May 20, 2021

Axios Science

Thanks for reading Axios Science. This week we look at the search for the start of plate tectonics, zombie wildfires, a spiral galaxy from the beginning of the universe and more — in 1,378 words, about a 5-minute read.

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1 big thing: The hunt for Earth's earliest movements

Illustration: Aïda Amer/Axios

At some point in Earth's history, the planet's crust began to move, eventually giving rise to continents, mountains and volcanoes and supplying the surface with life-sustaining nutrients and elements. New research points to that movement starting in at least some places more than 3 billion years ago.

Why it matters: Earth is the only planet known so far to show plate tectonics. One of the biggest questions in geoscience is when and how tectonic activity began and changed, and answers could also guide the search for signs of similar processes — and potentially life — on far-away worlds.

  • Estimates of the onset of plate tectonics range from 800 million to more than 4 billion years ago, but recent evidence is converging on that movement being underway globally around 3 billion years ago.

How it works: Our planet began an estimated 4.5 billion years ago as a ball of liquid metal and rock coalescing in the early solar system — what geologist Michael Ackerson of the Smithsonian National Museum of Natural History calls “gooey Earth.”

  • The planet then started cooling and, as it did, plates formed on the outermost layer that, at some point — possibly in fits and starts and here and there — began to move under one another.
  • That subduction process operates like a "conveyor belt," recycling and exchanging material and volatile chemicals between the surface of Earth and deep within it, says Ann Bauer, a geochemist at the University of Wisconsin-Madison.

The big picture: What constitutes plate tectonics and its onset is an open debate among scientists. Earth's modern plate tectonics is characterized by how much large blocks move each year, subduction occurring and mid-ocean spreading that creates new crust.

  • "They occur in unison on the modern Earth, but that doesn’t mean they started together or that they always occurred together," Harvard University geologist Roger Fu tells Axios in an email.
  • "There is no doubt there are some geochemical indicators of subduction" in the Archean eon spanning 4 billion to 2.5 billion years ago, says Michael Brown, a geologist at the University of Maryland. But the key question is what that means for when and how plate-like behavior became stable, continuous and propagated across the globe.

Background: Minerals like zircon that crystallize in ancient magma can contain tiny quantities of elements that serve as clues about the chemistry — and indirectly the geology — that formed them.

What's new: In a study of zircons from the Jack Hills of Western Australia — some of which, at 4.3 billion years old, are the oldest known material on Earth — Ackerson and his colleagues found an increase in aluminum in the minerals about 3.6 billion years ago.

  • The two possible ways aluminum got into the zircons "both require some process akin to plate tectonics," Ackerson says.

Another study of zircons from the Acasta Gneiss in northern Canada, led by Bauer and geologist Jesse Reimink of Penn State University, also suggested some kind of crustal motion formed the minerals between 3.6 billion and 3.8 billion years ago based on a shift in the ratios of isotopes of hafnium in the zircons during that time.

Yes, but: Just because these geochemical shifts can and typically do occur due to plate tectonics today "does not conclusively show that these conditions must have existed on the early Earth at the times they discuss," Fu says.

  • But, he adds, "something significant did seem to happen on the Earth at around that time" and evolution toward plate tectonics is "one clear possibility."

Go deeper.

2. Catch up quick on COVID-19
Expand chart
Data: CSSE Johns Hopkins University; Map: Andrew Witherspoon/Axios

"Coronavirus infections continue to plummet across the U.S. with new cases falling by 20% compared to last week," Axios' Sam Baker and Andrew Witherspoon write.

Dogs detected the presence of SARS-CoV-2 in people with 97% accuracy in a trial in France, per The Guardian's Jon Henley.

Preliminary results found an immune benefit from vaccinating people with two different COVID-19 vaccines (Oxford-AstraZeneca and Pfizer-BioNTech) for the first and second dose, Ewen Callaway reports for Nature.

"The first Americans to be vaccinated against the coronavirus could require a third 'booster' shot as early as September," the CEOs of Pfizer and Moderna told Axios' Caitlin Owens. But experts caution it is not proven if or when boosters will be needed.

3. "Zombie fires" set to increase as climate warms

A wildfire near the village of Vinzili, Russia, on May 18. Photo: Maxim Slutsky\TASS via Getty Images

"Zombie fires" may sound like something straight out of science fiction, but they're a real phenomenon that is likely to become more common in the area ringing the Arctic, and possibly the Arctic itself, as climate change continues, Axios' Andrew Freedman reports.

Why it matters: A new study, published in the journal Nature, provides conclusive evidence that zombie or "holdover fires" exist and can be monitored, and it helps to begin to quantify their impact on global climate change.

Context: Zombie fires are blazes that ignite and burn in one season and then smolder through the winter by slowly combusting within peat and other soils, emitting smoke but little or no flames. Then they reemerge during the next spring, erupting into flames once again.

  • Peat is damp soil that contains decaying plant material, and when burned, it can release large amounts of global warming pollutants.
  • Numerous zombie fires were reported in Siberia last summer, which featured a particularly severe fire season, and such fires were also anecdotally reported during the summer of 2019, Merritt Turetsky, a University of Colorado professor who studies peat and wildfires, tells Axios. (Turetsky was not involved in the new study.)

What they found: Between 2002 and 2018, zombie fires caused about 1% of the total burned area in the study regions. However, this varied considerably — in some years, such blazes accounted for nearly 40% of the total burned area.

  • Zombie fires in Alaska and the Northwest Territories emitted 3.5 million metric tons of carbon in that time. The majority of these emissions occurred in just two fire seasons: 2015 and 2010.
  • The carbon emissions from zombie fires comprise a relatively small amount (0.5%) of the total carbon emissions from fires in Alaska and the Northwest Territories. "Yet this fraction may grow larger with climate warming," the study states.

Read the entire story.

4. Worthy of your time

Photo illustration: Annelise Capossela/Axios. Photo: QAI Publishing/Universal Images Group via Getty Images

  • Astronomy's future waits on NASA's next big telescope (Miriam Kramer — Axios)
  • An AI has disproved five mathematical conjectures with no human help (Matthew Sparkes — New Scientist)
  • Deadly fungi are the newest emerging microbe threat all over the world (Maryn McKenna — Scientific American)
  • The cardiovascular secrets of giraffes (Bob Holmes — Knowable)

And one for the weekend...

5. Something wondrous

The bright center of the spiral galaxy, with arms stretching out from it. Photo: ALMA/ESO/NAOJ/NRAO, T. Tsukui & S. Iguchi

A spiral galaxy similar in shape to our Milky Way may have formed just 1.4 billion years after the Big Bang, far earlier than these types of galaxies were expected to emerge, Axios' Miriam Kramer writes.

Why it matters: Understanding how galaxies formed and evolved into what we see now is one of the enduring mysteries in astronomy, and this study takes astronomers one step closer toward solving it.

What they found: A new study, published in the journal Science this week, reports a spiral galaxy named BRI 1335-0417 formed less than 1.5 billion years after the Big Bang.

  • The galaxy appears to have arms stretching from a supermassive black hole and possibly a bulge of star formation at its center.
  • "These results may indicate that spiral structures have formed in a very short period of time after the disk formation, providing important circumstantial evidence to identify the formation process of these galactic structures," Takafumi Tsukui, an author of the new study, told Axios via email.
  • The authors of the study suggest the galaxy could owe its look to an interaction with a smaller galaxy (or galaxies) that may have destabilized gas in the outer part of the galaxy and triggered star formation.

The big picture: If these results are confirmed, it shows these complex, mature galaxies were coalescing before the peak in star formation in the early universe, when galaxies were thought to be building up their mass.

  • Earlier studies suggested that just after the Big Bang, the universe was populated by "protogalaxies" that were a collection of gas and dust that eventually gave rise, after billions of years, to the elliptical and spiral galaxies we see today.
  • The new study suggests that perhaps the universe started to settle down earlier than expected.

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