Research interests

I am interested in the study of meteorites to better understand the formation and evolution of our Solar System. My research approach is to use multiple techniques to characterise extra-terrestrial materials either in terms of composition or in terms of chronology.

One of my main specialities is the analysis of meteorites using noble gases (He-Xe) and halogens (Cl, Br, I), and chronology studies (e.g. Ar-Ar, CRE). More recently, I have been working on overall compositional studies of meteorites at micro- and nanometer- scales.

The chronometry and composition of planetary regoliths:

The surfaces of asteroids and rocky planets/moons represent excellent records of impact events within the Solar System. Most of our understanding of the impact flux in the inner Solar System is based off of analyses of lunar materials, and consideration of the Late Heavy Bombardment, which depicts either a major event or a change in bombardment rate at ~3.9 billion years (Ga).

My approach is to investigate  the prevalence of this event by performing chronological studies of materials from the asteroid belt using multiple decay systems - Ar-Ar,  U-Pb and Pb-Pb.

Additional questions to be considered on this theme include: Can we characterise and identify regolithic meteoritic materials?  Can secondary processes like weathering be quantitatively constrained.
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Students Involved:
Ioannis Kouvatsis (Ph.D. Student, Geological Sciences, UA)

Collaborators:
Kip Hodges (Arizona State University)
Tom Sharp (Arizona State University)
Joshua Snape (Vrije Universiteit)
Meenakshi Wadhwa (Arizona State University/Center for Meteorite Studies)
Martin Whitehouse (Swedish Museum of Natural History)

Micrometer and nanometer-scale studies of Extra-terrestrial materials:

Recent advances in nanometer-scale analytical techniques have opened a new pathway to exploring extra-terrestrial materials! As such, I am involved in a few different projects...

Undifferentiated Meteorites:
I am interested in understanding the structures and compositions of undifferentiated meteorites (chondrites) at micro- and nanometer-scales, to help determine when the first solids in the Solar System formed, and to determine what processes led to their formation. 

I am approaching this by performing a combined study using different analytical techniques including SEM (and FIB-SEM), EPMA, TEM, NanoSIMS and APT  to understand the textural and compositional properties of these early phases and materials.

Students Involved:
Ioannis Kouvatsis (Ph.D. Student, Geological Sciences, UA)

Collaborators:
Jan Leitner (Max Planck Institute for Chemistry)
Alberto Perez-Huerta (University of Alabama)
​Christian Vollmer (Universität Münster)

Cosmic Dust:
Atmospheric processing of Cosmic Dust can cause significant changes to the incoming materials, potentially leaving clues behind that can be studied using petrological and compositional techniques. We are interested in understanding the  elemental distributions within micrometeorites, and observing textural features that may relate to atmospheric entry.

We are approaching this using a combination of including SEM (and FIB-SEM),  with a focus on APT analysis. 

Students Involved:
Former Masters student Mark Boyd (currently in the PhD program at Imperial College London)

Collaborators:
Jesse Singh (Oxford University)
Paul Bagot (Oxford University)
Michael Moody (Oxford University)
Queenie Chan (Royal Holloway)
Matt Genge (Imperial College London)

Investigating melt inclusions in meteorites using nanometer-scale techniques

Melt inclusions are trapped phases within host minerals that are relicts of the magma that created them. Ultimately, they provide a snapshot of magmatic conditions at the time of formation, and the composition of the magma involved. Investigating melt inclusions within different meteorite types can inform us on magmatic processes on their respective parent bodies.

In this study, we are using a combination of petrological and compositional analytical techniques to characterise melt inclusions in different achondrite meteorites from Mars (shergottites, nakhlites) and from the asteroid Vesta (eucrites, diogenites), with comparison to melt inclusions within complex terrestrial systems (e.g., Stillwater, Theo's Flow etc.).

Our samples will be analysed using standard microscopy techniques (SEM, EPMA, EDS) as well as using novel atom probe tomography. We plan to expand this project to include characterisation of volatile contents as an extension of the Ar-Ar dating technique.

Students Involved:
Nathan Limbaugh (Ph.D. Student, Geological Sciences, UA)

Collaborators:
Bill Hames (Auburn University)
Lydia Hallis (University of Glasgow)
Ray Burgess (University of Manchester)

Lightning formation of chondrules

Chondrules are quenched melt droplets that are considered to represent some of the first materials to have formed in our Solar System. Of the mechanisms brought forward to help explain their formation, Nebula Lightning has been little studied, given the complexities involved with creating lightning strikes in a laboratory environment. Here, we are investigating whether spherule-like materials can be produced through lightning strikes, and if so, if they share a resemblance to chondrules within chondrite meteorites.

We are using a combination of laboratory experiments and microscopy to identify and classify spherules created by lightning strikes.

Students Involved:
Sarah Keenan (Masters Student, Geological Sciences, UA)

Collaborators:
Kim Genareau (Geological Sciences, UA)

Towards a unified Regolith Index for Howardite meteorites, with a study of space weathering

Howardites represent materials thought to originate from the regolith or surface of the asteroid Vesta - the largest differentiated asteroid in the asteroid belt. We are working to correlate physical features (nanophase iron) and chemical signatures (e.g. noble gases) with the magnetic parameters observed for howardite meteorites to assess the conditions of their formation and the extent of space weathering that took place.

​We are using a combination of magnetic susceptibility techniques (FMR, VSM) as well as microscopy (SEM, TEM) of howardite meteorites that have already been analysed for their noble gas contents.

​Students Involved:
Abutu Peter (Masters Student, Geological Sciences, UA)

Collaborators:
Tim Mewes (Physics and Astronomy, UA)

Petrology and COmposition of K-Pg boundary tektites

The K-Pg extinction event at ~66 Ma is notable for having wiped out numerous animal groups, including the dinosaurs, due to a catastrophic impact that occurred in the current-day Yucatan Peninsula. Tektites - glassy terrestrially-derived phases - form as a result of impact cratering processes, and can preserve multiple clues to impacting events. Here, we are studying tektites recovered from localities in Alabama to determine their formation processes, and to uncover additional clues about this major extinction event.

Students Involved:
Jess Clarke (Graduate Student, Geological Sciences, UA) 

Collaborators:
Tom Tobin (Geological Sciences, UA)

Additive Manufacturing & In-situ Resource Utilization (ISRU)

 I am involved in a couple of different projects that involve ISRU, with applications to planetary environments.

Regolith Bricks:
Strong, stable and durable building materials are vital for any consideration of construction on a planetary surface. It is important to also consider whether we can use resources, like planetary regolith, as a building material, to help offset the costs of importing materials from the Earth. In this project, we are experimenting with synthesizing regolith bricks using different analogues and epoxy combinations. 

Students Involved:
John Barton (Undergraduate Student, Geological Sciences, UA)

Collaborators:
Paul Rupar (Chemistry & Biochemistry, UA)
Jason Bara (Chemical & Biological Engineering, UA)

Friction Stir Welding:
Another aspect of additive manufacturing is to determine whether regolith materials can be extracted and combined with metals to create equipment or tools for use in a planetary environment. In this project, we are experimenting with friction stir welding (FSW) to create regolith/metal alloy composites.

Students Involved:
John Barton (Undergraduate Student, Geological Sciences, UA)
Jessica Lopez (Graduate Student, Engineering, UA)

Collaborators:
Paul Allison (Mechanical Engineering, UA)
Greg Thompson (Engineering, UA)

Regolith texture in howardite QUE 97001. Scale bar is 200 microns.

Graduate student Ioannis Kouvatsis scoring meteorite wafers during sample preparation for Ar/Ar dating.

Section of lunar feldspathic breccia NWA 11182. Scale bar is 4 cm across the image.

Graduate student Mark Boyd loading cosmic dust samples into the SEM.

Horizon highlighted in nanometer-scale tip created for APT analysis of chondrite Allende. Tip height is ~160 nm.

Slice of the Millbillillie eucrite (monomict). Scale bar is 4 cm across.

Cross-polarised light image of a melt inclusion within a host olivine crystal in a nakhlite meteorite. Melt inclusion is approximately 300 microns in width.

Scanning electron microscope (SEM) image (secondary electron mode) showing two spherules created by a high-current impulse experiment performed on chondrite analogue material. The spherules are mounted on copper tape recovered after the experiment.

Scanning electron microscope (SEM) image in back scattered electrons (BSE) showing the brecciated texture of a howardite meteorite.

Reflected light image of two tektites recovered from the Shell Creek Alabama site. Both tektites are spherical in appearance, and one seems to show possible layering within the sample.

Friction stir welding experiment to create a regolith/metal alloy composite.