You are not logged in. Please register or login.
- Topics: Active | Unanswered
Re: Saturn moon offers hints of early life on Earth
An image of Saturn's moon Titan captured by NASA's Cassini spacecraft.
By Dan Vergano, USA TODAY
Titan, the orange-shrouded moon of Saturn, may harbor hints to answering the riddle of life, three new studies suggest.
Saturn's largest moon, Titan possesses an ammonia and methane atmosphere that obscures its frozen surface from view. Since a 1980 Voyager I flyby, astrobiologists have been tantalized by the world, seeing it as a chilled time capsule of early planetary conditions at the start of the 4.6-billion year old solar system.
The surface of Titan "is still enshrouded in a cloud of mystery despite the initial flood of data," begins a current Journal of Geophysical Research report led by Roger Clark of the United States Geological Survey. That mystery persists, notwithstanding 68 overflights since 2004 by the international Cassini space probe, and an intentional plummet into the atmosphere by the 2005 European Space Agency's Huygens lander.. A 69th flyby of the moon, passing some 1,200 miles over the 3,000-mile-wide world, comes early Saturday, June 5.
Using new Cassini data, Clark and colleagues report that the moon's surface is a stew of organic compounds, benzene, ethane and methane. But what is interesting is that another compound, acetylene, appears absent.
Why is that interesting? Well, five years ago, NASA astrobiologist Chris McKay, suggested acetylene might make dandy fuel for any life living on the -290 degree surface of the moon. "One interpretation of the acetylene data is that the hydrocarbon is being consumed as food," noted a Jet Propulsion Laboratory statement highlighting the research this week.
Another interesting Titan find comes in the current Icarus journal, where Cassini planetary atmosphere investigator Darrell Strobel of Johns Hopkins University, reports about half as much hydrogen as expected on the surface of the moon. McCay predicted in a 2005 paper that life on Titan might eat both hydrogen and acetylene. "It's the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth," McKay said in the JPL statement, pointing to the possibility of methane-based life on the mystery moon.
Strobel is much more cautious in the Icarus report, writing surface hydrogen "is in substantial excess" of the amount that McKay predicted would be there, if life was running around gobbling up hydrogen molecules. .
But what makes all this discussion of a far-off, frozen world most interesting is a third paper by Eric Wolf and O. B. Toon of the University of Colorado, Boulder, in the current Science journal, suggesting an ammonia haze '” like Titan's current cloak '” may have insulated the early Earth, keeping it warm during the sun's dim youth.
AstronomersCarl Sagan and George Mullen noted the "Early Faint Sun Paradox" in 1972, finding that during the first billion years of the sun's 4.6 billion year life, it was about 30% less bright than today. The sun only slowly increased its luminosity to the point about 2 billion years ago where current greenhouse gas warming seen in the atmosphere would have been able to prevent worldwide glaciation. Nevertheless, the Earth didn't freeze over, and life even started in this time, with early fossil blue-green algae preserved in 3.4 billion-year-old rock.
While earlier studies theorized an ammonia-rich atmosphere on the early Earth should have produced cooling instead of global warming, Wolf and Toon suggest that instead a puffy ammonia and methane aerosol haze provided a powerful greenhouse gas insulating blanket for the early Earth. Aerosol particles of the right size, about 50 nanometers wide (.000002 inches), suspended in air would have trapped heat in the atmosphere.
"The Archean Earth (3.8 to 2.5 billion years ago) was probably enshrouded by a photochemical haze composed of fractal aggregate hydrocarbon aerosols. The fractal structure of the aerosols would have had a strong effect on the radiative (heat-trapping) properties of the haze," they find in an analysis, adding, "the haze would have provided a strong shield against ultraviolet light while causing only minimal anti-greenhouse cooling."
The young Earth would have resembled Saturn's haze-shrouded moon, Titan, the two scientists suggest. The idea "revitalizes the Miller-Urey hypothesis," a 1953 experiment that zapped ammonia, methane and water with electricity. After a week, the experiment yielded a small amount of organic chemicals, which the experimenters saw as precursors to life. The origin-of-life explanation went out of style after researchers came to doubt that the atmosphere contained that much ammonia, but the new paper puts it back into play.
"The Wolf and Toon result looks pretty convincing," says Princeton's Christopher Chyba, a pioneer in the early faint sun paradox field. He notes that cosmologists have several explanations for resolving the early, faint sun paradox, including a faster-spinning young Earth producing different heat-reflecting clouds, "and the real answer is probably a mix of them."
Titan is just one end of the spectrum for how "comparative planetology" can answer questions about our own world, he adds. Even if the early Earth was iced over, some astrobiologists have pointed to Europa, a frozen moon of Jupiter thought to harbor an interior ocean, as another model for where life might have gotten a start long ago.
Such comparisons are, "classic Carl (Sagan) thinking, looking at conditions on one world and asking what they mean for our own," Chyba adds. "In the big picture, I think what all these studies tell us is something about the value of exploring space to help us make sense of things on Earth."
Re: Saturn moon offers hints of early life on Earth
They're really stretching these theories pretty thin. There is a chance that some sort of life developed here, but like it mentions at the bottom of the article, time to switch focus to Europa. That should have been priority number one when they realized there is likely an ocean about a mile under that ice. If there's nothing down there, then they can pretty much rule out life anywhere in the solar system but here because if life isn't thriving in an ocean, it isn't thriving anywhere.
