Conel M. O'D. Alexander
Cosmochemistry; origin of chondrules, water, organic matter, circumstellar and interstellar grains.
B.S., Geology, Imperial College, University of London, 1983 Ph.D., Experimental Physics, University of Essex, 1987
Some 40 thousand tons of extraterrestrial material falls on Earth every year. This cosmic debris provides cosmochemist Conel Alexander with information about the formation of the Galaxy, the Solar System, habitable planets, and perhaps the origin of life.
Alexander studies the most primitive types of meteorite, chondrites, to find clues about what went on before and during the formation of our Solar System. His focus is on the two major constituents of chondrites: chondrules, up to millimeter-size spherical objects, and the fine-grained matrix that cements chondrites.
Chondrules formed as molten droplets and are the products of one of the most energetic, but as yet unidentified, processes operating in the early Solar System. Alexander uses measurements and modeling of the abundances and isotopic compositions of elements (e.g., sodium, potassium, iron, magnesium, and oxygen) that may have evaporated and recondensed to constrain the conditions during chondrule formation.
Matrix contains water, now in clay minerals, organic matter and presolar grains that are the focus of Alexander's other major interests. Presolar grains formed around dying stars before the formation of the Solar System. These relics retain information about Galactic chemical evolution, stellar nucleosynthesis, and dust processing in the interstellar medium.
Most of the organic matter in matrix is in tiny grains of macromolecular material. Similar material also seems to be present in comets. Whether this organic matter formed in the Solar System or the interstellar medium is a matter of lively debate, but either way it is probably the major source of Earth's carbon, nitrogen and noble gases.
Water is essential to the creation of a habitable planet. Chondrites were likely the major source of Earth's water. However, the origin of the water in chondrites - probably a mix of Solar System and interstellar water - is still not fully understood. The hydrogen and oxygen isotopes of water can provide strong constraints, but how they may have been modified in the meteorite parent bodies needs to be clarified first.