My field site, Borup Fiord Pass, is a valley in the Canadian High Arctic where there resides a very special glacier. Near the toe of this glacier (the glacier's edge) you can find large accumulations of yellow elemental sulfur on top of the ice. These deposits of sulfur form from sulfide-rich springs that emerge on the glacier or just at its edge. The sulfide carried by the springs is derived from the reduction (electronation) of sulfate by microorganisms that thrive in the subsurface. The yellow sulfur that appears at the surface may be partly formed through the activity of microbial life and also may feed microorganisms that are capable of oxidizing (de-electronating) elemental sulfur. This unique sulfur-dominated system may serve as an ideal analogue for icy environments in our solar system and beyond, especially those where subsurface fluids may emerge at the surface of an icy system (like maybe on Jupiter's moon Europa!).
I had the wonderful opportunity to visit this remarkable site for two weeks during the summer of 2014. Here is an image taken by John Spear, of the Colorado School of Mines, while flying over the glacier in a helicopter:
The image shows the region at the toe of the glacier where yellow sulfur staining was visible. The large sulfur covered area in this shot is about 100x100 square meters (about the size of a couple of American football fields). Interestingly, during our time at the site, we did not observe an active spring. Instead, what we found was that a very thick structure of ice had formed at the edge of the glacier. This icing is not only covered in sulfur, but is loaded with sulfur in various states (sulfide, elemental sulfur, and sulfate). We took samples from various regions on the sulfur icing, on the glacier, and in the melt water streams that ran down the valley. Below is a ternary diagram showing some of the data I've now analyzed for major cations in the samples as compared to some samples from previous years:
What this figure is showing is that there is a range of cation chemistry that can be observed in samples collected at the site. There are data here for active springs from previous years, sulfur deposits from 2009 and 2014, as well as melt water and stream water from around the site from 2000 and 2014. Most importantly, these data show that the sulfur icing is really similar to the sulfide-rich springs, which is part of why we reason that the spring was flowing and then that fluid was frozen in place to make the sulfur icing.
|Sulfur bubbles on a melt pool on a sulfur icing|
I was so intrigued by these sulfur bubbles that I had to know more about them. I took some of the material and ran x-ray diffraction (XRD) on it. XRD allows us to determine what minerals or other crystallized material is present within a sample. The XRD data revealed something very interesting. The data show elemental sulfur present in three different forms, known as allotropes. Usually, in nature, sulfur is most stable as eight-membered rings of sulfur atoms that are packed in a certain arrangement that is known as α-S8. (a.k.a. alpha-cyclooctasulfur). However, there are two other mineral forms of cyclooctasulfur that can also form in nature. These are known as the beta and gamma forms. β-S8 is a form of cyclooctasulfur that
forms when α-S8 is heated above ~96 C. It's extremely bizarre to find this form of sulfur in a sample from Borup Fiord Pass, where the fluid forming the sulfur icing likely never reached a temperature that high. Likewise, the gamma form of cyclooctasulfur, γ-S8 (which is also known as the mineral Rosickyite), usually only forms in high temperature environments. That said, Susanne Douglas and Heixong Yang published an article in the journal Geology in 2002 where they reported finding Rosickyite within an endoevaporitic microbial film. They hypothesized that processes of microbial sulfur metabolism that formed elemental sulfur favored the formation of γ-S8 over α-S8. If that's not exciting enough, Damnhait Gleeson, who was once a member of our lab at the University of Colorado Boulder, also previously reported finding rosickyite in a microbial sample, this time it was within a sample of sulfur collected at Borup Fiord Pass in 2009 by Katherine Wright (also a former member of our lab). Since rosickyite was previously detected at our site, it wasn't a huge surprise, but it's definitely exciting.
During my talk at AbSciCon, I'll be showing some images of the sulfur bubble material that I recently collected using an electron microscope. There's some really interesting structures to be found within these samples. I'm now hot on the trail of figuring out if I'm seeing the representation of gamma and beta cyclooctasulfur or perhaps something else all together. I don't know yet if these unique forms of sulfur and strange things that I'm seeing under the electron microscope are indicative of the biological processing of sulfur or if they've formed through an abiotic process at Borup Fiord Pass (which would also be very interesting), but it's nice to find new and exciting things when doing research.
There's a bit more that I'll be presenting at my talk at AbSciCon, however the talk is only supposed to be 10 minutes in length (which is a very short time for a talk). Fortunately, for the stuff that I don't get to cover in my talk, my colleague Chris Trivedi of the Colorado School of Mines will be presenting a poster with information about his work on our samples from Borup Fiord Pass. Hopefully, if people find our work interesting and want to know more following my talk, they'll then have a chance to check out Chris' poster as well.
|This is me saluting the sulfur stained glacier and the valley that holds it|
I'm definitely looking forward to the experiences I'll be having in the coming week at AbSciCon 2015. There's going to be a lot of great science to hear about and to talk about. I'm going to serve as a judge for student posters at the conference and I'll also be serving as a Meeting Mentor, spending half of one conference day with a high school student shadowing me at the conference. On top of all of this great stuff, on Monday evening there will be the final preliminary heat of the 3rd season of the NASA Famelab science communication competition. In case you don't know, I won the first preliminary heat of the competition in August of 2014, when I shared a story about my first day in the field at Borup Fiord Pass. I'm looking forward to watching a new line-up of scientists and science communicators as they compete in this final heat for Famelab. I have a feeling there are going to be some awesome talks and a lot of great stories.
I'll be adding more posts in the coming weeks that detail my experiences at AbSciCon, so look forward to those. I think I'll wrap this post up right now by sharing the video of the talk I gave when I competed in NASA Famelab in 2014. Here's looking forward to great science and good times at AbSciCon 2015!