Wednesday, June 07, 2023

GEOLOGY


Scientists discover ‘lost world’ of early ancestors in billion-year-old rocks


Peer-Reviewed Publication

AUSTRALIAN NATIONAL UNIVERSITY

The Protosterol Biota 

IMAGE: ARTIST’S IMAGINATION OF TWO PRIMORDIAL EUKARYOTIC ORGANISMS OF THE ‘PROTOSTEROL BIOTA’ ON THE OCEAN FLOOR. BASED ON MOLECULAR FOSSILS, ORGANISMS OF THE PROTOSTEROL BIOTA LIVED IN THE OCEANS ABOUT 1.6 TO 1.0 BILLION YEARS AGO AND ARE OUR EARLIEST KNOWN ANCESTORS. ORCHESTRATED IN MIDJOURNEY BY TA 2023. view more 

CREDIT: CREDIT: ORCHESTRATED IN MIDJOURNEY BY TA 2023



The discovery of a “lost world” of ancient organisms that lived in Earth’s waterways at least 1.6 billion years ago could change our understanding of our earliest ancestors.  

Known as the ‘Protosterol Biota’, these microscopic creatures are part of a family of organisms called eukaryotes. Eukaryotes have a complex cell structure that includes mitochondria, known as the “powerhouse” of the cell, and a nucleus that acts as the “control and information centre”.  

Modern forms of eukaryotes that inhabit Earth today include fungi, plants, animals and single-celled organisms such as amoebae. Humans and all other nucleated creatures can trace their ancestral lineage back to the Last Eukaryotic Common Ancestor (LECA). LECA lived more than 1.2 billion years ago. 

The discovery of the Protosterol Biota, published in Nature, was made by researchers from The Australian National University (ANU). According to the researchers, these organisms could have been the first predators on Earth.  

These ancient creatures were abundant in marine ecosystems across the world and probably shaped ecosystems for much of Earth’s history. The researchers say the Protosterol Biota lived at least one billion years before any animal or plant emerged. 

“Molecular remains of the Protosterol Biota detected in 1.6-billion-year-old rocks appear to be the oldest remnants of our own lineage – they lived even before LECA. These ancient creatures were abundant in marine ecosystems across the world and probably shaped ecosystems for much of Earth’s history,” Dr Benjamin Nettersheim, who completed his PhD at ANU and is now based at the University of Bremen in Germany, said. 

“Modern forms of eukaryotes are so powerful and dominant today that researchers thought they should have conquered the ancient oceans on Earth more than a billion years ago. 

“Scientists have long searched for fossilised evidence of these early eukaryotes, but their physical remains are extremely scarce. Earth’s ancient oceans rather appeared to be largely a bacterial broth. 

“One of the greatest puzzles of early evolution scientists have been trying to answer is: why didn’t our highly capable eukaryotic ancestors come to dominate the world’s ancient waterways? Where were they hiding?  

“Our study flips this theory on its head. We show that the Protosterol Biota were hiding in plain sight and were in fact abundant in the world’s ancient oceans and lakes all along. Scientists just didn’t know how to look for them – until now.”  

Professor Jochen Brocks from ANU, who made the discovery with Dr Nettersheim, said the Protosterol Biota were certainly more complex than bacteria and presumably larger, although it’s unknown what they looked like. 

“We believe they may have been the first predators on Earth, hunting and devouring bacteria,” Professor Brocks said.  

According to Professor Brocks, these creatures thrived from about 1.6 billion years ago up until about 800 million years ago.  

The end of this period in Earth’s evolutionary timeline is known as the ‘Tonian Transformation’, when more advanced nucleated organisms, such as fungi and algae, started to flourish. But exactly when the Protosterol Biota went extinct is unknown. 

“The Tonian Transformation is one of the most profound ecological turning points in our planet’s history,” Professor Brocks said.  

“Just as the dinosaurs had to go extinct so that our mammal ancestors could become large and abundant, perhaps the Protosterol Biota had to disappear a billion years earlier to make space for modern eukaryotes.”  

To make the discovery, the researchers studied fossil fat molecules found inside a 1.6-billion-year-old rock that had formed at the bottom of the ocean near what is now Australia’s Northern Territory. The molecules possessed a primordial chemical structure that hinted at the existence of early complex creatures that evolved before LECA and had since gone extinct.  

“Without these molecules, we would never have known that the Protosterol Biota existed. Early oceans largely appeared to be a bacterial world, but our new discovery shows that this probably wasn’t the case,” Dr Nettersheim said.   

Professor Brocks said: “Scientists had overlooked these molecules for four decades because they do not conform to typical molecular search images.” 

“But once we knew what we were looking for, we discovered that dozens of other rocks, taken from billion-year-old waterways across the world, were also oozing with similar fossil molecules.” 

Dr Nettersheim completed the analysis as part of his PhD at ANU before accepting a position at the University of Bremen. This work involved scientists from Australia, France, Germany and the United States. 

Tectonics matter: USU geoscientists probe geochemistry, microbial diversity of Peruvian hot springs


Heather Upin, Dennis Newell report microbial community composition is distinctly different in two tectonic settings

Peer-Reviewed Publication

UTAH STATE UNIVERSITY

Obtaining Microbial Sample from Peru's Aguas Calientas Pinaya 

IMAGE: UTAH STATE UNIVERSITY GEOSCIENTIST HEATHER UPIN COLLECTS A MICROBIAL SAMPLE FROM AGUAS CALIENTAS PINAYA IN PERU’S SOUTHERN ANDES. SHE AND USU COLLEAGUE DENNIS NEWELL PUBLISHED FINDINGS ABOUT MICROBIAL DIVERSITY IN PERUVIAN HOT SPRINGS. view more 

CREDIT: USU/DENNIS NEWELL



LOGAN, UTAH, USA -- South America’s Andes Mountains, the world’s longest mountain range and home to some of the planet’s highest peaks, feature thousands of hot springs. Driven by plate tectonics and fueled by hot rock and fluids, these thermal discharges vary widely in geochemistry and microbial diversity.

Utah State University geoscientists, along with colleagues from Montana State University, examined 14 hot springs within the southern Andes in Peru and discovered microbial community composition is distinctly different in two tectonic settings. Dennis Newell, associate professor in USU’s Department of Geosciences, and recent USU graduate Heather Upin, MS 2020, report findings in the April 11 online issue of Nature’s Communications Earth & Environment. Their research is supported by the National Science Foundation and the Geological Society of America.

“We know tectonic processes control hot spring temperature and geochemistry, yet how this, in turn, shapes microbial community composition is poorly understood,” says Newell, USU Geosciences graduate director.

The scientists collected geochemical and 16S ribosomal RNA gene sequencing data from hot springs in regions with contrasting styles of subduction — flat-slab and back-arc — and noted similarities in pH but found differences in geochemistry and microbiology.

“Flat-slab hot springs were chemically heterogeneous, had modest surface temperatures and were dominated by members of the metabolically diverse phylum Proteobacteria,” Newell says.

In contrast, the back-arc hot springs were more geochemically homogenous, had hotter water, exhibited high concentrations of dissolved metals and gases, and were home to heat-loving archaeal and bacterial organisms.

“These results tell us tectonics matter when it comes microbial community make-up, but little research has been conducted around the world to demonstrate this,” Newell says.

Further investigation, with efficient genomic research, at sites around the globe could reveal how microbes have evolved in tectonically diverse environments, he says.

Bubble, bubble, more earthquake trouble? Geoscientists study Alaska's Denali fault


Utah State University, University of Alaska Fairbanks researchers investigate fault system's mantle-to-crust connections

Peer-Reviewed Publication

UTAH STATE UNIVERSITY

Collecting Sample from Spring along Cantwell Segment of Alaska's Denali Fault 

IMAGE: UTAH STATE UNIVERSITY GEOCHEMIST DENNIS NEWELL COLLECTS DATA FROM A SPRING ALONG THE CANTWELL SEGMENT OF ALASKA’S DENALI FAULT. HE AND COLLEAGUES PUBLISHED FINDINGS IN THE JOURNAL ‘GEOLOGY,’ CITING EVIDENCE OF MANTLE-TO-CRUST CONNECTIONS THAT INCREASE THE POSSIBILITY OF A FUTURE MAJOR EARTHQUAKE. view more 

CREDIT: JEFF BENOWITZ




LOGAN, UTAH, USA -- The 1,200-mile-long Denali Fault stretches in an upward arc from southwestern Alaska and the Bering Sea eastward to western Canada’s Yukon Territory and British Columbia. The long-lived and active strike-slip fault system, which slices through Denali National Park and Preserve, is responsible for the formation of the Alaska Range.

“It’s a big, sweeping fault and the source of a magnitude 7.9 earthquake in 2002, that ruptured more than 200 miles of the Denali Fault, along with the Totschunda Fault to the east, causing significant damage to remote villages and central Alaska’s infrastructure,” says Utah State University geochemist Dennis Newell.

Understanding the restless fault’s mantle-to-crust connections provides critical information for understanding the lithospheric-scale fault’s seismic cycle, says Newell, associate professor in USU’s Department of Geosciences. He and colleagues Jeff Benowitz, an Alaska-based geochronologist, Sean Regan of the University of Alaska Fairbanks, and doctoral candidate Coleman Hiett of USU, collected and analyzed helium and carbon isotopic data from springs along a nearly 250-mile segment of the fault and published their findings, “Roadblocks and Speed Limits: Mantle-to-Surface Volatile Flux in the Lithospheric Scale Denali Fault, Alaska,” in the June 1, 2023 print issue of the journal Geology.

The research was funded by a one-year National Science Foundation Early-Concept Grant for Exploratory Research (EAGER) awarded to Newell and Regan in 2020.

“Active strike-slip faults like Denali have three-dimensional geometries with possible deep conduit connections below the Earth’s surface,” Newell says. “But we don’t know much about how and if these connections are maintained.”

To examine these possible deep connections, Newell and Regan sampled 12 springs along the Denali and Totschunda Faults, by way of helicopter and on foot, to the remote, mountainous regions of Alaska’s interior.

“Helium-3, a rare isotope of helium gas, in springs is a good indicator of whether or not an area has a connection to the Earth’s mantle,” Newell says. “Warm, bubbling springs west of the 2002 earthquake rupture, along the Cantwell segment of the Denali Fault, have a strong helium-3 signature, indicating intact connections to the mantle. In contrast, springs along the ruptured fault segment only have atmospheric gases, suggesting a ‘roadblock’ preventing the flow of mantle helium to the surface.”

These observations, he says, have implications for how groundwater pathways along the fault are changed by earthquakes, and the timescales on which they heal.

“The last major earthquake on the Cantwell segment was 400 years ago, and the helium data suggest those mantel connections have been reestablished,” Newell says. “These bubbling springs are indicative of the possibility of a future large destructive earthquake along the Denali Fault segment near Denali National Park, which receives some 600,000 visitors each summer.”

The geoscientists also seek data on how fast helium can move from the mantle to the crust along active faults.

“That’s the ‘speed limit’ part of our research,” Newell says. “This is important as it reveals mantle-to-surface volatile flux and how fluid pressure gradients may impact fault strength and seismicity along the fault.”

The fault’s mantle fluid flow rates fall in the range observed for the world’s other major and active strike-slip faults that form plate boundaries, he says, including California’s San Andreas Fault and Turkey’s North Anatolian Fault Zone. These types of faults host large, devastating earthquakes, such as February 2023’s deadly earthquake on the East Anatolia Fault, which caused widespread destruction in Turkey and Syria.

“Quantifying crust-to-mantle connections along major strike-slip faults is critical for understanding linkages between deep fluid flow, seismicity and fault healing,” Newell says.

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