Month: February 2019

The ‘Stuff’ of the Universe Keeps Changing

The composition of the universe – the elements that are the building blocks for every bit of matter – is ever-changing and ever-evolving, thanks to the lives and deaths of stars.

An outline of how those elements form as stars grow and explode and fade and merge is detailed in a review article published Jan. 31 is the journal Science.

“The universe went through some very interesting changes, where all of a sudden the periodic table – the total number of elements in the universe – changed a lot,” said Jennifer Johnson, a professor of astronomy at The Ohio State University and the article’s author.

“For 100 million years after the Big Bang, there was nothing but hydrogen, helium and lithium. And then we started to get carbon and oxygen and really important things. And now, we’re kind of in the glory days of populating the periodic table.”

The periodic table has helped humans understand the elements of the universe since the 1860s, when a Russian chemist, Dmitri Mendeleev, recognized that certain elements behaved the same way chemically, and organized them into a chart – the periodic table.

It is chemistry’s way of organizing elements, helping scientists from elementary school to the world’s best laboratories understand how materials around the universe come together.

But, as scientists have long known, the periodic table is just made of stardust: Most elements on the periodic table, from the lightest hydrogen to heavier elements like lawrencium, started in stars.
The table has grown as new elements have been discovered – or in cases of synthetic elements, have been created in laboratories around the world – but the basics of Mendeleev’s understanding of atomic weight and the building blocks of the universe have held true.

Nucleosynthesis – the process of creating a new element – began with the Big Bang, about 13.7 billion years ago. The lightest elements in the universe, hydrogen and helium, were also the first, results of the Big Bang. But heavier elements – just about every other element on the periodic table – are largely the products of the lives and deaths of stars.

Johnson said that high-mass stars, including some in the constellation Orion, about 1,300 light years from Earth, fuse elements much faster than low-mass stars. These grandiose stars fuse hydrogen and helium into carbon, and turn carbon into magnesium, sodium and neon. High-mass stars die by exploding into supernovae, releasing elements – from oxygen to silicon to selenium – into space around them.

Smaller, low-mass stars – stars about the size of our own Sun – fuse hydrogen and helium together in their cores. That helium then fuses into carbon. When the small star dies, it leaves behind a white dwarf star. White dwarfs synthesize other elements when they merge and explode. An exploding white dwarf might send calcium or iron into the abyss surrounding it. Merging neutron stars might create rhodium or xenon. And because, like humans, stars live and die on different time scales – and because different elements are produced as a star goes through its life and death – the composition of elements in the universe also changes over time.

“One of the things I like most about this is how it takes several different processes for stars to make elements and these processes are interestingly distributed across the periodic table,” Johnson said. “When we think of all the elements in the universe, it is interesting to think about how many stars gave their lives – and not just high-mass stars blowing up into supernovae. It’s also some stars like our Sun, and older stars. It takes a nice little range of stars to give us elements.”

European Waters Drive Ocean Overturning, Key For Regulating Climate

A new international study finds that the Atlantic meridional overturning circulation (MOC), a deep-ocean process that plays a key role in regulating Earth’s climate, is primarily driven by cooling waters west of Europe.

In a departure from the prevailing scientific view, the study shows that most of the overturning and variability is occurring not in the Labrador Sea off Canada, as past modeling studies have suggested, but in regions between Greenland and Scotland. There, warm, salty, shallow waters carried northward from the tropics by currents and wind, sink and convert into colder, fresher, deep waters moving southward through the Irminger and Iceland basins.

Overturning variability in this eastern section of the ocean was seven times greater than in the Labrador Sea, and it accounted for 88 percent of the total variance documented across the entire North Atlantic over the 21-month study period.

These findings, unexpected as they may be, can help scientists better predict what changes might occur to the MOC and what the climate impacts of those changes will be, said Susan Lozier, the Ronie-Rochele Garcia-Johnson Professor of Earth and Ocean Sciences at Duke University’s Nicholas School of the Environment.

“To aid predictions of climate in the years and decades ahead, we need to know where this deep overturning is currently taking place and what is causing it to vary,” said Lozier, who led the international observational study that produced the new data.

“Overturning carries vast amounts of anthropogenic carbon deep into the ocean, helping to slow global warming,” said co-author Penny Holliday of the National Oceanography Center in Southampton, U.K. “The largest reservoir of this anthropogenic carbon is in the North Atlantic.”

“Overturning also transports tropical heat northward,” Holliday said, “meaning any changes to it could have an impact on glaciers and Arctic sea ice. Understanding what is happening, and what may happen in the years to come, is vital.”

Scientists from 16 research institutions from seven countries collaborated on the new study. They published their peer-reviewed findings Feb. 1 in Science.

“I cannot say enough about the importance of this international collaboration to the success of this project,” Lozier said. “Measuring the circulation in the subpolar North Atlantic is incredibly challenging so we definitely needed an ‘all hands on deck’ approach.”

This paper is the first from the $32 million, five-year initial phase of the OSNAP (Overturning in the Subpolar North Atlantic Program) research project, in which scientists have deployed moored instruments and sub-surface floats across the North Atlantic to measure the ocean’s overturning circulation and shed light on the factors that cause it to vary. Lozier is lead investigator of the project, which began in 2014.

“As scientists, it is exciting to learn that there are more pieces to the overturning puzzle than we first thought,” said co-author Johannes Karstensen of the GEOMAR Helmholtz Centre for Ocean Research Kiel, in Germany.

“Though the overturning in the Labrador Sea is smaller than we expected, we have learned that this basin plays a large role in transporting freshwater from the Arctic,” Karstensen said. “Continued measurements in that basin will be increasingly important,” as the Arctic changes unexpectedly.

The new paper contains data collected over a 21-month period from August 2014 to April 2016.

Mudslides, Floods, Rain, Howling Winds, 10 Feet Of Snow: California Braces For Powerful, Dangerous Storm

With the polar vortex in full retreat, the USA’s wildest weather shifts to the West.

The dangerous cold and heavy snow that hobbled the northern U.S. this week wreaked plenty of havoc – with estimates as high as 24 dead – but a new form of deadly weather could be on the way. A powerful, dangerous rainstorm is forecast to batter the western United States over the next couple of days, especially California.

Heavy rain could trigger mudslides, rockslides and floods, while feet of snow will bury the mountains, the National Weather Service warned.

Forecasters say rain will arrive in the north late Friday afternoon and reach southern California late in the night, and last through Saturday night. A flash flood watch was in effect for millions of people in the Los Angeles area, where as much as a half-foot of rain could fall.

Flash flooding and debris flows will be a concern particularly near burn scar areas. “Southern California residents, in or below the recently burned areas, are urged to take the steps necessary to protect their property,” the weather service said.

“If you are in Southern California & live near a recent wildfire burn scar, take the incoming storm extremely seriously,” tweeted UCLA climate scientist Daniel Swain.

As the storm approaches, the biggest priority will be to keep people out of harm’s way, said Craig Sap, district superintendent of California State Parks. People may see a fire coming, but a debris flows gives little or no warning, he said. “If a hillside lets loose, there’s nothing you can do.”

The weather service in Los Angeles warned that “in addition to the heavy rain potential with this storm, the very strong southerly winds could be an equally concerning impact with this storm system.” The storm “could bring one of the strongest south-southeast wind events we have seen in recent years.”

The strong winds can bring down trees and cause power outages.

Up to 10 feet of snow could fall in the Sierra Nevada, where “travel is highly discouraged.” Winter storm warnings were in effect for hundreds of miles of mountainous regions of California, all the way from the Oregon border to north of Los Angeles.

“While the snow will be a further boost in the snowpack and add to the tremendous bases of snow at the ski resorts, it will lead to major travel disruptions,” AccuWeather meteorologist Bernie Rayno said.

Ancient Asteroid Impacts Played A Role In Creation Of Earth’s Future Continents

The heavy bombardment of terrestrial planets by asteroids from space has contributed to the formation of the early evolved crust on Earth that later gave rise to continents — home to human civilisation.

More than 3.8 billion years ago, in a time period called the Hadean eon, our planet Earth was constantly bombarded by asteroids, which caused the large-scale melting of its surface rocks. Most of these surface rocks were basalts, and the asteroid impacts produced large pools of superheated impact melt of such composition. These basaltic pools were tens of kilometres thick, and thousands of kilometres in diameter.

“If you want to get an idea of what the surface of Earth looked like at that time, you can just look at the surface of the Moon which is covered by a vast amount of large impact craters,” says Professor Rais Latypov from the School of Geosciences of the University of the Witwatersrand in South Africa.

The subsequent fate of these ancient, giant melt sheet remains, however, highly debatable. It has been argued that, on cooling, they may have crystallized back into magmatic bodies of the same, broadly basaltic composition. In this scenario, asteroid impacts are supposed to play no role in the formation of the Earth’s early evolved crust.

An alternative model suggests that these sheets may undergo large-scale chemical change to produce layered magmatic intrusions, such as the Bushveld Complex in South Africa. In this scenario, asteroid impacts may have played an important role in producing various igneous rocks in the early Earth’s crust and therefore they may have contributed to its chemical evolution.

There is no direct way to rigorously test these two competing scenarios because the ancient Hadean impact melts have been later obliterated by plate tectonics. However, by studying the younger impact melt sheet of the Sudbury Igneous Complex (SIC) in Canada, Latypov and his research team have inferred that ancient asteroid impacts were capable of producing various rock types from the earlier Earth’s basaltic crust. Most importantly, these impacts may have made the crust compositionally more evolved, i.e. silica-rich in composition. Their research has been published in a paper in Nature Communications.

The SIC is the largest, best exposed and accessible asteroid impact melt sheet on Earth, which has resulted from a large asteroid impact 1.85 billion years ago. This impact produced a superheated melt sheet of up to 5 km thick. The SIC now shows a remarkable magmatic stratigraphy, with various layers of igneous rocks.

“Our field and geochemical observations — especially the discovery of large discrete bodies of melanorites throughout the entire stratigraphy of the SIC — allowed us to reassess current models for the formation of the SIC and firmly conclude that its conspicuous magmatic stratigraphy is the result of large-scale fractional crystallization,” says Latypov.

“An important implication is that more ancient and primitive Hadean impact melt sheets on the early Earth and other terrestrial planets would also have undergone near-surface, large-volume differentiation to produce compositionally stratified bodies. The detachment of dense primitive layers from these bodies and their sinking into the mantle would leave behind substantial volumes of evolved rocks (buoyant crustal blocks) in the Hadean crust. This would make the crust compositionally layered and increasingly more evolved from its base towards the Earth’s surface.”

“These impacts made the crust compositionally more evolved — in other words, silica-rich in composition,” says Latypov. “Traditionally, researchers believe that such silica-rich evolved rocks — which are essentially building buoyant blocks of our continents — can only be generated deep in the Earth, but we now argue that such blocks can be produced at new-surface conditions within impact melt pools.”

6.6 Quake Hits Mexico; No Reports Of Deaths Or Serious Injuries

MEXICO CITY — A strong earthquake jolted southern Mexico on Friday, rattling nerves and swaying tall buildings hundreds of miles away in the capital, but there were no reports of serious damage, injuries or deaths.

 

The U.S. Geological Survey reported that the quake had a magnitude of 6.6. It was centered about 10 miles from the city of Tapachula in Chiapas state and struck at a depth of 40 miles.

Chiapas civil defense official Arturo Barrientos told The Associated Press that there were no reports of serious damage and authorities were monitoring the situation.

Barrientos said cracks appeared in a wall at an elementary school in the state capital, Tuxtla Gutierrez, but the children were evacuated safely.

“It was felt pretty strongly, but everything is normal. We went out into the street, and that was it,” Enrique Vidal, a lawyer who lives in Tapachula said via text message. “Those with children in schools went to look for them since there are buildings that are still damaged from 2017.”

The same region was rocked in September 2017 by a magnitude 8.1 earthquake that killed nearly 100 people and damaged thousands of buildings. A more damaging 7.1 quake in central Mexico later that month left more than 400 dead, including at least 228 in Mexico City.

“Fortunately there is no loss of human lives nor injuries that require hospitalization,” Luis Manuel Garcia, Chiapas’ civil defense secretary, told Foro TV. “Only nervousness.”

Friday’s quake was also felt in nearby Guatemala and farther away in El Salvador.

In Guatemala, the Red Cross reported some mud and rockslides along roads, and a bridge in the city of Quetzaltenango had some minor damage.

Along a central boulevard in Mexico City, which lies on lakebed soil that amplifies the effects of even faraway quakes, seismic alarms did not go off but some office workers briefly evacuated buildings.