Month: May 2018

New Find Shows Yucatan Peninsula Asteroid Strike Warmed Planet for 100,000 Years

A small team of researchers from the U.S. and Tunisia has found evidence that suggests a huge asteroid that struck the Earth approximately 66 million years ago caused the planet to warm up for approximately 100,000 years. In their paper published in the journal Science, the group describes their study of oxygen ratios in ancient fish bones and what it revealed.

Prior research has shown that approximately 66 million years ago, a massive asteroid struck the Earth at a point near what is now Chicxulub, Mexico. Other studies have suggested the sudden change in climate that resulted is what caused the dinosaurs to go extinct. The belief has been that the smoke and particles thrust into the atmosphere blocked out the sun causing the planet to cool for a long period of time. In this new effort, the researchers suggest the cooling period likely was shorter than thought and that it was followed by a lengthy hot spell. The researchers came to this conclusion by studying the bones and teeth of ancient fish.

The fish remains were sifted from sediment samples collected at a site in El Kef, Tunisia. During the time before and long after the asteroid strike, the area was covered by the Tethys Sea. The researchers looked at oxygen ratios in the fish remains as a means of determining the temperature of the water at the time that the fish died. Collecting samples from different layers allowed for building a temperature timeline that began before the asteroid strike and lasting hundreds of thousands of years thereafter. In looking at their timeline the group found that sea temperatures had risen approximately 5°C not long after the asteroid struck and had stayed at that temperature for approximately 100,000 years.

The researchers suggest the strike by the asteroid very likely released a lot of carbon dioxide into the atmosphere because the ground area where it struck was rich in carbonates. The strike very likely would have also ignited large long-burning forest fires which would have also released a lot of carbon into the air. The evidence suggests that the cooling after the impact was short-lived as massive amounts of carbon dioxide were released into the atmosphere setting off global warming.

The researchers note that a lot more work will need to be done to confirm their findings. Another site will have to be found with similar evidence, for example, to prove that the warming was not localized.

EOVSA Reveals New Insights Into Solar Flares’ Explosive Energy Releases

Last September, a massive new region of magnetic field erupted on the Sun’s surface next to an existing sunspot. The powerful collision of magnetic fields produced a series of potent solar flares, causing turbulent space weather conditions at Earth. These were the first flares to be captured, in their moment-by-moment progression, by New Jersey Institute of Technology’s (NJIT) recently expanded Owens Valley Solar Array (EOVSA).

With 13 antennas now working together, EOVSA was able to make images of the flare in multiple radio frequencies simultaneously for the first time. This enhanced ability to peer into the mechanics of flares offers scientists new pathways to investigate the most powerful eruptions in our solar system.

“These September flares included two of the strongest of the current 11-year solar activity cycle, hurling radiation and charged particles toward Earth that disrupted radio communications,” said Dale Gary, distinguished professor of physics at NJIT’s Center for Solar-Terrestrial Research (CSTR) and EOVSA’s director. The last flare of the period, on September 10, was “the most exciting,” he added.

“The sunspot region was just passing over the solar limb — the edge of the Sun as it rotates — and we could see the comparative height of the flare in many different wavelengths, from optical, to ultraviolet, to X-rays, to radio,” he recounted. “This view provided a wonderful chance to capture the structure of a large solar flare with all of its ingredients.”

Radio emissions are generated by energetic electrons accelerated in the corona, the Sun’s hot upper atmosphere. Modern solar physics relies on observations at many wavelengths; radio imaging complements these by directly observing the particle acceleration that drives the whole process. By measuring the radio spectrum at different places in the solar atmosphere, especially when it is able to do so fast enough to follow changes during solar flares, it becomes a powerful diagnostic of the fast-changing solar environment during these eruptions.

EOVSA, which is funded by the National Science Foundation, is the first radio imaging instrument that can make spectral images fast enough — in one second — to follow the rapid changes that occur in solar flares. This capability allows the radio spectrum to be measured dynamically throughout the flaring region, to pinpoint the location of particle acceleration and map where those particles travel. Images of solar flares at most other wavelengths show only the consequences of heating by the accelerated particles, whereas radio emission can directly show the particles themselves.

“One of the great mysteries of solar research is to understand how the Sun produces extremely high-energy particles in such a short time,” Gary noted. “But to answer that question, we must have quantitative diagnostics of both the particles and the environment, especially the magnetic field that is at the heart of the energy release. EOVSA makes that possible at radio wavelengths for the first time.”

Gary presented EOVSA’s new findings this week at the Triennial Earth-Sun Summit (TESS) meeting, which brings together the solar physics division of the American Astronomical Society (AAS) and the solar physics and aeronomy section of the American Geophysical Union (AGU).

“EOVSA’s new results have sparked lots of interest at the TESS meeting,” said Bin Chen, assistant professor of physics at CSTR, who is chairing a session focused on the intense solar activity that occurred last September. “A number of experts at the meeting commented that these results would add fundamentally new insights into the understanding of energy release and particle acceleration in solar flares.”

Among other discoveries, scientists at EOVSA have learned that radio emissions in a flare are spread over a much larger region than previously known, indicating that high-energy particles are promptly transported in large numbers throughout the explosive magnetic field “bubble” called a coronal mass ejection (CME).

“This is important because CMEs drive shock waves that further accelerate particles that are dangerous to spacecraft, astronauts and even people in airplanes flying polar routes. To date, it remains a mystery how these shock waves alone accelerate particles, because the physics is not understood,” he said. “One of the theories is that ‘seed’ particles must be present in the shock region, which can generate the waves necessary for further acceleration. It has long been speculated that flares, which are known to accelerate particles, may provide them. Previous observations, mainly with X-rays, always show those particles confined to very low heights and it has not been understood how such particles could get to the shock. The radio images show evidence for particles in a much larger region, giving them more opportunity to gain access to the shock region.”

Sunspots are the primary generator of solar flares, the sudden, powerful blasts of electromagnetic radiation and charged particles that burst into space during explosions on the Sun’s surface. Their turning motion causes energy to build up that is released in the form of flares.

EOVSA was designed to make high-resolution radio images of flares (1-second cadence), sunspot regions (20-minute cadence), the full Sun (a few per day) and hundreds of frequencies over a broad frequency band, making it the first solar instrument able to measure the radio spectrum from point-to-point in the flaring region.

“We are working towards a calibration and imaging pipeline to automatically generate microwave images observed by EOVSA, and make them available to the community on a day-to-day basis,” added Chen, who is leading the EOVSA pipeline effort.

“The most unexpected revelation so far from EOVSA is what we see at the lowest radio frequencies,” Gary noted. “Observations of flares based on high radio frequencies and based on X-ray observations show a flare that is a relatively small, compact region even though we see evidence for heating over a much larger area. Although we had rare observations from the past that seemed to show large radio sources, EOVSA has now made it routine to image large radio sources that are even bigger at lower frequencies.”

Initially, he and his colleagues were unable to tap into these new regions, however. After the array was completed, they realized that cell phone towers in the Owens Valley were causing much higher levels of radio frequency interference than expected. As a result, they designed “notch” filters that were able to cut out the frequencies most affected by cell towers.

“This is important because a lot of interesting solar radio bursts occur in the cell tower range (1.9-2.2 GHz). It is the lower frequencies that best show this new and not well understood phenomenon of large sources,” Gary said. “Somehow, the accelerated particles are being transported to a much greater volume of the corona than we thought.”

With new funding from NASA, Gary and colleagues will measure the spatially-resolved radio spectrum of solar flares, determine the particle and plasma parameters as a function of position and time, and then use 3-dimensional modeling, which his group has developed, to fully understand the initial acceleration and subsequent transport of high-energy particles.

The Sun goes through 11-year cycles of activity, and this past year may have provided the last flares we will see for the next four or five years,” Gary said. “For the next few years, we will focus our efforts on improving the active sunspot regions and full-disk images with the array. This imaging on a larger spatial scale is more challenging, but could be just as important, since the larger scale features govern the Sun’s influence on the Earth’s atmosphere and the solar wind.”

Study Of Ancient Fish Suggests Chicxulub Asteroid Strike Warmed Planet For 100,000 years

A small team of researchers from the U.S. and Tunisia has found evidence that suggests a huge asteroid that struck the Earth approximately 66 million years ago caused the planet to warm up for approximately 100,000 years. In their paper published in the journal Science, the group describes their study of oxygen ratios in ancient fish bones and what it revealed.

Prior research has shown that approximately 66 million years ago, a massive asteroid struck the Earth at a point near what is now Chicxulub, Mexico. Other studies have suggested the sudden change in climate that resulted is what caused the dinosaurs to go extinct. The belief has been that the smoke and particles thrust into the atmosphere blocked out the sun causing the planet to cool for a long period of time. In this new effort, the researchers suggest the cooling period likely was shorter than thought and that it was followed by a lengthy hot spell. The researchers came to this conclusion by studying the bones and teeth of ancient fish.

The fish remains were sifted from sediment samples collected at a site in El Kef, Tunisia. During the time before and long after the asteroid strike, the area was covered by the Tethys Sea. The researchers looked at oxygen ratios in the fish remains as a means of determining the temperature of the water at the time that the fish died. Collecting samples from different layers allowed for building a temperature timeline that began before the asteroid strike and lasting hundreds of thousands of years thereafter. In looking at their timeline the group found that sea temperatures had risen approximately 5°C not long after the asteroid struck and had stayed at that temperature for approximately 100,000 years.

The researchers suggest the strike by the asteroid very likely released a lot of carbon dioxide into the atmosphere because the ground area where it struck was rich in carbonates. The strike very likely would have also ignited large long-burning forest fires which would have also released a lot of carbon into the air. The evidence suggests that the cooling after the impact was short-lived as massive amounts of carbon dioxide were released into the atmosphere setting off global warming.

The researchers note that a lot more work will need to be done to confirm their findings. Another site will have to be found with similar evidence, for example, to prove that the warming was not localized.

Read more at: https://phys.org/news/2018-05-ancient-fish-chicxulub-asteroid-planet.html#jCp

How A Particle May Stand Still In Rotating Spacetime

When a massive astrophysical object, such as a boson star or black hole, rotates, it can cause the surrounding spacetime to rotate along with it due to the effect of frame dragging. In a new paper, physicists have shown that a particle with just the right properties may stand perfectly still in a rotating spacetime if it occupies a “static orbit”—a ring of points located a critical distance from the center of the rotating spacetime.

The physicists, Lucas G. Collodel, Burkhard Kleihaus, and Jutta Kunz, at the University of Oldenburg in Germany, have published a paper in which they propose the existence of static orbits in rotating spacetimes in a recent issue of Physical Review Letters.

“Our work presents with extreme simplicity a long-ignored feature of certain spacetimes that is quite counterintuitive,” Collodel told Phys.org. “General relativity has been around for a bit more than a hundred years now and it never ceases to amaze, and exploring the ways that different distributions of energy can warp the geometry of spacetime in a non-trivial way is key to a deeper understanding.”

In their paper, the physicists identify two criteria for a particle to remain at rest with respect to a static observer in a rotating spacetime. First, the particle’s angular momentum (basically its own rotation) must have just the right value so that it perfectly cancels out the rotation due to frame dragging. Second, the particle must be located precisely in the static orbit, a ring around the center of the rotating spacetime at which the particle is neither pulled toward the center nor pushed away.

A key point is that not all astrophysical objects with rotating spacetimes have static orbits, which in the future may help researchers distinguish between different types of astrophysical objects. As the physicists explain, in order to have a static orbit, a rotating spacetime’s metric (basically the function that describes spacetimes in general relativity) must have a local minimum, which corresponds to the critical distance at which the static orbit is located. In a sense, a particle may then be “trapped” at rest in this local minimum.

The physicists identify several astrophysical objects that have static orbits, including boson stars (hypothetical stars made of bosonic matter that, like black holes, have immense gravity but do not emit light), wormholes, and hairy black holes (black holes with unique properties, such as additional charge). On the other hand, Kerr black holes (thought to be the most common kind of black hole) do not have metrics with local minima, and so do not have static orbits. So evidence for a static orbit could provide a way to distinguish between Kerr black holes and some of the less common objects with static orbits.

While the physicists acknowledge that it may be unlikely to expect a particle with just the right angular momentum to exist at just the right place in order to remain at rest in a rotating spacetime, it may still be possible to detect the existence of static orbits due to what happens nearby. Particles initially at rest near the static orbits are predicted to move more slowly than those located further away. So even if researchers never observe a particle standing still, they may observe slowly moving particles in the vicinity, indicating the existence of a nearby static orbit.

“Acknowledging the existence of the static ring helps us appreciate better what to plan and expect from future observations,” Collodel said. “For instance, we can search for the ring in order to identify possible exotic objects, such as the boson star, or even assure with confidence (upon observing the ring) that an AGN [active galactic nucleus] is not powered by a Kerr black hole. In the future we plan to investigate how the presence of the ring might affect accretion disks, which are at this stage much easier to observe, and if it could shield some objects from infalling matter.”

Subglacial Valleys And Mountain Ranges Discovered Near South Pole

Researchers have discovered mountain ranges and three huge, deep subglacial valleys from data collected during the first modern aerogeophysical survey of the South Pole region.

The findings are the first to emerge from extensive ice penetrating radar data collected in Antarctica as part of the European Space Agency PolarGAP project and have been published in the journal, Geophysical Research Letters.

Although there are extensive satellite data that help image the surface of the Earth and its deep interior, there was a gap around the South Pole area, which is not covered by satellites due the inclination of their orbits. The PolarGAP project was therefore designed to fill in the gap in the satellite data coverage of the South Pole and in particular acquire the missing gravity data.

Airborne radar data were also collected to enable mapping of the bedrock topography hidden beneath the ice sheet. The data reveals the topography which controls how quickly ice flows between the East and West Antarctic ice sheets.

The team, led by Northumbria University, has mapped for the first time three vast, subglacial valleys in West Antarctica. These valleys could be important in future as they help to channel the flow of ice from the centre of the continent towards the coast.

If climate change causes the ice sheet to thin, these troughs could increase the speed at which ice flows from the centre of Antarctica to the sea, raising global sea levels.

The largest valley, known as the Foundation Trough, is more than 350km long and 35km wide. Its length is equivalent to the distance from London to Manchester, while its width amounts to more than one and a half times the length of New York’s Manhattan Island.

The two other troughs are equally vast. The Patuxent Trough is more than 300km long and over 15km wide, while the Offset Rift Basin is 150km long and 30km wide.

Lead author Dr. Kate Winter a Vice-Chancellor’s Research Fellow in Northumbria University’s Department of Geography and Environmental Sciences, explains: “As there were gaps in satellite data around the South Pole, no one knew exactly what was there, so we are delighted to be able to release the very first findings to emerge from the PolarGAP project.

“We now understand that the mountainous region is preventing ice from East Antarctica flowing through West Antarctica to the coast. In addition we have also discovered three subglacial valleys in West Antarctica which could be important in the future.

“If the ice sheet thins or retreats, these topographically-controlled corridors could facilitate enhanced flow of ice further inland, and could lead to the West Antarctic ice divide moving. This would, in turn, increase the speed and rate at which ice flows out from the centre of Antarctica to its edges, leading to an increase in global sea levels.”

Dr. Winter adds: “The data we have gathered will enable ice sheet modellers to predict what will happen if the ice sheet thins, which will mean we can start to answer the questions we couldn’t answer before.”

Dr. Winter worked with researchers from Newcastle University, British Antarctic Survey, the Technical University of Denmark, the Norwegian Polar Institute and the European Space Agency on the paper, Topographic steering of enhanced ice flow at the bottleneck between East and West Antarctica.

Dr. Fausto Ferraccioli, Head of Airborne Geophysics at British Antarctic Survey and the Principal Investigator of the European Space Agency PolarGAP project, explained: “Remarkably the South Pole region is one of the least understood frontiers in the whole of Antarctica.

“By mapping these deep troughs and mountain ranges we have therefore added a key piece of the puzzle to help understand how the East Antarctic Ice Sheet may have responded to past change and how it may do so in the future. Our new aerogeophysical data will also enable new research into the geological processes that created the mountains and basins before the Antarctic ice sheet itself was born.”

Dr. Neil Ross, Senior Lecturer in Physical Geography at Newcastle University, added: “Understanding how the East and West Antarctic Ice Sheets interact is fundamental to our understanding of past, present and future global sea level. These new PolarGAP data give us both insights into how the landscape beneath the ice influences present ice flow, and a better understanding of how the parts of the great Antarctic ice sheets near to South Pole can, and cannot, evolve in response to glaciological change around their margins.

“There is a need to follow up the extensive aerogeophysical PolarGAP survey with detailed field investigations and numerical modelling of the glaciological processes operating in this frontier region of Antarctica.”

How Stratospheric Life Is Teaching Us About The Possibility Of Extreme Life On Other Worlds

The presence of microbial life in Earth’s stratosphere is not only opening up a new arena in which to study extremophiles, but is increasing the range of possible environments in which we may find life on other planets. This is the conclusion of a new study that summarizes what we know about stratospheric life so far.

The stratosphere is the atmospheric zone that lies directly above the dynamic troposphere where we live, but it is mostly a mystery when it comes to the life that exists there.

You might not realize it when you’re staring out a plane window (we fly through the lowest levels of the stratosphere when we’re cruising over 35,000 feet), but there are all kinds of microorganisms out there, according to Professor Shiladitya DasSarma, who is a microbiologist at the University of Maryland School of Medicine, USA , and a co-author on the new study, which is published in the journal Current Opinion in Microbiology.

“Generally, people don’t think of microbes being airborne,” he tells Astrobiology Magazine. “But there’s a saying in microbiology: Everything is everywhere.”

However, there are “very few studies at the present time” that look at the atmospheric biome. Part of the issue is that there is a low density of cells in a large volume of air. But when you look at it globally, the numbers are significant: 1021is the current estimate for the number of cells lifted annually into the atmosphere.

Still, the space involved is vast: “When you’re talking about the entire atmosphere of a planet, how do you do a survey of that?” asks Priya DasSarma, a research scientist also from the University of Maryland and the study’s lead author. She suggests it would have to be a community exercise with a long timeline, which would eventually result in what she calls an ‘Atlas of Stratospheric Microbes’.

“A program like that would be incredibly productive and interesting and worthwhile,” she says, not only for what it could tell us about life on Earth, but also how cells could survive and even adapt to life on other planets. That has implications when it comes to planetary protection (not exposing other planets to terrestrial germs), and to astrobiology more generally.

“When we measure the response of terrestrial life in extreme environments on Earth, we can learn more about habitability across the Solar System and where to refine the search for life elsewhere,” says Dr. David J. Smith, a senior microbiologist in the Space Biosciences Division at NASA’s Ames Research Center.

Conditions in the stratosphere are brutal – it’s a dry, cold, hypobaric (i.e. low pressure), ultraviolet-drenched environment, which is why it serves as an apt analog to life on other worlds with similar conditions.

“The temperatures, UV and dryness are similar to Mars, so it’s a great proxy,” says Shiladitya DasSarma. Nevertheless, life persists. Bacteria and fungi usually perish in this kind of environment, but those that survive do so via a few strategies. For instance, forming spores is a tried-and-true way to protect genetic material.

Yet even non-spore-forming extremophiles have mechanisms to protect themselves. “There’s a wide variety of stress-survival mechanisms,” says Shiladitya DasSarma. “For UV, a number of [extremophiles] have DNA damage-repair mechanisms. Others have additional, more quiescent methods, like extreme halophiles that can survive very low-water situations because their proteins are designed to hold onto whatever small amount of water is present.”

Contaminating other worlds

If life can survive the conditions in the stratosphere, perhaps life can also survive in space. When it comes to microbes hitchhiking on interplanetary spacecraft, it’s going to be increasingly important that we know which of these bacteria, archaea or fungi can survive, since we know from the stratosphere studies that cold temperatures, UV radiation and other factors won’t kill every last cell.

Currently, space agencies including NASA have a mandate not to expose other planets to Earth’s microfauna, so precautions are taken before launching landers. In most cases there’s not likely to be much that will remain alive after a spacecraft has been doused in cosmic rays. However, we know from experience how hardy invasive species on Earth can be – there’s a reason life is “everywhere” on Earth.

“We know Mars is a dusty planet and spacecraft coated in dust might shade some microbial hitchhikers,” says Smith, who published a paper in 2017 examining this idea. “Also, a portion of bioburden [the amount of microbes surviving on spacecraft] are embedded deep inside the spacecraft’s hardwarewhere they are protected from radiation, substantially reducing or completely eliminating the effects of UV.” With just minimal protection, microbes can use the same strategies that allow them to survive in the stratosphere – like DNA repair of UV damage, or water storage – to stay alive far from Earth.

It’s important to keep in mind that surviving does not necessarily mean thriving. Just because an organism makes it to, say, Mars, doesn’t mean it will be viable and reproduce. That’s why knowing more about extremophiles, particularly those in Earth’s stratosphere, is key.

Conversely, at some point we may actually want some of these microorganisms to thrive, because good bacteria are going to be important partners for us when we set up human colonies. “If we want to go to Mars and inhabit it, we are going to want to bring whatever microbes and macrobes [i.e. larger lifeforms] with us that we need to survive there,” says Priya DasSarma. “But we don’t want to bring anything that contaminates or destroys the environment that we’re going to.”

Knowing how and why tough organisms persist in the stratosphere above our heads will be important when it comes to protecting planets that we explore in the short term. Meanwhile, looking farther into the future, those same extreme lifeforms could eventually help us to survive on other worlds as we expand out into the galaxy.

First Seismic Evidence For Mantle Exhumation At An Ultraslow-Spreading Center

A mountain range with a total length of 65,000 kilometers runs through all the oceans. It marks the boundaries of tectonic plates. Through the gap between the plates material from the Earth’s interior emerges, forming new seafloor, building up the submarine mountains and spreading the plates apart. Very often, these mid-ocean ridges are described as a huge, elongated volcano. But this image is only partly correct, because the material forming the new seafloor is not always magmatic. At some spreading centres material from the Earth’s mantle reaches the surface without being melted. The proportion of seabed formed this has been previously unknown.

Scientists from the Universities of Kiel (Germany), Austin (Texas, USA) and Durham (Great Britain) have now published data in the international journal Nature Geoscience that, for the first time, allow a detailed estimation on how much seafloor is formed by mantle material without magmatic processes. “This phenomenon occurs especially where the seabed spreads at paces of less than two centimeters per year,” explains Prof. Dr. Ingo Grevemeyer from the GEOMAR Helmholtz Centre for Ocean Research Kiel, lead author of the study.

One of these zones is located in the Cayman Trough south of the island of Grand Cayman in the Caribbean. In 2015, the researchers used the German research vessel METEOR to investigate the seafloor seismically, i.e. by using sound waves. Sound signals sent through different rocks or sediment layers, are being reflected and refracted in different ways by each layer. Rock, which has been melted and solidified on the seabed, has a different signature in the seismic signal than rock from the Earth’s mantle, which has not been melted.

But scientists had a problem so far: The contact with the seawater changes the mantle rocks. “After this process called serpentinisation mantle rocks are barely distinguishable from magmatic rocks in seismic data,” says Professor Grevemeyer. Until now, mantle rock on the seabed could only be detected by taking samples directly from the seafloor and analyzing them in the laboratory. “But that way you only get information about a tiny spot. A large-scale or even in-depth information on the composition of the seabed cannot be achieved,” says Grevemeyer.

However, during the expedition in 2015, the team not only used the energy of ordinary sound waves — it also detected so-called shear waves, which occur only in solid materials. They could be recorded very clearly thanks to a clever selection of measuring points.

From the ratio of the speed of both types of waves, the scientists were able to differentiate mantle material from magmatic material. “So we could prove for the first time with seismic methods that up to 25 percent of the young ocean floor is not magmatic at the ultra-slow spreading centre in the Cayman trough,” says Ingo Grevemeyer.

Since there are similar spreading centres in other regions, such as the Arctic or Indian Ocean, these results are of great importance for the general idea about the global composition of the seabed. “This is relevant, if we want to create global models on the interactions between seabed and seawater or on processes of plate tectonics,” summarizes Professor Grevemeyer.