Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


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


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:

More articles from Earth Sciences:

nachricht Wandering greenhouse gas
16.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht Unique Insights into the Antarctic Ice Shelf System
14.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>