Collaboration with Dr. Laurie Barge from NASA JPL
The Iski Research Group has begun a collaboration with Dr. Laurie Barge at NASA JPL. Dr. Barge is currently leading several projects that examine origin of life type conditions. She has an ongoing collaboration with TU regarding the development of lab-simulated hydrothermal vents [1]–[3] on the early Earth and other worlds. The hydrothermal minerals deposited in these experiments include iron hydroxycarbonates, or green rusts, which are highly reactive and possibly catalytic for driving redox reactions relevant to the origin of life. Discussions began between Dr. Iski and Dr. Barge about developing a collaborative method in which green rust mineral deposits could be locally probed while controlling a potential gradient across the sample surface with nanoscale resolution, allowing one to image the separate interactions of the reduced and oxidized iron species within the mineral layers. This particular type of investigation has never been attempted and may garner new and important information about how electron transfer and potential differences across gradients could affect these types of early Earth systems. One of the persistent experimental questions regarding these hydrothermal minerals is, do the Fe2+ and Fe3+ sites on the surfaces of iron hydroxide minerals behave differently in terms of interactions with other anions (e.g. organics, phosphates) and also how are the redox reactions facilitated between the Fe2+ centers and substrates such as nitrate / nitrite? The answers to these questions depend on the nanoscale surface structure of the mineral, which to date, has never been investigated for the iron hydroxides. The reason for the lack of investigations on this subject is because the experiment requires nanoscale resolution which is facilitated by EC-AFM, a highly specialized instrument which is not currently available in Dr. Barge’s lab. From the perspective of the Iski Lab at TU, there has been no opportunity to collaborate with a group capable of synthesizing these types of materials. It is essential to work with a group capable of making the minerals so that they can control the overall surface roughness, which needs to be minimal in order for the microscope to work at an optimal level.
The Iski research lab is specially equipped to investigate and characterize surfaces with micron to atomic scale resolution using an Agilent/Keysight PicoScan 5500 scanning probe microscope with electrochemical attachments. This microscope is configured such that samples can be submerged under various electrolytic solutions and imaged while a potential is applied to the surface. With EC-AFM, it is possible to perform electrochemistry at specific potentials and simultaneously approach the AFM tip and examine exactly how the associated redox chemistry affected the nanoscale surface structure. The unique combination of electrochemical data acquisition with molecular level resolution offered by EC-AFM can give new insights into how iron hydroxide mineral surfaces could act as redox catalysts in prebiotic hydrothermal systems. This can generally be translated into how a potential gradient across sediments / chimneys containing these minerals in early Earth vents may have driven emergent metabolic reactions.
References:
[1] L. M. Barge et al., “Self-assembling iron oxyhydroxide/oxide tubular structures: laboratory-grown and field examples from Rio Tinto,” Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, vol. 472, no. 2195, Nov. 2016.
[2] L. M. Barge et al., “From Chemical Gardens to Fuel Cells: Generation of Electrical Potential and Current Across Self‐Assembling Iron Mineral Membranes,” Angewandte Chemie International Edition, vol. 54, no. 28, pp. 8184–8187, 2015.
[3] B. T. Burcar, L. M. Barge, D. Trail, E. B. Watson, M. J. Russell, and L. B. McGown, “RNA Oligomerization in Laboratory Analogues of Alkaline Hydrothermal Vent Systems,” Astrobiology, vol. 15, no. 7, pp. 509–522, Jul. 2015.