Earth’s Atmosphere Came from Outer Space
This was announced as the finding of Greg Holland, Martin Cassidy of the University of Manchester, UK and Chris Ballentine of the University of Houston. It is satisfying for me to see that uniformitarian scientists are ‘coming around,’ but they have a long way to go. For example, their paper in 11 December edition of Science Magazine begins with a summary of the standard model of terrestrial planet formation, i.e. that they initially formed by accretion of dust (heavy element) particles in the inner solar system. Another error is the notion that the dust particles somehow morphed into carbonaceous chondrite meteorites, and that they represent the primordial make-up of the Earth. The third is the assumption that the solar spectrum represents the early makeup of the nebula from which the terrestrial planets formed. This absorption spectrum is primarily that of billions of carbonaceous chondrites, ejected from priori-Mars in the last 6,000 years, which have fallen into the solar atmosphere.
The research that led to the conclusion stated in the title of this post, involved the comparison of heavy noble gas (krypton and xenon) isotope ratios from the interior of the Earth and from the atmosphere. These ratios provide the ‘purest’ measure of relative concentrations of heavy versus light elements, eliminating many variables, plus they are noble gases, i.e. they do not react with other elements to form compounds. The CO2 samples used were collected from the Bravo Dome gas field in New Mexico.
The ratios of lighter to heavier isotopes of Kr and Xe indicate that the ratio of heavier ones to lighter ones is greater in the mantle than in the atmosphere. The authors state that their finding discounts the notion, held by some scientists, that the oceans were originally incorporated in the entire body of the Earth and came to the surface via volcanic eruptions.
The authors sum up their conclusions as follows:
“Taken together, the Kr and Xe data are consistent with the early mantle acquiring a composition that is mass-fractionated and depleted in the lighter isotopes relative to the solar nebula. A source that provides both this signature and a mechanism of delivery to the early earth is accretion of meteoric material similar to the Average Carbonaceous Chondrite (AVCC).” [Here they assume the AVCC composition represents the original solar nebula.]
One author added in an interview: “Therefore the atmosphere and oceans must have come from somewhere else, possibly from a late bombardment of gas and water-rich materials similar to comets.” This is a reference to the putative late heavy bombardment, dated at about 4 billion years BP, which supposedly formed the lunar maria. However, the accumulation of the oceans via comets has been rendered highly improbable by recent studies of comets revealing that they are not primarily water but rock with aquifers which eject a small amount of water vapor providing their visibility.
The materials comprising the early Earth were blasted out of Jupiter by an enormous impact some 3.9 billion years ago, and are all ‘from outer space’. The plasma sphere which rebounded from Jupiter immediately contracted with the heavier elements becoming concentrated toward the center (mass fractionation). Inevitably a tiny amount of the heavy noble gases were trapped in the interior as the Earth cooled. Even though the difference in mass between the heavier and lighter isotopes is minute, slightly more of the heavier isotopes became trapped in the interior than in the atmosphere and oceans.
Most of the lighter elements, which characterize the biosphere, were preferentially lost to space due to the great heat of the flaming proto-Earth, but remained floating in the inner solar system and eventually settled on the surface once the planet cooled sufficiently. The lighter isotopes of the heavy noble gases therein comprise a higher proportion in the atmosphere.
Jupiter is primarily water in the form of methane gas hydrates, explaining the formation of the vast oceans of our planet. But the great heat of the proto-Earth caused the preferential loss of hydrogen while the fire-ball was essentially an atomic soup – too hot for any compounds to exist. The oxygen freed from water and the nitrogen freed from ammonium hydroxide formed our atmosphere. Similarly, the carbon released from methane formed the basis of life on Earth.
Although the Bronze and Iron age influx of the oceans and atmosphere from priori-Mars included some material blasted from deep in its interior, its atmosphere and oceans far outweighed the amount from the interior, and would not alter the findings of the cited paper.