The Path Forward: Publication, Teaching, and a Summer “Abroad”

I recently sent off my manuscript to the coauthors for review. Our goal is to finish up the final revisions to submit it in time for Icarus’ Special Cassini edition issue. I also received an offer to teach Astrobiology in the Winter 2019 term. Beyond that, have been granted funding to travel home (abroad) to Atlanta for the summer where I will work with my old adviser Dr. Britney Schmidt and her PhD student Jacob Buffo on a project I touched on in June 2018. Although, first I have to finish proctoring and grading for Earth Rocks this semester.

I have my work cut out for me, and I think we are the point where I’m in need of a good old timeline to set some goals for myself.

Manuscript

The manuscript has been sent to the coauthors. We have to make revisions to their suggestions. Then we have to send it to the Cassini team to repeat the process before the actual submission in January.

  • December 21st: Deadline for coauthors to return suggestions
  • January 1st: Deadline to send updated draft to Cassini RADAR Team
  • January 10th: Deadline for Cassini RADAR Team to return suggestions
  • January 10th-15th: Make final revisions and submit to Icarus

Teaching Astrobiology

I applied to teach Astrobiology (I think a 3rd year course) in lieu of Catherine next semester. I got the offer (which I was expecting), so I can officially say I will be teaching it next semester. Catherine has generously offered me all her material for the lecture and labs. However, I still have to prepare for the lectures and decide if there are any changes I want to make. I suppose this all will seem obvious, but I think it’s necessary to approach this large problem step by step to avoid issues.

I have to organize the course material (Class site, etc.). Then create a timeline for the different subjects. I need to decide when lectures are covered and how to fit labs around them. The class project needs deadlines set up. These are all initial steps that need to be taken this month.

Even though I have the lectures, I need to sit down and develop my own approach for each lecture. That means, reading through each respective chapter and making sure I have an idea of what I am presenting it and how I want to communicate it. This is the most taxing thing I think. I need to begin this this month as soon as possible because I want to make sure I’m not falling behind with the course. Ideally, I’ll have 4 weeks (8 days) worth of material lined up, but I still need to make sure I have a clear plan on how to continue the process as the semester continues.

I have plans to change at least one of the labs. I need to get into contact with a professor at the University of Washington to get started. That may or may not happen, but I need to start working on that. With that in mind, I want to work through at least some of the labs to see if there is room for improvement. Particularly the one I helped make two years ago. I’d put these tasks as lower priority because what we have works, I’d just like to see if we can make it better. I’ll translate it to excel later.

  • December 7th:
    • Set up OWL (online site), make schedule, update syllabus, organize material from Catherine. Plan Project timeline.
    • Get in contact with Dr. Rory Barnes at UW!
    • Review First Lab: Lab 1: What is Life?
  • December 10th-14th:
    • Set up meeting with Gavin to discuss first couple lab and course set up (he won’t be here until the day of lab that first week). 
    • I could include the second TA, but I am not sure if it’s for sure.
  • December 14th:
    • Prepare lectures for Ch 1: Astrobiology and Life
    • Review Lab 2: Solvents for Life
  • December 21st:
    • Prepare lectures for Ch 3: Life’s Structure
    • Review Lab 3: Viking Labeled Release
  • January 4th:
    • Prepare lectures for Ch 5: Energy for Life
    • Review Lab 4: Titan’s primordial soup
  • January 7th-9th: Meet with 2nd TA
  • January 11th:
    • Prepare lectures for 1st half of Ch 6: The Tree of Life
    • Set up Outline to new lab
    • Do Lab 1; Ch1
  • January 18th:
    • Prepare for 2nd half of Ch 6: The Tree of Life
    • Develop Methods and Question for new lab
    • Do Lab 2; Ch3
  • January 25th:
    • Prepare lectures for Ch 7: The Limits of the Biospace
    • Complete/Troubleshoot lab; send to TAs to complete and make suggestions
    • Do Lab 3; Ch5
  • February 1th:
    • Prepare lectures for Ch 16: The Habitability of Planets
    • Do Lab 4; Ch11
    • Review Lab 5: Is it science?
  • February 7th:
    • Prepare lectures for Ch 17: The Astrobiology of Mars
    • Do Lab 5; Ch12
    • Review Lab 6: Tree of life
  • February 14th:
    • Prepare lectures for Ch 18: The Astrobiology of Icy Moons
    • Do Lab 6; Ch6p1
  • February 21th:
    • Prepare lectures for Ch 19: Exoplanets (Last Chapter)
    • Review/ Edit/ Update Lab 10: Icy satellites lab (Cassini INMS)
      • Lab 7 would be the new lab developed earlier in semester.
  • February 28th:
    • Do Ch6p2; Midterm/ Lab break
    • Review Lab 8: Remote sensing and Intro to JMARS
  • March 1st:
    • Do Lab 7; Ch7
    • Review Lab 9: Mars landing site selection
  • March 8th:
    • Do Lab 8; Ch16
    • Review Lab 10: Icy satellites lab (Cassini INMS) L11
  • March 15th: Do Lab 9; Ch17
  • March 22nd:
    • Do Lab 10; Ch19
    • Begin project presentations
  • March 29th: More presentations; Report Due
  • April 5th: Grade reports
  • April 12th or so: Finals

Organics in Titan Crater Melt

I’m going to use some of the content I proposed this internship for background.

Dr. Schmidt and her team have been studying the Antarctic ice as an analogue for the Europa ice-ocean interface. Mr. Buffo has been developing a model of this boundary on Earth where it can be tested and validated, and then a few parameters are changed for application to the Europa environment. It follows the interactions between the salt impurities and the ice. One thing we see on Earth, is that even when the water-ice is pure, salty brine layers may still form within the ice.
Dr. Schmidt, Mr. Buffo, and I are working to apply his model to Titan melt ponds to better understand how the organics will be collected in the ice. The biggest obstacle in applying this to Titan will be substituting Titan organics for the salty brines being modeled on Earth. It requires an understanding of their physical properties in water. Some assumptions will need to be made, but we believe this will help improve Dragonfly’s search for biomolecules on Titan.

I did a rough plan for the internship, which will extend between Monday May 13th, 2019 and Friday August 30th, 2019. chose the middle of May to allow ample time for finals to be completed and processed at both universities. The nearly 4-month internship is meant to provide abundant time for learning, troubleshooting, and application. I ended it in August because classes at Western University begin in September.

Below is a plan for while I am there.

  • 2 weeks for troubleshooting issues I have understanding the existing model
  • 2 weeks to familiarize myself with Mr. Buffo’s results
  • 1 week discussing how we will go about applying the code to Titan
  • Titan atmospheric and melt pond environment
  • 3 weeks implementing Titan specific molecules in the code
  • 2 weeks troubleshooting using the new molecule
  • 6 weeks to apply the molecule for different crater environments
    • 2 weeks modeling 40km crater sized melt pond near the surface for non-draining ponds
    • 4 weeks modeling ~80km crater sized melt pond near the surface (2 weeks) and near the middle of the melt pond (2 weeks) for a non-draining and draining ponds

That’s probably not new for Catherine, but for others it may be. It’s also nice to have it here to reference more easily. I still take it a step further, because May is a ways away and I need to begin looking at this more closely. Realistically, I’ll be tackling the very problems that are listed above, but nevertheless I’ll write out clear deadlines to strive for.

  • January 18th: Understand how the existing model works. Run, repeat, experiment. Review all available reading material.
  • February  1st: Understand the role of brines/salts vs organics. Understand what is required to substitute it and what out options are.
  • February 8th: Test the limits of the existing code. What can be changed. What it does to the system.
  • February 15th: Try regular code under Titan physical conditions (rather than composition).
  • March 29: Try a new molecule (HCN? vs salinity)
    • Find required chemical and physical inputs for molecule
      • may require some code based methods
    • Try testing it
  • April: With finals and projects, I’ll leave this free. Plus, if I make it to the March 29th step, I feel certain thats where I’ll need to sit down with Jacob to begin making the code work.
  • May: Take it from there to the list above.

Bonus: Crevasses in Greenland Glaciers

Several years ago, I submitted a paper for my undergraduate work with Dr. Schmidt mapping crevasses or fractures on Helheim glacier. This observational paper was rejected. Firstly, it was my first attempt and there is plenty of room for improvements writing wise, but more fundamentally, they needed more. They need use to analysis our results and to quantify them.

 

Dr. Catherine Walker, Britney’s one time post doc, was going to do modeling using them. I’m not sure where that went, but we wanted to get my work published as well. More specifically I want to. I began working on quantifying these results. I had hoped to get it done much sooner. That has not happened. There has been a lot of troubleshooting mixed with long bits of no progress do to other responsibilities by all parties involved. We have all tried to return our eyes to this to bring it to fruition. I have been working with undergraduate student Kathrine Udell who has done similar work to what I’ve done. Shes done other types of mapping in addition to fractures. I did not. However, I’ve worked to get results for my glacier, Helheim and for her’s, Kangerdlugssuaq Glacier. 

I should take a step back and say, I’ve developed a code in matlab to quantify the maps. Katherine has helped me refine it to both improve our results and identify the best way to present the data. Presentation has been the biggest hurdle. Deciding how to talk about this type of data. This is already become more detailed than I intended, but long story short, I developed a grid to measure the fractures across the glacier. We’re looking at including orientation as well. This is a quick view of the most recent output.

orientation

I don’t want to get lost in the methodology, but the point is, we reaching our close. We don’t plan on working on this over the summer because we intend it to be submitted by then, so I need a plan. I need a plan that somehow gets me a paper with all I have ahead of me.

  • December 14: Outline of paper with major Figures and a clear idea of other figures left to make.
  • December 21: Finalize figures and send in depth outline to Britney, Catherine (Walker) and Katherine with a K (this has been my life for the last 2 years).
  • January 14th-25th (after Icarus paper is submitted): Methodology
  • January 28th-February 15th: Results
  • February 18th-28th: Introduction and conclusion.
  • March 1st: Send out for review.

I need to run these dates by them, but I like them and think its reasonable. Up to now, I haven’t done much with the paper. I’ve been so lost in the methodology; we have finally reached a point where we are comfortable with the approach we are using. Obviously, this is my lowest priority, but it’s something I need to think about. I’m glad I at least have something written out there. 

Update: I’ve discussed this with my adviser, and I’m being too ambitious. I need to postpone this until the summer.

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A month in the life….

How long has it been? A while I’m sure, so let’s recap. Let’s start with last week. I went to bed last Sunday with a splitting headache. Was I dehydrated? I must have been for it to have been so bad. Come to find out the next day, I had a serious case of the flu. Barely able to get out of bed, I suffered miserably. It was probably the worst I’ve had it in years. Even when I tried to rest, I was miserable. Naturally, it made for a bad work week. I could barely manage enough energy to make food let alone work. I tried to TA Tuesday; that was a mistake. I didn’t stay long. Hopefully, none of the students got sick. I didn’t make the same mistake Thursday, but I was mildly better. Or rather, I had to be. I had an application that I had intended to do at the start of the week but was unable to do. Now I made myself do it. I submitted the application to work in Atlanta with Dr. Britney Schmidt and her student for a about four months from mid May to the end of August. Hopefully, it gets accepted.

Prior to that, I visited Mexico with my mother and older sister on a cruise. I had a great time visiting with my family and exploring the underground river caves in Mexico. We also explored some awesome Mayan ruins as well.

For Halloween, I was Winifred Sanderson. My sister and her boyfriend were Tina and Gene from Bob’s Burgers (see cover photo).

I am applying to be the instructor for the course in Astrobiology. Lets hope I get the job. I don’t think I’ve mentioned, but there is an update happening to the Astrobiology Primer. The primer is a guide to learning and teaching leading concepts in astrobiology. I have signed up to help. It is still in its early stages. Most of the chapters have been developed, and we are decided on who will be the editors vs authors of chapters. I hope to help author parts of it. More to come later.

In other news, I got an updated draft of my manuscript to Catherine a few weeks ago, but there’s more to do there. That is my priority this week. I’ll add updates on this as things progress before our meeting Wednesday.

I’ve updated all of the figures so all is left is to deal with words for the next few days. That keeps me on track to update by the end of the week I think. Here is a quick review.

F1CM.png
A nice figure on identifying craters, now with a plain radar image to compare to.

 

F4Methods.png
A figure to highlight the stereo methods being compared in our work. This isn’t entirely new, but I updated it to hopefully more clearly compare how a uses a statistical average, and b calls 8 profiles (highlighted in white) that I use to find the crater dimensions.

F7 crater count adjusted dist.png
Another slight update. Stacked the figures, but my thesis actually doesn’t even include part b though.

F9 Technique Comp.png
The most up to date comparison plot between the different crater depths using stereo by H and by N, and SARTopo. Significant changes since last shown on my blog, but since last iteration in my paper I just added a subtle error bar at ~D=100km to include the N Stereo that is outside the plot (i.e. at 0m). I also fixed km to m in the depth y axis.

 

Topo Results (11.12).png
Finally, this wasn’t changed this go around, but it is slightly different from my thesis version. Symbols are slightly bigger, and the red symbols have a black outline and the black symbols a white outline. I also removed the stereo data since we have an entirely different figure dedicated to it.

I updated my methods and results to include stereo data measured using a new method. I have to go back and make a few more changes. The way I discuss the results needs improving, but the figures are done like I said (at least for now). Work in progress.

 

The impact of my time at Barringer Crater (AKA Meteor Crater)

I spent the last week touring Meteor Crater in Arizona. It was a unique opportunity sponsored by LPI that gave us unprecedented access to meteor crater to aid in our understanding of impact cratering processes. It began with 3 days of touring the crater followed by 4 days of investigating a particular problem.

This was lead by the lead scientist at Meteor Crater and the head scientist at LPI (the Lunar and Planetary Institute).

Introduction to Meteor Crater

trail guide
We toured along the east rim then back along the west rim to view the crater from a different perspective. Then we traveling into the crater itself and explored the crater floor (making our way up slightly to view a piece of the crater wall up close; available in Guide book, D. Kring, 2017).

We toured along the east rim then back again along the west rim viewing the crater from two different perspectives. On the second day we explored the interior of the crater. The beauty of Meteor Crater lies in its location and how well preserved it is.

Think about the Grand Canyon. It’s only ~150 km away from Meteor Crater, and in fact they both lie on the Colorado Plateau which means the geologic layers are the same (at least before impact).

mc cp
The Grand Canyon and Meteor Crater lie on the Colorado Plateau (the ~edge is drawn in red). Therefore, the geologic layering that exists is the same for both.

You may have already learned that the Grand Canyon is like a picture through time. Cosmos, a Space Time Odyssey illustrated this with an nice animation that separates each layer to highlight how each different layer has a different history for how it formed.
02463f7fe

 

gc mc layers
The Grand Canyon layering compared to the section effected by meteor crater (Moenkopi, Kaibab, and Coconino). From Meteor Crater Guide book, ch2 by D. Kring, 2017).

Meteor Crater penetrated through to the top 3 or four layers, Moenkopi, Kaibab, and Coconino. You can learn more about these in D. Kring’s guidebook (2017), but they each speak to a different environment by which they form. Coconino likely formed by sand dunes. Kaibab formed when Arizona was covered by a sea of varying depths (with fossils). Moenkopi formed during a time of a flood plain, similar to the Florida Everglades.

IMG_20181007_135208
Kaibab Limestone with fossils (exposed by an ejected boulder ~10m in size).

What happens when impacted is that the impactor (~30m in size) penetrates ~30m below the surface releasing large amounts shock pressures into the ground that rebound into the meteorite.

shock
From Kring 2017 guidebook

It acts like poking a pen through paper. The paper breaks and the ring bends back. In fact, they bend back over one another, folding. The result is that the lowest layer is folded on top of the other layers inverse to how they are normally layered. The diagram below shows the “fold hinge” having been mostly blown out in ejecta while the Moenkopi remains. However, overtime, this hinge is eroded (as well as the upper layer) and it becomes more difficult to see.

impact overturn
From Kring 2017 Guidebook

This overturned rim consists of a part of the blanket of ejecta that extends outside the crater.

fg
A Geologic cross section to summarize the crater geology.

This overturn is idealized. Sections eroded. Some shear; sections of Kaibab are missing between Coconino and Moenkopi because it slid outward further into the ejecta blanket. Furthermore, Kring suggests there were likely two other types of ejecta. A base-surge unit of the finest particles thrown up by as ejecta that is the last to fall and coat the rim and ejecta. This unit is known to exist from atomic bomb testing that formed craters. The other unit, which actually was the target of our research project, was known as Fall-out or Fall back ejecta.

Research Project: Fallback ejecta at the west rim

Fallback material is a layer of debris that is deposited over the overturned ejecta/rim. Kring describes its radial extent as unknown in the field book, but in person he made it seem as though its radial extent would be minimal. He described it as highly shocked material that is shot nearly straight up into the air before falling back down. This suggests that the layer it produces should be a mix of material, rather than distinctly inverted layers of the original target rock (see figure below). The idea that it goes straight up suggests it can’t extend too far out (without further modification).

 

fallback
Example of Fallback ejecta consisting of a mix of materials

Our research objective of this trip was to investigate region of possible fallback material by mapping its extent and identifying key characteristics within it. This means looking for key things like moankopi above the two layers (when it should be below) or evidence of high impact pressures with things like shocked Coconino.

Note, a previous version of this blog went into more detail about the project. I regret that decision. The blog wasn’t meant to expose too many details about the project, especially with the potential for publication. I have a habit of discussing my research openly, and I realize this is a unique situation that deserved more discretion.

General Thoughts and Take Away

I wish I had a clearer idea of what to expect going into this. The first 3 days or so are introduction. The next day is an applied field project to expose us to the area and investigating a problem. We measured ejected boulders to calculate their velocities. Then we moved on to this project, but the transition went from being guided to self ran. There wasn’t a clear distinction that, hey, from here on out you’re guiding yourself. That lead to a bit of confusion at the start, and even Kring blowing up at us, even going so far as to call us “by far the worst group of students I’ve ever had,” after telling us we were picked for this very competitive school because were believed to be the best of the best. That bothered me and several others. That isn’t how you teach. That isn’t how you motivate. What’s worse, I have to ask myself do I really want to talk about this here? Because, I could risk throwing away my chance to get another field school sponsored by Kring or LPI. At the same time, the thought that I’d be willing to work with someone who would treat me this way makes me feel…pathetic.

SAMSUNG
The group picture I tried to take and failed because a certain someone was too eager to check their own camera.

Note, images of Meteor crater are not to be reproduced for professional use. Images must legally be obtained by contacting Meteor Crater enterprises.

A minor setback in finishing up manuscript, now fixed.

Issues with results

Last Friday was one of many deadlines for which I was set to have a new draft of my manuscript (of my masters research) to my adviser, Dr. Catherine Neish. I was set back by a problem with my newest results that I noticed as I was discussing (i.e. writing) about them. To recap, I have measured crater morphometry (diameters, depths) using SARTopo, a low resolution topography on Titan. Then I compared it to Catherines stereo results (of higher topography) to ensure the low resolution data was reliable. I then replicated her results because the methodology of the measurements were different. Hers being an average of the entire 2D regions. While mine are averages of individual profiles (up to 8). Obviously, these results would differ, especially if there are fluctuations in the topography. However, I noticed that one of my crater measurements was significantly lower than Catherine’s.

Troubleshooting

At first, I assumed it was differences in the methodology. After all, the point of me doing this was because we feared they would be different, but I studied it closer by looking at the 8 individual measurements I took to make sure the lower result was just a matter of averaging lower areas. This wasn’t the case though. Every profile was significantly lower depths which didn’t add up. It ended up being a simple problem. I was weighting scaled images. As in, I used black and white images  where the white region was the max height and black the min height. This will not give precise measurements and will skew the data.

All in all, it wasn’t that off, but for Shikoku it was. That meant I had to go back extracted precise text file matrices of the data. I had another issue in this process where I was using the wrong file for Shikoku to extract the data. Stereo files vs radar images have different resolutions. That’s how I was differentiating them. Except, Shikoku had several 1404m resolution files; this wasn’t the case for the others. I started to use the wrong one. I don’t think this was the problem originally because I used an image already made (by Catherine I assume). Still, the problem is now resolved.

Results

These updates and fixes have significantly improved my results. Before, they all lied below or within error of SARTopo, but some of them disagreed with Catherine’s results. Now they are more in line. That is, Foresti and Hano are unnaturally low compared to SARtopo (~110 and 70m respectively). This has been explained before; there is a problem in the stereo processing where it likely doesn’t have enough representative features in the radar images to identify a difference in the two. Before, Hano was comparable to SARTopo, and I figured Catherine’s results were just because there was significant variance in the topography (some very low and very high) regions. Although, this isn’t what I find. Its around 50-70m in each profile, never reaching 100.

All the others lie slightly above SARTopo results, but they lie well within the margins of error. The highest are observed with Soi and Shikoku (+80 and +90m respectively). All in all, this is the result we were looking for. The results are slightly higher because SARTopo does average the results downward. Dr. Livio Tornabene actually made a point to point this out in my Thesis notes where he pointed out a paper that proved this was happening on Mars with two different topography sources. This is something I’m adding to the manuscript because it is relevant, and they actually take terrain to floor depths too.

Despite being slightly lower, they lie within the error, so these results can be considered reliable. Here is a plot of the values. Neish stereo results with a square, H18 results with triangle, and SARTopo with circle. The 6 stereo craters are color coded along with corresponding SARTopo. If there is no stereo, the SARTopo values are left grey. One last thing I want to point out is that every stereo measurement (save Forseti, which is not reliable) is higher using my (H18) method. This is what I expected. Neish and others used an averaging of a region of floor and rims, but we used peaks. Therefore, you’d expect the highest points in Neish and others to be lower, or at least I did.

stereo depth 10.18
Titan Crater Depths measured with SARTopo and stereo from Neish and from H18 (this work). turquoise is Ksa, green Santorini, yellow Shikoku, orange is Soi, and the blue ones are Hano (light) and Forseti (dark).

 

Other news and closing thoughts

I hope to have the manuscript sent to Catherine by Friday. Next week I will be gone to go to the meteor crater field camp. As far as future work goes, I’ve emailed McMaster about working with them to do some tests on the production of long chain polymers in a cold wet environment like Titan’s. I may end up emailing Dr. Britney Schmidts student at GA Tech about modeling impurities in a freezing water melt lens, but I have a meeting with a few people in that group tomorrow. I’ll begin my inquiry there.

The new normal: White House press briefings continue to get shorter and more infrequent

This is not a research update. This is a long facebook post I decided to turn into a short blog post. I have very strong beliefs, but usually I try to let the reporters do the reporting. Except this time, they’re not reporting enough about something they should be.

There was only one White House press briefing in September. This is not normal, yet no one is talking about it. I first heard about it in a brief segment on NPR’s Politics podcast. Except even there, there was no real coverage. Rather, it was one reporter expressing her surprise (in a sentence or two) at the lack of interest. I don’t like to rely on CNN as my source here (even though we’re dealing with a simple fact) just because people on the will be more likely to dismiss its importance from mere association (a success of Trump’s targeting them as biased). Unfortunately, they’re the only ones talking about it. That speaks to how little press it’s getting.

Bush briefings were on average 32 minutes. Obama’s 70 minutes. Trumps began about on par with Bush’s (~25-30 minutes). By June of 2017, the Washington Post said the Trump briefings were getting shorter and more infrequent. While this was technically true, CNN made the point that this only holds true compared to Obama. As I’ve already mentioned, Bush’s were the same length.
However, that has changed. They have been getting consecutively shorter and more infrequent since January 2018. The length has decreased, on average, 3 minutes each month as of June 2018. That’s ~15 minute briefings.

WHPB
From Washington Post

Fast forward to now and we’re down to one briefing last month. This isn’t normal, and these are a crucial part of our right to be informed. Furthermore, it represents a growing lack of transparency that exists in the Trump administration and their attempts to stifle the free press. This shouldn’t just fade into the background. It deserves to be reported.

Titan Crater Topography Through Stereo

To give a little background, I updated the crater population on Titan by identifying all the craters at the end of Cassini. Then I characterized their morphometry using limited topography in SARTopo, which give thin lines of low resolution topography where overlapping images were taken within a single swath. With this, I define certain parameters to study how the crater was changing. Crater size (diameter) is crucial because the shape of the crater is often presented as a function of diameter. The depth is also important because it gives quantitative constrains on how degraded a crater is from its original (deeper) depths. I took it a step further and measured rim heights as well.

However, the reason I have had to continue studying this is because I have been comparing SARTopo to standard stereo topography. Stereo is similar in that it is acquired where we have entire RADAR swaths overlapping. This provides a 3D look at the crater rather than a single (may 2 or 3) profile through the crater. Furthermore, SARTopo is at ~10km per pixel resolution. Stereo is more like ~2km per pixel. This is relevant because we measured “freshness” of a Titan compared to Ganymede craters. Ganymede is ~same size and density as Titan, so it is expected tat its craters will form in similar manners. The problem is that the topography on Ganymede is ~1.5km per pixel. This is significantly less than Titan, and it becomes a problem when measuring sharp peaks (i.e. low wavelength topography) because lower resolution averages these peaks with surrounding lower topography giving artificially lower rim heights. However, you see that Titan stereo resolution is more on par with Ganymede topography, so we can use it as a test case to see 1) how it compares to SARTopo and 2) if degradation still remains.

Unfortunately, we have come across yet another problem. The Titan stereo results (presented in various Neish et al. papers) was measured using a method that takes statistics of the entire rim and floor values rather than a single profile. I would argue that this is probably the most representative measurement of the crater parameters. However, our comparison is with Ganymede using previously published results from Bray et al. (2012). Brey et al. (2012) averages up to 8 profiles through Ganymede craters; we need Titan stereo measurements that mirror the Bray et al. (2012) methods for it to be comparable.

So, without getting to into the details, I found the 6 craters with stereo (Ksa, Soi, Santorini Facula, Shikoku, Forseti, and Hano). I uploaded the DEM png’s into matlab and manually assigned lat and long values (that was annoying). That may not have been necessary, but I wanted to be able to go back and see where the data was taken. Then I decided to take 8 precise profiles from the crater. I did this by creating a vector (list) of angles from the y-axis then found the right x and y values for each profile. This took a lot of troubleshooting, and I am fairly impressed with my ability to get this done one step at a time. It was particularly difficult where we had partial coverage. I almost just went with the two best craters we had and let it be, but I really wanted to include all the data we had.

The first thing to notice is that not all craters have full coverage, so results are limited to where we do have coverage. I tried to extend up to 5r out (as with Bray et al) where possible. However, I never ended up needing the extra topography because I didn’t go so far as to back out topography. Each black x represents the rim point I found. Then a show 3 of the best examples we have data for with the 8 profiles for Ksa, Soi, and Shikoku where you can see how these values where found. The rims and floor positions are marked with blue marks; the red marks are from previous literature for reference.

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The Final Result

What I have done is re-purposed my previous plot of rim to floor depths (the traditional depth measurement) to include H18 stereo measurements. Ganymede craters are in black. Titan craters are color coded for the 6 stereo craters to compare Neish stereo, H18 stereo, and SARTopo. SARTopo is shown in red if there is no stereo to compare to. What we notice is that there is a 3:2 ratio of craters that have SARTopo depths larger than stereo. Forseti (blue) is lower than SARTopo, well outside the margin out error, but ~same as Neish measurements. Hano (light blue) is lower than SARTopo but more on par than the ~0km depth from Neish et al. Soi (orange) and Ksa (cyan), the ones with the best coverage, show SARTopo slightly below stereo but well within the margin of error for each. While Shikoku (yellow) is below SARTopo, well outside the margin out error. H18 stereo is about the same as Neish et al. for Santorini (green) but slightly above.

 

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Rim to floor depths of Titan (circle, triangle, square) and Ganymede Craters (diamond, line). SARTopo is in circles. Neish stereo in squares. H18 stereo in triangles. The 6 craters in stereo are color coded in both stereo and SARTopo (if available). SARTopo without stereo is shown in red.

 

Starting Off Right: My Trip to Dragon Con and Work Ahead

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So, I spent the weekend visiting friends at Dragon Con in Atlanta. It was a blast, and this year I made sure to get at least 5 hours of sleep each night. Unfortunately, that meant I kept missing early panels I wanted to go see. I ended up spending most of my time playing games with my friends that I don’t see very often. Although, I did manage to attend two panels. One was hosted by Cecil Baldwin, of the Welcome to Nightvale Podcast. It was on queer representation in Horror films. There are a few new horror films I want to watch now, and even more that I want to rewatch with a new point of view. The other panel was on the mature themes in a Handmaids Tale. I still haven’t finished season 2, but I still enjoyed it. The panel asked some interesting questions like what constitutes rape in this world. Even consensual sex between June and Nick is arguable a form of rape because that wouldn’t be happening if she wasn’t in this position. It essentially her best attempt to assert some control over her own life. Then there was a question over the justification for violence, and if it is justified, then when is that threshold where it becomes okay?
All in all, I regret not seeing more. I didn’t make it to a single Space, Science, or Skeptic panel. To be clear, I wanted to, but in the moment, it is easy to get invested in gaming for hours on end. Then its a question of navigating from Hotel A to Hotel B which makes some panels more difficult than others. There is just simply too much to see and do.

The gaming was mostly Ultimate Werewolf. Although as a group, we tend to play all sorts of deception games including secret Hitler, Two Rooms and Boom, etc. It is a great way to have fun and get to know new people.

The trip wasn’t perfect. It’s long and stressful (but I don’t regret it). Still, my car stopped working on my way home and I had to spend the day in Michigan at a mechanic. It was over 90F (32C) and it was terrible. Luckily, they got it going, but I think it may be time for me to begin making arrangements to say goodbye.

Now, lets get to business. My current agenda has me finishing the Titan Craters paper by updating the Stereo results. That is my number one priority at the moment. From there, I need to move on to my new project(s). With that in mind, I have a few ideas to discuss further with Catherine. We’ve already spoken about studying how molecules will freeze in an impact melt pond. I’m also interested in testing the stability of a melt pond in an impact crater. If we have a porous subsurface, water will drain out, but how fast? The slower it is, the more time the pores have to fill with frozen water. My idea is that we may be able to model at what porosities a pond may remain. A shrinking pond also introduces the possibility (if flimsy) of wet-“cold-dry” cycles. This is a stretch, but McMaster University showed us how they are simulating wet-dry cycles with their planetary simulator to encourage polymerization. It likely will not happen at these cold temperatures, but I am curious how these molecules may act when frozen in a rigid ice matrix. Furthermore, if we consider a pond that is draining yet simultaneously freezing, we might imagine a hanging roof of frozen ice that may break and remix partially. Again, its a stretch, but I spent a week hearing about this wet-dry cycle and tried my best to think how if at all it could happen on Titan. Even if we disregard this cycling, the question of melt pond dynamics in a porous environment is still interesting.  I need to talk to Britney and her group, but I think Jacob, who is working on ice-water interactions in Antarctica and Europa because I think this type of project is still similar.

Other courses of action are, investigating Impact craters in RADAR. I assume that would involve RADAR processing (roughness, CPR, etc.) then mapping and inferring and possible ground truth planning. One other project which we spoke about (but one I am not all that excited about) is mapping fractures to river orientations. That is something I still need to discuss with Oz to get feedback about the report I made.

I also remind you all that I will be gone from October 6th to 14th (I think) for the Meteor crater course. I will also be gone for a cruise during Halloween (very sad about that).