Unusual Martian Region Leaves Clues To Planet’s Past

Researcher Don Hood from LSU and colleagues from collaborating universities studied an unusual region on Mars — an area with high elevation called Thaumasia Planum. They analyzed the geography and mineralogy of this area they termed Greater Thaumasia, which is about the size of North America. They also studied the chemistry of this area based on Gamma Ray Spectrometer data collected by the Mars Odyssey Orbiter, which was launched in 2001. What they found was the mountain ridge that outlines Greater Thaumasia was most likely created by a chain of volcanoes. The results were published recently in the Journal of Geophysical Research-Planets.

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“The chemical changes we see moving northwestward through the region is consistent with the mantle evolving on Mars. Our research supports that this whole area was built as a volcanic construct,” said Don Hood, LSU Department of Geology and Geophysics doctoral candidate and lead author of the paper.

The chemical composition changes throughout the region. Silica and H20 increase and potassium decreases from southeast to northwest.

“The chemical composition shifting is the key progression that tells us that this environment was most likely shaped by a series of volcanic events that continually erupted from a changing mantle composition,” Hood said.

Hood and colleagues from Stony Brook University, University of Tokyo and Lehigh University ruled out another hypothesis that the abundance of H20 and potassium was caused by water interacting in rock.

“We looked for evidence of aqueous alteration through other geochemical means and didn’t find it,” he said.

The geography of the region has many shield volcanoes that are similar to the ones found in Hawaii. However from geochemical analyses, the researchers found that the sulfur that is present was most likely deposited as a volcanic ash. Volcanic ash from various areas could be evidence of explosive volcanism on Mars, which would be an important clue for piecing together the history of Mars. It is significant because explosive eruptions emit a lot of gas that can stay in the atmosphere and can cause global cooling and warming events.

“Whether there was explosive volcanism on Mars and how much of it there was is an important question in terms of finding out what the past climate was like,” Hood said.

Supercomputer Comes Up With A Profile Of Dark Matter

In the search for the mysterious dark matter, physicists have used elaborate computer calculations to come up with an outline of the particles of this unknown form of matter. To do this, the scientists extended the successful Standard Model of particle physics which allowed them, among other things, to predict the mass of so-called axions, promising candidates for dark matter. The German-Hungarian team of researchers led by Professor Zoltán Fodor of the University of Wuppertal, Eötvös University in Budapest and Forschungszentrum Jülich carried out its calculations on Jülich’s supercomputer JUQUEEN (BlueGene/Q) and presents its results in the journal Nature.

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“Dark matter is an invisible form of matter which until now has only revealed itself through its gravitational effects. What it consists of remains a complete mystery,” explains co-author Dr Andreas Ringwald, who is based at DESY and who proposed the current research. Evidence for the existence of this form of matter comes, among other things, from the astrophysical observation of galaxies, which rotate far too rapidly to be held together only by the gravitational pull of the visible matter. High-precision measurements using the European satellite “Planck” show that almost 85 percent of the entire mass of the universe consists of dark matter. All the stars, planets, nebulae and other objects in space that are made of conventional matter account for no more than 15 percent of the mass of the universe.

“The adjective ‘dark’ does not simply mean that it does not emit visible light,” says Ringwald. “It does not appear to give off any other wavelengths either — its interaction with photons must be very weak indeed.” For decades, physicists have been searching for particles of this new type of matter. What is clear is that these particles must lie beyond the Standard Model of particle physics, and while that model is extremely successful, it currently only describes the conventional 15 percent of all matter in the cosmos. From theoretically possible extensions to the Standard Model physicists not only expect a deeper understanding of the universe, but also concrete clues in what energy range it is particularly worthwhile looking for dark-matter candidates.

The unknown form of matter can either consist of comparatively few, but very heavy particles, or of a large number of light ones. The direct searches for heavy dark-matter candidates using large detectors in underground laboratories and the indirect search for them using large particle accelerators are still going on, but have not turned up any dark matter particles so far. A range of physical considerations make extremely light particles, dubbed axions, very promising candidates. Using clever experimental setups, it might even be possible to detect direct evidence of them. “However, to find this kind of evidence it would be extremely helpful to know what kind of mass we are looking for,” emphasises theoretical physicist Ringwald. “Otherwise the search could take decades, because one would have to scan far too large a range.”

The existence of axions is predicted by an extension to quantum chromodynamics (QCD), the quantum theory that governs the strong interaction, responsible for the nuclear force. The strong interaction is one of the four fundamental forces of nature alongside gravitation, electromagnetism and the weak nuclear force, which is responsible for radioactivity. “Theoretical considerations indicate that there are so-called topological quantum fluctuations in quantum chromodynamics, which ought to result in an observable violation of time reversal symmetry,” explains Ringwald. This means that certain processes should differ depending on whether they are running forwards or backwards. However, no experiment has so far managed to demonstrate this effect.

The extension to quantum chromodynamics (QCD) restores the invariance of time reversals, but at the same time it predicts the existence of a very weakly interacting particle, the axion, whose properties, in particular its mass, depend on the strength of the topological quantum fluctuations. However, it takes modern supercomputers like Jülich’s JUQUEEN to calculate the latter in the temperature range that is relevant in predicting the relative contribution of axions to the matter making up the universe. “On top of this, we had to develop new methods of analysis in order to achieve the required temperature range,” notes Fodor who led the research.

The results show, among other things, that if axions do make up the bulk of dark matter, they should have a mass of 50 to 1500 micro-electronvolts, expressed in the customary units of particle physics, and thus be up to ten billion times lighter than electrons. This would require every cubic centimetre of the universe to contain on average ten million such ultra-lightweight particles. Dark matter is not spread out evenly in the universe, however, but forms clumps and branches of a weblike network. Because of this, our local region of the Milky Way should contain about one trillion axions per cubic centimetre.

Thanks to the Jülich supercomputer, the calculations now provide physicists with a concrete range in which their search for axions is likely to be most promising. “The results we are presenting will probably lead to a race to discover these particles,” says Fodor. Their discovery would not only solve the problem of dark matter in the universe, but at the same time answer the question why the strong interaction is so surprisingly symmetrical with respect to time reversal. The scientists expect that it will be possible within the next few years to either confirm or rule out the existence of axions experimentally.

The Institute for Nuclear Research of the Hungarian Academy of Sciences in Debrecen, the Lendület Lattice Gauge Theory Research Group at the Eötvös University, the University of Zaragoza in Spain, and the Max Planck Institute for Physics in Munich were also involved in the research.

Hurricanes From Three Million Years Ago Give Us Clues About Present Storms

Studying hurricane and tropical storm development from three million years ago might give today’s forecasters a good blueprint for 21st century storms, says a team of international researchers that includes a Texas A&M University atmospheric sciences professor.

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Robert Korty, associate professor in the Department of Atmospheric Sciences at Texas A&M, along with colleagues from China, Norway, and the University of Wisconsin, have had their work published in the current issue of PNAS (Proceedings of the National Academy of Sciences).

The team studied storm development from the Pliocene era, roughly three million years ago, and chose that time period because it was the last time Earth had as much carbon dioxide as it does now, and the changes in climate from it can play a major role in storm formation and intensity.

Using computer models and simulations, the team found an increase in the average intensity during the period and the storms most often moved into higher latitudes — to a more northward direction.

“There seems to be a limit on how strong these ancient storms might be, but the number getting close to the limit appears to be larger during warmer periods,” Korty explains.

“They reached their peak intensity at higher latitudes, following an expansion of tropical conditions with warming. It is consistent with smaller changes in the same patterns that we have observed over recent decades and project to continue over the next 100 years. I think it gives us greater confidence in some trends we are witnessing about how storms may change in future years.”

Researchers today know that the oceans continued to be relatively warm during the Pliocene era, though there has been some uncertainty where waters were warmest. Their study found that the increase in average intensity and in the poleward expansion occurred regardless of where the greatest change in temperatures occurred in the Pliocene.

Korty says the study adds more evidence “that future storms are likely to be stronger in their intensity and to remain strong even as they move out of the tropics.”

New Model Explains The Moon’s Weird Orbit

The moon, Earth’s closest neighbor, is among the strangest planetary bodies in the solar system. Its orbit lies unusually far away from Earth, with a surprisingly large orbital tilt. Planetary scientists have struggled to piece together a scenario that accounts for these and other related characteristics of the Earth-moon system.

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A new research paper, based on numerical models of the moon’s explosive formation and the evolution of the Earth-moon system, comes closer to tying up all the loose ends than any other previous explanation. The work, published in the October 31, 2016 Advance Online edition of the journal Nature, suggests that the impact that formed the moon also caused calamitous changes to Earth’s rotation and the tilt of its spin axis.

The research suggests that the impact sent Earth spinning much faster, and at a much steeper tilt, than it does today. In the several billion years since that impact, complex interactions between Earth, the moon and sun have smoothed out many of these changes, resulting in the Earth-moon system that we see today. In this scenario, the remaining anomalies in the moon’s orbit are relics of the Earth-moon system’s explosive past.

“Evidence suggests a giant impact blasted off a huge amount of material that formed the moon,” said Douglas Hamilton, professor of astronomy at the University of Maryland and a co-author of the Nature paper. “This material would have formed a ring of debris first, then the ring would have aggregated to form the moon. But this scenario does not quite work if Earth’s spin axis was tilted at the 23.5 degree angle we see today.”

Collisional physics calls for this ring of debris — and thus the moon’s orbit immediately after formation — to lie in Earth’s equatorial plane. As tidal interactions between Earth and the moon drove the moon further away from Earth, the moon should have shifted from Earth’s equatorial plane to the “ecliptic” plane, which corresponds to Earth’s orbit around the sun.

But today, instead of being in line with the ecliptic plane, the moon’s orbit is tilted five degrees away from it.

“This large tilt is very unusual. Until now, there hasn’t been a good explanation,” Hamilton said. ” But we can understand it if Earth had a more dramatic early history than we previously suspected.”

Hamilton, with lead author Matija Cuk of the SETI institute and their colleagues Simon Lock of Harvard University and Sarah Stewart of the University of California, Davis, tried many different scenarios. But the most successful ones involved a moon-forming impact that sent Earth spinning extremely fast — as much as twice the rate predicted by other models. The impact also knocked Earth’s tilt way off, to somewhere between 60 and 80 degrees.

“We already suspected that Earth must have spun especially fast after the impact” Cuk said. “An early high tilt for Earth enables our planet to lose that excess spin more readily.”

The model also suggests that the newly-formed moon started off very close to Earth, but then drifted away — to nearly 15 times its initial distance. As it did so, the sun began to exert a more powerful influence over the moon’s orbit.

According to the researchers, both factors — a highly tilted, fast spinning Earth and an outwardly-migrating moon — contributed to establishing the moon’s current weird orbit. The newborn moon’s orbit most likely tracked Earth’s equator, tilted at a steep 60-80 degree angle that matched Earth’s tilt.

A key finding of the new research is that, if Earth was indeed tilted by more than 60 degrees after the moon formed, the moon could not transition smoothly from Earth’s equatorial plane to the ecliptic plane. Instead, the transition was abrupt and left the moon with a large tilt relative to the ecliptic — much larger than is observed today.

“As the moon moved outward, Earth’s steep tilt made for a more chaotic transition as the sun became a bigger influence,” Cuk said. “Subsequently, and over billions of years, the moon’s tilt slowly decayed down to the five degrees we see today. So today’s five degree tilt is a relic and a signature of a much steeper tilt in the past.”

Hamilton acknowledges that the model doesn’t answer all the remaining questions about the moon’s orbit. But the model’s strength, he says, is that it offers a framework for answering new questions in the future.

“There are many potential paths from the moon’s formation to the Earth-moon system we see today. We’ve identified a few of them, but there are sure to be other possibilities,” Hamilton said. “What we have now is a model that is more probable and works more cleanly than previous attempts. We think this is a significant improvement that gets us closer to what actually happened.”

Cosmic Connection: How Human Cells Are Like Neutron Stars

We humans may be more aligned with the universe than we realize.

According to research published in the journal Physical Review C, neutron stars and cell cytoplasm have something in common: structures that resemble multistory parking garages.

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In 2014, UC Santa Barbara soft condensed-matter physicist Greg Huber and colleagues explored the biophysics of such shapes — helices that connect stacks of evenly spaced sheets — in a cellular organelle called the endoplasmic reticulum (ER). Huber and his colleagues dubbed them Terasaki ramps after their discoverer, Mark Terasaki, a cell biologist at the University of Connecticut.

Huber thought these “parking garages” were unique to soft matter (like the interior of cells) until he happened upon the work of nuclear physicist Charles Horowitz at Indiana University. Using computer simulations, Horowitz and his team had found the same shapes deep in the crust of neutron stars.

“I called Chuck and asked if he was aware that we had seen these structures in cells and had come up with a model for them,” said Huber, the deputy director of UCSB’s Kavli Institute for Theoretical Physics (KITP). “It was news to him, so I realized then that there could be some fruitful interaction.”

The resulting collaboration, highlighted in Physical Review C, explored the relationship between two very different models of matter.

Nuclear physicists have an apt terminology for the entire class of shapes they see in their high-performance computer simulations of neutron stars: nuclear pasta. These include tubes (spaghetti) and parallel sheets (lasagna) connected by helical shapes that resemble Terasaki ramps.

“They see a variety of shapes that we see in the cell,” Huber explained. “We see a tubular network; we see parallel sheets. We see sheets connected to each other through topological defects we call Terasaki ramps. So the parallels are pretty deep.”

However, differences can be found in the underlying physics. Typically matter is characterized by its phase, which depends on thermodynamic variables: density (or volume), temperature and pressure — factors that differ greatly at the nuclear level and in an intracellular context.

“For neutron stars, the strong nuclear force and the electromagnetic force create what is fundamentally a quantum-mechanical problem,” Huber explained. “In the interior of cells, the forces that hold together membranes are fundamentally entropic and have to do with the minimization of the overall free energy of the system. At first glance, these couldn’t be more different.”

Another difference is scale. In the nuclear case, the structures are based on nucleons such as protons and neutrons and those building blocks are measured using femtometers (10-15). For intracellular membranes like the ER, the length scale is nanometers (10-9). The ratio between the two is a factor of a million (10-6), yet these two vastly different regimes make the same shapes.

“This means that there is some deep thing we don’t understand about how to model the nuclear system,” Huber said. “When you have a dense collection of protons and neutrons like you do on the surface of a neutron star, the strong nuclear force and the electromagnetic forces conspire to give you phases of matter you wouldn’t be able to predict if you had just looked at those forces operating on small collections of neutrons and protons.”

The similarity of the structures is riveting for theoretical and nuclear physicists alike. Nuclear physicist Martin Savage was at the KITP when he came across graphics from the new paper on arXiv, a preprint library that posts thousands of physics, mathematics and computer science articles. Immediately his interest was piqued.

“That similar phases of matter emerge in biological systems was very surprising to me,” said Savage, a professor at the University of Washington. “There is clearly something interesting here.”

Co-author Horowitz agreed. “Seeing very similar shapes in such strikingly different systems suggests that the energy of a system may depend on its shape in a simple and universal way,” he said.

Huber noted that these similarities are still rather mysterious. “Our paper is not the end of something,” he said. “It’s really the beginning of looking at these two models.”