̽��ֱ�� of Cambridge - Alexandra Turchyn

Shrinking Arctic glaciers are unearthing a new source of methane

cmm201 — Thu, 06 Jul 2023 14:23:15 +0000

As the Arctic warms, shrinking glaciers are exposing bubbling groundwater springs which could provide an underestimated source of the potent greenhouse gas methane, finds new research published today in Nature Geoscience.

Link identified between continental breakup, volcanic carbon emissions and evolution

sc604 — Thu, 20 Jul 2017 18:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, used existing measurements of carbon and helium from more than 80 volcanoes around the world in order to determine its origin. Carbon and helium coming out of volcanoes can either come from deep within the Earth or be recycled near the surface, and measuring the chemical fingerprint of these elements can pinpoint their source. When the team analysed the data, they found that most of the carbon coming out of volcanoes is recycled near the surface, in contrast with earlier assumptions that the carbon came from deep in the Earth’s interior. “This is an essential piece of geological carbon cycle puzzle,” said Dr Marie Edmonds, the senior author of the study.

Over millions of years, carbon cycles back and forth between Earth’s deep interior and its surface. Carbon is removed from the surface from processes such as the formation of limestone and the burial and decay of plants and animals, which allows atmospheric oxygen to grow at the surface. Volcanoes are one way that carbon is returned to the surface, although the amount they produce is less than a hundredth of the amount of carbon emissions caused by human activity. Today, the majority of carbon from volcanoes is recycled near the surface, but it is unlikely that this was always the case.

Volcanoes form along large island or continental arcs where tectonic plates collide and one plate slides under the other, such as the Aleutian Islands between Alaska and Russia, the Andes of South America, the volcanoes throughout Italy, and the Mariana Islands in the western Pacific. These volcanoes have different chemical fingerprints: the ‘island arc’ volcanoes emit less carbon which comes from deep in the mantle, while the ‘continental arc’ volcanoes emit far more carbon which comes from closer to the surface.

Over hundreds of millions of years, the Earth has cycled between periods of continents coming together and breaking apart. During periods when continents come together, volcanic activity was dominated by island arc volcanoes; and when continents break apart, continental volcano arcs dominate. This back and forth changes the chemical fingerprint of carbon coming to Earth’s surface systematically over geological time, and can be measured through the different isotopes of carbon and helium.

Variations in the isotope ratio, or chemical fingerprint, of carbon are commonly measured in limestone. Researchers had previously thought that the only thing that could change the carbon fingerprint in limestone was the production of atmospheric oxygen. As such, the carbon isotope fingerprint in limestone was used to interpret the evolution of habitability of Earth’s surface. ̽��ֱ��results of the Cambridge team suggest that volcanoes played a larger role in the carbon cycle than had previously been understood, and that earlier assumptions need to be reconsidered.

“This makes us fundamentally re-evaluate the evolution of the carbon cycle,” said Edmonds. “Our results suggest that the limestone record must be completely reinterpreted if the volcanic carbon coming to the surface can change its carbon isotope composition.”

A great example of this is in the Cretaceous Period, 144 to 65 million years ago. During this time period there was a major increase in the carbon isotope ratio found in limestone, which has been interpreted as an increase in atmospheric oxygen concentration. This increase in atmospheric oxygen was causally linked to the proliferation of mammals in the late Cretaceous. However, the results of the Cambridge team suggest that the increase in the carbon isotope ratio in the limestones could be almost entirely due to changes in the types of volcanoes at the surface.

“ ̽��ֱ��link between oxygen levels and the burial of organic material allowed life on Earth as we know it to evolve, but our geological record of this link needs to be re-evaluated,” said co-author Dr Alexandra Turchyn, also from the Department of Earth Sciences.

̽��ֱ��research was funded by the Alfred P. Sloan Foundation, the Deep Carbon Observatory and the European Research Council.

Reference:
Emily Mason, Marie Edmonds, Alexandra V. Turchyn. ‘Remobilization of crustal carbon may dominate volcanic arc emissions.’ Science (2017). DOI: 10.1126/science.aan5049.

Inset Image: Schematic diagram to show the possible sources of carbon in a subduction zone volcanic system.

Researchers have found that the formation and breakup of supercontinents over hundreds of millions of years controls volcanic carbon emissions. ̽��ֱ��results, reported in the journal Science, could lead to a reinterpretation of how the carbon cycle has evolved over Earth’s history, and how this has impacted the evolution of Earth’s habitability.

̽��ֱ��link between oxygen levels and the burial of organic material allowed life on Earth as we know it to evolve, but our geological record of this link needs to be re-evaluated.

Alexandra Turchyn

Image courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center

ISS013-E-24184 (23 May 2006) --- Eruption of Cleveland Volcano, Aleutian Islands, Alaska is featured in this image photographed by an Expedition 13 crewmember on the International Space Station.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Licence type:

Public Domain

Metabolism may have started in our early oceans before the origin of life

cjb250 — Fri, 25 Apr 2014 15:12:59 +0000

In a study funded by the Wellcome Trust and the European Research Council researchers at the ̽��ֱ�� of Cambridge reconstructed the chemical make-up of the Earth’s earliest ocean in the laboratory. ̽��ֱ��team found the spontaneous occurrence of reaction sequences which in modern organisms enable the formation of molecules essential for the synthesis of metabolites. These organic molecules, such as amino acids, nucleic acids and lipids, are critical for the cellular metabolism seen in all living organisms

̽��ֱ��detection of one of the metabolites, ribose 5-phosphate, in the reaction mixtures is particularly noteworthy, as RNA precursors like this could in theory give rise to RNA molecules that encode information, catalyze chemical reactions and replicate.

It was previously assumed that the complex metabolic reaction sequences, known as metabolic pathways, which occur in modern cells, were only possible due to the presence of enzymes. Enzymes are highly complex molecular machines that are thought to have come into existence during the evolution of modern organisms. However, the team’s reconstruction reveals that metabolism-like reactions could have occurred naturally in our early oceans, before the first organisms evolved.

Life on Earth began during the Archean geological eon almost 4 billion years ago in iron-rich oceans that dominated the surface of the planet. This was an oxygen-free world, pre-dating photosynthesis, when the redox state of iron was different and much more soluble to act as potential catalysts. In these oceans, iron, other metals and phosphate facilitated a series of reactions which resemble the core of cellular metabolism occurring in the absence of enzymes.

̽��ֱ��findings suggest that metabolism predates the origin of life and evolved through the chemical conditions that prevailed in the worlds earliest oceans.

“Our results show that reaction sequences that resemble two essential reaction cascades of metabolism, glycolysis and the pentose-phosphate pathways, could have occurred spontaneously in the earth’s ancient oceans,” says Dr Markus Ralser from the Department of Biochemistry at the ̽��ֱ�� of Cambridge and the National Institute for Medical Research, who led the study.

“In our reconstructed version of the ancient Archean ocean, these metabolic reactions were particularly sensitive to the presence of ferrous iron which was abundant in the early oceans, and accelerated many of the chemical reactions that we observe. We were surprised by how specific these reactions were,” he added.

̽��ֱ��conditions of the Archean ocean were reconstructed based on the composition of various early sediments described in the scientific literature which identify soluble forms of iron as one of the most frequent molecules present in these oceans.

Alexandra Turchyn from the Department of Earth Sciences at the ̽��ֱ�� of Cambridge, one of the co-authors of the study said: “We are quite certain that the earliest oceans contained no oxygen, and so any iron present would have been soluble in these oxygen-devoid oceans. It’s therefore possible that concentrations of iron could have been quite high”.

̽��ֱ��different metabolites were incubated at temperatures of 50-90˚C, similar to what might be expected close to the hydrothermal vents of an oceanic volcano. These temperatures would not support the activity of conventional protein enzymes. ̽��ֱ��chemical products were separated and analyzed by liquid chromatography tandem mass spectrometry.

Some of the observed reactions could also take place in water but were accelerated by the presence of metals that served as catalysts. “In the presence of iron and other compounds found in the oceanic sediments, we observed 29 metabolism-like chemical reactions, including those that produce some of the essential chemicals of metabolism, for example precursors to the building blocks of proteins or RNA,” says Dr Ralser.

“These results indicate that the basic architecture of the modern metabolic network could have originated from the chemical and physical constraints that existed on Earth billions of years ago.”

Copy adapted from an original press release from the Wellcome Trust.

Reference
Keller et al. (2014) Mol Syst Biol 10:725. Non-enzymatic glycolysis and pentose phosphate pathway-like reactions in a plausible Archean ocean

̽��ֱ��chemical reactions behind metabolism – the processes that occur within all living organisms in order to sustain life – may have formed spontaneously in the Earth’s early oceans, according to research published today.

̽��ֱ��basic architecture of the modern metabolic network could have originated from the chemical and physical constraints that existed on Earth billions of years ago

Markus Ralser

Dhilung Kirat

After storm

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

Licence type:

Attribution