Calculations favor reducing atmosphere for early earth: Was Miller-Urey experiment correct?

Washington University in St. Louis ^ | 07 September 2005 | Tony Fitzpatrick

[PatrickHenry]

Using primitive meteorites called chondrites as their models, earth and planetary scientists at Washington University in St. Louis have performed outgassing calculations and shown that the early Earth's atmosphere was a reducing one, chock full of methane, ammonia, hydrogen and water vapor.

In making this discovery Bruce Fegley, Ph.D., Washington University professor of earth and planetary sciences in Arts & Sciences, and Laura Schaefer, laboratory assistant, reinvigorate one of the most famous and controversial theories on the origins of life, the 1953 Miller-Urey experiment, which yielded organic compounds necessary to evolve organisms.

Chondrites are relatively unaltered samples of material from the solar nebula, According to Fegley, who heads the University's Planetary Chemistry Laboratory, scientists have long believed them to be the building blocks of the planets. However, no one has ever determined what kind of atmosphere a primitive chondritic planet would generate.

"We assume that the planets formed out of chondritic material, and we sectioned up the planet into layers, and we used the composition of the mix of meteorites to calculate the gases that would have evolved from each of those layers," said Schaefer. "We found a very reducing atmosphere for most meteorite mixes, so there is a lot of methane and ammonia."

In a reducing atmosphere, hydrogen is present but oxygen is absent. For the Miller-Urey experiment to work, a reducing atmosphere is a must. An oxidizing atmosphere makes producing organic compounds impossible. Yet, a major contingent of geologists believe that a hydrogen-poor, carbon dioxide-rich atmosphere existed because they use modern volcanic gases as models for the early atmosphere. Volcanic gases are rich in water, carbon dioxide, and sulfur dioxide but contain no ammonia or methane.

"Geologists dispute the Miller-Urey scenario, but what they seem to be forgetting is that when you assemble the Earth out of chondrites, you've got slightly different gases being evolved from heating up all these materials that have assembled to form the Earth. Our calculations provide a natural explanation for getting this reducing atmosphere," said Fegley.

Schaefer presented the findings at the annual meeting of the Division of Planetary Sciences of the American Astronomical Society, held Sept. 4-9 in Cambridge, England.

Schaefer and Fegley looked at different types of chondrites that earth and planetary scientists believe were instrumental in making the Earth. They used sophisticated computer codes for chemical equilibrium to figure out what happens when the minerals in the meteorites are heated up and react with each other. For example, when calcium carbonate is heated up and decomposed, it forms carbon dioxide gas.

"Different compounds in the chondritic Earth decompose when they're heated up, and they release gas that formed the earliest Earth atmosphere," Fegley said.

The Miller-Urey experiment featured an apparatus into which was placed a reducing gas atmosphere thought to exist on the early Earth. The mix was heated up and given an electrical charge and simple organic molecules were formed. While the experiment has been debated from the start, no one had done calculations to predict the early Earth atmosphere.

"I think these computations hadn't been done before because they're very difficult; we use a special code" said Fegley, whose work with Schaefer on the outgassing of Io, Jupiter's largest moon and the most volcanic body in the solar system, served as inspiration for the present early Earth atmosphere work.

NASA's Astrobiology Institute supported this work.

[Thatcherite]

generally to be answered with hate by the anti-God crowd

I guess that I am probably part of the "anti-God" crowd but I try to stay the humorous side of hateful (not always successfully) and I apologise when I realise that I have overstepped the mark. I'll apologise on behalf of everyone on the "evo" side for any offense that may have come your way (possibly even from me on an angry day). Sometimes I find the YECers in particular enraging and irritation can spill over into aggression against those with whom I probably have a minimal dispute about the mechanisms driving documented biological change.

Incidentally Glenn Morton managed to reconcile his Christian faith with the geological data using a broadly similar approach to the one you describe. Given your background of a change in faith you might find his story interesting.

[spinestein]

[I've come across the Creationist suggestion that fossils are just God's little joke, a 'test' of our faith--which always struck me as just a tad perverse. I mean, are we really to worship a God who sets out, like an evil schoolteacher, to 'trick' us into giving the wrong answer, and thereby spend all eternity in fire and brimstone? Mercifully, this is not a prevailing view of a healthy majority of Christians!]


There is the similar conjecture that fossils are placed in the ground by Satan to confound people into the false belief of evolution and other non-Biblical ideas.

I find it more parsimonious to think that evolution is just the scientific explanation for the diversity of species, rather than believe that an evil demon, opposed to the will of God, creates a myriad of bogus evidence that exactly replicates conclusive and justifiable support for a scientific theory for the purpose of seemingly making monkeys out of men and stealing their souls.

[spinestein]

[Consider instead the Catholic tradition that the Bible is fundamentally God's divinely inspired Truth (capital intended!), but revealed through parables, stories, Teachings, Law, history, birth records, etc. That is, every Truth in the bible is exactly real and is revealed by the stories, and every story illustrates the Truth in its own way, but every story itself may not be literally the truth.]


This is EXACTLY what was taught to me during an eight year stint at a Catholic school. It still seems pretty wise to me, 24 years later.