... newer stories
Montag, 17. September 2012
Mars Bluebarries mit Biosignaturen!!!
klauslange,17:10h
Die bekannten Mars-Kügelchen 'Blueberries' wurden aussschließlich als rein chemisch entstanden angesehen. Doch nun zeigt eine Forschergruppe, dass solche speziellen Kügelchen auf der Erde stets Biosignaturen enthalten, also unter Mithilfe von Mikroben entstanden sind:
Concretions, preferentially cemented masses within sediments and sedimentary rocks, are records of sediment diagenesis and tracers of pore water chemistry. For over a century, rinded spheroidal structures that exhibit an Fe(III) oxide–rich exterior and Fe-poor core have been described as oxidation products of Fe(II) carbonate concretions. However, mechanisms governing Fe(III) oxide precipitation within these structures remain an enigma. Here we present chemical and morphological evidence of microbial biosignatures in association with Fe(III) oxides in the Fe(III) oxide–rich rind of spheroidal concretions collected from the Jurassic Navajo Sandstone (southwest United States), implicating a microbial role in Fe biomineralization. The amount of total organic carbon in the exterior Fe(III) oxides exceeded measured values in the friable interior. The mean δ13C value of organic carbon from the Fe(III) oxide–cemented exterior, δ13C of −20.55‰, is consistent with a biogenic signature from autotrophic bacteria. Scanning electron micrographs reveal microstructures consistent with bacterial size and morphology, including a twisted-stalk morphotype that resembled an Fe(II)-oxidizing microorganism, Gallionella sp. Nanoscale associations of Fe, O, C, and N with bacterial morphotypes demonstrate microorganisms associated with Fe(III) oxides. Together these results indicate that autotrophic microorganisms were present during Fe(III) oxide precipitation and present microbial catalysis as a mechanism of Fe(III) oxide concretion formation. Microbial biosignatures in rinded Fe(III) oxide–rich concretions within an exhumed, Quaternary aquifer has broad implications for detection of life within the geological record on Earth as well as other Fe-rich rocky planets such as Mars, where both Fe(II) carbonate and Fe(III) oxide–rich concretions have been identified.
Quelle: Fachjournal Geology
Concretions, preferentially cemented masses within sediments and sedimentary rocks, are records of sediment diagenesis and tracers of pore water chemistry. For over a century, rinded spheroidal structures that exhibit an Fe(III) oxide–rich exterior and Fe-poor core have been described as oxidation products of Fe(II) carbonate concretions. However, mechanisms governing Fe(III) oxide precipitation within these structures remain an enigma. Here we present chemical and morphological evidence of microbial biosignatures in association with Fe(III) oxides in the Fe(III) oxide–rich rind of spheroidal concretions collected from the Jurassic Navajo Sandstone (southwest United States), implicating a microbial role in Fe biomineralization. The amount of total organic carbon in the exterior Fe(III) oxides exceeded measured values in the friable interior. The mean δ13C value of organic carbon from the Fe(III) oxide–cemented exterior, δ13C of −20.55‰, is consistent with a biogenic signature from autotrophic bacteria. Scanning electron micrographs reveal microstructures consistent with bacterial size and morphology, including a twisted-stalk morphotype that resembled an Fe(II)-oxidizing microorganism, Gallionella sp. Nanoscale associations of Fe, O, C, and N with bacterial morphotypes demonstrate microorganisms associated with Fe(III) oxides. Together these results indicate that autotrophic microorganisms were present during Fe(III) oxide precipitation and present microbial catalysis as a mechanism of Fe(III) oxide concretion formation. Microbial biosignatures in rinded Fe(III) oxide–rich concretions within an exhumed, Quaternary aquifer has broad implications for detection of life within the geological record on Earth as well as other Fe-rich rocky planets such as Mars, where both Fe(II) carbonate and Fe(III) oxide–rich concretions have been identified.
Quelle: Fachjournal Geology
... link (1 Kommentar) ... comment
Opportunity findet kleine Kügelchen auf dem Mars
klauslange,16:55h
Schon einmal fand der Minirover kleine Kügelchen auf dem Mars, die dann den Spitznamen 'Blueberries' erhielten. Nun wurde der Rover wieder fündig, doch die neuen Kügelchen haben eine ganz andere Struktur und Zusammensetzung als die bekannten Blueberries. Die nächsten Wochen sollen Licht ins Dunkel bringen. Schade das der neue Rover Curiosity nicht einen solchen Fund gemacht hat. Mit Opportunity ist die Analyse weitaus schwieriger und indirekter.
New Scientist berichtet:
NASA scientists working on the Opportunity mission at first thought the spheres looked like structures known as Martian blueberries. These iron-rich orbs, discovered at the rover's landing site in 2004, are thought to have formed millions of years ago, when the Red Planet was likely warm enough to host liquid water.
In some places minerals precipitated out of the water as it diffused through rock, leaving behind hard masses. Erosion eventually exposed the spherules embedded in outcrops, like blueberries in a muffin.
Similar spheres have been found in sandstones in the US Southwest, and some scientists think they may hold clues to finding microbial life on Mars.
But when Opportunity took a closer look at the new spheres using its X-ray spectrometer, the rover found that they don't "taste" like blueberries.
For one, the spheres don't contain nearly as much iron. They're also much more tightly clustered than previous groups of blueberries, and they have a more fragile disposition.
"They seem to be crunchy on the outside, and softer in the middle," Opportunity's principal investigator, Steve Squyres of Cornell University, said in a NASA statement.
"They are different in concentration. They are different in structure. They are different in composition. They are different in distribution. So, we have a wonderful geological puzzle in front of us."
New Scientist berichtet:
NASA scientists working on the Opportunity mission at first thought the spheres looked like structures known as Martian blueberries. These iron-rich orbs, discovered at the rover's landing site in 2004, are thought to have formed millions of years ago, when the Red Planet was likely warm enough to host liquid water.
In some places minerals precipitated out of the water as it diffused through rock, leaving behind hard masses. Erosion eventually exposed the spherules embedded in outcrops, like blueberries in a muffin.
Similar spheres have been found in sandstones in the US Southwest, and some scientists think they may hold clues to finding microbial life on Mars.
But when Opportunity took a closer look at the new spheres using its X-ray spectrometer, the rover found that they don't "taste" like blueberries.
For one, the spheres don't contain nearly as much iron. They're also much more tightly clustered than previous groups of blueberries, and they have a more fragile disposition.
"They seem to be crunchy on the outside, and softer in the middle," Opportunity's principal investigator, Steve Squyres of Cornell University, said in a NASA statement.
"They are different in concentration. They are different in structure. They are different in composition. They are different in distribution. So, we have a wonderful geological puzzle in front of us."
... link (0 Kommentare) ... comment
... older stories
