MOUNTAIN VIEW, Calif., Dec. 19 (UPI) -- Meticulous analysis of meteorite samples indicates sugar from space may have sweetened the odds of life on Earth -- and perhaps elsewhere, researchers report.
At least two rocky remnants of the solar system's birth that fell from the sky contain sugar-like substances critical to molecules found in all living things, the National Aeronautics and Space Administration scientists have found.
The range of organic compounds called polyols, close chemical relatives of sugars such as glucose and used commercially as sugar-free sweeteners such as sorbitol and mannitol, form part of the backbone of the molecules' DNA -- which endows each organism with its unique genetic blueprint -- and RNA -- the first key molecules shown capable of acting as a catalyst for important chemical reactions. Polyols also serve as life's primary energy storehouses.
The discovery of these essential building blocks of life in the leftovers of planet formation some 4.5 billion years ago that survived their plunge to Earth supports the view that organic compounds showered from the heavens to "seed" life on Earth rather than springing from scratch on the young planet, researchers said in the British journal Nature. It also increases the odds of the existence of extraterrestrial life, scientists told United Press International.
"By discovering sugar compounds in meteorites, we now know that one more ingredient for the recipe of life was present in the early solar system," said Mark Sephton of the Open University in Milton Keynes, England, who wrote an accompanying commentary.
"As the delivery of meteorites is a process that is not exclusive to the Earth, similar materials will have arrived on other planets such as early Mars or as yet undiscovered worlds in other solar systems," he told UPI. "The possibility of discovering life elsewhere in the solar system or universe is now greater. The materials in (the meteorites) are a sample of what will have been kicking around in the early solar system. It is likely that these compounds were caught up in other bodies forming at the same time."
George Cooper, research scientist in the exobiology branch of NASA's Ames Research Center in Mountain View, Calif., and his team probed pieces of the carbon-rich Murchison and Murray meteorites, already known to brim with other organic compounds, such as amino acids, the molecular building blocks of proteins.
While sugars were detected in other meteorites as long ago as 1952, the scientists then were uncertain of their origin.
"They could not be sure that they weren't just detecting terrestrial contamination," Sephton said.
Refined tools and techniques have taken some of the guesswork out of the investigations.
"Because of modern instrumentation, this study is very much more definitive," Cooper told UPI. "A portion of some of the individual compounds may be from Earth life, but because of the sheer number and distribution of compounds -- some are found on Earth and some are rare on Earth -- coupled with their similarity in structure, the majority are almost certainly from space."
Scientists have long thought meteorites and comets played a role in life's origins. Showering Earth during the heavy bombardment period some 3.8 billion to 4.5 billion years ago, they carried oxygen, sulfur, hydrogen, nitrogen and other materials that may have been critical to life.
"This discovery shows that it's highly likely organic synthesis critical to life has gone on throughout the universe," said Kenneth Souza, acting director of astrobiology and space research at Ames. "Then, on Earth, since the other critical elements were in place, life could blossom."
Cooper and his team identified a small sugar called dihydroxyacetone and several sugar-like substances, known as sugar acids and sugar alcohols, in the Murchison and Murray meteorites. These are important to life as it exists today. They also detected a sugar alcohol, glycerol or glycerin by scientific name, which modern-day cells use to build walls, and uncovered preliminary evidence of other compounds that may contain larger sugars key to cellular metabolism, such as glucose.
The compounds had not previously been detected even though the organically well-endowed Murchison meteorite has been the center of scientific attention since its arrival -- heralded by a sonic boom -- on an otherwise quiet Sunday morning in September 1969 near the small town of Murchison in Western Australia. For the next three decades, this celestial offering was to become the most extensively studied meteorite by scientists interested in extraterrestrial organic matter, Sephton said.
"The first suggestions that Murchison contained organic molecules came from the initial eyewitness reports which commented on solvent smells emanating from the stone," he recalled.
"The early investigations of the organic inventory of Murchison were performed by laboratories which had been preparing for the return of samples from the Apollo missions. Several classes of organic compounds were quickly recognized, including amino acids, carboxylic acids, aliphatic hydrocarbons and aromatic hydrocarbons. In more recent times the steady stream of scientific articles arising from studies on the organics in Murchison indicates that this meteorite still has much to disclose."
Murray, which fell with less fanfare in Kentucky on Sept. 20, 1950, contains similar chemical contents.
"Because meteorites are the only direct evidence of an early source of biologically important organic compounds for the Earth, the lack of definitive proof of polyols in such objects leaves major gaps in our understanding of the chemistry of the first replicating organisms," Cooper told UPI. "There may have been ways of producing such compounds on the early Earth but because of processes such as weathering, the evidence for such compounds have long been erased."
Numerous mysteries remain, and much more meteorites research is needed to determine the true significance of the new findings, scientists said.
"We may never know what particular compounds were important for the very start of life -- we weren't there to observe!" Cooper said. "Similar chemicals are seen by astronomers around the universe, but we don't know yet if similar chemistry might form life in other places."
The quest to solve the puzzles will continue, investigators said.
"If we are to appreciate the origins of life, we need to understand what happened in the early solar system. Meteorites have sat unchanged for billions of years. They are a window, back to a time when the solar system was born and just before the first life appeared," Sephton said.
