Advances in Nuclear Forensics: GSA 2014 Technical Session

The lunar basalts in my doctoral research were almost four billion years old, plus or minus a couple hundred million years. The rocks I study now were created on July 16th, 1945, at 05:29:45 AM (Mountain War Time). It’s a strange thing to know so precisely. But how can I pinpoint the exact second of creation? Because these rocks are trinitite, the glassy result of a sandy New Mexico desert experiencing the first atomic bomb blast.

trinitite_top_and_bottom

Two views of a common green glass variety of trinitite. Image from the Simonetti Lab at Notre Dame.

The first nuclear bomb test, codenamed Trinity, was performed at the White Sands Proving Grounds (near Alamogordo, New Mexico). The device, Gadget, was an implosion-type design with a plutonium (Pu-239) core. The heat resulting from the 18 kiloton explosion melted the desert sand surface out to distances of 400 meters from ground zero. trinitite_thin_section The surface sand melted to form a glassy layer (1-2 cm) on top of incipiently melted desert sand together, these form trinitite (alternatively, Alamogordo glass). This post-detonation material is a valuable tool in nuclear forensics research. Trinitite incorporated pieces of Gadget and the blast tower, and one of our goals is to identify and characterize the distribution and composition of individual components through geochemical and radionuclide analysis. At right, a vertical cross-section of trinitite is shown in thin section.

The analysis of postdetonation material (like trinitite) is one arm of the nuclear forensics field. An effective nuclear forensic analysis requires technical information and relevant databases, and specialized skills and expertise to generate, analyze, and interpret the data. This analysis combined with law enforcement and intelligence data can provide valuable information on the provenance of such materials, and processing history so as to improve source attribution. Identifying the source(s) of stolen or illicitly trafficked nuclear materials will therefore prevent, or make more difficult, terrorist acts that would use material from these same sources. Moreover, effective forensic analysis of postdetonation materials in the unlikely event of a nuclear terrorist attack is also expected to deter individuals or groups involved, and provides incentives to countries to enhance their security and safeguards relative to their nuclear materials and facilities.

The microscopic and macroscopic appearance, as well as the elemental and isotopic composition of nuclear materials, i.e. its ‘signature’ reflects its entire history. The term ‘signature’ is used to describe material characteristics that may be used to link nuclear samples to people, places, and processes, much as a written signature can be used to link a document to a particular person. Forensic methods employed to establish signatures in nuclear materials typically combine physical and chemical (e.g. X-ray fluorescence, scanning electron microscopy, electron microprobe analysis, secondary ion mass spectrometry) characterization and radiometric measurements (e.g. alpha, beta and gamma spectroscopy). The methodologies and interpretation of forensic analyses are constantly being advanced and perfected.

gsa-logo_14CAt this year’s annual meeting of the Geological Society of America, the Notre Dame crew (Drs. Tony Simonetti, Sara Mana, and myself) are chairing a session to update the geoscience community on the latest developments of nuclear forensics. The cleverly-titled session, “Advances in Nuclear Forensics”, will emphasize analytical techniques, database development, and implications for our ability to identify and possibly prevent nuclear attacks and trafficking of illicit nuclear materials.

UPDATE (Aug 9, 2014): The session has been designated a poster session.

Note: A significant portion of this post was reused from our session proposal, which isn’t published by GSA.

Further Resources:

Pat’s Field Trip (Guide?) to Mt. St. Helens, Part II

Pat: We left off last time resting our legs in the Sunrise Visitor Center parking lot. It was a good stop, but now it is time to leave Sunrise and continue on our way to Mt. St. Helens. Turns out our Sunrise jaunt lasted almost until sunset, so we’ll have to stop somewhere for the night. Fortunately, it is the offseason and we have our pick of spots in the La Wis Wis Campground. Definitely pick a spot along the Ohanapecosh River to get easy access to the riverside. Perfect for morning tea. In fact, I’ll step out for a moment to finish my cuppa, and let Morgen step in.

Sitting_by_river

Morgen: Morgen here! I’m the lady pointing at the river. Pat has (perhaps rather foolishly), left his blog in my hands, so I’ll do my best to help finish this story. First, a disclaimer:  I am not a geologist. I’m an environmental engineer studying bacterial motility, so if you’re hoping for lots of insightful geologic-y things, you’re out of luck. Thanks to Ms. Frizzle and her magic school bus, I know the difference between igneous, sedimentary and metamorphic rocks, but that’s pretty much it. Regardless, I will do my best to learn you a thing or two.

P: Try not to spend all morning down by the river. There’s still a two-hour woodsy drive to Mt. St. Helens. Unlike from the west, our eastern approach doesn’t yield any glimpses of Mt. St. Helens until you are within the park. It is a fun, windy road through the Gifford Pinchot National Forest, with little indication of the nearby volcanic history. Then, suddenly, you get Mt. St. Helens’d.

Mt. St. Helens entrance sign

The Cascade Peaks overlook, on the edge of the lateral blast zone (location).

P: While not the first roadside pullout, the Cascade Peaks overlook is located on the edge of the lateral blast zone to the northeast. Some of the tall pines in this area are untouched, but many, like the one in the photo above, are skeletons of their former selves. Ten miles out, we are in the zone of the “standing dead”. Even here, the air temperature during the eruption exceeded 100°C (Winner and Casadevall 1983) and killed many trees, but the force of the blast had dissipated enough to leave them baking upright. A little further on and the landscape changes rapidly.

Mt_St_Helens_blast_zone_edge_pan

The blast zone is readily apparent today, dotted by new growth. Mt. Adams looms in the background, thinking “Soon…”.

P: Those of you with a passing interest in volcanoes have likely seen photos of once-forested hillsides newly draped in a blanket of tree trunks.

M: Seeing this in person can be somewhat unnerving, given that trees are supposed to a) stand upright, and b) not be stripped of branches, leaves, bark, etc. It’s a stark reminder of the power the Earth periodically unleashes on the surface.

Trees_on_ground

Fallen trees aligned with the blast direction, interspersed with new growth.

M: The Windy Ridge Observatory lies at the end of the winding trek through the blast zone. It certainly deserved its name, and the constant winds may help to explain why the Johnson Ridge Observatory is the more visited of the two. A short hike brings you to a wonderful vantage point, from which you can see Spirit Lake, clogged with trees blown into it by the 1980 eruption, and St. Helen’s caldera.

Spirit_Lake_Johnston_Ridge

Spirit Lake and Johnston Ridge (on horizon about 1/3 from left) viewed from Windy Ridge.

P: Is there a word for the desensitization that follows word repetition? When you say, for example, “pine” ad nauseam: Pine. Pine. Pine, pine pine pine pine, pine pinepinepine. Eventually, “pine” becomes just another sound, and you lose the mental association with the tree (or cone). That, I think, is the dissonance that takes root when I see photos of Spirit Lake. We all know that the tan raft up there is made up of individual trees, but it’s all just “tree, tree, treetreetreetree…yeah, that’s a lot of trees. Look, water.” Being there, it is much easier to make that connection between the trees and the scarred hillsides from which they came.

Mt_St_Helens_close

Mt. St. Helens from the top of Windy Ridge Observatory.

M: Mt. St. Helens’ caldera got its unique shape due to the nature of the eruption that created it. Before magma began building up, St. Helens was an almost perfect example of a composite volcano (imagine Mt. Fuji in Japan if you need a modern equivalent). Unfortunately, this perfection was not to last, as the magma building up under the earth caused the northern face of the mountain to bulge. When the eruption finally did occur, it blasted out, not up, leaving the inside of the volcano’s crater exposed.

Thirty-three years after that eruption, Pat and I decided that it was the crater, or as close as we could get without extensive permits and preparations, that was our destination for the day’s hike. This meant Loowit Falls. 

P: It was a park ranger that suggested Loowit Falls, which originates in Crater Glacier. Having hiked the trail herself, she was spot on with the timing, distance, and difficulty of the hike (plus a little extra for photos).

M: Leaving Windy Ridge, we embarked on a nearly ten-mile (round trip) hike through the blast zone. If you go, bring plenty of water, and remember to reapply your sunscreen often, as there is little in the way of shade. The path is pretty well-marked, but if you get confused (as happened to us repeatedly when we had to walk through dry stream beds) the park rangers have erected stone markers to guide you. Think 2010 Vancouver Olympics logo, and you have a rough idea of what some of the markers looked like.

Mt_St_Helens_Mountain_Goats

A herd of mountain goats lounging on Mt. St. Helens’ slopes.

M: While out and about, you may be fortunate enough to spot some mountain goats (see above). Unlike deer, who returned to the blast zone less than a week after the eruption, mountain goats have taken a little longer to warm back up to the place. However, this is mostly due to their need to eat butting up against the mountain’s lack of suitable vegetation.

P: We would have missed them entirely if not for stopping to talk with a Father/Son pair returning from Loowit Falls. It is easy to miss what you weren’t looking for.

Loowit_Falls

Loowit Falls from as close as we could get.

MPerhaps the greatest downside to this particular hike is that Loowit Falls is inaccessible from the trail. You can clearly see it from the trail’s end, but how close you get to it depends in large part on the zoom capabilities of your camera. While this is disappointing, it is also somewhat refreshing: The Mt. St. Helens National Volcanic Monument is meant to afford scientists the chance to watch nature recover without (major) interference from people. The fact that we’re allowed to hike through this living laboratory at all is pretty amazing, so being kept back from a waterfall in order to preserve it (and, one presumes, our own safety and well-being) is a small price to pay.

Mt_St_Helens_walking

Hey, who’s that young lady walking so purposefully towards the Lonely Mountain…I mean Mt. St. Helens? She looks like she’d be really good at pointing at rivers during morning tea.

P: In reaching Loowit Falls, our visit to Mt. St. Helens has reached a turning point. As in, we have to turn around. Although the mountain is at our backs, we are faced with constant reminders that we are in a transient landscape. After 33 years, the Pacific Northwest is well on its way to reclaiming the environment. Willows grow dense along the banks where water is in plentiful supply, and together we wander through the remnants of May 18th, 1980.

Spirit_Lake_from_Loowit_Falls

Mt. Rainier thoughtfully peeks over the horizon to make sure we’re okay.

MWell, the sun is setting, and we still have a two hour drive ahead of us, dinner to make, and an air mattress to exhaustively fall upon before going to sleep. Maybe tomorrow as we drive home we’ll get in one last hike. The White Pass ski hill offers some spectacular views of Mt. Rainier. Wait…what’s that, Self? You’d rather not hike anymore? You’d rather drive to Yakima and get a burger and fries at Miners?  Well, I guess we can do that instead.

Helens_Hike

P: Thus Part II concludes, having attained our goal of visiting Mt. St. Helens. What could be in store in Part III of our Mt. St. Helens guide? It’s starting to look like a Peter Jackson film. I’ll let Morgen have the last word since she was kind enough to help me get this post out there.

M: And so, good reader, I must bid you farewell.  I hope I didn’t bore you with my rock-less tale.  As a thank you for sticking with me, I’m going to write every geology-related word I can think of in 60 seconds:  Metamorphic, plate tectonics, magma, lava, plagioclase, olivine, mineral, thin section, crystal size distribution, titanium, microprobe, rock hammer, iron banded formations, calcite, sediment, cooling, partition coefficients, and ROCKS!
Best wishes!

Geologist Photographer, Photographer Geologist

The TV screen flickered to life as my family arranged themselves on the couch. On-screen, an aerial photo of Porto Rafti, a small seaside town east of Athens, Greece, marked the beginning of a two-week undergraduate geology department field trip to Cyprus. Figuring it was a once-in-a-lifetime opportunity, I had diligently photographed everything notable. I began regaling the family with photos of layered gabbro, sheeted dikes, pillow basalts, slag, boudinage, gypsum, corals, umber, and more. But halfway through, my dad interrupted to ask, “So, were there any people on this field trip with you”?

Or Dinosaurs? Dinosaurs would be fine, too. (Source: Jurassic Park / University Studios)

Or Dinosaurs? Dinosaurs would be fine, too. (Image source: Jurassic Park / Universal Studios)

It was a jarring question, and I realized my family was about to be bored out of their skulls.  If the roles were reversed it would be like sitting through “And here were are standing in front of the Historical Building. And here we are inside The Building. Oh, and this is a great one of your father pointing out the millwork on the ceiling joists”. I had wanted to share with them my portraits of Cyprus and the fascinating geology of an ophiolite. They wanted smiling faces in front of stuff – and not just for scale. The story on screen was not the one they expected, and I wound up fast-forwarding through most of the geology-centric photos.

brittle_ductile_faultsCommon advice when speaking to the ‘public’ is to respect your audience, which would have served me well. Photos are a form of communication, and as in all forms it is important to keep the audience in mind so part of the image stays with them. Sometimes the form is academic, to fill the frame with brittle and ductile faults (right). We can annotate, measure, discuss, hypothesize, and argue about the rocks. These are the sorts of photos to put in conference talks, the simplest “true” photos of the Geologist as Photographer Wedge.

However, geology is a global science, and geologists have the opportunity to photograph some wonderful locations (even in our own backyard, or in the lab). Extending beyond the utilitarian will naturally draw more interest to geological phenomena. There are multiple ways to improve image aesthetics, the simplest of which is to improve technical ability: composure, lighting, post-processing, etc. Tips and resources are everywhere, and a subset deal specifically with geological photography. However, there’s a field resource I think is underused by almost every geologist photographer: Humans. And not just for scale.

People crowd outcrops, poke their head into frame at inopportune times, shy away from the camera, or maybe only ever show their backside. But at the same time, they are interacting with the environment, picking up rocks, and pointing out interesting features. Capturing these aspects can be difficult, but when done properly will make for more dynamic photos. You can still get the academic shots and record sweeping vistas. It’s something I’ve noticed more by following National Geographic’s new blog PROOF, which tells some behind the scenes stories from Nat Geo photographers.

BIF and JeremyAn easy place to start is with your trip leader, as they typically gesture at everything and point out interesting features that everyone can see. Geologists get animated in the field, too, and are more animated in front of an outcrop.

Candid shots are rather more difficult, but it seems worth the effort when a broader audience will be interested in the photos. I think visiting zoos has helped me to practice for the field (not to draw too close a comparison…), because you get a feel for how patient and predictive you need to be to get a good photo. For example, one of my current favorites is of a relatively simple geologic feature, below:

students on rocks

Notre Dame students examine a large-scale reduction band in the Jacobsville Sandstone at Presque Isle Park, Marquette, MI.

Field work (and field trips) typically involve long hours, so it is not uncommon to be in the out for both the morning and evening golden hour. Above, our early morning expedition was rewarded with a clear sunrise on Lake Superior. For the geologists, the reduction band in the Jacobsville sandstone shows up clearly as the large ‘diagonal’ band at our feet. But there’s another layer of texture on top that draws other viewers in. The group was not scattered across the band for long, and I had to get into position and adjust my aperture to get a well-exposed and properly framed shot before the next shift.

People feature in more than half the photos (approaching 65%) from my last two field trips, up from less than a third in the Cyprus trip mentioned above. I’ll end with an encouragement for everyone to try and take more interesting photos of people in the field, and include one more photo below. The two halves show the same thing (ejecta strewn fields) on two planetary bodies, and it is the humans that tie the photos together.

Top: Boulder field at Camelot Crater from the Apollo 17 mission. Panorama compiled by Warren Harold of NASA/JSC. Bottom: Looking outward from the rim of Meteor Crater

Top: Boulder field at Camelot Crater from the Apollo 17 mission. Panorama compiled by Warren Harold of NASA/JSC. Bottom: Looking outward from the rim of Meteor Crater

This was originally intended to be part of Accretionary Wedge #56 (Geologist as Photographer) but wound up heading in a different direction and taking too long to be included.

AW#58: Signs

July’s impromptu Accretionary Wedge is Signs! (geological or geographical). Obviously I’m going geological. Enjoy a photo from the Catskills trip previously featured in the Field Stories Wedge. This photo is from later the same day, as the group discussed structural interpretations of a roadcut just out of frame. Although you can’t see it, you should believe in the road cut because of the FALLEN ROCK ZONE sign. Believe!

Class and Fallen Rock Zone Sign

Caution: Geologists and Fallen Rocks!

Warning signs are great markers for geology stops, and this sign is a classic example from Upstate New York. As a bonus, discussing structures on the side of a busy highway (or on-ramp, in this case) is also a classic “sign you might be a geologist”!

AW#57: Seeing geology everywhere

“Do you see geology in unexpected places? Do you often find yourself viewing the world through geology-tinted glasses? Do you have any adorable cat pictures that could be used to illustrate geology?” -Evelyn, Accretionary Wedge #57 call for posts

All liquids spilled on a work desk are naturally drawn to electronics and important papers. No counter-arguments allowed, that’s the rule. But don’t you wish your desk had better drainage? Subtle pathways that divert disastrous fluids to safety? With a little imagination, I think my desk would have pretty good drainage.

What i my desk?

What is my desk? Wood veneer, of course! Click for geology-vision.

I see two parallel N-S valleys with drainage to the south. These hopefully abandoned stream beds are separated by a long narrow ridge with an asymmetric profile like a drumlin. Don’t quite see it on the photo above? Click through for a mockup. And why not a drumlin? This is after all Indiana. Or…maybe Upstate New York? Yes, I rather like that. My New York hometown, here at my desk in Indiana. In fact, it takes no time at all to find similar landforms in a USGS 1:24000-scale map.

What is my desk?

What is my desk? A contour map, of course! A staple for field geologists. (Source: USGS topographic map of a square mile near my hometown)

Although with no elevations for reference, maybe my interpretation is off. Are my drainage pathways in the right spot? Or could those two “valleys” on my desk actually be additional ridges, making this more like a Valley-and-Ridge Province? There’s no way to know for sure, but that’s fine as long as it could make sense.

Creating wood grain landscapes is a fun way to pass the time in waiting rooms…or in your office when your mind goes blank from writing a dissertation. Staring at my desk, which is no longer my desk, but a symbol. A swarm of lines. A wealth of information. The view from a few hundred meters straight up in the air. And in all directions as far as the eye can see, geology is everywhere!

The long road to ALSEP data recovery

The human presence on the Moon did not end with Gene Cernan’s final footsteps, nor with Jack Schmitt’s final words before the Apollo 17 lunar module launched from the lunar surface on December 14th, 1972. The remnants of the six Apollo endeavors will, of course, remain on the lunar surface indefinitely as monuments of 20th Century space exploration. But for five years after Apollo 17, a human presence on the Moon was maintained through a collection of experiments at each landing site called the ALSEP program.

ALSEP lunar mass spec

Down-Sun picture of the Lunar Mass Spectrometer with the main hub and antenna in the background. (Image from the Apollo Lunar Surface Journal)

Over 5000 ARCSAV tapes were produced during the years of ALSEP data collection, and today most of these are missing

When the Apollo Lunar Surface Experiments Package (ALSEP) program was terminated on September 30th, 1977, it brought an end to 8 years of continuous data collection on a planetary body – a record that would stand (I believe) until Opportunity rolled past 3000 sols in 2012. And, much like Opportunity, ALSEP experiments long outlived their nominal one-year lifetimes. The ALSEP program relayed real-time data on seismicity (natural and astronaut-made), solar wind strength, ion flux, shallow surface heat flow and more to the distributed Manned Space Flight Network on Earth. Analog magnetic tapes (14-track range tapes) from the distributed network were collected at the Johnson Space Center (JSC) for further processing and re-recording. Range tapes made between November 1969 and February 1973 were to be permanently archived at Goddard Space Flight Center. Between 1973 and February 1976, a day’s worth of data from each site were stored onto separate magnetic tapes (7-track digital ARCSAV tapes) so range tapes could be recycled. Data processing was moved offsite (1976-1977) to the University of Texas, where the use of ARCSAV tapes were replaced by 9-track digital tapes (work tapes). And throughout this eight year period, numerous tapes were made for preliminary reports by PIs (PI tapes). Well over 5000 ARCSAV tapes were produced during the years of ALSEP data collection, and today most of these are missing.

SDS Sigma 7 tapes

In fact, if this tape rack represented the entirety of the ALSEP data collection, we would only have about three tapes (Image by fastlizard4 on Flickr)

The extended-mission life of ALSEP operations created some unanticipated issues for PIs. For example, the six passive seismic experiments recorded data 24-hours a day, enough to fill over one thousand range tapes per year for each site. The ever-growing volume of data tapes were increasingly difficult for PIs to work with, though this was abated somewhat by transferring to higher data-density tapes. The sharp decline in post-Apollo funding – NASA’s budget dropped by a third in the 1970’s – meant some PIs could not devote the hours necessary for data processing and maintenance. Although PIs were instructed to archive tapes with the Washington National Record Center (WNRC), the requirements were vague and poorly enforced and so only an estimated 50% of the PI data were archived. In some cases this was only a subset of processed, “scientifically important” data as selected by PI teams.

Records show something like 3270 ARCSAV tapes made between April 1973 to February 1976 were sent to WNRC. Records also show a massive withdrawal of analog tapes from WNRC, prompted by the tape shortage in 1980, which included ~2800 ARCSAV tapes as Goddard Space Flight Center staff searched high and low for reusable/recyclable tapes. Fortunately, the 7-track digital tapes were not their target (the Apollo 11 landing footage tapes were probably not as fortunate), but instead of returning them to WNRC the ARCSAV tapes were stored in the basement of GSFC. Many of these were later destroyed in a 1990 building flood, and the trail of surviving tapes goes cold after they were removed from the basement of GSFC during cleanup.

Modern computers could do so much more with the ALSEP tapes than was previously possible, if only the data were available. The potential was highlighted in the 1990’s when the University of Texas ’76-’77 tapes were reprocessed and made available on the National Space Science Data Center. But a concerted effort to find the missing tapes wouldn’t get off the ground until 2004, when the presidential mandate for space exploration sparked a resurgence in lunar research in terms of both interest and funds. With practically zero ground-truth characterization of the lunar surface (apart from returned samples and meteorites) and lunar atmosphere, the ALSEP program was a natural target for reevaluation. Suddenly there was a call for these tapes that were nowhere to be found. The NLSI Recovery of Missing Data Focus Group was formally convened in 2007 and is a multi-institutional, (mostly) volunteer-run effort led by some of the original ALSEP PIs.

ALSEP dust detector data tape

Apollo 12 dust detector PI tape of days 465-468 (Source: Prof. Brian J. O’Brien PI and SpectrumData)

It is through the efforts of the ALSEP focus group that most of what we know of the tapes has come to light. Every year at the Lunar & Planetary Science Forum (in March) and Lunar Science Forum (in July), the group has a side meeting where they share their successes and frustrations. And there have been successes. In 2010, ~450 ARCSAV tapes made between April and June of 1975 were recovered from WNRC. And at some point, a large quantity of ALSEP data was condensed onto microfiche and microfilm, and also backed up on paper. For LPSC this year, an abstract from the group announced the complete restoration of seven lunar data sets. Another eight data sets are in the final stages and will likely be completed by LPSC, with a promise of more to come. In short, many raw data tapes have been recovered…and also some processed data tapes, and reprocessed tapes of processed data tapes, and prints of raw and processed data…now what?

Hopefully “restoration” should hint at something more involved than slapping an ARCSAV tape in a reader and ripping it onto a hard drive like a CD. Well…OK, that is part of it. But unsurprisingly, such tape readers in working condition are increasingly rare, and at least some of the ARCSAV data recovery was outsourced to data recovery/conversion companies or citizens. Prof. Brian J. O’Brien (Australian government) was an original PI for the Early Apollo Surface Experiments Package (EASEP) and ALSEP Dust Detectors (Apollo 11, 12, 14, and 15) and the Charged Particle Lunar Environment experiment (Apollo 14). He maintained possession of a number of original tapes (including the one pictured above), and is working with SpectrumData to recover quality data.

And quality is the other main issue here. Tape quality degrades over time. Converting tape formats can introduce transcription errors. Processed data might be missing metadata on conversion programs, units, calibrations, random transcription errors, or whatever “corrections” the PI deemed necessary. Even in raw data tapes, anomalies occasionally occur because, after all, they came from the Moon.

It's all the way past those trees and everything.

It’s all the way past those trees and everything. (Photo by poikiloblastic)

Without relevant metadata (including telemetry to assess transmission quality), the tapes would be worse than useless because any product would rest on a flawed foundation. That remains a major obstacle to data restoration. Significant progress in terms of tapes acquired and metadata resolved has been via cooperation with PI teams and their universities, with one PI even lending an ALSEP experiment notebook to scan for use in calibrating a data set. Prior to archiving with the Planetary Data System, data sets undergo peer review. The ALSEP-recovered-data-related abstracts submitted to LPSC this year are a promising sign of the science return we can expect to see from these important datasets in the years to come.

References:

Almost all of the details above are collected from focus group meetings at the NLSI Lunar Science Forum (2011 & 2012), as well as ALSEP Data Recovery Focus Group progress abstracts submitted to the Lunar and Planetary Science Conference (2011 & 2013). My contribution to the focus group thus far has been to introduce myself at the beginning of said meetings.

ALSEP system and experiment reports are available from the LPI website.

Recovered EASEP and ALSEP data sets are archived in the Planetary Data System Geoscience Node.

Related: Lunar Orbiter Image Recovery Program (LOIRP)

Remove a carbon coat from thin sections with methanol

tl;dr: methanol is great but don’t let it kill you

Thin sections, oh glorious thin sections! They are little slices of truth, windows into the processes that shape all rocks. And for a variety of reasons, geologists do terrible things to them. Thin sections are subjected to staining, acid etching, laser beams and more. In my case, my samples are all subjected to the electron microprobe for in-situ mineral analysis. The first step in this process is to coat each thin section in carbon. Samples are placed in a carbon evaporator, which creates a vacuum (down to at least ~10^-4 torr) and coats the sample in a ~20nm thick carbon layer. This is great for analytical work, but it dulls everything in plane polarized light, can mask birefringence colors, and just forget about trying reflect light microscopy.

Carbon coated lunar basalt 70135,64 looks mostly “normal” in plane-polarized light (though a bit dim). Most major phases are easily identifiable (plag = plagioclase; px = pyroxene), but reflected light is necessary to identify opaques…

Same area of lunar basalt 70135,64 shown in reflected light. Not only can you still not identify the opaque phases, but you’ve lost the boundaries between plagioclase and pyroxene!

It’s just a big gray mass of cracks. If you need to take a second look at your sample, that carbon coat will just have to go! Despite being only 20nm thick, the coating is surprisingly resilient. You must also take care not to damage the thin section, so what do you do? There are various ways to approach carbon coat removal, and I thought it would be useful to highlight two common methods: grit and methanol

Removing a carbon coating with Al-polish

Use a fine grit Al-oxide powder and water to polish off the carbon coat. This quote from a mineral forum post suggests several ways to remove a carbon coat, including:

The simplest way to remove a carbon coat or a gold coat is via a 1 micron Al2O3-H2O slurry (1 part Al2O3 to 8 parts H2O) on a Buehler Polishing Cloth ( Catalog No. 40-7218 Microcloth with adhesive for a 8 inch wheel) aka “moleskin”. Gentle rubbing of the thin section or grain mount by hand on the mole skin polishing cloth (on a flat surface) with a generous amount of the slurry will completely remove the coating both on the surface of the mineral grains as well as in between the cracks and grain boundaries. This is due to the the action of the very fine short hairs of the moleskin. The Al2O3 can be easily removed under a running tap (preferably distilled water) or else (if fussy) in distilled water for five minutes under ultrasound. Afterwards the thin section or grain mount should be dried using a soft cloth or a kleenex wipe.

I really like the idea of using a polishing cloth, as it is rather difficult to remove carbon from low areas (e.g., cracks) with only a kimwipe. Removing Al2O3 buildup in these areas can also prove difficult. In addition, this method gets messy, and I am always worried about over-polishing and losing the sample. That is why I prefer to use methanol.

Removing a carbon coating with methanol

Methanol is also an effective carbon coat remover, with one caveat: Methanol is extremely toxic! You should already be wearing gloves during cleaning to prevent your gross human oils from transferring to the thin sections, but in the case of methanol it is an absolute necessity to have proper hand protection. I also prefer to work under a fume hood to prevent inhalation (and because it smells wicked strong). Methanol is my preferred method because it is clear and evaporates rapidly, making for an easy assessment of the status of carbon removal and leaves almost nothing to clean up.

Before, during, and after carbon coat removal. Methanol preferentially removed carbon from the sample, so it was cleaned before the surrounding epoxy. The thin section is 1″ diameter.

How I removed this carbon coat with methanol:

  1. Wear safety gloves
  2. Place the thin section on a flat surface
  3. Moisten a kimwipe with a drop or two of methanol
  4. Hold the thin section in place and rub the kimwipe in a variably circular motion, applying gentle pressure
  5. Regularly change the face of the kimwipe being rubbed on the thin section. This minimizes the risk of loosened material scratching the surface.
  6. Keep the kimwipe moist but not too juicy with methanol
  7. Check your progress in reflected light. The image below is the nearly-cleaned thin section, with a couple trouble spots to finish up. Checking your progress early and often is the best way to get your eye in on carbon coat removal. You won’t know when it’s all gone if you have no idea what it looked like before you started!

A couple of minutes work on 70135,64 and the carbon coat is nearly gone. Now we can see the opaque phases in 70135,64 are mostly ilmenite, with some exsolution troilite (and unlabeled Fe-metal and possible melt inclusions) popping out that we would have missed previously.

70135,64 after methanol removal of the carbon coat. Notice the change from the previous picture – we uncovered a new exsolution feature in the lower left ilmenite grain. The ugly methanol droplets are also almost all gone, and the remaining “bubbles” are melt inclusions.

A few swipes with a methanol-dipped kimwipe is also a quick way to remove all those annoying loose particles surrounding laser ablation pits.

Wedge Fifty: The Catskills Conundrum

The following mystery was written for Accretionary Wedge #50, hosted by Evelyn of Georneys. This month we are invited to:

Share a fun moment from geology field camp or a geology field trip. You can share a story, a picture, a song, a slogan, a page from your field notebook– anything you like!

On to the story…

The Brunton Compass is a field geology staple. Image from the Brunton website (click to visit).

Every geologist worth their rock salt recognizes – and hopefully knows how to use – a Brunton Compass (Evelyn gave them their due in B is for Brunton). Housing a compass (with adjustable declination), clinometer and mirror at less than 10 ounces, the Brunton is important as much for its form as its function. One of the more common uses of a Brunton is to take strike and dip measurements of strata. Strike indicates the compass direction of the originally horizontal bedding plane (i.e. the orientation). Dip is the angle relative to horizontal in the downward direction of the bedding plane, measured with a simple adjustable bubble level.

Visualizing strike and dip can be tough at first, and it’s easier done than said. That’s why, on an undergraduate class trip to the Catskills, our first task of the day was to warm up with some Brunton practice – and we needed some warming up. It was crisp late September morning, and many of us were sporting geology club hoodies, warm hats and gloves. Fortunately the Catskills record a smorgasbord of interesting geologic events to get the blood flowing, and our first stop of the day was a doozy.

The “Taconic Unconformity” near Catskill, NY. Steeply dipping Ordovician sandstone interbedded with shale (right) lies unconformibly below a not-quite-as-steeply dipping Silurian-age limestone and medium-grained sandstone (left).

There is no evidence of deformation on the discontinuity (it is an angular unconformity), but there is a fault zone as well, with slickenlines. Ron Schott’s gigapan of the area shows the broader context, though I couldn’t find any slickenlines. Anyway, Bruntons in hand, we spread out over the outcrop to measure the strike and dip of the surfaces with slickenlines. Some of the not-quite-awake students worked in pairs.

It is not difficult to persuade geologists to climb. Here the structures class swarms an outcrop in the Catskills to practice using a Brunton in taking strike and dip measurements.

After our Professor had made the rounds to see everyone had the general idea, we collected together and reached a general consensus of strike and dip measurements. The slickenlines were striking towards the west-northwest and were dipping around 45 degrees south…I think. My notes from this trip aren’t very good, but everyone seemed to be in agreement. Well, almost everyone.

One student spoke up about some wonky strike measurements she had recorded. Sometimes they would be striking west, but then other areas seemed to say the slickenlines were striking north or southwest. Her dip measurements were spot on, but she was getting no consistency with strike. It wasn’t a method issue, as she demonstrated she used the normal strike-taking steps. We had a mystery on our hands! A nice little brain teaser to start the morning. The Prof started running through a process of elimination to find the source of error.

It is possible for magnetic minerals in rocks to mess with the compass and give erroneous strike measurements, but that was ruled out as the rest of us were getting consistent results. The Prof took strike in one area, then had her measure the same location and it was way off. They swapped Bruntons with the same result. A little frustrated, the student took off her fingerless mittens to get a better feel when taking strike measurements. She remeasured the strike and finally read a west-northwest strike. The Prof gave her back her Brunton, and the needle once again pointed west-northwest. Things seemed back to normal…but what caused the slew of mis-measurements that morning?

The Prof figured it out first. He asked to see a mitten, which had a flap that could be folded back to make a fingerless glove. The student had been using it in the fingerless configuration, with the flap held securely to the back of the mitten. The Prof folded the flap near the back of the mitten and smiled as several small but powerful hidden magnets pulled the flap back into place with a dull thud.

Sampling Gruithuisen

The following is an abstract I wrote for – but never submitted to – the 2011 micro-symposium on The Importance of Solar System Sample Return Missions to the Future of Planetary Science. Because of time constraints I had to limit myself to a single presentation on how and why we sample crater ejecta (PDF of that abstract here).

Introduction:  The case for planetary differentiation has been well established for inner Solar System planets. Samples from meteoritic material and robotic and manned missions have contributed to current models of planetary evolution. A key early finding of the Apollo missions was evidence for a lunar magma ocean (LMO) and the early differentiation of terrestrial planets [1, 2]. This model was later applied to other rocky planets such as the Earth, Mars, and Venus.

Silicic volcanism represents a compositional end-member of planetary differentiation. As late-stage products, these evolved magmas may be used to place constraints on mantle sources and processes. Silicic magma in sufficient quantities may also play a role in early planetary mantle dynamics, magmatism and crustal evolution.

Non-terrestrial silicic volcanism is potentially identified on Venus (e.g., Pancake Volcanoes) and the Moon (e.g., Gruithuisen Domes) [3, 4]. Of these locations, the Moon is both uniquely preserved and accessible to robotic and manned missions. The Gruithuisen Domes were a Constellation region of interest, and much work has been done to characterize the area.

Samples to determine the extent and range of products of differentiation are among the highest lunar science priorities [5, 6]. Silicic volcanic terranes are rare in the current lunar sample collection. Those that have been identified are of uncertain provenance [4]. Origins as the products of silica-liquid immiscibility or basaltic underplating have been proposed for non-mare domes, but it is unclear whether they are volumetrically minor late stage residual melt or form large intrusive (and extrusive) bodies [7, 8].

Gruithuisen Dome region

Image and caption from [NASA/GSFC/Arizona State University]: “All three of the Gruithuisen domes and the surrounding terrain are shown in WAC frame M117752970. Image width is 64 km and illumination is from the left.” Click the photo to visit the post on the LROC website.

Gruithuisen Domes:  Located on the northeast margin of Oceanus Procellarum, the Gruithuisen Domes area contains three dome structures: Gruithuisen Delta (27 km diameter), Gruithuisen Gamma (19 km), and Gruithuisen Northwest (7.5 km) [4]. As nearside non-mare volcanic features, they represent an accessible and valuable scientific site. Spectral observations indicate the domes are low in iron and titanium compared to mare and are also enriched in thorium (~20-40 ppm), similar in nature to rhyolite domes on Earth [7,9]. Emplacement and rheology models also indicate similarities with rhyolite [10]. Elevation profiles of central summit craters are consistent with non-impact origin [6].

The Gruithuisen Domes are located in a geologically complex region proximal to highland and mare units. On the basis of crater counts and geologic mapping, the timing of dome emplacement has been calculated as 3.85-3.72 Ga (Late Imbrian), earlier than the ≤3.55 Ga surrounding mare units [7, 11]. A significant contribution of sample return would be the establishment of an absolute age for these units and the association with the surrounding mare and underlying highlands. [Click here to visit the featured post on the Gruithuisen Domes at the LROC website.]

Sample Missions:  Scientific potential is significant for a stationary lander, and only increases if mobile rovers and manned missions are also considered.

Automated Sample Return.  There are several potentially key areas of focus for a sample return mission from the Gruithuisen Domes. The summits of larger domes are plateaus large enough to target for automated landing. Targeting the plateaus may avoid issues associated with landing on mare or highland terrane. Flank slopes (11-18 degrees [6]) may present problems for a lander, but are manageable by rover. A single sample return from the Gruithuisen Domes would likely yield rock types currently lacking in the lunar sample collection.

Manned Sample Return.  Adding a human element enhances the diversity and quality of collected samples. Mobile missions are currently restricted to a 10km radius around the lunar module on slopes of less than 25 degrees. Within these architectural constraints, a single mission could fully explore one dome or sample the flanks of two domes and the surrounding mare.

References:

  1. J. A. Wood et al. (1970) Lunar anorthosites and a geophysical model of the Moon. Proceedings of the 11th Lunar Science Conference, 965-988.
  2. P. H. Warren (1985) The magma ocean concept and lunar evolution. Annual Reviews of Earth & Planetary Science 13, 201-240.
  3. J. H. Fink et al. (1993) Shapes of Venusian “pancake’ domes imply episodic emplacement and silicic composition. Geophysical Research Letters 20, 261-264.
  4. J. W. Head and T. B. McCord (1978) Imbrian-Age Highland Volcanism on the Moon: The Gruithuisen and Mairan Domes. Science 199, 1433-1436.
  5. NRC (2007) The Scientific Context for Exploration of the Moon, 107p.
  6. S. E. Braden et al. (2010) Morphology of Gruithuisen and Hortensius Domes: Mare vs nonmare volcanism (PDF). Lunar and Planetary Science Conference XXXXI, #2677.
  7. S. D. Chevrel et al. (1999) Gruithuisen domes region: A candidate for an extended nonmare volcanism unit on the Moon. Journal of Geophysical Research 104, 16515-16529.
  8. S. E. Braden et al. (2007) Unexplored Areas of the Moon: Nonmare Domes. Planetary Science Decadal Survey, 2013-2022.
  9. J. J. Hagerty et al. (2006) Refined thorium abundances for lunar red spots: Implications for evolved, nonmare volcanism on the Moon. Journal of Geophysical Research 111, E06002.
  10. L. Wilson and J. W. Head (2003) Deep generation of magmatic gas on the Moon and implications for pyroclastic eruptions. Journal of Geophysical Research 108, 5012.
  11. R. Wagner et al. (2002) Stratigraphic sequence and ages of volcanic units in the Gruithuisen region of the Moon. Journal of Geophysical Research 107(E11), 5104.

Flippin’ Rocks

click to view Flickr group

Thanks to this post by Rebecca in the Woods, I found out that today is International Rock Flipping Day! The purpose of IRFD from the main post at Wanderin’ Weeta:

It’s a day set aside to explore a too-often forgotten part of our world, one we walk past every day, and rarely are aware of; our nearest neighbours, the vibrant life under our feet.

I needed to take a walk, so I grabbed my phone and headed out with a friend to circle St. Mary’s Lake on the Notre Dame campus. Unfortunately the college landscapers apparently decided against leaving any rocks of size lying about for passerby’s to trip on. Instead we headed home and I had to settle for some concrete rip-rap near an apartment complex.

rock unflipped

The “rock” in its natural state

It became unusually blurry and overexposed when flipped (a defense mechanism?)

rock flipped

The “rock”, flipped

Getting closer, there was a slug that didn’t seem to perturbed to being exposed. His buddy the worm schlooped underground when I got too close:

snail and worm

Mr. Snail and The Worm hanging out

And bonus creature, clinging to the underside of the “rock” was this guy:

Spider!

Spider chilling out

I placed the rock back in place, being careful not to crush the slug. Happy International Rock Flipping Day!