Each year, the Lunar and Planetary Science Conference condenses more and more people into the Waterway Marriott in The Woodlands, Texas. It’s reaching a critical mass. This year, around 2,046 abstracts were accepted for presentation in talk or poster form. There’s too much to sift through except in your specific field, but I wanted to branch out a bit. So I put out a call on Twitter for a random number between 1001 and 3046 (the numbering system starts at 1001). Lockwood chose 2601, and from that abstract (PDF link) we have the topic of this post: Plumes on Enceladus.
This well-written abstract covers a few interesting points on using satellite photos to infer geological processes. The Cassini spacecraft has a narrow angle camera with broadband filters. These filters allow specific wavelengths of light, ranging from ultraviolet to infrared, to pass through. The wavelengths of light, in turn, are affected by objects they bounce off of. Different minerals reflect or absorb specific wavelengths of light differently, a feature used in many remote observations of planetary bodies to infer (deduce?) surface composition.
Paul Schenk and the other authors of this abstract used surface images filtered using two infrared spectra and one ultraviolet spectrum. One of the main goals of their analysis was to use our observations of Enceladus to use as a comparison to what we are beginning to study on Europa. There are issues to be worked out, with, for example, how the orientation of the spacecraft relative to the surface of a world will affect the observed spectra. If light is uniformly scattered by an object, then we can observe it from any angle and it will look the same. But if there is directionality to the scattering, then the angle we observe will affect what we observe. That will be an issue if we have more limited observations (like at Europa).
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.
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. 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.
At 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.
Ian D. Hutcheon, Michael J. Kristo and Kim B. Knight (2013) Nonproliferation nuclear forensics (PDF), in: Uranium: Cradle to Grave (edited by Peter C. Burns and Ginger E. Sigmon). Mineralogical Association of Canada Short Course 43, 377-394.
For the past four years, the Lunar Graduate Conference (LunGradCon) was held the Sunday prior to the Lunar Science Forum. The Forum’s host organization was recently restructured into the Solar System Exploration Research Virtual Institute. This is something I’ve mentioned before, and it means future Forums will be broader in scope. The final lunar-centric forum was scheduled for July 16-18, 2013 at NASA Ames in California. However, NASA travel restrictions and nebulous budget cuts to planetary science forced lunatics and research organizations alike to tighten their belts. Despite promises to the contrary, most scientists I spoke with believed the Forum would end up cancelled. Thus it was a bit of a mixed bag when an April e-mail announced a change in format to an all-virtual Forum. Three months before the meeting. Three months before LunGradCon.
LunGradCon would have been in Mountain View, California, which is lovely in mid-July. Our host was the NASA Ames Research Center, where in the past we’ve taken tours of the wind tunnels and helicopter research wings. We were making plans to expand our tours to include SETI and the vertical gun range. And although travel to California can be costly, the majority of our budget was allocated toward travel funds for all attendees. Suffice to say, we never had a problem enticing grad students to fly out early to network and present among their peers. But with no Lunar Science Forum to glom on to, the numbers just weren’t there. We had to adapt or cancel.
The LunGradCon planning committee was really non-plussed about the situation. With no in-person component, what did we have to look forward to? Another day of staring at a computer and listening to talking heads? With conferences, if you only go to talks and posters then you are missing out on half the experience. The other half is networking, with real human interactions, introductions, collaborations, and commiserations at the bar. My gut reaction was to vote to cancel in protest with an accompanying statement from the committee (maybe leaving out the part about the bar).
Honestly though, canceling would have been a selfish snap decision. LunGradCon was not singled out for a virtual makeover. Times are tough all over, and planetary science in general has taken quite a hit. We could pick up our toys home and refuse to play this new game, but that would take us out of the conversation. We would also lose the opportunity to reconnect with LunGradCon alums and build new contacts in the lunar graduate student community. And bare bones, that is what LunGradCon was established to do. So we put out the call for registrants and abstracts and left it up to the community to decide if they wanted a virtual conference. It turns out they did.
The amount of interest from graduate students exceeded my expectations. There was a fairly even split of registrants between returning (15) and new (18), from 23 different institutions. Unfortunately, I was too busy with planning committee details during the conference to note the maximum number of people to join the day of. We had a good number of talks to keep LunGradCon brief and engaging, with scheduled time for extra discussion and overviews on lunar research.
The participants roundly agreed (via post-conference survey) that LunGradCon went over rather well. I was pleased to see some old colleagues and make new acquaintances. The conference opened with an icebreaker that everyone enjoyed (despite it running over time, which was our fault for not scheduling enough time for it). International students found it easier to join a virtual conference compared to getting visitor badges for NASA Ames, and we had students presenting from Canada, Germany and India. More questions were asked during discussion sessions compared to some previous years – we think it was a combination of participants having more time to flesh out questions before asking, the detached nature of virtual questions providing a comfort zone, and the ability to revisit questions from earlier in the day. Kerri had also compiled a glossary of terms that proved a valuable resource for many students listening to talks outside their field.
Some of my worries did, unfortunately, play out. A major selling point of LunGradCon is to provide a peer-only environment for students to present their work and get feedback on content, style, cohesion, etc. Normally these are handouts everyone fills out during/after each talk. This year the forms were Google Docs and we only had responses from ~1/3 of the group for each presenter. I was certainly forced to leave a few forms blank, as were several planning committee members. We were engaged in a surprising number of tech troubleshooting and schedule issues. The session chairs reported similar distractions on occasion.
This year’s meeting was successful, but I hope that future SSERVI Forum and LunGradCon meetings will be more tangible. There really is no substitute for meeting people face to face. Lastly, after guiding the conference into the digital realm, the Heidi-Jamey-Kerri-Patrick organizing committee is disbanding. Jamey Szalay is sticking around as a link to the past, and we are bringing in some excellent new planning committee members. And with a virtual conference under our belt, I am more confident in the ability of LunGradCon to continue bringing students together in any venue.