Jupiter, has long been suspected to have a global ocean heated, largely heated by it’s tides with Jupiter.

For example, Enceladus lacks Europa’s chaos terrains. While there is contention as to what exactly classifies as chaotic terrain, these are regions of lumpy, disrupted matrix material formed from the preexisting surface by an endogenic process (Collins and Nimmo, 2009; Figueredo and Greeley, 2004). Greeley et al. (200) subdivided the chaos terrains to help distinguish between each region. “Platy chaos material” is where preexisting terrain is still observable only moved around like puzzle pieces. “Knobby chaos material” are regions of irregular shapes that are elevated above the surrounding matrix. Later, Figueredo and Greeley (2004) further defined these areas as “elevated” versus “subdued.”  They are complex yet fascinating because they indicate that Europa may have what it takes for life to thrive (Kereszturi and Keszthelyi, 2013). These regions may be evidence of subsurface activity facilitating mixing with the surface, and previous attempts have been made to model the formation of these but have been deemed unsatisfactory (Collins and Nimmo, 2009). Recent findings support the hypothesis that these terrains may arise from subsurface water lenses that form underneath the surface, between the deeper ice and the upper 3 km of the ice, facilitating ice-water interactions and giving rise to the distinct morphologies of chaos (Schmidt et al., 2011). This and previous models provide a process that explains some observations of chaos terrains.  We hypothesize that the geology that exists before the formation of a water lens controls what the eventual chaos terrain morphology will be.

Here is an example of the Conamar Chaos region.
Here is an example of the Conamara Chaos region.
Here is an example of the Murias Chaos Region
Here is an example of the Murias Chaos Region
Heating beneath the surface, but above the ocean, is hypothesized to create lens' of water that breaks the upper surface into these chaotic formations.
Heating beneath the surface, but above the ocean, is hypothesized to create lens’ of water that breaks the upper surface into these chaotic formations (Schmidt et al., 2011)
See on the left, icebergs breaking apart here on earth compared to the zoomed in picture of the Conamara chaos region.
See on the left, icebergs breaking apart here on earth compared to the zoomed in picture of the Conamara chaos region region on the right. There is an uncanny resemblance to icebergs on the right, broken and refrozen similar to what we see on earth.

Overview of proposed work:

The purpose of this research is to study the effect of the existing geologic terrains on the formation of chaotic regions. Europa’s surface is full of different geologic features. In addition to the chaotic terrains it has craters, planes, bands, and ridges (Figueredo and Greeley, 2004). Each of these features are created through various means, but our interest is in their effect on the region after the formation of a subsurface lens because we suspect these are the process by which these chaos terrains are formed. We will use archival image data from Galileo spacecraft of Europa to analyze each of the chaotic terrains on Europa to understand the underlying features and how they reached their current state.

This image and description is from Figueredo and Geeley (2004). Fig. 3. Type examples of the geologic units identified on Fig. 2: (a) crater material, (b) chaos, (c) elevated chaos, (d) subdued chaos, (e) double ridge, (f) single ridge, (g) ridge complex, (h) medial-trough ridge, (i) smooth band, (j) ridged band, (k) lineated band, (l) ridged plains, (m) subdued plains, (n) subdued-pitted plains. Where necessary, arrows indicate the feature under consideration.
This image and description is from Figueredo and Geeley (2004).
Fig. 3. Type examples of the geologic units identified on Fig. 2: (a) crater material, (b) chaos, (c) elevated chaos, (d) subdued chaos, (e) double ridge, (f) single ridge, (g) ridge complex, (h) medial-trough ridge,
(i) smooth band, (j) ridged band, (k) lineated band, (l) ridged plains, (m) subdued plains, (n) subdued-pitted plains. Where necessary, arrows indicate the feature under consideration.

Methods and techniques to be used:

For the past nine months, I have worked with Dr. Britney Schmidt (faculty in EAS) and Dr. Catherine Walker (postdoctoral fellow) as I studied changes to Helheim Glacier in Greenland. The study included tracking calving events, ice bergs and the terminus position, but it began by analyzing the crevasses in the glacier for a particular year. These were traced creating intricate maps of the crevasses in the ice. Seven Maps for years between 2001 to 2014 were created and compared.

The same general approach will be used to study Europa. First, a chaos terrain is chosen from the available image data set. Then the general features in the chaotic region and surrounding it will be mapped and traced. This goes beyond just tracing fractures in the ice. This includes any identifiable features such as ridges, planes, bands, or distinct matrix material that stands out from its surroundings with its own features. These features are separated out into layers to consider possible deformations or dislocations that may have caused these features to become dislodged or altered in place as the liquid lens forms below the surrounding area. Lastly, we will consider what is known about the composition and structure of the ice and the influence it would have on the dynamics that have led to these changes.

All of these observations will allow us to form a set of initial conditions to model from using previously postulated processes for the formation of chaotic regions. Then we compare these results to reality to see if these initial conditions explain why chaos terrains look so different if they experience the same or similar processes during their formation.

Objectives and goals for the semester project:

Objective Timeline
Identify and Retrieve Cataloged Images for Chaos Terrains

·         Arran Chaos, Conamara Chaos, Murias Chaos, Narbeth Chaos, Rathmore Chaos, Thera Macula

Week 1
Separate by Chaos Terrain Type (platy chaos material/ knobby chaos material)

·         Priority on Platy Chaos Material

Week 1
Begin study on Conamara Chaos Terrain

·         Identify features (ridges, planes, bands, etc.) in chaos and surrounding terrain

Week 1
·         Relate chaos terrain features to surrounding terrain features Week 2
·         Identify potential orientations and structure of the original landscape

o   Consider path traveled if there is enough information in the features

Week 2
Repeat this process for three to four more chaos terrains (dependent on time) Weeks 3–10
Predict how these initial terrain structures would deform using the previously proposed models for chaos terrain creation Weeks 11–15
Compare model results with actual to identify the model reliability Weeks 16–17

Relation of any past research:

While working on Helheim, I studied the crevasses. I also studied the change in the terminus position over the last decade and tracked iceberg creation and motion down the glacier fjord. I studied the atmospheric conditions and compared it with the glacier data to analysis the impact it had on the glacier flow and calving rate. I’m in the process of concluding my work on the Helheim Glacier. I’ve submitted a poster to International Glaciological Society and an abstract to American Geophysical Union. In December, I’ll be presenting my work at the American Geophysical Union conference. I’m in the process of finalizing a paper to submit for publication by the end of October.

Here is a view of Helheim Glacier, At the front are the lines indicating where the glacier breaks off (the terminus position). It's color coded by year. The background image is of year 2001. Notice, in the front you can see icebergs, and on the glacier are clear fractures, or crevasses.
Here is a view of Helheim Glacier, At the front are the lines indicating where the glacier breaks off (the terminus position). It’s color coded by year. The background image is of year 2001.
Notice, in the front you can see icebergs, and on the glacier are clear fractures, or crevasses.

References                                                

Carr, M. H., Belton, M. J., Chapman, C. R., Davies, M. E., Geissler, P., Greenberg, R., … Veverka, J. (1998). Evidence for a subsurface ocean on Europa. Nature, 391, 363–365. http://doi.org/10.1038/34857

Cassen, P., Reynolds, R. T., & Field, M. (1979). • a • Qr f (• present, 6(9), 731–734.

Collins, G., & Nimmo, F. (2009). Chaotic terrain on Europa. Europa, The University of Arizona Space …, 259–281. Retrieved from http://books.google.com/books?hl=en&lr=&id=Jpcz2UoXejgC&oi=fnd&pg=PA259&dq=Chaotic+Terrain+on+Europa&ots=vWUdSwHa7x&sig=lhhxXOlYxxJKVnYIR4yQF-Ekgr8

Figueredo, P. H., & Greeley, R. (2004). Resurfacing history of Europa from pole-to-pole geological mapping. Icarus, 167(2), 287–312. http://doi.org/10.1016/j.icarus.2003.09.016

Greeley, R., Figueredo, P. H., Williams, D. a., Chuang, F. C., Klemaszewski, J. E., Kadel, S. D., … Tanaka, K. L. (2000). Geologic mapping of Europa. Journal of Geophysical Research, 105(E9), 22559. http://doi.org/10.1029/1999JE001173

Kereszturi, A., & Keszthelyi, Z. (2013). Astrobiological implications of chaos terrains on Europa to help targeting future missions. Planetary and Space Science, 77, 74–90. http://doi.org/10.1016/j.pss.2012.08.028

Kivelson, M. G., Khurana, K. K., Russell, C. T., Volwerk, M., Walker, R. J., & Zimmer, C. (2000). Galileo magnetometer measurements: a stronger case for a subsurface ocean at Europa. Science (New York, N.Y.), 289(5483), 1340–1343. http://doi.org/10.1126/science.289.5483.1340

Schmidt, B. E., Blankenship, D. D., Patterson, G. W., & Schenk, P. M. (2011). Active formation of “chaos terrain” over shallow subsurface water on Europa. Nature, 479(7374), 502–5. http://doi.org/10.1038/nature10608

Squyres, S. W., Reynolds, R. T., Cassen, P. M., & Peale, S. J. (1983). Liquid water and active resurfacing on Europa. Nature, 301(5897), 225–226. Retrieved from http://dx.doi.org/10.1038/301225a0

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