Scientists Find Easy Way to Test Meteorites for Chemicals
Scientists at Stanford University and UC San Diego have found an easy way to detect minuscule amounts of organic chemicals inside meteorites, a technique that promises to shed new light on the origin of the solar system as well as to answer more down-to-earth questions.
The laser technique could give researchers quick access for the first time to a comprehensive range of clues about how organic chemicals formed in the dusty cloud from which the planets condensed 4.5 billion years ago. It could bolster or debunk the notion that a cosmic rain of meteorites seeded the early Earth with organic compounds, ultimately making life possible here.
The technique also may be an easy, non-destructive method of analyzing everything from fossils to Martian soil to computer chips.
“The problem with standard chemical techniques for doing organic analyses of meteorites and other rare materials is that they are laborious, destroy the sample and require one to 10 grams of the material to be tested,” said Jeffrey L. Bada, a geochemist at UCSD’s Scripps Institution of Oceanography.
Savings of Time
“Our method can reduce the analysis time from a month or more to just a few minutes, and we need only a microgram, or one millionth of a gram, to do the test,” Bada said.
A report on the new way to analyze meteorites is being published today in Science magazine. Bada co-authored the paper with Richard N. Zare, a Stanford chemistry professor who developed the analytical process, and Stanford graduate students John Hoon Hahn and Renato Zenobi.
Meteoritic composition is considered important because, when a rock plummets to Earth from space, it carries relatively unaltered information about conditions that existed when planets condensed out of the gas and dust cloud known as the solar nebula. The nature and amounts of organic compounds in meteorites might reflect, for instance, the temperature of the nebula at the time the rocks formed.
“Just the fact that we can detect them now in such a rapid way is going to give us a data base that we didn’t have a year ago” for studying the evolution of organic chemicals, Bada said.
In conventional mass spectrometry, a meteorite chunk as big as 100 grams must be ground up and put through months of processing and purification before the “mass spectrum” of its organic components can be taken, Bada said.
Scientific Process
The mass spectrometer delivers an electrical charge to the gaseous sample and moves the resulting charged, or ionized, molecules through an electromagnetic field. A detector records their movement through the field, creating a mass spectrum of their molecular weights. These then can be compared to standard tables of molecular weights to identify the sample’s components.
Zare’s technique instead uses laser light to create the ions needed for a mass spectrum.
In the experiment reported on in Science, the surface molecules from about a milligram of ground meteorite--the equivalent of about two grains of sand--were vaporized with an infrared laser. The gas was hit with an ultraviolet laser that selectively ionized it. Again, an electrical field pushed the ions toward a detector to identify them via their molecular weights. The process takes about two minutes.
Further research also has shown it works with a meteorite sample as small as a millionth of a gram, Zare said.
Other Applications
From a more practical standpoint, Zare said, using different lasers in his mass spectrometer would give it a wide range of applications in science and industry.
“The same technique can be applied to looking at fossils or various geological formations, or to prospect to see if rocks contain oil,” Zare added.
Because the laser method does not break the organic molecules apart, it also might be useful in helping biomedical researchers identify proteins and hormones in minute amounts, Zare said.
