Posts by AltonParrish:

Cosmic Doomsday: Dark Energy, The Fate Of The Universe And The End Of Earth

July 24th, 2012

By Alton Parrish.

Dark energy makes up about 70 percent of the current content of the Universe and thus holds the ultimate fate of our Universe. Several possible scenarios are possible depending on the properties of dark energy; one is that the Universe will end in a so-called big rip. This interesting topic was recently explored by five researchers from the University of Science and Technology of China, the Institute of Theoretical Physics at the Chinese Academy of Sciences, Northeastern University, and Peking University. Their work, entitled “Dark energy and fate of the Universe”, was published in Sci China-Phys Mech Astron 2012, Vol. 55 No. 7.

Estimated distribution of dark matter and dark energy in the universe

Credit: Wikipedia
For millennia, human beings have been pondering two ultimate questions: “Where do we come from?” and “Where are we going?” Over that time, these questions have spurred theological and philosophical debate. Thanks to the rapid development of modern cosmology in the past three decades, scientists nowadays have obtained some important clues to answer these questions. The standard “inflation + hot big bang” framework has been developed to explain the origin of the Universe. However, to forecast the destiny of the Universe, researchers have realized that the nature of dark energy is key.According to the Big Bang model, the Universe expanded from an extremely dense and hot state and continues to expand today. A common analogy explains that space itself is expanding, carrying galaxies with it, like spots on an inflating balloon. The graphic scheme above is an artist’s concept illustrating the expansion of a portion of a flat universe.

Credit:Wikipedia
In the absence of a consensus on what dark energy is, a phenomenological description of the equation-of-state parameter w—the ratio of pressure and density of dark energy—provides an important means for investigating dark energy dynamics. Properties of dark energy will decide the ultimate fate of the Universe. In particular, if w<-1 at some time in the future, dark energy density will grow to infinity in finite time, and its gravitational repulsion will tear apart all the objects in the Universe. This “big rip” (or “cosmic doomsday”) scenario is the major focus of the paper. “We want to infer from the current data what the worst fate would be for the Universe”, said the authors.
The Hubble Ultra Deep Field showcases galaxies from an ancient era when the Universe was younger, denser, and warmer according to the Big Bang theory.

Credit: Wikipedia
To foresee that fate, it is important to choose an appropriate parameterization that covers the overall expansion history of the Universe. The most popular Chevallier-Polarski-Linder (CPL) parameterization, in fact, is not suitable in predicting the future evolution of the Universe because in this form w will diverge when the redshift parameter approaches -1. Thus, the authors invoke a divergence-free parameterization, called the Ma-Zhang (MZ) parameterization, to predict the evolution of the Universe.One of the more intriguing questions is: “If a doomsday exists, how far are we from it?” After constraining the MZ parameter space via a Markov Chain Monte Carlo method, the authors found that by using the current observational data tBR – t0 = 103.5 Gyr for the best-fit result, and tBR – t0 = 16.7 Gyr at the 95.4% confidence level (CL) lower limit. Here tBR denotes the time of the big rip, and t0 denotes the present day. “In other words, at worst (95.4% CL), the time remaining before the Universe ends in a big rip is 16.7 billion years”, said the authors.
This panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. The galaxies are color coded by redshift.
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Credit: Wikipedia
Thus the constrained parameter space indicates that it is very likely that in the future w<-1. If so, one may ask another interesting question: “How about the destinies of the gravitationally bound objects in the Universe, such as galaxies and stars?” In fact, if w indeed ever becomes less than -1, dark energy’s gravitational repulsion will continuously increase until it overcomes all forces holding objects together and all objects will be torn apart. No object would escape this fate, but obviously systems more tightly bound would exist for longer.
Using the MZ parameterization, the authors speculated on a series of possible consequences before the cosmic doomsday. For example, for the worst situation, namely the 95.4% CL lower limit, the Milky Way will be torn apart 32.9 Myr before the big rip; two months before doomsday, the Earth will be ripped from the Sun; five days before the doomsday, the moon will be ripped from the Earth; the Sun will be destroyed 28 min before the end of time; and 16 min before the end, the Earth will explode.
This is an artist’s concept of the Universe expansion, where space (including hypothetical non-observable portions of the Universe) is represented at each time by the circular sections. Note on the left the dramatic expansion (not to scale) occurring in the inflationary epoch, and at the center the expansion acceleration. The scheme is decorated with WMAP images on the left and with the representation of stars at the appropriate level of development.
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Credit: NASA/WMAP Science Team
However, from what we already know of the dynamical properties of dark energy, one thing is all very clear, we still have a very long future ahead.

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Sumatra 8.6 Mega-Earthquake Largest Ever Recorded, Highest Resolution Of Underwater Rupture

July 24th, 2012

By Alton Parrish.

The powerful magnitude-8.6 earthquake that shook Sumatra on April 11, 2012, was a seismic standout for many reasons, not the least of which is that it was larger than scientists thought an earthquake of its type could ever be. Now, researchers from the California Institute of Technology (Caltech) report on their findings from the first high-resolution observations of the underwater temblor, they point out that the earthquake was also unusually complex—rupturing along multiple faults that lie at nearly right angles to one another, as though racing through a maze. according to  Kimm Fesenmaier of Caltech.

The colored circles on the large map indicate the complex spatial rupture pattern as a function of time during the Sumatra earthquake in April 2012. The white star indicates the epicenter of the magnitude-8.6 mainshock. The area shaded in darker red in the inset indicates the location of the area of study.
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Credit: Caltech/Meng et al.
The new details provide fresh insights into the possibility of ruptures involving multiple faults occurring elsewhere—something that could be important for earthquake-hazard assessment along California’s San Andreas fault, which itself is made up of many different segments and is intersected by a number of other faults at right angles.”Our results indicate that the earthquake rupture followed an exceptionally tortuous path, breaking multiple segments of a previously unrecognized network of perpendicular faults,” says Jean-Paul Ampuero, an assistant professor of seismology at Caltech and one of the authors of the report, which appears online today in Science Express. “This earthquake provided a rare opportunity to investigate the physics of such extreme events and to probe the mechanical properties of Earth’s materials deep beneath the oceans.”Most mega-earthquakes occur at the boundaries between tectonic plates, as one plate sinks beneath another. The 2012 Sumatra earthquake is the largest earthquake ever documented that occurred away from such a boundary—a so-called intraplate quake. It is also the largest that has taken place on a strike-slip fault—the type of fault where the land on either side is pushing horizontally past the other.The earthquake happened far offshore, beneath the Indian Ocean, where there are no geophysical monitoring sensors in place. Therefore, the researchers used ground-motion recordings gathered by networks of sensors in Europe and Japan, and an advanced source-imaging technique developed in Caltech’s Seismological Laboratory as well as the Tectonics Observatory to piece together a picture of the earthquake’s rupture process.
The earthquake ruptured along multiple faults. Dotted lines indicate interpreted fault planes. Colored arrows indicate the direction of rupture.
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Credit: Caltech/Meng et al
Lingsen Meng, the paper’s lead author and a graduate student in Ampuero’s group, explains that technique by comparing it with how, when standing in a room with your eyes closed, you can often still sense when someone speaking is walking across the room. “That’s because your ears measure the delays between arriving sounds,” Meng says. “Our technique uses a similar idea. We measure the delays between different seismic sensors that are recording the seismic movements at set locations.” Researchers can then use that information to determine the location of a rupture at different times during an earthquake. Recent developments of the method are akin to tracking multiple moving speakers in a cocktail party.Using this technique, the researchers determined that the three-minute-long Sumatra earthquake involved at least three different fault planes, with a rupture propagating in both directions, jumping to a perpendicular fault plane, and then branching to another.”Based on our previous understanding, you wouldn’t predict that the rupture would take these bends, which were almost right angles,” says Victor Tsai, an assistant professor of geophysics at Caltech and a coauthor on the new paper.The team also determined that the rupture reached unusual depths for this type of earthquake—diving as deep as 60 kilometers in places and delving beneath the Earth’s crust into the upper mantle. This is surprising given that, at such depths, pressure and temperature increase, making the rock more ductile and less apt to fail. It has therefore been thought that if a stress were applied to such rocks, they would not react as abruptly as more brittle materials in the crust would. However, given the maze-like rupture pattern of the earthquake, the researchers believe another mechanism might be in play.”One possible explanation for the complicated rupture is there might have been reduced friction as a result of interactions between water and the deep oceanic rocks,” says Tsai. “And,” he says, “if there wasn’t much friction on these faults, then it’s possible that they would slip this way under certain stress conditions.”Adding to the list of the quake’s surprising qualities, the researchers pinpointed the rupture to a region of the seafloor where seismologists had previously considered such large earthquakes unlikely based on the geometry of identified faults. When they compared the location they had determined using source-imaging with high-resolution sonar data of the topography of the seafloor, the team found that the earthquake did not involve what they call “the usual suspect faults.”

“This part of the oceanic plate has fracture zones and other structures inherited from when the seafloor formed here, over 50 million years ago,” says Joann Stock, professor of geology at Caltech and another coauthor on the paper. “However, surprisingly, this earthquake just ruptured across these features, as if the older structure didn’t matter at all.”

Meng emphasizes that it is important to learn such details from previous earthquakes in order to improve earthquake-hazard assessment. After all, he says, “If other earthquake ruptures are able to go this deep or to connect as many fault segments as this earthquake did, they might also be very large and cause significant damage.”

Along with Meng, Ampuero, Tsai, and Stock, additional Caltech coauthors on the paper, “An earthquake in a maze: compressional rupture branching during the April 11 2012 M8.6 Sumatra earthquake,” are postdoctoral scholar Zacharie Duputel and graduate student Yingdi Luo. The work was supported by the National Science Foundation, the Gordon and Betty Moore Foundation, and the Southern California Earthquake Center, which is funded by the National Science Foundation and the United States Geological Survey.

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Saturn’s Strange Moon: River Networks On Titan Point To A Puzzling Geologic History

July 22nd, 2012

By Alton Parrish.

Findings suggest the surface of Saturn’s largest moon may have undergone a recent transformation.

For many years, Titan’s thick, methane- and nitrogen-rich atmosphere kept astronomers from seeing what lies beneath. Saturn’s largest moon appeared through telescopes as a hazy orange orb, in contrast to other heavily cratered moons in the solar system.

In 2004, the Cassini-Huygens spacecraft — a probe that flies by Titan as it orbits Saturn — penetrated Titan’s haze, providing scientists with their first detailed images of the surface. Radar images revealed an icy terrain carved out over millions of years by rivers of liquid methane, similar to how rivers of water have etched into Earth’s rocky continents.

While images of Titan have revealed its present landscape, very little is known about its geologic past. Now researchers at MIT and the University of Tennessee at Knoxville have analyzed images of Titan’s river networks and determined that in some regions, rivers have created surprisingly little erosion. The researchers say there are two possible explanations: either erosion on Titan is extremely slow, or some other recent phenomena may have wiped out older riverbeds and landforms.

“It’s a surface that should have eroded much more than what we’re seeing, if the river networks have been active for a long time,” says Taylor Perron, the Cecil and Ida Green Assistant Professor of Geology at MIT. “It raises some very interesting questions about what has been happening on Titan in the last billion years.”

A paper detailing the group’s findings will appear in the Journal of Geophysical Research-Planets.

What accounts for a low crater count?

Compared to most moons in our solar system, Titan is relatively smooth, with few craters pockmarking its facade. Titan is around four billion years old, about the same age as the rest of the solar system. But judging by the number of craters, one might estimate that its surface is much younger, between 100 million and one billion years old.

What might explain this moon’s low crater count? Perron says the answer may be similar to what happens on Earth.

“We don’t have many impact craters on Earth,” Perron says. “People flock to them because they’re so few, and one explanation is that Earth’s continents are always eroding or being covered with sediment. That may be the case on Titan, too.”

For example, plate tectonics, erupting volcanoes, advancing glaciers and river networks have all reshaped Earth’s surface over billions of years. On Titan, similar processes — tectonic upheaval, icy lava eruptions, erosion and sedimentation by rivers — may be at work.

But identifying which of these geological phenomena may have modified Titan’s surface is a significant challenge. Images generated by the Cassini spacecraft, similar to aerial photos but with much coarser resolution, are flat, depicting terrain from a bird’s-eye perspective, with no information about a landform’s elevation or depth.

Images from the Cassini mission show river networks draining into lakes in Titan’s north polar region.

Image: NASA/JPL/USGS

“It’s an interesting challenge,” Perron says. “It’s almost like we were thrown back a few centuries, before there were many topographic maps, and we only had maps showing where the rivers are.”

Charting a river’s evolution

Perron and MIT graduate student Benjamin Black set out to determine the extent to which river networks may have renewed Titan’s surface. The team analyzed images taken from Cassini-Huygens, and mapped 52 prominent river networks from four regions on Titan. The researchers compared the images with a model of river network evolution developed by Perron. This model depicts the evolution of a river over time, given variables such as the strength of the underlying material and the rate of flow through the river channels. As a river erodes slowly through the ice, it transforms from a long, spindly thread into a dense, treelike network of tributaries.

Black compared his measurements of Titan’s river networks with the model, and found the moon’s rivers most resembled the early stages of a typical terrestrial river’s evolution. The observations indicate that rivers in some regions have caused very little erosion, and hence very little modification of Titan’s surface.

“They’re more on the long and spindly side,” Black says. “You do see some full and branching networks, and that’s tantalizing, because if we get more data, it will be interesting to know whether there really are regional differences.”

Going a step further, Black compared Titan’s images with recently renewed landscapes on Earth,

including volcanic terrain on the island of Kauai and recently glaciated landscapes in North America. The river networks in those locations are similar in form to those on Titan, suggesting that geologic processes may have reshaped the moon’s icy surface in the recent past.

Oded Aharonson, a professor of planetary science at the California Institute of Technology, says analyzing geologic processes on Titan may help scientists understand how rivers form. “Besides Earth, Titan is the only world where we see active river networks forming as a result of an active hydrologic cycle,” Aharonson says. “The finding suggests the process of river erosion on Titan is currently responding to resurfacing or resetting of the surface.”

“It’s a weirdly Earth-like place, even with this exotic combination of materials and temperatures,” Perron says. “And so you can still say something definitive about the erosion. It’s the same physics.”

This research was supported by NASA’s Cassini Data Analysis Program.
Contacts and sources:
Jennifer Chu, MIT News Office

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The Lost Pyramid of El Zotz Uncovered, Yields Insight Into Mayan Religion

July 21st, 2012

By Alton Parrish.

Diablo Pyramid Found: El Zotz Masks Yield Insights Into Maya Beliefs

A team of archaeologists led by Stephen Houston has made a new discovery at the Maya archaeological site in El Zotz, Guatemala, uncovering a pyramid believed to celebrate the Maya sun god. The structure’s outer walls depict the god in an unprecedented set of images done in painted stucco. In 2010, the team uncovered a royal tomb filled with artifacts and human remains at the same site. Researchers believe the pyramid was built to link the deceased lord to the eternal sun. A tracing of an image found at the El Zotz archaeological site in Guatemala depicts the Maya sun god. “The stuccos provide unprecedented insight into how the Maya conceived of the heavens,” said archaeologist Stephen Houston, “how they thought of the sun, and how the sun itself would have been grafted onto the identity of kings and the dynasties that would follow them.”



Credit: Stephen Houston

The team of archaeologists led by Brown University’s Stephen Houston has uncovered a pyramid, part of the Maya archaeological site at El Zotz, Guatemala. The ornately decorated structure is topped by a temple covered in a series of masks depicting different phases of the sun, as well as deeply modeled and vibrantly painted stucco throughout.



Credit: Brown University

The team began uncovering the temple, called the Temple of the Night Sun, in 2009. Dating to about 350 to 400 A.D., the temple sits just behind the previously discovered royal tomb, atop the Diablo Pyramid. The structure was likely built after the tomb to venerate the leader buried there.

Houston says that through this find, much of it pristinely preserved, researchers are gaining a significant amount of new information about the Maya civilization.


“The Diablo Pyramid is one of the most ambitiously decorated buildings in ancient America,” Houston says. “The stuccos provide unprecedented insight into how the Maya conceived of the heavens, how they thought of the sun, and how the sun itself would have been grafted onto the identity of kings and the dynasties that would follow them.” This latest discovery was made public earlier today during a press conference in Guatemala City, hosted by the Instituto de Antropologia e Historia de Guatemala, which authorized the work. Houston says the team is still in the beginning stages of the temple’s excavation, with more than 70 percent still to be uncovered. The Maya later built additional levels on top of the original structure, which helped to preserve the stuccos, but this also makes excavation more difficult. While excavating the tomb in 2009, Houston and his team discovered a small portion of the carvings peeking out from looter’s tunnels that had been dug several decades earlier. The archaeologists have only been able to clear narrow tunnels around the building to get a look at the masks and other carvings. There are several sections, including whole sides, an area of the roof, and the base still to be excavated. To get a better idea of what the building would have looked like in its original form, Houston is working with a team from the Center for Advanced Spatial Technologies (CAST) at the University of Arkansas, which uses photogrammetric techniques to create 3-D images of the stuccos. Houston is using those images, as well as hundreds of color photographs taken during the excavation, to create drawings of the building.Renderings indicate that a large solid platform made up the base of the pyramid, which consisted of two or three narrower terraces with the temple sitting at the top. The previously discovered tomb sits just beneath the main platform. A sanctuary was eventually built on top of the tomb to offer protection to the space. Houston says that at one time most of the temple would have been covered in ornate stuccos and that it is possible much of it has survived.

The excavation of the El Zotz site became more important last year, when it was named one of the World Monuments Fund’s 67 international cultural heritage sites at risk. The site is known for one of the very few carved wooden lintels with hieroglyphic text to have survived from pre-Colombian Mesoamerica.



Stephen Houston

“(The sun) was an icon which they linked very deliberately to royal lines, royal identity, and royal power. It’s the most dominant celestial feature. It’s something that rises every day and penetrates into all nooks and crannies, just as royal power presumably would.”
Credit: Arturo Godoy
The team is learning much more about the temple’s purpose. Sitting on a high escarpment overlooking the main part of El Zotz, an ancient Maya city, the pyramid would have been a spectacular presence 1,600 years ago, according to Houston. Painted a saturated red, the temple was intended to announce its presence and the power of the ruling dynasty. It would have been at its brightest during the rising and setting of the sun and visible up to 15 miles away. The stucco masks on the walls of the temple appear to depict several celestial beings, including the sun, which the Maya thought of as a god (“K’inich Ajaw”). Standing five feet tall, several of the masks illustrate different phases of the sun as it moves from east to west in the sky over the course of the day. One mask displays fish-like characteristics, a representation of the rising sun on the horizon, which the Maya associated with the Caribbean to the east. Jeweled bands running between each mask contain archaic representations of Venus and other planets acting as the sky in this solar representation. “The sun was a key element of Maya rulership,” Houston says. “It was an icon which they linked very deliberately to royal lines, royal identity, and royal power. It’s the most dominant celestial feature. It’s something that rises every day and penetrates into all nooks and crannies, just as royal power presumably would. This building is one that celebrates this close linkage between the king and this most powerful and dominate of celestial presences.” The structure was built during a challenging time in the Maya world. The people of El Zotz and Tikal, another large Maya city nearby, were, for the first time, experiencing contact with and intrusions from the people of Teotihuacan, ancient America’s largest metropolis located near modern-day Mexico City. The pyramid may have been erected to signal local power at a time of intrusion and political turbulence. Another finding indicates that the Maya saw the building as a living being rather than just simply a physical structure. At one point, possibly when the Maya were preparing to add new construction to the existing building, the nose and mouths of the masks, as well as identifying glyphs on the forehead diadems, were systematically mutilated, according to Houston, as a way to deactivate the building.Despite the obvious care that was taken in constructing the building, it wasn’t used for long. Houston says evidence at the site shows that the building was abandoned sometime in the A.D. 400s, possibly because of a break in the dynastic order.

Houston, a 2008 MacArthur fellow, is the Dupee Family Professor of Social Science and professor of anthropology at Brown.

Houston’s co-director of the site has been Edwin Román, a Ph.D. candidate at the Long Institute of Latin American Studies at the University of Texas–Austin. They are working with a group of Brown graduate students and researchers, including Thomas Garrison, a former postdoctoral fellow at the Joukowsky Institute and the Department of Anthropology and currently on staff at the University of Southern California, and Sarah Newman, Nicholas Carter, Yeny Gutiérrez, and Boris Beltrán. Photography was done by Arturo Godoy and Alexa Rubinstein.

Fieldwork in 2012 was directed by Edwin Román and Thomas Garrison, with Houston as scientific adviser.

The work at El Zotz has been supported by funding from the National Science Foundation, the National Endowment for the Humanities, private sources, and, for the 2012 field season, by PACUNAM, a Guatemalan charity.

Contacts and sources:
Courtney Coelho
Brown University

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