Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Thick marine beds of siderite suggest early high carbon dioxide in atmosphere

27.05.2004


Carbon dioxide and oxygen, not methane, were prevalent in the Earth’s atmosphere more than 1.8 billion years ago as shown by the absence of siderite in ancient soils but the abundance of the mineral in ocean sediments from that time, according to a Penn State geochemist.



"The absence of siderite in some ancient soils has been linked to low carbon dioxide levels in the atmosphere, levels that would be too low to compensate for the cooler sun 2.2 billion years ago," says Dr. Hiroshi Ohmoto, professor of geochemistry and director of the Penn State Astrobiology Research Center. "The absence of siderite in these soils, however, does not constrain atmospheric carbon dioxide, but occurred because the oxygen and acidity of well-aerated soils caused iron to form into other minerals."

Previous researchers suggested that the greenhouse gas methane compensated for the low carbon dioxide levels, making the Earth warm enough for water to flow.


Ohmoto; Yumiko Watanabe, research associate Penn State, and Kazumasa Kumazawa, Oyo Corp. Miyazaki City, Japan, report in today’s (May 27) issue of the journal Nature, that the abundance of large, massive siderite-rich beds in pre-1.8 billion year old sedimentary sequences and their carbon isotope ratios indicates that the atmospheric carbon dioxide concentration was more than 100 times greater than today, causing the rain and ocean water to be more acidic than today. This high carbon dioxide content, without methane provided the necessary greenhouse effect to maintain liquid oceans in the early Earth.

Previous research recognized that siderite forms in soils when the carbon dioxide pressure in the atmosphere is above a certain level. No siderite in some ancient soils therefore implied lower levels of carbon dioxide.

Ohmoto and his associates, however, looked at four, rather than one, parameters involved in siderite formation. They investigated the effects of carbon dioxide, oxygen, acidity and amounts of iron in solution. The acidity of rainwater in the past was greater than it is now, and they found that the combination of greater acidity and oxygen in the atmosphere, not a low content of carbon dioxide, was the reason for the absence of siderite in some ancient soils.

At the same time that siderite is missing from soils, it is abundant in ocean sediments before 1.8 billion years ago and formed thick bands of mineable ores. The high abundance of siderite in marine sediments and their carbon isotope ratios can be explained only if the carbon dioxide pressure in the atmosphere was more than 100 times, perhaps as much as 1000 times, higher than today’s level. If the methane content was as high as the level suggested by previous researchers, the combination of high carbon dioxide and methane could have made the early Earth too hot for life. But geologic evidence suggests the life flourished in the oceans and land since at least 3.5 billion years ago. Therefore, the atmospheric methane content must have been very low.

"The atmosphere cannot have high contents of both methane and oxygen," says Ohmoto. "If one is high, the other must be low, or both must be low. So, the combination of high oxygen, high carbon dioxide and low methane was a perfectly happy scenario on Earth prior to about 1.8 billion years ago.

"How the Earth’s atmosphere changes through time is related to how it maintains habitable conditions on the planet," adds the Penn State researcher. "If we understand geological history better, we may understand how life evolved and may evolve in the future. Perhaps it will make us realize how humans should or should not interfere with the Earth’s systems." Understanding of the Earth’s early atmospheric history will also tell us what to look for when looking for life on extra-solar plants.

A’ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu/

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>