During an expedition off the South American coast, an international team of ocean scientists discovered that the gases ethane and propane are widespread, and are being produced by microorganisms in deeply buried sediments.
Prof. Kai-Uwe Hinrichs (Research Center Ocean Margins, University of Bremen), co-author Prof. John Hayes (Woods Hole Oceanographic Institution), and colleagues report new findings on the production of energy-laden gases in a paper in this week's online edition of the renowned Proceedings of the National Academy of Sciences of the U.S.A. (PNAS). The findings suggest that microbes in the deeply buried, vast ecosystem below the seafloor carry out hitherto unrecognized processes, which are highly relevant to both our understanding of global element cycles and the metabolic abilities of Earth's microbial biosphere.
"In a way, the finding was coincidental," Hinrichs states. Onboard the research drilling vessel JOIDES Resolution, the geochemist, now at the University of Bremen but then at Woods Hole Oceanographic Institution (WHOI), analyzed the gases in sediments buried up to 400 meters in the Equatorial Pacific off Peru. "We were swamped with samples: in nearly a thousand samples of up to 40 million-year-old sediment, we analyzed the gas content." Despite work shifts of up to 14 hours, the shipboard scientists soon had a backlog of unanalyzed samples, which turned out to be lucky. "When we later looked at the samples, we noticed that concentrations of ethane and propane were suspiciously high," Hinrichs adds. Soon the scientists realized that these gases were not artifacts or contaminants, but that they must have slowly escaped from the sediment.
The researchers began to wonder how to account for the presence of these gases. Normally, ethane and propane are known as typical products of fossil fuel generation at elevated temperatures and pressure, without direct involvement of microbes. In the PNAS article, the team argues that microbes played a key role in the formation of these hydrocarbons.
"Sediments contain organic material (the fossil remnant of oceanic plants and animals)," Hinrichs explains. "This material, a key ingredient in the carbon cycle, is the major food used by the deep biosphere. During its decomposition by microbes, acetate--the ionic form of acetic acid--is formed. We think that bacteria use hydrogen to convert acetate into ethane. Addition of inorganic carbon and hydrogen provides a route to propane."
In support of their hypothesis for a biological origin of the gases, the researchers point to several clues: "First, the sampling locations are remote from reservoirs of oil and natural gas, so that this source can be eliminated," Hinrichs says. "Moreover, the abundance of stable isotopes of carbon are markedly different from those in gases formed at high temperature," adds co-author John Hayes, a geochemist at Woods Hole Oceanographic Institution (WHOI).
Co-author Wolfgang Bach, geochemist and professor at the Bremer Research Center points out, "We also were able to demonstrate that under the conditions prevailing at depth, these processes could yield just enough energy for growth of bacterial communities."
The paper leads to several new questions that will be addressed in future work. In a current PhD project in the Organic Geochemistry Group at the Research Center Ocean Margins, experiments are being conducted to locate the sedimentary sites where the gases are hidden. "Interlayer spaces of clay minerals are the best candidates right now," Hinrichs says. Other experiments are currently being designed to find out more about how the gases are being formed. He adds, "One important goal right now is to study these processes under controlled conditions in the lab to verify or refine the proposed mechanism." Hinrichs knows that it may not be easy to simulate processes from the deep biosphere, but the geochemist hopes to identify and replicate the conditions needed to stimulate the microbes to produce a lot of these energy carriers.
Nancy Light | EurekAlert!
Fossil coral reefs show sea level rose in bursts during last warming
19.10.2017 | Rice University
NASA finds newly formed tropical storm lan over open waters
17.10.2017 | NASA/Goddard Space Flight Center
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
19.10.2017 | Materials Sciences
19.10.2017 | Materials Sciences
19.10.2017 | Physics and Astronomy