Finalizing the work on Pluto’s Craters

Examples of volatiles modifying Pluto’s surface.

Way back in March I wrote about my upcoming work at LPSC. I recommend you check that out for a full introduction to this, but I will give a quick run down before I get into the major details of this post. Pluto’s crust is thought to be entirely water ice. However, the extremely low temperatures lead to other ices being stable on the surface. The primary ices are carbon monoxide (CO), methane (CH4), and nitrogen (N2). We know ice can be very malleable on geologic timescales (e.g. glaciers on earth, craters on Europa), but the rates of medication vary based on the ice parameters and the conditions of the surface. Water ice on Pluto is extremely rigid and strong, but the same cannot be said for the other ices. They are both more prone to viscous relaxation (i.e. flattening due to gravity), and at least nitrogen is known to cycle from the surface and into the atmosphere (and losing some of its supply in the process). My work posits impact craters as a means to constrain the ways in which these ices would contribute to the modification of craters. As I discuss in my previous post, the two processes primarily effecting impact craters is escape erosion (like nitrogen) and relaxation. The extent to which this modifies the craters will depend on what ice the crater is made of. My work using the degradational state (how shallow is the crater) to constrain what type of ice the crater must be formed in, and we use the surficial compositional data to test (or more aptly, constrain) what the ice is made of. This gives us information about the volatile content in the region of the crater and the history of these volatiles.

A sketch of an upcoming figure where I discuss the way would expect impact craters to modify based on the type of ice it forms in. Left is right after formation and right is theoretically today. Orange Highlighter is used to demonstrate where would expect to measure “pure” ice on the surface, and orange stripes are used to show where we would expect it to be biased by surficial deposits.

In my previous post, we conclude that H2O, N2 and CH4 ices are the most likely to have craters form within them. In my figure I show a serious of possible scenarios. 1) a crater formed in a very thick layer of N2. Over time this would easily relax (flatten) and the N2 is almost certainly lost as well, leaving no trace today. 2) The same situation occurs, but in CH4 ice. This is both stronger and less likely to escape away. Nevertheless, it will still relax on the timescales of the solar system (i.e. Pluto), so we would expect to see a crater formed in CH4 ice that is shallower than expected. 3) Imagine scenario 1 but the crater dips into the bedrock H2O ice, creating a crater formed in an upper layer of N2 ice and a base of water ice. The water ice is too strong to relax, and the N2 will likely be loss. Therefore, we are likely left with a crater that appears to be formed in H2O but is significantly degraded. 4) we reimagine scenario 3 with CH4 instead of N2, and the upper layer doesn’t escape. In fact, we are left with a pristine crater that appears to be formed in CH4 ice. Then, 5) (not shown) we have the standard scenario of a crater formed in pure water ice which would be unlikely to modify at all.

As the title suggests, I am working on finalizing this work and compile it into a publisher manuscript. I had completed most of the work by LPSC. There were two major steps left for me to complete it. 1) I needed to figure out how small to go in the craters I measured; I only measured down to 15 km sized craters because of time constraints. 2) I needed to add a step in the code to remove the terrain slope (large scale topographic variations that craters likely impacted into). This would essentially put the terrain at ~0 km and leave only the crater topography. I did this when I measured Titan impact crater depths, but I didn’t for Pluto do to time constraints. This is a major step because it requires me to redo all the measurements I’ve done. This isn’t hard, just tedious. At 8 profiles for each crater with over 300 hundred craters, that’s thousands of crater profile measurements. Alternatively, I could use the profile positions (assuming I saved them) that I measured for each profile and automate it to find the height at those same positions. I would love some feedback on that idea, but right now I am planning to do it all manually. I have added the step in the code to remove the terrain slope which leaves the step of processing the craters again (one way, or another).

Sadly, we are not done yet. After presenting at LPSC, my conclusions prompted me to consider a major assumption of mine. That is, are the surficial composition measurements reflective of the underlying ice? The surface is covered with material, including surficial ices. I posit in this work that there are only so many possible formations a crater can form, and it speaks to the type of ice it needs for that crater shape to be viable. The compositional data is intended to act as further confirmation, with limited reach. Nevertheless, I wanted a way to demonstrate this is a fair assumption, so I started to consider what type of measurements I could take to test this claim. Let’s take another look at my figure above.

My figure demonstrates where we would expect to measure the highest amounts of the ice the crater is formed in with orange highlighter. In the areas of orange strips, this is expected to be covered, at least in part, but surficial deposits. My work at LPSC considered the crater composition of the rim to rim. That is, we would expect to include some of the purist and most biased regions of the crater. If I want to test whether these measurements are reflective of the crater ice layer, I should be able to measure the composition in each region and show the rims are richer in the predicted ice than the floor of the crater. With 300+ craters, the big question is how do I do that? I could map precise regions in ArcGIS, but that would take so much time. Still, it is likely the most accurate approach. The alternative, that I am currently working on, is to import the data to MATLAB. I can automate the process and take measurements of set sizes around the rims (10%, 20%, etc). Except, I don’t know how wide to make this. Nevertheless, I am currently in the process of doing this. The other option is to process the eight topographic profiles and mark where I want the rim and flow to be measured. This would take about as much time as in ArcGIS. I wish I could just do that with the points I use to take the depth measurements, but the region where I tell it to look for the peak rim is not necessarily what I would constitute the entire rim. Why? Simply put, profiles get really weird.

Now, here I am. The main purpose of this post is to think through what I am doing and request feedback. Although, after writing this I am beginning to think the best option is to map these regions in ArcGIS but only do it for the largest 100 craters (or some sufficiently large sample size). I don’t necessarily have to test all the craters, but in this scenarios I might want to focus on the craters richest in N2 and CH4, seeing as these are the ones where the assumption applies. Now I am very disheartened because I’ve spent days working to do this process in MATLAB, and I am seriously considering switching to ArcGIS because I literally talked myself into it. Let me know what you think!

Volatile degradation of Pluto’s craters

This is an introduction review for what I cover in my upcoming LPSC oral presentation (2555).

examples of geology on Pluto

Anyone familiar with Pluto knows it has a diverse range of geologic features. I show just a few of these in the figure above. The range of terrains that exist on Pluto diversifies it’s surface giving it a unique beauty, even compare to other worlds like Mars or Venus (that’s a science fact). I cannot help but compare these images to the picture of Pluto I had in my mind growing up. The picture I had was define by the episode of the Magic School Bus when the Friz takes the kids on a Journey through the solar system. At the end, they visit Pluto (considered the last planet in the Solar System at that time). It was this dark desolate place similar to the moon or Mercury.

Pluto as seen on the Magic School Bus

New Horizon’s shattered that picture in my mind, and I think the difference between the two is part of why I love Pluto so much. It proved to be much more than I ever expected. Why is that? Perhaps it was a lack of imagination. The team at the Magic School Bus failed to consider how significantly volatiles might modify the surface.

More images of Pluto focusing on the role of volatiles

Much of what we see on Pluto’s surface are in fact driven by volatile processes. Anyone moderately familiar with Pluto is likely to know about Sputnik Planitia, the giant lake or sea of N2 that traps heat and produces beautiful convection cells. There are other lakes, dendritic networks, glacier flow. All of this exists because the volatiles methane, carbon monoxide and nitrogen are unstable at Pluto conditions. This range of modification can be studied and quantified on an individual basis, but on a global basis as well. That is, we can consider how it shapes Pluto’s crater population which can work as reference point for how much degradation is occurring.

The focus of this post will be on Stern et al., 2015’s work looking at how Pluto’s volatile inventory can be responsible for the loss of craters. The figure shows how erosion will decrease the crater population count (R) and erosion with relaxation. What does this mean? When we think erosion, we think slow degradation driven by the removal of material, usually through the application of a physical force. Stern et al is referring to the loss of material to the atmosphere, I think by sublimation. Pluto is thought to have loss a great deal of volatiles over time. They enter the atmosphere and get sputtered away by various means. To be clear, Pluto’s bedrock is water ice. Stern et al is referring to craters that form in thick layers of volatile ice, specifically N2. These structures will fade away, and with it, the crater itself. Similarly, craters that form in N2 (or even CH4) ice will relax on the timescales that Pluto has existed. Relaxation will flatten craters, but rims are retained, but those rims can easily be loss.

Stern et al. 2015 estimates how much the overall cater population (R ~ crater count) would be modified by varying amounts of erosion (top) and erosion with relaxation (bottom).

I want to take this discussion a bit further because it suggests we can make predictions about the type of craters we should expect to find. Obviously, craters formed in pure water ice should be retained. Craters formed in sufficiently thick N2 ice (as thick as a crater depth) may relax on the order of thousands of years (millions at the most). Craters formed in thick CH4 ice would not be as conducive to relaxation. At the temperatures observed on Pluto, we might expect this to happen on the order of billions of years. We may see some craters entirely degraded (or flattened), but there may be some that are partially relaxed. CH4 is also less volatile than N2, so the structures would not be as susceptible to loss. This implies we should expect to see craters rich in methane and partially degraded, likely because it is formed in methane ice.

The temperatures expected on Pluto (left) and the relaxation rates of ices (right).

There are other in-between states to consider as well. What about craters that form in a thick layer of N2 or CH4 but not so thick that the crater can relax. In this instance, the crater base would be made of water ice. This base would uphold the other ice, preventing the crater to relax. However, N2 ice is likely to still erode away. Therefore, we will likely see partially degraded craters, depleted in N2 and CH4 (beyond surficial deposits) because they are the remnants of a dual ice crater. With CH4, the ice will be less conducive to erosion, so we might expect to see fairly pristine craters rich in CH4 because they have a water ice base.

These predictions have been tested by New Horizons. We have elevation data and compositional data as well. The compositional data is surficial, so there are limitations to what we can say about a crater. However, it offers first order constraints on what is present and what type of ice the crater may be formed in. We have used this data to study the degradation of craters on Pluto and relate them to the volatile abundances in their region. In doing so, we can constrain the volatiles in the region and the history of volatiles on Pluto.

Check out our talk at the 52nd LPSC to see our results!

Research Update 2-2-21

When was my last research update? I think it was in November, so let’s take a moment to catch up. If you’re curious, I did use a Dice-QNG, but I got the “pick myself option.”

Pluto research at LPSC

I began the year updating my Pluto remote sensing project results for an LPSC abstract with Catherine and Dr. Veronica Bray. This was a bit of a bumpy ride because the process wasn’t as streamlined as I had hoped. I had to do a good deal of editing to process the data again. I am not sure how much of it was past mistakes versus me not remembering exactly the process I had set up. I am 85% sure it was the former. Nevertheless, I spent a couple weeks getting it ready to streamline the process to produce more results. The results I had on my poster were not complete due to a mistake during the project that I had to rush to finish. Nevertheless, I persisted. I realized part way through processing the results that I did not need to process all of the data. I only needed enough to represent the greater population. In the end, I got a good amount of data; it was enough to write the abstract and apparently get me a talk. I am not particularly excited about another virtual talk.

Paper Drafts and Updates

In December, I got my paper out to my co-authors. I got feedback in early to mid January, after my LPSC abstract was up. In addition to the feedback from co-authors, I presented to the Dragonfly astrobiology group who had some recommendations. There were no major revisions on behalf of the co-authors. However, the Dragonfly group and Catherine recommended I amend my results to include a smaller concentration, 1 ppt (0.1%) HCN. The basic idea being that may be how low the actual HCN content will be. My co-authors also recommended I update one of my temporal graphs to have consistent color bar limits, but that was much easier.

I was a little nervous about the addition. It shouldn’t be a difficult thing to accomplish, but it’s always a hurdle to feel finished and have to dive back in. I got the sf2 (mushy layer model) results fairly quickly, and the only other step was the 2D heat transfer model. When I approached this, I decided to reproduce my other results too. I had made an assumption my first go around that did not get a great response from the co-authors. They didn’t push back against it, but they were confused. Ultimately, I decided it was better not to use that assumption. It’s not worth fixating on what the assumption was, but since I was reproducing my results, I figured I would do so at a slightly higher resolution.

This proved unnecessarily difficult. I don’t think the results appear particularly smoother. What’s more, I had to lower it again for 100 ppt melt of 250 m thickness because the melt started reaching 250+ ppt as it froze, which is outside the boundaries the model has to use to approximate the amount frozen in the ice. This was resolved by using as lower resolution, simply because it did not become as concentrated in larger increments. There was another issue of results not being convertible to a matlab .mat file. I didn’t understand why originally, but now I recognize the file size was too large, and not because of my increment size or my melt sheet size (although the latter plays a role), it was my time steps were all saved magnifying the file size. Then a larger melt sheet has more time steps, which led to my largest melt sheet files continuedly not working. Clearly, I figured it out. Yay me.

Some additional changes I made was to make the HCN concentration axis (x) to be logarithmic. The upper and lower profiles are now distinct in the figure. Unfortunately, this may prove somewhat problematic. The profiles are not as distinct across the initial concentrations used. It is hard to say whether this is limits in the model (it is at very low thermal gradients) or an actual characteristic of HCN. The other result figure is updated as well with constant limits on the color bars, and it definitely improved the figure. One of the coauthors expressed dislike for the jet-color map. I meant to change it, but I forgot. It just doesn’t seem worth recreating this figure for that.

Upcoming Plans

I have made corrections to some comments in the paper, but I need to finalize that. I had hope to get to that by the end of January, but the figure updates too more time for the reasons I mentioned above. I am going to try and get it done today and tomorrow. I would say Friday, but I need to grade Friday. I also need to get this out so we can get one more round of edits to send it for publication. I also need to switch my attentions back to Pluto because I have about a month to get a substantial update to that project. I think that is enough time. With the MATLAB process streamlined, it is mostly tedious work to do (i.e. mapping, extract crater depths, etc.). Lastly, I need to sit down and get a review of something Rick requested as a part of my comps exam follow up. I am going to aim to do that at the group meeting following the deadline for my LPSC presentation submission. I don’t know when that is. I don’t even have an email (that I know of) telling me I got a presentation.

Research Updates | November 2020

November Calendar (October/December)

S	M	T	W	R	F	S
1	2	3	4	5	6	7
8	9	10	11	12	13	14
15	16	17	18	19	20	21
22	23	24	25	26	27	28
29	30	1	2	3	4	5

This is an ongoing post of research updates during the month. Updates are provided every few days, and you can easily reach the update by clicking the link in the calendar.

11/4/20 – Plans for the month and election update

I have quite a few things to accomplish for the month. Lets break it down.

1. With my first draft finished, I need to move forward with the Pluto results. I think, I would like to have this mapped by our next meeting (11/18/20) and have the depth profiles by the end of the month (12/2/20). Then we can set up a meeting with collaborator in December to decide how to move forward.
2. Catherine and I have a meeting 11/13/20 with McGill. I need to prepare for that. That will include reviewing notes from last time and prepare for updates from the team. What I hope to bring is 1) my own results and plans to move forward and 2) a proposal for an experiment idea we discussed before. That is, an experimental apparatus to model an organic freezing in water to test the SF2 model.
3. On that note, I need to think about how to move forward. That means adapt the SF2 model to work with an alternative chemistry, ideally an amino acid that is denser than water. The first steps mean reviewing the material we have on how it acts in water like with HCN. At the same time, I would like to update my results for my paper while it is being edited by me and my coauthors. I have the SF2 results; I need to process them to get a new set of fits (extrapolation) and thermal model. I think I can do this in the amount of time edits will take. However, I would like feedback on if this is necessary. If yes, lets aim for final results by end of the month. Similarly, I would like to have my initial research for an alternative chemistry by the end of the month. That paves the way for implementation in December.
4. In the same vain, I need to put together a presentation for my lab on some topics discussed in my PhD comps. This is related to chemistry and the water-organic relationship, so I think the two goals go hand in hand. The goal is to present these results in December.
5. Lastly, I need to make a poster of my results. I think I will just apply my presentation. I am not sure what the timeline is for AGU, and I’ll decide on this later in the month.

In other news, one of the worst scenarios is playing out in the election. That is, Biden’s path to victory is a slow one dependent on absentee ballots. Trump has already screamed fraud and called for them not to be counted. If this isn’t a crime I don’t know what is.

An image of the already marked tweet made by Trump. Note, the first version of this tweet misspelled the word “polls” as “poles”.

11/18/20 grading and editing and last minute modeling

Earlier this month we had the Dragonfly meeting. That was a long yet fascinating experience. I look forward to following future meetings. I’m in a bit of a unique position to join titan research at the end of a long mission (Cassini), and now I get to watch the making of one. It was at times a little technical for me, but I still enjoyed the experience. Naturally, I wish it had been in person. Not only for the lovely trip to Baltimore (or wherever it would have been), but because it’s difficult to stay focused behind a screen with no one around to see you distracted.

I’ve also been working on the second draft of my HCN paper. Catherine had some great advice (naturally) on how to improve the paper and the results which involved a few more model runs. Luckily, I had already been running more models since I was finalizing the paper, so I was in a position to update my results right away. Unfortunately, things did not go as planned.

When I was finalizing my first draft, I tabulated my variables and constants in my model. Naturally, I validated all the sources I had listed for my values in my code. It was then that I noticed I had one of my values off or my source had changed. I updated it, but it didn’t seem like a major update so I didn’t expect it to change much. However, after looking at the new data I had ran while I edited my first draft, I realized it was a fairly significant offset. Que full system check.

I did several things. One, I reran all my codes for new results. What I found was that updating my values had streamlined the code. It ran faster, and worked at more extremes that it struggled with before. This means, if correct, I may not have to extrapolate. Then second, I needed to make sure the change was because I updated my values and not a major mistake in the code I made. This meant I tried to recreate my old code with the old results. As hard as I tried, I couldn’t do it. I wouldn’t say I tried everything, but I felt like I could only afford so much time for this. Alternatively, I downloaded Jacobs fresh code and input the values as my current sources documented them. It reproduced my most recent results. This means, while I may not be able to recreate my original results (which concerns me), I can at least test assured that the change isn’t a mistake I made in the main code in some other area. All I can say is, my parameter values are accurate, and I can reproduce these results from scratch.

Example results with original data and new data. New data is on the right, with the added overlap at the top right starting from scratch with Jacob’s code. Notice the artifact on the left red line that no longer exists. This is comforting because it did not make sense, and was a big reason why I couldn’t use higher concentrations because it seemingly wasn’t stable enough.

I have some ideas on what was the key change that caused the results to change. However, without investing more time on troubleshooting I chat say for sure. One thing I have failed to do, largely because of confusion, is install GitHub which I believe saves various versions of your code for reference. This would have made troubleshooting a much easier process.

For now, I have been reproducing all my results, and more. To the point that, I think I won’t need to use extrapolation. However, I am pushing my luck when it comes to finalizing this second draft by Friday. I very well may be able to finalize my SF2 model results today and begin the heat transfer model. Although, I have doubts. It seems very likely this is going to take a few more days. If I don’t get this buy Friday (I have lab Thursday too), I think next Wednesday is achievable.

The yearly AGU conference is online where I will be presenting a poster.

I have not even mentioned that my AGU poster is due Friday. That will be done today, perhaps tomorrow, so I have time for feedback from Catherine.

PS: my power was out when I woke up this morning which meant I one, woke up late despite planning to write this, and two, had to write this in my phone.

Research Updates | October 2020

October Calendar (September/November)

October is, objectively, the most wonderful month of the year, and it felt like it came and went faster than any other month. October began in a rush to submit my DPS presentation. I was not that concerned. I had just presented my research in July (which felt more recent than it was), and the virtual platform opened up how we give the presentation.

The final stretch leading up to the 9th (the submission of my presentation) was to produce some final results for my project. this required sacrifices. That is to say, I had to settle for simplifications rather than continually strive for perfect results. Catherine made it clear, at some point, I have to settle for what I have and move forward. This means I used the results of the SF2 model for lower concentration and extrapolated for the higher concentrations since getting a full profile at higher concentrations was a big hurdle. I think this was a good fit because the minimal data I got for 50 and 75 ppt matched up well with the fit. The next step was the 2D thermal model. This was mostly effective. I had to download an updated version and modify it for Titan, and in the process, I struggled to get the model to take the higher order fit of the HCN-water phase diagram. That is to say, I had to use a lower order fit that is less precise. Lastly, I struggled with the time steps being output because the results I presented had a thin liquid level, but it is effectively frozen. It should be entirely frozen. What’s more, the time scales are half the length, if not more, of what other predictions have for models of this size. These are all things I need to improve moving forward.

A look at the program with a view of my presentation format.

In terms of the presentation, I was frustrated with the DPS set up (going in, and after). However, I intended to make use of the prerecorded method they used. I regularly film and edit YouTube videos. This is has not only prepared me for easy editing techniques, but it trained to be fairly comfortable talking to a camera. I debated trying to record all at once or breaking it down to each slide. Each slide, I could perfect the conversation, but I risk sounding rehearsed. The entire presentation, I risk making mistakes or going over in time. I opted to go be slide. This was not effective. I got burnt out very quickly, and I found I would never be satisfied with what I said. So I stopped, and recorded all the way through. I did that one time, and it was fairly good. It was too long and had several mistakes. Rather than rerecord, I decided to give it the YouTube treatment and piece together a concise and continuous conversation with abrupt cuts throughout. This is a common occurrence on BookTube. I remove mistakes often, and I often have a bad stutter. I also do it when I want to trim down excess conversation. I had to make sacrifices to trim this down, and I did so fairly easily. It is a tedious process but one I am fairly fluent at. I am curious to hear peoples thoughts on that approach, especially as it fits into a professional setting. For the slides, I exported them as images and input them into my video editor. In retrospect, I could have had higher resolution slides by recording my screen of the presentation because I could not control the output of the slides. I am sad that I have a poster for AGU because I would have liked to do this again, with this knowledge, at least rather than a poster.

The current iteration of the paper on the HCN project.

As we shifted to the actual conference, I also began to write up the results of my work for the manuscript I started earlier this year. I finished that on time, and it wasn’t that hard to actually write. The tough part was sitting down and writing. Once started, I find putting my thoughts to paper fairly easy. I had adapted my PhD proposal into the paper at large earlier in the semester to the point that I only needed my results. I also needed to finalize a couple tables, but that was easy enough.

Check out my November research update (hopefully an ongoing report) for my plans moving forward!

In the meantime, enjoy some October bike ride photos.

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Research Updates | September 2020

September Calendar (Summer/October)

S	M	T	W	R	F	S
30	31	1	2	3	4	5
6	7	8	9	10	11	12
13	14	15	16	17	18	19
20	21	22	23	24	25	26
27	28	29	30	1	2	3

This is an ongoing post of research updates during the month. Updates are provided every few days, and you can easily reach the update by clicking the link in the calendar.

9/4/20 – Floor finished, apartment arranged (not research)

My apartment is finally finished being renovated. My new flooring looks really good and brightens the room. The old flooring was a much darker brown. It was done when I got home September 2nd, but it took me a while to get up the energy to organize everything. I particularly like my idea to swap the table and the couches. The living room has always been on the other side of the room where the window is. This has allowed me to put most of my books in that room. The lighting is great for YouTube videos, and I also just like things being different. I spend most of my time with my books and a my table than on my couches, so this works out.

The view of my place coming in.

The view in the back corner to show you my book cases. Note, I’ve only read the books directly across against the wall orthogonal to the window. That shows you how many books I need to read 😐

9/8/20 – Labor Day Weekend

On another personal note, labor day weekend was Dragon Con. Of course, Covid-19 turned it virtual. It was not the same, but I did enjoy playing werewolf with friends and others.

Playing Zoom Werewolf at Virtual Dragon Con. FYI: 12AM is EARLY, not late.

Okay, I have made good progress on my HCN models. Unfortunately, the results speak to a level instabilities above 10%. I met with Jacob (Dr. Buffo) to discuss it, and we have clear plan to move forward. I’m going to work with what I have and extrapolate. The model can only do so much. If you would like to see my results, I am happy to share, but I won’t be posting it publicly. This includes good results for up 5% and okay for 10% as well as testing the affect of varying spatial increments on 1 and 5% (to use it on higher concentrations of 10% and up).

Right now I am running a few more models for 2.5% and 7.5% so we can create a detailed 3D curve of values to better extrapolate forward. These lower concentrations should not take too long. The goal is still up to 25% concentration to ~25m depth pond. I am going to start working on Figures for my paper. Initial figures are set for September 14th, and hopefully by September 16th I can get an extrapolated figure to produce with a paper draft to be sent to Catherine. Then I’d give myself another week to run 2D model (maybe a little ambitious) followed by a final (1st?) draft on September 28th.

Simultaneously, I am working on mapping Pluto. There was no progress with this in August, and the first bit of September I’ve been focused on producing results. That said, I’ve begun mapping. My goal here is to have the entire surface mapped September 18th and the craters depths processed by the end of the month (September 30th). With this timeline, it might be a good idea to set up a meeting with Dr. Bray in mid October.

My initial results of mapping craters over the N2 content on Pluto.

9/22/20 – Progress Update

The last couple weeks were fairly productive, but I did not achieve my goals. The goal was to have my HCN Concentration in the ice vs depth (thermal gradient) completed by the 16th. I have not. They are in working condition, but I need more data for 5% and 7.5%. This is going to take time because I have to start at shallower depth due to stability issues. On a positive note, I have verified that I can increase the dt with negligible effects on the results. This should allow the models to run to a deep enough depth by the time the paper is finished and needs the finalized figures (~mid October?). I am working on extrapolating the data I have, but it is proving to be more difficult than I realized. It is a new task for me, interpolating and extrapolating in 3D in MATLAB. It is just taking time. I have made progress on the paper. Is virtually good to go minus the results and discussions.

I haven’t worked on the Pluto work because it doesn’t feel as urgent. I honestly don’t know if I ought to give this any time until I get the paper done. The goal now is finish mapping by October 9th with the data processed by ~mid October (14th). I am doing that because I need to get the HCN results done for DPS in October.

I start TAing Thursday, but luckily all my labs are on the same day. The goal is to make those days the day to work on labs. Other days will stay for research.

Research Updates | Summer 2020

This has not been the best of summers. Sure, I successfully completed my comprehensive exam, but beyond that, life has been tough. The pandemic began effecting us in March. It was another 6 months before I got to see my family again, the longest I’ve ever been away. Even that, was because my grandmother died. That was a very difficult experience made only worse by the pandemic. For a full discussion of that, I invite you to watch my Friday Reads for that week.

Nevertheless, we’ve all had it rough, and, as always, we manage. As the summer began I shifted focus to my comps, and it left me disheveled such that my routine fell apart. With it went my blog. I am here to summarize my research, and to bring us back into the routine of more regular updates. Of course, it is difficult to be specific about details months later, but I will do my best to summarize the last few months.

June

By June, the Remote Sensing class was over, but we had assignments to complete. I tried to complete one lab a week, but that fell apart after the first lab. I ended up spending a lot of time updating my proposal after getting feedback from Dr, Pratt. That involved creating a few new figures, but the biggest objective was to review the literature pertaining to the model and the fundamental approaches it uses. The need to complete this is, I think, what broke my routine of blogging and pomodoro.

Life became less about focused work about meeting deadlines. Luckily, I learned a lot in this process. I do regret that I never discussed the papers in my Science Paper blog post. I want to return to this, but it was hard to justify a deep dive in one paper when I needed to review so many so quickly. Nevertheless, I hope to review some of the material and present it in that post to 1) refer back to and 2) discuss with the lab.

July

In the end, I was very happy with the updates to the proposal. I sent it out to my committee very early into July. At this point, I had hoped to create a more structured studying approach, but I got overwhelmed with the labs for the Remote Sensing course. I quickly finished these and promptly moved on to the project. I was very frustrated with these labs. Although, I can’t complain much because I learned a lot of things in the process.

I dove into the project understanding things I had struggled to follow several years ago for my Titan crater mapping. It is in fact why I’ve steered away from using ArcGIS when possible, but I feel much more comfortable with it now. That helped me push through the project.

My project was to map craters on Pluto, take there depths, and relate the crater degradation to the N₂ content in the craters. This was based on past research which suggested that N₂ cycling will lead to 1) erosion and 2) relaxation. Sadly, I made a critical error when importing my data into MATLAB (where I took the depths and related it to the N₂ content). I had separated pristine craters from degraded craters in my crater maps based on what the new Robbins et al. (2020) defined as pristine. When importing the crater data, I assigned the diameter and N₂ content of the pristine craters to the degraded craters.

I believe this was a issue with sorting the data, so I patched the error and rushed to recalculate my results. In the end, I only processed the pristine craters. This severely limited my ability to analyze what was happening. I intend to completely redo my code after the project if the project was carried forward (it was).

SEction ofPluto overlain with craters mapped and N2 Content

In the final week or so leading up to my comps, I took time create flash cards. Essentially, I was reviewing the basics when it came to Titan. I had hoped to do this sooner, but it didn’t pan out. Luckily, the proposal process was a very good review, especially addressing Dr. Pratt’s suggestions. I didn’t review the note cards much, but the act of making them gave me a sufficient framework of what I needed to know. Obviously, I ended up passing with some recommendations (although these were minimal).

August

August began very well(ish). I was fresh off my exam, and let myself relax. I still did a bit of work each day the first week. Although, I didn’t stress too much about it. Things were complicated early on when my place flooded, again. A new emergency window in my basement unit wasn’t done right. It already required my floor needing replaced, and after it happened again, but worse, we had to speed up the process because of mold. I moved into an Airbnb (not at my expense). This lasted 2+ weeks, and made it hard to work.

Luckily, I was able to work from school for a bit. Most of my time was spent troubleshooting the code as I wanted to get it to work at higher concentrations. I ended up getting to work well enough. I don’t remember the other things I did, and I didn’t log it in Pomodoro at all. It doesn’t help that my grandmother died half way through. That ended up monopolizing the rest of my month. Again, see my Friday Reads for that week if you’re interested in a more personal discussion.

In the meantime, remember to check out my September updates.

My grandmother and I in 2014, Thanksgiving I think.

Research Updates | May 2020

May Calendar (April/June)

S	M	T	W	R	F	S
26	27	28	29	30	1	2
3	4	5	6	7	8	9
10	11	12	13	14	15	16
17	18	19	20	21	22	23
24	25	26	27	28	29	30
31	1	2	3	4	5	6

This is an ongoing post of research updates during the month. Updates are provided every few days, and you can easily reach the update by clicking the link in the calendar.

5/1/20 – particles vs solidification fronts

This was a so-so week. I’m doing pretty good at 4-5 pomodors a day, but I have had even slower days. Today I am clocking in 6 pomodors though. Still, I’ve done a bit of reading. I’ve started discussing some papers in a new blog post, you can find it here. Like this, I will update it monthly (assuming I can keep it up). I use as an outlet to discuss the paper as a review, and then I discuss its relevance to me. I’m also tacking on some papers referenced in it that are worth looking further into it.

I talk about sediment and particle entrapment (as opposed to solutes), and one thing Catherine pointed out was that solutes may not act the same as particle. The difference between a particle and a solute is just that a solute becomes a homogeneous mixture, sometimes breaking down (I think). HCN is miscible; that is just the liquid equivalent of soluble. I’ll discuss the mechanics over on the paper review post. I am not going to finish the paper today, but I am going to do an overview of it for now.

Also, I found this site that lets you easily import a pdf and fairly well read it to you. It isn’t perfect. It limits you to 20 minutes a day of moderate quality voice (no limit on low quality). However, a VPN does fix that issue. Nevertheless, it has helped me stay focused. If you know me, you know I am an auditory learner, so even if I have to go back several times, it helps having that to help me follow it along.

5/13/20 – Remote sensing, paper reading, and comps review

Since we last spoke, we had the remote sensing short course. It was informative and mostly enjoyable experience, but it was also exhausting at times. I made significant progress on each of the daily labs. Although, I still have a good bit of work left to do in addition to the project we grad students have to develop.

I am trying to work a little bit on the labs and on other things since I have so much time. I finished reviewing a paper I had begun before the class (you can read my thoughts here). I am going to continue doing that paper review post which I think is working well. Overall, this week has gone well. I think the remote sensing course helped get me in the mindset of treating my days at home like work days (sucks we didn’t do it sooner!).

Monday I reached 7 pomodoros. Tuesday wasn’t the best at 5, and that includes a meeting which is a questionable task. Today I think I will clock in at 7 pomodors (and end the day a bit early!). Granted, that includes one for the group meeting, but a 2 hour meeting deserves one pomodoro in my opinion. It is interesting to see how I work on different tasks. Today, I got carried away by Garhard’s comments on my proposal. I was very engaged, and it made it easier to focus. Alternatively, reading a paper or writing are very different activities that I often get distracted from. I think that is also reflected by my tendency to obsess on one task. I start each day with a plan; I try to dedicate time to everything I need to work on. I inevitably focus most of my time more on one task. Granted, I make a point to shift focus the next day, but it still makes it hard to do multiple things in a day. That is disappointing because things like reading or writing end up being sprints that are tough to maintain (as I’ve mentioned). All that said, it is interesting to reflect back on my tasks. I have a saved account on pomodoro, so I can see what I did when.

In regards to Gerhard’s comments, I felt good about most of them, and those that I was unsure about I feel I know how to go about answering them. That said, there were definitely things I am going to push back on because I am confident in my work (or so I keep telling myself).

a beautiful montage of Cassini images from Cosmos Possible Worlds

5/29/20 – A belated update

As I write, the date is June 11th, and needless to say I’ve fallen short of my blogging goals. I’m going to try and summarize the rest of this month to best of my abilities because I still like to have for here. It helps that I logged my time on Pomodoro. This was fresh off of the remote sensing class, and I was trying to balance research and the class responsibilities. I’m trying to balance my daily activities. More often than not, I find my self spending entire days on one thing (labs and class project vs studying for comps). Overall, if it works it works, and it seems I am spending equal time for each.

In the last week of May, I met with Gerhard about my proposal. This has me worried for my comps, not because I wasn’t prepared, but because of the level of anxiety I had around the meeting. Realistically, I don’t think I should be worried. We had two very productive meetings. In one I answered all of his questions with ease while also identifying a couple areas where I could stand to research the Titan background. In the other, we talked about the model and where his focus is going to be; it’s the paper I base this off of.

We came to the conclusion that the proposal could stand some edits, and after talking to my other committee members, we agreed on letting the proposal run a bit long. I needed to spend more time discussing 1) the numerical methods used and 2) the broad uses of the mushy layer model and reactive transport models. I did a broad review of the material with great help from Jacob, and you can find some of my discussions in my May paper log. I’ll probably go back and do a review for one of the other papers I read too, so keep an eye out for that (3rd) listing on that post.

I successfully finished lab one for the class. My goal is to finish at least one a week. I also need to make time for work on the project so I don’t leave myself with just two weeks to do the project.

Selective Log of Scientific Papers | 2020

List of Papers

• [1] Clayton et al., 1990 – Effects of Advancing Freeze Fronts on Distributions of Fine-grained Sediment Particles in Seawater and Freshwater
• [2] Remble and Worster 1999 – The interaction between a particle and an advancing solidification front

[1] Clayton et al., 1990 – Effects of Advancing Freeze Fronts on Distributions of Fine-grained Sediment Particles in Seawater and Freshwater

Summary (4/30). This work discusses an experimental study of sediment (dirt) particles in water as it freezes. It assumes some level of mixing has occurred sufficient enough for the sediment to be suspended in the water. The experiment is performed in a small tube with insulated edges to simulate natural scenarios. The authors track the change in salinity and sediment distribution in the ice. The findings suggest salinity removal is higher for slower freeze rates, and the same appears to be true for the sediment. However, sediment much less sediment is removed than salt, with 94% remaining in the ice. Finer particles migrated further than coarser sediment particles.

Discussion. This study says a lot of interesting things, but it is important to note the authors do not touch on mechanisms or venture to guess why sediment particles act different than salt. To me, it implies further dependence on particle size which is reflected by the distribution of sediment by size. Does this suggest HCN (or other organic molecules) will be less resistant to removal than salt? Is the difference in particle sizes significant enough to matter for HCN as it does with sediment used?

Addendum. I think it is safe to equate dissolved molecules (i.e. solutes) with suspended particles. I found this interesting virtual lab that helped me conceptualize the idea. It shows how water will break down salt into the atoms it is made of, perhaps with a slight charge. Alternatively, sugar will break down but only into individual sugar molecules. Fundamentally, these are still particles suspended in the water. We might imagine that the inter molecular forces are more important than larger particles, but fundamentally, they are just particles suspended in water. Therefore, the basics physics should still be applicable. For more on the physics, see the next paper (Remble and Worster 1999).

Further reading: Corte 1962; Reimnitz and Kempema 1979, 1987;

List of Papers

[2] Remble and Worster 1999 – The interaction between a particle and an advancing solidification front

Intro Summary (5/1). I am still reading through this but I wanted to start by reviewing the basic mechanism here as an introduction to the paper (as defined in the paper). When an ice surface approaches a particle in the liquid, the distance (H) between the two shrink. As it gets within a critical distance, intermolecular forces (e.g. van der Waals interactions) come into play and force the two apart. Whether the particle becomes entrapped depends on whether the ice front velocity exceeds a critical velocity that is essentially faster than the particle will move due to these forces. This was known prior to this paper, and this paper explores the idea further. I’ll summarize the entire paper after I finish it, but for now I want to discuss this idea as it relates to my project.

Schematic diagram of a freezing front impinging upon
a foreign particle. From paper. Explanation in text above.

Summary (5/11). This work uses the fundamental physics of particle entrapment to calculate critical solidification velocities (i.e. how fast the water freezes) needed to trap a particle of a given size. They consider the effects of different scenarios of inter molecular forces and briefly consider the effect of buoyancy on the process. As a particle approaches the ice interface, thermomolecular pressures repel the particle. However, within one particle diameter, the process is slowed. Once the solidification velocity reaches a critical point, the particle will become entrapped. The critical velocity is inversely related to the particle radius (e.g. larger particles move slower). Significant buoyancy differences will effect the forces at play, either hindering or encouraging particle entrapment.

Discussion. This is an interesting look at the role of intermolecular forces in this process. I want to look back at Buffo et al. (2018 and 2020) to see if 1) he references this paper and 2) how it relates to his work. I know I’ve seen van der Waals interactions mentioned in the code at the very least. Worster et al. mention that particles with different conductivity will react differently, so I need to think about the conductivity of organics vs water (probably closer than salt?). There is another point in here where Worster says that the higher thermal gradients promote particle repulsion, but that seems to conflict with sea ice observations which suggests thermal gradients are a major factor. This is also only mentioned in passing, so I don’t know what to make of it. My main take away is to investigate intermolecular forces more closely and the role they play.

Further Reading. Israelachvili 1992; Sen et al., 1997; Dash et al., 2006

List of Papers

Research Updates | April 2020

April Calendar (March/May)

S	M	T	W	R	F	S
29	30	31	1	2	3	4
5	6	7	8	9	10	11
12	13	14	15	16	17	18
19	20	21	22	23	24	25
26	27	28	29	30	1	2

This is an ongoing post of research updates during the month. Updates are provided every few days, and you can easily reach the update by clicking the link in the calendar.

4/7/20 – slow and steady wins the race

Modeling is still going strong. Sadly, the code I had running at school was reset, I assume from a power outage? If it happens again I will probably stop running code at school. Meanwhile, Jahnavi and I have gotten into the rhythm of reading pretty much every day. My comps are being set in July (date TBD?). I don’t love that idea, but I would rather do that then start our time back on campus stressed to the max. I think it’s also less intimidating over video. In other news, I have begun making an outline for a paper write up of the stuff I am working on. I suppose working on that will help prepare me for comps as I think more and more about what I am doing and the background around it. Although, I need figure out a good pattern to studying. I think once I met up with my committee I will get a better idea what I need to study.

4/14/20 – Writing, Studying, Modeling, and Time Management

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Images from night bike rides taken with my Google Pixel Night View

Modeling has continued as ever. I am fast approaching the point where I will have to reasses my results to decide if there are any points missing. I think I may have everything I need for HCN after the next week or so which is great seeing as I need to start composing a paper of this stuff. I haven’t actually made any progress on that front. Pretty much all of the work I’ve done has been toward an introduction chapter for my thesis. The purpose there is to use that as a means to study. I am not sure how or if I am going to handle doing that and the paper I need to write.

I am waiting on feedback from Gerhard and I got some feedback (more pending) from Rick. I’ve composed an outline for my Chapter 1 thesis, but I am thinking I will start focusing on the area he mentioned which was terrestrial understanding of organics in ice as he does not seem convinced that this sea ice model is applicable (or so is the implication I’ve garnered). I think the problem is he’s thinking on a molecular level when this is a bit larger. As I have described before, we are modeling “average” inclusions in the form of brine channels. In a 1-D model we can’t detail the actual channels, but is more of a bulk look at the system. I intend to document terrestrial studies (limited by life which may act differently) and the basic chemistry/physics. Of course, I will also compare this to clathrates which are different all together than what we expect to find here.

This week I returned to my handy-dandy pomodoro timer. I am going to start using that to help motivate myself to work. Again, 6-8 pomodoro’s is the goal. Today, I ended up doing 4 which sounds so bad, but I expect its the best I’ve accomplished as of yet. As I’ve said before, I work well with goals and boundaries. I am hoping this will help motivate me because it becomes a challenge of sorts. If I want to read, I need to work; the sooner I focus the sooner I will be done with what really isn’t that big of a goal, especially without others around to distract. Although, I am including meetings in this which isn’t exactly “focused work,” but I figure given the situation I can justify being a little lenient with myself.

On the side of self care, I’ve had a good run of focused reading. I also have a decent biking routine; every(ish) evening or night I go for an hour or so bike ride. It is a beautiful ride at night. Plus, there are fewer people (next to none). You can see one of my rides below and more pictures above.

4/22/20 – So so goings on

Things have improved somewhat. It is a little embarrassing to discuss my proficiency, but things have improved. My goal everyday is 6-8 pomodor timers, same at work. Over the last week I’ve ranged from 4-7 pomodors a day, I’d guess ~5 on average. I suppose compared to my goals that really isn’t that bad, but it still feels so insufficient. I’m working on improving my sleep schedule, but it’s hard. Just last night I went to bet at 1:30 and woke up at 7:30 because I’ve become accustomed to limited sleep. Then when I wake up that early, it is hard to get up and to work because it feels like free time which is absurd. Its the time I need to get to my 6-8 pomodor’s.

Work wise, models are going slow. One crashed when I accidentally unplugged my computer and it died over night (luckily one stayed in hibernation or something). I also finished grading the astrobiology reports with Jahnavi, and to our surprise, we were pretty close in our grades. Other than that, I had a fantastic weekend participating in the #StayHome Reading Rush. It was great reading experience, and I think I left it a little less stressed. I definitely wasn’t feeling as many anxiety symptoms by the time it was over. You can watch my vlog of that on my channel if you’re interested in hearing more!

Here is a short video of my ride (as I don’t #StayHome) one evening. I made it for my vlog and decided to upload it alone to my personal YouTube page too.

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4/24/20 – Living the Loop

Have you ever seen lost? There is this iconic introduction of this one character, Desmond, in a bunker, and we basically see his daily routine that never ends, until it does. To quote Carl Sagan, “That’s here. That’s home. That’s us.” That is why I know how important it is I nail down a routine here. Honestly, I think I have a pretty steady work flow. It isn’t as much as I’d like, but it’s a matter of refining the routine. That said, there are days, that is, yesterday, that aren’t great. Thursday was not a good day for work. It was very unproductive. I had hoped to make up for it on Friday, but that didn’t happen. I’m probably going to pull in 6 pomodors today when all is said and done.

We’re over a month in. Should I be past this point? Should be I lying here, or, at least be less up front about all this? Maybe I’m too comfortable. In any case, I’m getting some work done. I am really liking the Titan reading sessions with Jahnavi; that is the one thing we do fairly consistently. Today, I also got some paper writing done. My goal is 3 or so pomodors for writing and reviewing each. That didn’t happen, and I didn’t end up reviewing today. I have imported my relevant proposal info into my manuscript file. now, I am working on refining it and adding parts I need that weren’t in the proposal. That is results and a discussion of my thermal model which will act as a review.

I didn’t do it today, but I want to spend my current thesis time reviewing specific papers. Write up what I learn in a way that can fit into my thesis but also work as a standalone review. I feel weird talking about it instead of doing it, but #goals I guess.

4/27/20 Paper update

Today was not a bad day. I am on my 7th pomodor (updating my blog being the task). I spent most of my time working on my manuscript. I was making some tables about the variables being used, and reached the point where I need to talk about the results and the fits we use to approximate them. I looked at the results I’ve produced in the last few weeks in MATLAB. They are not great. The results using dz = 10 cm look different, and I need to figure out why. I’ve started coding lower concentrations that I have data for at dz = 10 cm to compare and see what the difference is. I need to figure out if its an overall problem with using 10 cm, or if there is something else I am missing. If dz doesn’t work, I am at a loss how to move forward because it doesn’t want to work with the usual dz = 1 cm.

Honestly, the fact that it doesn’t want to run at 1 cm for higher concentrations doesn’t make sense. At the higher concentrations, the system remains stagnant, and doesn’t convect when it does for the higher density difference. The only other change is a lowering in the melting temperature. I couldn’t pinpoint the problem the last time I reviewed the code, but I think I may go over it again and try to figure out why the critical Rayleigh number isn’t being reached.

Since I spent the day focusing on the paper and the results for it, I think I’ll devote tomorrow to thesis review starting by reviewing a few papers. I had hoped to do it today, but I got carried away with the 1D model issues.

Research Updates | March 2020

March Calendar (February/April)

S	M	T	W	R	F	S
1	2	3	4	5	6	7
8	9	10	11	12	13	14
15	16	17	18	19	20	21
22	23	24	25	26	27	28
29	30	31	1	2	3	4

This is an ongoing post of research updates during the month. Updates are provided every few days, and you can easily reach the update by clicking the link in the calendar.

3/24/20 – A month long update

I’ve fallen behind on my blog updates the last few weeks. Let’s recap why. The main reason was that I was working on labs and my proposal. It was taking more of my time, and I was becoming aware of the looming (desired) deadline. As such, I found it harder to come in and start with the blog. As with most things, this a pattern of behavior. It is easy to lose the habit. I actually haven’t blogged much research or otherwise. Most of my free time has been on my YouTube channel instead. As we transition to spring, I will try to get back in the swing of things. Of course, there are a lot of factors at play with that.

I’ll start with the research side of things. I finished my proposal, and I have sent it off to my committee for review. We also set a date for my defense! Was it April 24th or 21st? I don’t remember. I’m busy that day anyway because of the social distancing and all. Our labs have been canceled because they aren’t the easiest to do remotely. The group project is still being done by Nigel. I mean, he hasn’t been very communicative, so I am not concerning myself with it. I am still running models at school, but they are running slowly. I need to figure out how (and if) it is possible to get these higher concentration runs to work at higher time steps. Then I am also continuing to study for the comps exam whenever that may be.

On that note, I think we all know we are working from home. It is good and bad (mostly bad). I need to get a routine down, and I do think updating this blog is a good way to start that. I am trying to shower and dress for a virtual meeting each day so I don’t get stuck in laziness. I’ve also been doing a bunch of stuff around the house, yet it is still a wreck. I’ve also tried to start making videos more frequently (every other day perhaps) given all my free time. Obviously, that isn’t a priority over work, but one doesn’t rule out the other.

I am trying to focus, but for my own mental health, I am not letting myself get too overworked if I have a unproductive day. At some point, I say the rest of the day is mine regardless of my progress. Obviously, I need to start thinking of methods to get my routine going. Naturally, this is a tough time for everyone. I fear (and know) I have overreacted. Things aren’t as bad as they could get, but we can only take it one step at a time. We all have our own coping mechanisms. Mine are mostly eating too much. To overcome that, I try to make a smoothing to help pace myself (these are huge and can last hours). I also am trying to make myself to bike every couple days (I haven’t gotten to doing it daily yet). Other than that, I am video chatting with people more. I played Ultimate Werewolf on Zoom and that was a lot of fun.

3/27/2020 – My Week of Stress and Isolation

This has been a tough week. Things really haven’t gotten as bad as the could. I’ve moved past the initial phase of constantly worrying that every little discomfort may be a symptom. Sadly, I’ve only become increasingly worried for my family. I’m sure it goes without saying this hasn’t been the most productive week. Nevertheless, I’m here to talk about what I’ve done to hold myself accountable and to encourage myself to strive for more to say next time!

I’ve been playing around with my models, and I’ve managed to begin to get results for 10%+ concentration at higher (50m+) depths. It seems using a larger dz makes it more stable? Although, I am worried that might mess with the result accuracy or precision.

3/31/2020 – Inching Forward

I spoke to Jacob, and he thinks 10 cm should be just small enough to get reliable results. The trick is needing a dz that is smaller than the actual “mushy layer”. This is the layer where we have a mix of phases occurring which has convection driven by changes in concentration (buoyancy) and temperatures. I am still trying to understand the problem with higher concentrations. For whatever reasons, the Raleigh number it produces is just very small, but higher concentrations should create a bigger density difference between it and the ice. There is no reason why that should hinder the convection. I am running a couple at 5 cm dz as well. Once I get some results I am going to compare these with my 1 cm dz to get a better senses of what effect this has on it.

I need to study more. Jahanvi and I are going to start doing meetings to keep reading Lorenz’s book. I think I might start writing a background chapter for my Thesis. It is the best way for me to review and study for my comps which are only NaN weeks away.