Search: Geological chemistry
Earth's most severe mass extinction - an event 250 million years ago that wiped out 90 percent of all marine species and 70 percent of land vertebrates - was triggered by a collision with a comet or asteroid, according to a team led by The University of Washington, Seattle, USA. Evidence is based upon elegant findings involving carbon molecules called buckminsterfullerenes (C60, Buckyballs) with the gases helium and argon trapped inside their cage structures.
The scientists do not know the site of the impact 250 million years ago, when all Earth's land formed a supercontinent called Pangea. However, the space body left a calling card - a much higher level of complex carbon molecules called buckminsterfullerenes, or Buckyballs, with the noble (or chemically nonreactive) gases helium and argon trapped inside their cage structures. Fullerenes, which contain 60 or more carbon atoms and have a structure resembling a soccer ball or a geodesic dome, are named for Buckminster Fuller, who invented the geodesic dome.
The researchers know these particular Buckyballs are extraterrestrial because the noble gases trapped inside have an unusual ratio of isotopes. For instance, terrestrial helium is mostly helium-4 and contains only a small amount of helium-3, while extraterrestrial helium - the kind found in these fullerenes - is mostly helium-3.
"These things form in carbon stars. That's what's exciting about finding fullerenes as a tracer," according to Luann Becker, one of scientific team involved. The extreme temperatures and gas pressures in carbon stars are perhaps the only way extraterrestrial noble gases could be forced inside a fullerene, she said. These gas-laden fullerenes were formed outside the Solar System, and their concentration at the Permian-Triassic boundary means they were delivered by a comet or asteroid.
The European Space Agency's Beagle 2 is approaching Mars for a landing (bouncy, but hopefully soft) on Christmas Day (will we hear "The Beagle has landed" !). Part of its mission is to look for chemical traces of life. One of the tests will be for methane in the martian atmosphere. Methane is a byproduct of life but will not last long in the Martian atmosphere, so a positive result would be interesting. Other experiments will determine C-12/C-13 ratios since a high value is indicative of life. Two NASA craft will follow on a month later.
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A NASA scientist has discovered sugar and several related organic compounds in two meteorites -- providing the first evidence that another fundamental building block of life on Earth might have come from outer space.
Dr. George Cooper and coworkers from the NASA Ames Research Center found the sugary compounds in two carbon-rich (or carbonaceous) meteorites. Previously, researchers had found inside meteorites other organic, carbon-based compounds that play major roles in life on Earth, such as amino acids and carboxylic acids, but no sugars.
These discoveries add an important new piece to the puzzle of the origins of life on Earth, and supports the notion that seeds of life might be spread far and wide around the cosmos.1
"Finding these compounds greatly adds to our understanding of what organic materials could have been present on Earth before life began," Cooper said. "Sugar chemistry appears to be involved in life as far back as our records go." Recent research using ratios of carbon isotopes have pushed the origin of life on Earth to as far back as 3.8 billion years, he said. (An isotope is one of two or more atoms whose nuclei have the same number of protons but different numbers of neutrons.)
"This discovery shows that it's highly likely organic synthesis critical to life has gone on throughout the universe," said Kenneth A. Souza, acting director of astrobiology and space research at Ames. "Then, on Earth, since the other critical elements were in place, life could blossom."
- 1. Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth,
, Nature, 12/2001, Volume 414, Issue 6866, p.879 - 883, (2001)
At least one sugar and a variety of sugar derivatives (polyols) have been found in the Murray and Murchison carbonaceous meteorites. The idea that extraterrestrial material may have played a role the origin of life on Earth stems in large part from the previous discovery of amino acids in these meteorites, and the presence of polyols adds weight to the argument. The sugar has been identified as dihydroxyacetone, which can readily yield higher sugars including ribose (as in an 'RNA world') in aqueous solution with minerals, and the polyols include glycerol, a constituent of all cell membranes.Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth, , Nature, 12/2001, Volume 414, Issue 6866, p.879 - 883, (2001)
The Hubble telescope has identified oxygen and carbon in the atmosphere of an extrasolar planet for the first time. The oxygen and carbon are evaporating from a "hot jupiter" planet HD 209458b, orbiting a star lying 150 light-years from Earth. HD 209458b is only 4.3 million miles from its Sun-like star, completing an orbit in less than 4 days. This is not a sign of life!
Lands, rivers and methane springs: latest images of Titan. Titan's atmosphere is mostly nitrogen but there is also methane and many other organic compounds.
Mosaic of river channel and ridge area on Titan. Credit: ESA/NASA/JPL/University of Arizona: http://www.esa.int/SPECIALS/Cassini-Huygens/SEM48881Y3E_0.html