#365papers – January 3, 2017
Webb, Wang, Braams, Bowman, and Miller, 2017. Equilibrium clumped-isotope effects in doubly substituted isotopologues of ethane: Geochimica et Cosmochimica Acta, v. 197, p. 14-16.
What’s it about?
Ethane is a molecule with two carbon atoms and six hydrogen atoms. Most carbon in the universe is carbon-12, having six protons and six neutrons in its nucleus. Some carbon is carbon-13, with an extra neutron to make seven. A very, very tiny bit of carbon is carbon-14, with two extra neutrons. Carbon-12 and carbon-14 can replace carbon-12 in ethane. Likewise, hydrogen, an element with one proton and neutrons, can also have a neutron (deuterium or hydrogen-2), or maybe two neutrons (tritium or hydrogen-3). Atoms that vary in the number of neutrons in the nucleus are called isotopes. Some are stable (like carbon-12 and hydrogen), and others are radioactive. This study ignores carbon-14 and tritium, as they are both radioactive. Carbon-13 and deuterium are both stable.
The focus of any clumped isotope analysis is molecules with two of the more uncommon forms of an element. For ethane, that could be two carbon-13 atoms, two deuterium atoms, and one carbon-13 with a deuterium atom.
Why does it matter?
The amount of ‘clumping’ of isotopes (two carbon-13 atoms, two deuterium atoms, or one of each) is often related to the temperature at which the molecule formed. It can also be related to the metabolic pathways that led to the molecule’s formation, if it’s of a biological origin. This can help us understand the source of ethane if we find it ‘in the wild.’
Why did I read this?
I keep asking myself the above question. I couldn’t make much sense of this paper to be honest. I picked it up because I am interested in clumped isotopes of carbonate as a potential paleothermometer. A lot of work has been done to understand how clumped isotopes from fossil bones or soils can be used to learn what temperature the world was in the past. I thought this paper would be interesting, but got lost as soon as I got through the introduction.