Mysterious Deep-Earth Seismic Signature Explained

New research on oxygen and iron chemistry under the extreme conditions found deep inside Earth could explain a longstanding seismic mystery called ultralow velocity zones. Published in Nature, the findings could have far-reaching implications on our understanding of Earth’s geologic history, including life-altering events such as the Great Oxygenation Event, which occurred 2.4 billion years ago.

Sitting at the boundary between the lower mantle and the core, 1,800 miles beneath Earth’s surface, ultralow velocity zones (UVZ) are known to scientists because of their unusual seismic signatures. Although this region is far too deep for researchers to ever observe directly, instruments that can measure the propagation of seismic waves caused by earthquakes allow them to visualize changes in Earth’s interior structure; similar to how ultrasound measurements let medical professionals look inside of our bodies.

These seismic measurements enabled scientists to visualize these ultralow velocity zones in some regions along the core-mantle boundary, by observing the slowing down of seismic waves passing through them. But knowing UVZs exist didn’t explain what caused them.

However, recent findings about iron and oxygen chemistry under deep-Earth conditions provide an answer to this longstanding mystery.

It turns out that water contained in some minerals that get pulled down into Earth due to plate tectonic activity could, under extreme pressures and temperatures, split up — liberating hydrogen and enabling the residual oxygen to combine with iron metal from the core to create a novel high-pressure mineral, iron peroxide.

Led by Carnegie’s Ho-kwang “Dave” Mao, the research team believes that as much as 300 million tons of water could be carried down into Earth’s interior every year and generate deep, massive reservoirs of iron dioxide, which could be the source of the ultralow velocity zones that slow down seismic waves at the core-mantle boundary.

To test this idea, the team used sophisticated tools at Argonne National Laboratory to examine the propagation of seismic waves through samples of iron peroxide that were created under deep-Earth-mimicking pressure and temperature conditions employing a laser-heated diamond anvil cell. They found that a mixture of normal mantle rock with 40 to 50 percent iron peroxide had the same seismic signature as the enigmatic ultralow velocity zones.

For the research team, one of the most-exciting aspects of this finding is the potential of a reservoir of oxygen deep in the planet’s interior, which if periodically released to Earth’s surface could significantly alter Earth’s early atmosphere, potentially explaining the dramatic increase in atmospheric oxygen that occurred about 2.4 billion years ago according to the geologic record.

“Finding the existence of a giant internal oxygen reservoir has many far-reaching implications,” Mao explained. “Now we should reconsider the consequences of sporadic oxygen outbursts and their correlations to other major events in Earth’s history, such as the banded-iron formation, snowball Earth, mass extinctions, flood basalts, and supercontinent rifts.”

Lightning, With A Chance Of Antimatter

In a collaborative study appearing in Nature, researchers from Japan describe how gamma rays from lightning react with the air to produce radioisotopes and even positrons — the antimatter equivalent of electrons.

“We already knew that thunderclouds and lightning emit gamma rays, and hypothesized that they would react in some way with the nuclei of environmental elements in the atmosphere,” explains Teruaki Enoto from Kyoto University, who leads the project.

“In winter, Japan’s western coastal area is ideal for observing powerful lightning and thunderstorms. So, in 2015 we started building a series of small gamma-ray detectors, and placed them in various locations along the coast.”

But then the team ran into funding problems. To continue their work, and in part to reach out to a wide audience of potentially interested members of the public as quickly as possible, they turned to the internet.

“We set up a crowdfunding campaign through the ‘academist’ site,” continues Enoto, “in which we explained our scientific method and aims for the project. Thanks to everybody’s support, we were able to make far more than our original funding goal.”

Spurred by their success, the team built more detectors and installed them across the northwest coast of Honshu. And then in February 2017, four detectors installed in Kashiwazaki city, Niigata recorded a large gamma-ray spike immediately after a lightning strike a few hundred meters away.

It was the moment the team realized they were seeing a new, hidden face of lightning.

When they analyzed the data, the scientists found three distinct gamma-ray bursts. The first was less than one millisecond in duration; the second was a gamma-ray afterglow that decayed over several dozens of milliseconds; and finally there was a prolonged emission lasting about one minute.

Enoto explains, “We could tell that the first burst was from the lightning strike. Through our analysis and calculations, we eventually determined the origins of the second and third emissions as well.”

The second afterglow, for example, was caused by lightning reacting with nitrogen in the atmosphere. The gamma rays emitted in lightning have enough energy to knock a neutron out of atmospheric nitrogen, and it was the reabsorption of this neutron by particles in the atmosphere that produced the gamma-ray afterglow.

The final, prolonged emission was from the breakdown of now neutron-poor and unstable nitrogen atoms. These released positrons, which subsequently collided with electrons in annihilation events releasing gamma rays.

“We have this idea that antimatter is something that only exists in science fiction. Who knew that it could be passing right above our heads on a stormy day?” says Enoto.

“And we know all this thanks to our supporters who joined us through ‘academist’. We are truly grateful to all.”

The team still maintains over ten detectors on the coast of Japan, and are continually collecting data. They look forward to new discoveries that may await them, and Enoto hopes to continue seeing the participation of ordinary citizens in research, expanding the bounds of scientific discovery.

First Interstellar Asteroid Is Like Nothing Seen Before

On Oct. 19, 2017, the Pan-STARRS 1 telescope in Hawai`i picked up a faint point of light moving across the sky. It initially looked like a typical fast-moving small asteroid, but additional observations over the next couple of days allowed its orbit to be computed fairly accurately. The orbit calculations revealed beyond any doubt that this body did not originate from inside the Solar System, like all other asteroids or comets ever observed, but instead had come from interstellar space. Although originally classified as a comet, observations from ESO and elsewhere revealed no signs of cometary activity after it passed closest to the Sun in September 2017. The object was reclassified as an interstellar asteroid and named 1I/2017 U1 .

“We had to act quickly,” explains team member Olivier Hainaut from ESO in Garching, Germany. “`Oumuamua had already passed its closest point to the Sun and was heading back into interstellar space.”

ESO’s Very Large Telescope was immediately called into action to measure the object’s orbit, brightness and colour more accurately than smaller telescopes could achieve. Speed was vital as `Oumuamua was rapidly fading as it headed away from the Sun and past the Earth’s orbit, on its way out of the Solar System. There were more surprises to come.

Combining the images from the FORS instrument on the VLT using four different filters with those of other large telescopes, the team of astronomers led by Karen Meech (Institute for Astronomy, Hawai`i, USA) found that `Oumuamua varies dramatically in brightness by a factor of ten as it spins on its axis every 7.3 hours.

Karen Meech explains the significance: “This unusually large variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape. We also found that it has a dark red colour, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it.”

These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

Preliminary orbital calculations suggested that the object had come from the approximate direction of the bright star Vega, in the northern constellation of Lyra. However, even travelling at a breakneck speed of about 95,000 kilometres/hour, it took so long for the interstellar object to make the journey to our Solar System that Vega was not near that position when the asteroid was there about 300,000 years ago. `Oumuamua may well have been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with the Solar System.

Astronomers estimate that an interstellar asteroid similar to `Oumuamua passes through the inner Solar System about once per year, but they are faint and hard to spot so have been missed until now. It is only recently that survey telescopes, such as Pan-STARRS, are powerful enough to have a chance to discover them.

“We are continuing to observe this unique object,” concludes Olivier Hainaut, “and we hope to more accurately pin down where it came from and where it is going next on its tour of the galaxy. And now that we have found the first interstellar rock, we are getting ready for the next ones!”

Space Dust May Transport Life Between Worlds, Research Suggests

Life on our planet might have originated from biological particles brought to Earth in streams of space dust, a study suggests.

Fast-moving flows of interplanetary dust that continually bombard our planet’s atmosphere could deliver tiny organisms from far-off worlds, or send Earth-based organisms to other planets, according to the research.

The dust streams could collide with biological particles in Earth’s atmosphere with enough energy to knock them into space, a scientist has suggested.

Such an event could enable bacteria and other forms of life to make their way from one planet in the solar system to another and perhaps beyond.

The finding suggests that large asteroid impacts may not be the sole mechanism by which life could transfer between planets, as was previously thought.

The research from the University of Edinburgh calculated how powerful flows of space dust — which can move at up to 70 km a second — could collide with particles in our atmospheric system.

It found that small particles existing at 150 km or higher above Earth’s surface could be knocked beyond the limit of Earth’s gravity by space dust and eventually reach other planets. The same mechanism could enable the exchange of atmospheric particles between distant planets.

Some bacteria, plants and small animals called tardigrades are known to be able to survive in space, so it is possible that such organisms — if present in Earth’s upper atmosphere — might collide with fast-moving space dust and withstand a journey to another planet.

The study, published in Astrobiology, was partly funded by the Science and Technology Facilities Council.

Professor Arjun Berera, from the University of Edinburgh’s School of Physics and Astronomy, who led the study, said: “The proposition that space dust collisions could propel organisms over enormous distances between planets raises some exciting prospects of how life and the atmospheres of planets originated. The streaming of fast space dust is found throughout planetary systems and could be a common factor in proliferating life.”

How The Earth Stops High-Energy Neutrinos In Their Tracks

For the first time, a science experiment has measured Earth’s ability to absorb neutrinos — the smaller-than-an-atom particles that zoom throughout space and through us by the trillions every second at nearly the speed of light. The experiment was achieved with the IceCube detector, an array of 5,160 basketball-sized sensors frozen deep within a cubic kilometer of very clear ice near the South Pole. The results of this experiment by the IceCube collaboration, which includes Penn State physicists, will be published in the online edition of the journal Nature on November 22, 2017.

“This achievement is important because it shows, for the first time, that very-high-energy neutrinos can be absorbed by something — in this case, the Earth,” said Doug Cowen, professor of physics and astronomy & astrophysics at Penn State. The first detections of extremely-high-energy neutrinos were made by IceCube in 2013, but a mystery remained about whether any kind of matter could truly stop a neutrino’s journey through space. “We knew that lower-energy neutrinos pass through just about anything,” Cowen said, “but although we had expected higher-energy neutrinos to be different, no previous experiments had been able to demonstrate convincingly that higher-energy neutrinos could be stopped by anything.”

The results in the Nature paper are based on one year of data from about 10,800 neutrino-related interactions. Cowen and Tyler Anderson, an assistant research professor of physics at Penn State, are members of the IceCube collaboration. They are coauthors of the Nature paper who helped to build the IceCube detector and are contributing to its maintenance and management.

This new discovery with IceCube is an exciting addition to our deepening understanding of how the universe works. It also is a little bit of a disappointment for those who hope for an experiment that will reveal something that cannot be explained by the current Standard Model of Particle Physics. “The results of this Ice Cube study are fully consistent with the Standard Model of Particle Physics — the reigning theory that for the past half century has described all the physical forces in the universe except gravity,” Cowen said.

Neutrinos first were formed at the beginning of the universe, and they continue to be produced by stars throughout space and by nuclear reactors on Earth. “Understanding how neutrinos interact is key to the operation of IceCube,” explained Francis Halzen, principal investigator for the IceCube Neutrino Observatory and a University of Wisconsin-Madison professor of physics. “We were of course hoping for some new physics to appear, but we unfortunately find that the Standard Model, as usual, withstands the test,” Halzen said.

IceCube’s sensors do not directly observe neutrinos, but instead measure flashes of blue light, known as Cherenkov radiation, emitted after a series of interactions involving fast-moving charged particles that are created when neutrinos interact with the ice. By measuring the light patterns from these interactions in or near the detector array, IceCube can estimate the neutrinos’ energies and directions of travel. The scientists found that the neutrinos that had to travel the farthest through Earth were less likely to reach the detector.

Most of the neutrinos selected for this study were more than a million times more energetic than the neutrinos produced by more familiar sources, like the Sun or nuclear power plants. The analysis also included a small number of astrophysical neutrinos, which are produced outside the Earth’s atmosphere, from cosmic accelerators unidentified to date, perhaps associated with supermassive black holes.

“Neutrinos have quite a well-earned reputation of surprising us with their behavior,” says Darren Grant, spokesperson for the IceCube Collaboration, a professor of physics at the University of Alberta in Canada, and a former postdoctoral scholar at Penn State. “It is incredibly exciting to see this first measurement and the potential it holds for future precision tests.”

In addition to providing the first measurement of the Earth’s absorption of neutrinos, the analysis shows that IceCube’s scientific reach extends beyond its core focus on particle physics discoveries and the emerging field of neutrino astronomy into the fields of planetary science and nuclear physics. This analysis also is of interest to geophysicists who would like to use neutrinos to image the Earth’s interior in order to explore the boundary between the Earth’s inner solid core and its liquid outer core.

“IceCube was built to both explore the frontiers of physics and, in doing so, possibly challenge existing perceptions of the nature of universe. This new finding and others yet to come are in that spirt of scientific discovery,” said James Whitmore, program director in the National Science Foundation’s physics division. Physicists now hope to repeat the study using an expanded, multiyear analysis of data from the full 86-string IceCube array, and to look at higher ranges of neutrino energies for any hints of new physics beyond the Standard Model.

Iceland’s Biggest Active Volcano Shows Signs Of Reawakening

Iceland’s biggest active volcano is being kept under close surveillance amid signs it is waking up after centuries of slumber.

A new 1km-wide caldera – a basin-shaped volcanic depression – has been discovered by scientists in Öræfajökull, which translates as “wasteland”, in the south of the island.

The Icelandic Met Office has also received reports of the surrounding area smelling of sulphur, while geothermal water has been released from the volcano into a river on the surrounding glacier, reports Iceland Magazine.

Scientists believe this water caused a section of the volcano to collapse, producing the new caldera.

Although scientists say there are no imminent signs of an eruption, Iceland’s Civil Protection Agency has declared an uncertainty phase – a warning that there may be a threat in the near future – while its Met Office has issued a yellow warning. If you’re planning to take a vacation to Iceland, you might want to keep a close eye on the Iceland weather as well as the Met Office’s updates, just to be on the safe side, being able to watch the eruption first hand would also be quite a spectacle.

Bryndís Ýr Gísladóttir, natural resource specialist at the Met Office, told newspaper Morgunbladid: “We issued a yellow warning for security reasons because we actually don’t know that much about Öræfajökull glacier, nor how it behaves because its last eruption occurred in 1727, and 1362 before that.”

Öræfajökull features Iceland’s highest peak and is thought to be one of the most powerful volcanoes in Europe. It is responsible for the country’s second deadliest eruption after a steam blast in 1362 deposited 10 cubic kilometres of debris across farmland and killed all inhabitants across dozens of farms.

Although still sparsely populated, the region can attract thousands of tourists at the height of the holiday season. The Icelandic Civil Protection Agency estimates there would only be a 20-minute warning before any eruption.

The volcano last erupted in 1727, and as a result volcanologists have a limited ability to predict when any eruption would occur.

With the growing seismic and geothermal activity of recent weeks, monitoring of the volcano is being increased.

Several Villages Hit By Volcanic Ash After Mt. Agung Erupts In Bali

Volcanic ash has fallen onto a number of villages surrounding Mount Agung in Bali following an eruption at the island’s tallest volcano on Tuesday afternoon, less than a month after the alert level was lowered.

At least five villages were affected by the ash, including Pidpid, Nawakerti, Bukit Galah, Sebudi and Abang Village. The villages are located within the danger zone of the volcano, kompas.com reported.

Authorities from the Energy and Mineral Resources Ministry’s Volcanology and Geological Hazard Mitigation Center (PVMBG) visited the villages following reports from local residents’ to authorities at the Mount Agung monitoring station.

“The PVMBG Emergency Response Team found [volcanic] ash, however, the intensity of the ash [falling on the villages] is still light,” head of mitigation sub-directorate at PVMBG, Devi Kemal, said on Tuesday evening.

Devi further advised residents not to panic and follow the authorities instructions. “Everyone should remain calm and follow PVMBG recommendations,” Devi said.

Mount Agung, which has been experiencing increased activity in recent months, erupted and spewed black smoke at 5:05 p.m. on Tuesday, with the height of the smoke reaching more than 700 meters from the peak of the mountain.

Residents are advised to stay away from areas within a 6 kilometer radius of the volcano. The volcano’s status is set at the third highest alert level, the National Disaster Mitigation Agency (BNPB) has previously said.

The alert level for the volcano that had forced more than 100,000 residents to flee was lowered late last month, from the highest level to the third highest level, although authorities said there was still a chance of eruption.