Petroleum in space? Ain’t that a gas! – Part 5
space
Serpentinization occurs in hot deep-sea vents, Atreya explains, where hydrogen (released from iron- or magnesium-rich rock) reacts with carbonaceous gases, grains and minerals, to produce methane.
Another source of methane, on Earth, he reports, is volcanism—whose importance, in the case of Mars, scientists tend to downplay.Martian volcanoes have been extinct for four million years. But methane molecules released into the planet’s atmosphere, can survive for only 300 to 600 years, before ultraviolet radiation breaks them up.
Also, there is more methane in the atmosphere of Mars than sulfur dioxide: Yet volcanism produces larger quantities of the latter, than it does methane, effectively ruling out volcanic processes.
The third source of terrestrial methane is living organisms. “Of the 1,750 parts per billion by volume (ppbv) of methane in Earth’s atmosphere,” writes Atreya, “90 to 95 percent is biological in origin”.
He reports as well, that “Grass-eating ungulates such as cows, goats and yaks belch out one fifth of the annual global methane release,” the gas being “a metabolic by-product of the bacteria in their guts”.
According to NASA, these “methanogens” transfer electrons from hydrogen atoms to carbon dioxide molecules and use the liberated heat as energy, for growth. Methane is generated as a waste product.Added to this, Atreya says, is output from “termites, rice paddies, swamps, leakage of natural gas (itself a result of past life) and photosynthetic plants”.
The widely presumed (but not universally accepted) biogenic explanation of how Earth got its abundant natural gases, raises the possibility that methane on Mars may have a similar origin.
“If Mars possessed an Earth-like biosphere in the past,” speculates John F. McGowan III, of NASA Ames Research Centre, “[it] may contain subsurface deposits of oil and natural gas, indicating past life”.
In “Oil and Natural Gas On Mars,” McGowan argues, “Subsurface oil and natural gas…would probably cause seepage of hydrocarbon gases such as methane at favorable locations on the surface”.
Telemetry from the European Space Agency’s Mars orbiter, as interpreted by Atreya, tend to bare McGowan out—hinting at greater methane concentrations over areas containing subsurface water ice.
Concurringly, O. Mousis et.al. hypothesize that methane on Mars “would more likely derive from hydrothermal reactions with olivine-rich material”—an apparent allusion to serpentinization.
“If they do exist,” the authors contend, “Martian methane clathrates would be stable only at depth in the cryosphere [frozen undersurface] and sporadically release some methane into the atmosphere…”
This inference is derived from the fact that methane clathrate production on Earth is essentially biological, and that the crystals are found in the frozen, permafrost regions of the planet.
Thus the detection of natural gas in the Martian atmosphere, and the prospects for finding evidence of past or present life on the Red Planet are intertwined, inextricably.
As I indicated earlier though, not everyone thinks Earth’s oil and gas are biogenic in origin. Russian, and some Western, scientists are exponents of an abiogenic petroleum theory.
They believe terrestrial petroleum—or much of it, anyway—are primordial hydrocarbons, which have existed since the formation of the planet, more than four billion years ago.
Abiogenic partisans base their argument on the results of experiments showing that petroleum can form at depths of 100 to 300 km and on the confirmed existence of oil and natural gas in Earth’s mantle.
Hence Mars may contain more than mere atmospheric methane. “This theory,” notes McGowan, “almost certainly predicts large deposits of oil and natural gas beneath the Martian surface”.
*To be continued.
