I found a way to celebrate the end-of-year. I’m planning to erase my marker board (finally!), so as I do I’ll tell the science stories for each part. Ready? (Thread following. There will be interruptions. Might take a couple days to finish.) #2019 
First, this was from spring of 2019. Can anyone guess what this is? Something about robots, obviously. A list. Actually, a table with column headings listing robot properties...
3/ This is from analyzing robots from a lunar robotic mining competition! Most years it has been sponsored by NASA, but this year it was sponsored by Caterpillar and held in Alabama.
4/ For a decade I have been serving as a judge at NASA’s competition. Years ago I started taking notes on the robots to analyze performance and learn how to build better lunar rovers. We now have data on 470 lunar rovers!
5/ The marker board shows remnants of thinking how to organize the data to get better analysis. One result from the analysis, presented at a conference, was “The Robot Equation” that tells how to design a rover so it won’t get stuck in lunar soil.
6/ We were shocked to learn that individual properties of the robots are not correlated to their ability to drive in lunar soil. For example, the drive train gear ratio has no correlation to drivability (scale from 1-5 where 5 means a robot that is immune from getting stuck).
7/ This is why analyzing 470 robots has been so beneficial. I was able to find a correlation of 7 robot parameters that predicts which robots are basically immune from getting stuck in lunar soil. "The Robot Equation"🤖🤖🤖 Here is a subset of data from one year's competition.
8/ Now here's the best part! We never told the Robot Equation to the college teams participating in the competition. They don't have access to the data. They can't see any features that correlates to better driving in lunar soil. Yet every year, the robots evolve better & better.
9/ The competition is an amazing event that creates this kind of progress. So that's the story behind those scratches on the top left part of my marker board. Great memories from another year of scientific & engineering progress. Time to erase it, making room for 2020!
10/ OK, here’s the next piece: the blue writing in the center-left portion of the board. Any guesses what this is about? I bet @kmcannon knows!
11/ Those are chemical formulas for some of the clay minerals that went into asteroid regolith simulants created by @UCF and Deep Space Industries. DSI got bought and stopped making simulant, but @ExolithLab led by @kmcannon has continued and expanded the work.
12/ I was working on a method the quantity how “good” a simulated extraterrestrial soil is. NASA wanted us to do this because simulants are often misunderstood and misused. (People treat them like dirt. #BadJoke) So we needed to create a “Figure of Merit” system for NASA dirt...
13/ I mean, there’s dirt and there’s **NASA dirt**. If it is NASA dirt, then it explores the universe and it creates transformative technology and it motivates students to excel in school and it changes the world for the betterment of humanity. We expect a lot from NASA dirt😅
14/ So the contract NASA gave to @UCF and to Deep Space Industries was to create not just the “dirt” (the simulated regolith), but also a mathematical and geological basis to tell whether a pile of dirt is up to the level of being **NASA dirt**. This is its Figure of Merit.
15/ One of the challenging parts of grading NASA dirt is that many asteroids contain really weird clay minerals. If we make fake asteroid regolith using Earth’s minerals, will the clay that we use be good enough? Veeery tricky and complicated question!
16/ For example, here's a High Resolution Transmission Electron Micrograph of the Orgueil meteorite (it fell in France in 1864). The bar is 100 Angstroms long, for scale. Let me explain...
(Image credit: Tomeoka & Buseck, Geochimica et Cosmochimica Acta 52:6, 1627-1640 [1988].)
(Image credit: Tomeoka & Buseck, Geochimica et Cosmochimica Acta 52:6, 1627-1640 [1988].)
17/ The thin dark and light layers are two different minerals: Serpentine clay and Saponite clay. The layers are just 7 angstroms and 10 angstroms wide -- JUST A FEW ATOMS WIDE, each layer! Asteroids are AMAZING. How the heck can we create fake dirt to simulate THAT???🤯🤯🤯
18/ It is weird because geological processes that operate on asteroids are different than the processes on Earth. "Extraterrestrial" is best translated as "super freaky little-green-people mind-blowing different than everything we thought we knew from Earth". #LooseTranslation
19/ So when NASA says, "create, for the betterment of humanity and all that NASA does, a method that compares fake asteroids with real asteroids, and by the way make it good".....then uhh, we have a challenge.
20/ That’s the story behind why there are remnants of chemical formulas of clay minerals on my marker board at the end of 2019. I was racking my brain trying to compare mathematically the freaky asteroid clay with the best-we-can-afford-to-make simulant. A quote from our paper:
21/ Taking a break for my son’s orchestra concert. Will pick up this thread ASAP. TBC...
22/ Resuming this thread. Here’s the next thing on the marker board (being erased for 2020). This year I did a study for @ulalaunch on extracting water from the Moon. The study was spearheaded by @george_sowers. The dome sketched here is George’s concept.
23/ ULA funded our team at @UCF to develop modeling that predicts the flow of heat and water vapor through lunar soil to predict the efficiency of this form of lunar mining. Then, ULA hosted a workshop on this topic. The final report is here: philipmetzger.com/wp-content/upl…
24/ Here is the tent concept from that report (this is what is shown on the marker board). Large mirrors on the time of a cold, dark, lunar crater shine sunlight into the tent to heat the ground beneath it to release vapors. They flow into cold traps where they are re-frozen.
25/ I sketched it on the marker board to explain how the computer model would be structured to predict which way the water vapor will flow through the soil. We were concerned to make them flow in the correct direction into the tent. Story: ucf.edu/news/ucf-seeks…
26/ This was one of three projects over the past few years develop by that computer model. The other two projects were the Resource Prospector mission, which NASA cancelled (and now replaced with VIPER), and the World Is Not Enough (WINE) project with @Honeybee_Ltd.
26/ For Resource Prospector, I did modeling of thermal properties of lunar soil for 2 reasons. First, to predict whether the reduction in temperature swings at the lunar poles may have left the soil in a fluffier state, more difficult to drive in. arxiv.org/pdf/1801.05754…
27/ So we did experiments (building upon experiments done by two of my NASA interns years ago, one of whom is the amazing planetary scientist Dr. Ryan Watkins! @Ryan_N_Watkins), and I did thermal simulations of the Moon to compare to the experiments. The result indicates that...
28/...it is *possible* but still unproven that the soil may be somewhat looser in the upper 10-20 cm or so than at equatorial locations on the Moon. That will make it more different for rover wheels to turn without getting stuck since the length scale is similar to a rover wheel.
29/ Interesting side note: in science we are always faced with conflicting data and we make progress by explaining how they fit together. A recent study argued the soil is *not* looser in the polar regions on the basis of images of boulders rolling down slopes in polar craters.
30/ Here's the study of boulder tracks, by V.T. Bickel and David Kring. It's a fantastic study, but the boulders are roughly the size of a house so they probe the soil at depths too deep for a rover wheel, IMO. The top 10 cm is just "fluff", to a boulder. nesf2019.arc.nasa.gov/sites/default/…
31/ What we really need is a rover to drive around into and back out of some permanently shadowed craters on the Moon to get ground-truth about the soil conditions in the top 10-20 cm, to see if it's fluffier than the sunlit Apollo, Surveyor, Lunakhod, and Chang'e sites, or not.
32/ End of rabbit trail. I was studying the possibly fluffy soil conditions by writing compute models of the thermal conditions on the Moon to see if thermal cycling makes the soil get more compact. The second reason Resource Prospector wanted this thermal modeling was...
33/...to learn how fast the soil will cool down after driving a drill into the soil. A drill creates a lot of heat as the drill bit rubs and breaks grains of soil. We want to drill into lunar soil to study the ice below the surface, so we don't want to put heat into the soil!
34/ This is the opposite of mining the lunar soil, where we WANT to put heat into the soil. When we are prospecting, we want to leave it undisturbed so we can see what is there in the soil. Either way, we need computer modeling to predict how the ice will react to the heat.
35/ Here is the computer modeling showing the heat that develops around the drill bit below the surface, and other picture showing the surface temperature on the Moon as it rotates in the sunlight heating and cooling naturally. It is the same basic model that did both of these.
36/ One of the hard parts of writing this computer model was figuring out how heat spreads in lunar soil after vapor also builds up in the soil. There is a bad shortage of lab experiments on this part of the physics, and the data sets that DO exist disagree with each other.🙃
37/ In 2019 Julie adapted this model into a full 3-dimensional form so she can simulate multiple heat pipes pounded into the lunar ground, carrying heat down to the ice. She made a lot of progress and presented it in Luxembourg. More to come on this!
38/ Also, this red text is from that computer model. It is the equation that I developed to predict heat flows in lunar soil as a function of how porous or “fluffy” the soil is (n) and how much gas pressure (like from water vapor) is in the soil (p). It turned out pretty nice!
39/ Next part of the marker board: these black equations and the wavy diagram. This measures how much water comes out of Epsom salt when you heat it. About 40% of the weight of epsom salt is water molecules attached to the mineral. FORTY PERCENT! Even though it is totally dry.
40/ Such minerals explain a mystery: how can there be water in asteroids this close to the sun? It is too hot in this part of the solar system for ice, and small bodies like asteroids don’t have enough gravity to hang onto water. They should have lost their water by now, right?
41/ The “frost line” in the solar system tells where it gets cold enough for ice to be stable at the surface of an airless, low gravity body. Closer to the sun, the ice will evaporate and fly away in the solar wind. Farther out, ice can condense like frost and survive.
42/ The outer part of the asteroid belt has a lot of water. We know because asteroids from there contain lots of clay, which is formed by water breaking down other minerals like olivine. (Images: Olivine & Montmorillonite [clay], Rob Lavinsky, iRocks.com CC BY-SA3.0)
43/ Clays can be hydrated minerals, meaning that water molecules are attached into the crystal structure of the mineral. The clay hangs onto these water molecules stronger than it could hang onto ice, so the water can survive closer to the sun. (Image: en.m.wikipedia.org/wiki/Montmoril…)
44/ In the Honeybee WINE project (mentioned above) we developed a small spacecraft that can suck this type of stable water out of asteroid clay and turn the water into steam for rocket propulsion.
45/ It takes rather high temperature to suck water out of a rock — several hundred degrees C. It is easily do-able for the WINE spacecraft, but we wanted to do some tests using lower temperature to save the extra expense and stretch the project farther for NASA’s best benefit.
46/ This shows the amount of water that comes out at each temperature from a certain meteorite that came to Earth from a clayey asteroid. You can see the math symbols in the caption are the same as the marker board. The right figure is a version of the one on the marker board.
47/ That figure is from the manuscript that I just re-submitted to the journal on Christmas Eve, and it is in the arxiv here: arxiv.org/pdf/1912.10622… Anyhow you can see the temperatures go up to 1000 degrees C. Water is really stable in clay! It takes a lot of heat to extract.
48/ So in the WINE project we were figuring how to do tests at lower temperatures to save NASA some money. (The high temperature tests should be done later with higher fidelity prototypes. No point in doing the tests extra times at low fidelity.) So I suggested we use epsomite.
49/ The problem with using epsomite is that it is pure white so it looks nothing like a carbonaceous asteroid. Using epsomite as an asteroid simulant (even a low fidelity simulant) would invoke the giggle factor. We didn't want distraction about color of the regolith.
50/ So I mixed dark powders into the epsomite until its albedo (reflection of light) closely matched the dark color of asteroid Ceres. I did experiments using coal, magnetite powder, and carbon black. We chose magnetite powder for a variety of reasons.
51/ You can see the "TG" (termogravimentric) curve of Epsomite drops to 60% by 200 degrees C. That means, if you heat epsomite to just 200 deg then 40% of its mass will come out as steam, even though the mineral was bone-dry. (All the water molecules were part of the mineral.)
52/ After darkening it up to look like Ceres, it was a great low-temperature water extraction simulant. Our hardware only had to go up to 200 degrees, which meant we could use lower cost materials and save NASA's money on early prototypes. (Later prototypes do high temperature.)
53/ So that explains that part of the marker board. Here's something funny about it. (Funny now, not when it happened.) A couple years ago I was mixing buckets of the high fidelity version of the simulant to ship to Honeybee for tests. It was almost Christmas & I was hurrying...
54/ It's totally safe on your hands so I was mixing by hand to hurry the process. I WAS wearing proper breathing protection, so no worries. But as I said, I was hurrying. It was about 7 pm and students were done with final exams and going home for the break. I was almost done...
55/ I ran out of anthracite coal so I came up with the idea to mix charcoal briquets with sphagnum moss to produce the correct elemental ratios and aromaticity. Good enough! I quickly researched their chemistries and calculated the amounts, then ran to Home Depot to buy both...
