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Powerful supernova could explain extinctions at the end of the Devonian period

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Aug. 18 (UPI) — New research suggests harmful cosmic rays from a nearby supernova might have caused the extinction events that form the boundary between the Devonian-Carboniferous periods.

Around 360 million years ago, a lengthy period of biodiversity declines culminated in a series of extinction events that saw 19 percent of all families and 50 percent of all genera disappear.

Scientists have previously unearthed a diversity of Late Devonian plant spores that show evidence of being burnt by ultraviolet light, signs of a prolonged ozone-depletion event.

“Earth-based catastrophes such as large-scale volcanism and global warming can destroy the ozone layer, too, but evidence for those is inconclusive for the time interval in question,” lead researcher Brian Fields said in a news release.

“Instead, we propose that one or more supernova explosions, about 65 light-years away from Earth, could have been responsible for the protracted loss of ozone,” said Fields, professor of astronomy and physics at the University of Illinois, Urbana-Champaign.

Today, the closest supernova threat is the star Betelgeuse, located 600 light-years away. Scientists estimate a supernova would have to occur within 25 light-years to present a significant threat to life on Earth.

Millions of years ago, however, a variety of closer stars may have presented a graver threat, researchers contend.

Scientists determined that other cosmic threats, like a gamma-ray burst, solar eruption or meteorite explosion, are too short-lived to account for Devonian-Carboniferous extinctions. Some researchers estimate consisted of a half-dozen different events spread out over thousands, even millions, of years.

According to the new study, published Tuesday in the journal PNAS, a supernova could have delivered a one-two punch of electromagnetic energy.

After an initial blast of UV, X-rays and gamma rays, a barrage of supernova debris can sustain a constant supply of irradiation. The effects of a single supernova, scientists estimated, could affect Earth for up 100,000 years.

The researchers suggest a series of supernovas might have poisoned Earth with ultraviolet rays for a few hundred thousands years.

“This is entirely possible,” said grad student Jesse Miller. “Massive stars usually occur in clusters with other massive stars, and other supernovae are likely to occur soon after the first explosion.”

Currently, the possibility that supernova radiation triggered the Devonian-Carboniferous extinctions is only a theory. But researchers claim it’s a theory that could be confirmed by the discovery of radioactive isotopes plutonium-244 and samarium-146 in rocks from the period.

“When you see green bananas in Illinois, you know they are fresh, and you know they did not grow here. Like bananas, Pu-244 and Sm-146 decay over time,” Fields said. “So if we find these radioisotopes on Earth today, we know they are fresh and not from here — the green bananas of the isotope world — and thus the smoking guns of a nearby supernova.”

Fields and his colleagues are currently working out what Pu-244 or Sm-146 isotope concentrations might look like in Devonian-Carboniferous era rocks, so that scientists will know what to look for if and when they go prospecting.

“The overarching message of our study is that life on Earth does not exist in isolation,” Fields said. “We are citizens of a larger cosmos, and the cosmos intervenes in our lives — often imperceptibly, but sometimes ferociously.”



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Ryugu’s rubble suggests its short life has been rather turbulent

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Sept. 21 (UPI) — The asteroid Ryugu is a loose assemblage of fragments from a collision between two asteroids, according to new research published Monday in the journal Nature Astronomy.

Some asteroids are composed of large, solid pieces of rock, but Ryugu is more like a rubble pile than a rock. It is too small and fragile to have remained intact for very long — scientists estimate Ryugu formed between 10 million to 20 million years ago.

“Ryugu is too small to have survived the whole 4.6 billion years of solar system history,” Seiji Sugita, professor of planetary sciences at the University of Tokyo in Japan, said in a news release. “Ryugu-sized objects would be disrupted by other asteroids within several hundred million years on average.”

“We think Ryugu spent most of its life as part of a larger, more solid parent body,” Sugita said. “This is based on observations by Hayabusa-2 which show Ryugu is very loose and porous. Such bodies are likely formed from reaccumulations of collision debris.”

For the latest study, scientists used images collected by Hayabusa-2 to identify the different types of rock on Ryugu. Researchers were able to uncover clues to the asteroid’s violent past by analyzing the ratios of different rock types.

“Ryugu is considered a C-type, or carbonaceous, asteroid, meaning it’s primarily composed of rock that contains a lot of carbon and water,” said postdoctoral researcher Eri Tatsumi. “As expected, most of the surface boulders are also C-type; however, there are a large number of S-type, or siliceous, rocks as well. These are silicate-rich, lack water-rich minerals and are more often found in the inner, rather than outer, solar system.”

The presence of siliceous rocks suggests Ryugu was formed from the rubble created by a collision between between a small S-type asteroid and a larger C-type asteroid.

“We used the optical navigation camera on Hayabusa2 to observe Ryugu’s surface in different wavelengths of light, and this is how we discovered the variation in rock types. Among the bright boulders, C and S types have different albedos, or reflective properties,” said Tatsumi.

Once Hayabusa-2 returns rock samples to Earth, scientists plan to compare the asteroids geochemical composition to meteorites samples found on Earth.

“This could in turn tell us something new about the history of Earth and the solar system as a whole,” Tatsumi said.



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Study highlights carbon sequestration services provided by U.S. forests

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Sept. 21 (UPI) — Forests in the United States currently sequester approximately three decades worth of carbon dioxide emitted by the American fossil fuel industry, according to a new a study.

What’s more, forests and harvested wood products uptake approximately 14 percent of economy-wide CO2 emissions in the United States annually.

Despite declining carbon emissions in the United States, the contribution of forests to emissions offsets has remained stable. This, researchers say, suggests the ability of U.S. forests to absorb new carbon — an ability driven largely by forest regrowth — is slowly declining.

To better understand the ability of afforestation and reforestation activities to improve carbon sequestration capabilities, researchers analyzed data from more than 130,000 national forest inventory plots.

The findings — published Monday in the journal Proceedings of the National Academy of Sciences — confirmed that there is potential for U.S. forests to capture and store more carbon.

Researchers used forest inventory plots to estimate the total carbon storage capabilities provided by forests in the United States. Their analysis showed each acre of forest in the United States stores nearly 700 metric tons of CO2. But the data also showed forests are underperforming.

“There are opportunities on existing forestland to increase the contribution of forests to climate change mitigation,” researchers wrote in their paper.

Researchers found nearly 82 million acres of productive forestland in the U.S. are understocked with trees, characterized by tree coverage of less than 35 percent.

“Currently, there is federal infrastructure to produce and plant approximately 65 million seedlings per year, and state and private capacity is approximately 1.1 billion tree seedlings per year,” researchers wrote.

These efforts sequester between 16 and 28 million metric tons of CO2 annually.

According to the study’s authors, concentrating tree-planting efforts on understocked forest acreage could significantly increase carbon sequestration capacity in the United States.



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Bobcat fire threatens historic Mount Wilson Observatory

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Sept. 21 (UPI) — Days after officials declared the historic Mount Wilson Observatory in Los Angeles County safe from an aggressive fast-moving blaze, firefighters on Monday were attempting to beat back the Bobcat fire as it attempted to work its way up the mountain.

The Angeles National Forest said Sunday that the fire, which has grown to be one of the largest in the county’s history, was “threatening all of the values” on Mount Wilson. Officials had said Friday said it was safe after crews deployed strategic firing to protect the iconic observatory in the San Gabriel Mountains.

Strong winds and low humidity overnight helped the blaze to grow a few thousand acres to 105,345 acres as of 8 a.m. Monday, the Angeles National Forest said in a statement. It was 15% contained.

Engines, hand crews and aircraft on Monday were deployed to the north side of Mount Wilson to extinguish spot fires, the service said.

“Bobcat fire is making a hard push at Mount Wilson,” the Angeles National Forest said on Twitter. “Defensive strategic operations are beginning from Mount Wilson to the west.”

Thomas Meneghi, the observatory’s executive director, told the Los Angeles Times, that on Sunday eight additional strike units were seen being dispatched to the area after it was deemed safe two days prior.

“Just when I thought the danger was over — it wasn’t,” he said.

The observatory said on its Facebook Page Monday evening that the fire has picked up and is making its way toward the Mount Wilson drainage on the northwestern slope.

The Times reported that it’s the second time the observatory, historic for its role in space exploration, has been under threat of fire with crews protecting it from the Station fire of 2009, which holds the title for the county’s largest blaze at some 160,000 acres.

Due to the Bobcat fire encroaching on communities, the Los Angeles County Sheriff’s Office issued evacuations orders Monday for those who live in south and west of Upper Big Tujunga and east and north of Angeles Forest Highway, while the Los Angeles County Office of Emergency Management ordered residents of Camp Colby to leave the area immediately.

“This warning has been upgraded to an evacuation ordered,” the service announced via Twitter. “If you are in the identified area GO NOW! EVACUATE.”

Los Angeles County Fire Chief Daryl Osby told reporters and residents during a virtual press conference Monday evening that firefighters “scratch and claw” to protect every property they can.

Osby said this year has been a record fire season for California, with thousands of firefighters battling some 27 blazes, but added “the scary thing about all this” is that the fire season for Southern California wasn’t near finished.

Cal Fire said more than 3.6 million acres have been burned in nearly 8,000 fires, resulting in 7,097 structures impacted and at least 26 deaths.

Gov. Gavin Newsom called the wildfire season “historic” in a press conference on Monday, stating that last year, there were only 5,316 fires burning some 157,000 acres.

The Democratic governor said evictions have forced 23,154 people from their homes, adding that more than 6,400 structures have been wholly destroyed.

Six major fires continue to burn in the state, he said, including the August fire, the largest in the state’s history at 846,000 acres, which was at 34% contained.

In Plumas and Lassen counties, the North Complex fire, the fifth-largest ever in the state at 294,000 acres was at 64% contained, compared to 36% on Wednesday.

The Creek fire, in Fresno and Madera counties, was the seventh-largest fire in state history, and was at 278,000 acres and contained at 27%.

Concerning the Bobcat fire, he said they were deploying as many resources as possible to battle the blaze.

“We’re putting all the resources we possibly can on all these complexes but focusing, as we should, on that Bobcat fire,” he said.

Nationally, 78 large fires have consumed some 3.9 million acres this season, according to the national interagency Fire Center.

In Oregon, the Department of Forestry said some 7,500 personnel have been assigned to 10 major fires in the state.

The state’s Office of Emergency Management has confirmed nine people have died in the fires and five people were missing as of Monday.

Some 1 million acres have been burned statewide, destroying 2,268 residences and an additional 1,556 instructions, it said in a statement.

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