MIT scientists create new method to detect the origins of methane

An MIT-led team of researchers has developed an instrument capable of quickly and accurately analyzing samples of methane, pinpointing how they were formed. The breakthrough could give scientists a greater understanding of the role the gas plays in global warming.

Methane is a potent force in global warming. It is second only to carbon dioxide when it comes to trapping heat inside the atmosphere for extended periods of time, and can originate from a range of different sources, including lakes, livestock and natural gas pipelines.

more…

more …

The new method, catchily known as tunable infrared laser direct absorption spectroscopy, is designed to detect the ratio of methane isotopes in samples. Methane molecules consist of up to four hydrogen atoms combined with a single carbon atom, the latter of which can be one of two isotopes – carbon-12 or carbon-13. The hydrogen in the molecule is also found in two forms, one of which is deuterium – an isotope with an extra neutron.

In the study, the researchers focused on detecting molecules containing both an atom of carbon-13 and a deuterium atom, believing the rare molecule to be a signal of the formation temperature of methane, which is an important indicator of the origin of the molecule.

——

Two comments. How do you tune a laser? And I don’t see why isotope ratio would be expected to correlate with formation temperature.

mollwollfumble said:

How do you tune a laser?

This guy.

he also does pianos.

mollwollfumble said:

Two comments. How do you tune a laser? And I don’t see why isotope ratio would be expected to correlate with formation temperature.

I can’t help with the laser question, sorry.

Different stable isotopes of an element have very slightly different chemical and physical properties because of their mass differences. For elements of low atomic number, the mass differences are sufficiently large for physical, chemical, and biological processes to “fractionate” or change the relative proportions of various isotopes.

Stable isotope fractionation is a well-researched tool. Oxygen isotope fractionation is a common paleothermometer in geochemistry (eg paleoclimate inferences from oxygen isotopes preserved in ice cores). Carbon isotope fractionation used as a biogenic-or-not separation tool.

——————————

For example, from:

http://en.wikipedia.org/wiki/Kinetic_fractionation

A naturally occurring example of kinetic fractionation is the evaporation of seawater to form clouds. In this instance, isotopically lighter water molecules (i.e., those with 16O) will evaporate slightly more easily than will the isotopically heavier water molecules with 18O.

Heavier isotopes favor the less energetic liquid phase of water during evaporation and condensation. Water vapor is enriched with light isotopes relative to sea water. Clouds are depleted of light isotopes relative to water vapor. This results in higher latitude waters being isotopically “light”. As water vapor is driven poleward by Earth’s energy budget and rotating Hadley cells, the heavy isotopes are left behind as clouds and rain.

During this process the oxygen isotopes are fractionated: the clouds become enriched with 16O, the seawater becomes enriched in 18O. Thus, rainwater is observed to be isotopically lighter than seawater.

——————————————-

For some background reading, see below (the first one is a great summary):

http://wwwrcamnl.wr.usgs.gov/isoig/res/funda.html

http://en.wikipedia.org/wiki/Isotope_fractionation

http://en.wikipedia.org/wiki/Equilibrium_fractionation

http://en.wikipedia.org/wiki/Kinetic_fractionation

how do you tune a laser

change its frequency I guess

http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lasmod.html

The OP article hints it may be possible to derive a “molecular production rate” tool using stable isotopes from two elements in the one molecular species. That is seriously interesting, but will need a lot of calibrating.

Could this method be used to determine the source of methane detected on Mars

Bump for mwf.

A BRIGHT, white fireball which flashed across Perth skies this morning was likely to be a “pretty big chunk of meteorite’’, according to a Curtin University geology expert.

A Gidgegannup woman was one of the first to report the meteorite and quickly went searching for it in a paddock on her property, Mindaroo Stud, some 45km east of Perth.

Angela Whife says she went to check on her cows that are calving at about 8.30am this morning when she saw a bright light in the sky.
“The first thing I thought was it’s a shooting star, but then I thought it’s a bit strange because you wouldn’t see shooting stars in the daytime,” she said.

“And it looked round, white in colour and it had a tail of about a metre, metre and a half behind it. It would have been about 10 metres above the ground I suppose when I first saw it and then it landed about 20 metres away from me.”

perth has had an exciting weekend.. nudists, meteorites… whats next?

wrong thread