Kieren Howard

I use X-ray Diffraction (XRD) to study primitive meteorites, called chondrites. From the mineralogy of meteorites, I infer the nature of asteroids at the point of accretion, revealing the starting components of planets. Inside of asteroids, minerals and amorphous silicates that formed at high-temperatures, reacted with molten ices to produce secondary, clay like minerals - an evolution known as aqueous alteration.  Using quantified mineral abundances, my research has defined the degree of aqueous alteration experienced by carbonaceous chondrites and by extension their parent body asteroids. 

Integrating bulk meteorite mineral abundances, determined by XRD, with infrared (VIS/NIR) and mid-infrared (MIR) reflectance spectra, allows astronomers to match meteorite samples to parent body asteroids and to understand the surface mineralogy of asteroids viewed remotely from ground, air and space based telescopes. This is critical in an era of targeted sample return missions to asteroids. 

I continue to be interested in meteorite impacts, the field where my research career began, I’m especially interested impact glasses, tektites and the fate of biomass under impact conditions.

My approach to research is based on collaborations, I aim to produce data that addresses my own research questions and helps to facilitate the research of others.

Selected Publications

• Breitenfeld L.B., Rogers D., Glotch T.D., Hamilton V.E., Christensen P.R., Lauretta D.S., Gemma M.E., HOWARD  K.T., Ebel E.S., Kim G., Kling M., Nekvasil H., DiFrancesco N. (2021). Machine Learning Mid-Infrared Spectral Models for Predicting Modal Mineralogy of CI/CM Chondritic Asteroids and Bennu.  Journal of Geophysical Research: Planets: 10.1029/2021JE007035
• T.Hiroi T,  Kaiden H., Imae N., Misawa K., Kojima H., Sasaki S., Matsuoka M.,  Nakamura M., Bish D.L., Ohtsuka K., HOWARD K.T., Robertson K.R., Milliken R.E. (2021).  UV-visible-infrared spectral survey of Antarctic carbonaceous chondrite chips. Polar Science 29: 100723.
• Abreu, N.M.,  Corrigan, C.M., Hezel, D.C.,  Keller,  L.P.,  HOWARD, K.T., De Gregorio, B.T., Crispin, K.L., Gray, J. and Wang, H. (2019).  Amorphous and Nano-Crystalline Materials in Pristine Carbonaceous Chondrite Meteorites. Microscopy and Microanalysis 25, 2452-245
• McAdam, M.M, Sunshine, J.M, HOWARD, K.T.,  Alexander, C. M. O’D.,  McCoy, T.J. and  Bus, S.J. (2018). Spectral evidence for amorphous silicates in least-processed CO meteorites and their parent bodies. Icarus 306, 32-49
• Takir, D.,  HOWARD, K.,  Yabuta, H.,  McAdam, M.,  Hibbitts,C. and  Emery, J.  (2018). Linking water-rich asteroids and meteorites: implications for asteroid space missions. In Abreu, N.M. (ed) Primitive meteorites and asteroids, 371-408.
• A. Garenne, P. Beck, G. Montes-Hernandez, O. Brissaud, B. Schmitt, E. Quirico, L. Bonal, C. Beck, K.T. HOWARD (2016). Bidirectional reflectance spectroscopy of carbonaceous chondrites: Implications for water quantification and primary composition.  Icarus, 264: 172-183. 
• HOWARD, K.T., Alexander, C.M.O’D, Schrader, D., Dyl K.A (2015). Classification of hydrous meteorites (CR, CM and C2 ungrouped) by phyllosilicate fraction: PSD-XRD modal mineralogy and planetesimal environments. Geochimica et Cosmochimica Act, 149: 206-222. 
• McAdam, M., Sunshine, J., K.T. HOWARD, Kelly, M.S., McCoy, T.J. (2015). Aqueous Alteration on Asteroids: Linking the Mineralogy and Spectroscopy of CM and CI Chondrites.  Icarus, 249: 320-332.
• HOWARD, K.T. et al., (2013). Biomass preservation in impact melt ejecta.  Nature Geoscience, 6: 1018-20.
• Alexander  C.M.O.D., HOWARD K.T., Bowden R., Fogel M.L. (2013). The classification of CM and CR chondrites using bulk H, C and N abundances and isotopic compositions, Geochimica et Cosmochimica Acta, 123, 244-260.
• Alexander  C.M.O.D., Bowden R., Fogel M.L., HOWARD K.T., Herd C.D.K., Nittler L. (2012). The provenances of asteroids, and their contributions to the volatile inventories of the terrestrial planets. Science 337, 721-723.
• HOWARD K.T., Benedix G.K., Bland P.A., Cressey G. (2011). Modal Mineralogy of CM chondrites by PSD-XRD, Part 2:  degree, nature and settings of aqueous alteration. Geochimica et Cosmochimica Acta 75: 2735-2751.
• HOWARD K.T. (2011). Invited Review: Volatile enhanced dispersal of high-velocity impact melt and the origin of tektites.  Proceedings of the Geologists Association 122: 363-382.
• HOWARD K.T., Benedix G.K., Bland P.A., Cressey G. (2010). Modal Mineralogy of CV3 chondrites by PSD-XRD. Geochimica et Cosmochimica Acta 74: 5084-5097.
• HOWARD K.T., Benedix G.K., Bland P.A., Cressey G. (2009). Modal Mineralogy of CM2 chondrites by PSD-XRD, Part 1:  total phyllosilicate abundance and the degree of aqeous alteration. Geochimica et Cosmochimica Acta 73: 4576-4589.