Month: March 2019

Researchers Find Ancient Maya Farms In Mexican Wetlands

Archaeologists with the University of Cincinnati used the latest technology to find evidence suggesting ancient Maya people grew surplus crops to support an active trade with neighbors up and down the Yucatan Peninsula.

They will present their findings at the annual American Association of Geographers conference in Washington, D.C.

The Mayan civilization stretched across portions of Mesoamerica, a region spanning Mexico and Central America. The oldest evidence of Maya civilization dates back to 1800 B.C., but most cities flourished between 250 and 900 A.D. By the time Spanish ships arrived in the 1500s, some of the biggest cities were deserted. Researchers at UC are trying to piece together the life history of the Maya before the Spanish conquest.

Nicholas Dunning, a professor of geography in UC’s McMicken College of Arts and Sciences, was part of a research team that found evidence of cultivation along irregular-shaped fields in Mexico that followed the paths of canals and natural water channels at a place called Laguna de Terminos on the Gulf of Mexico. The archaeologists expect to find evidence of habitation when they begin excavations.

The extensive croplands suggest the ancient Maya could grow surplus crops, especially the cotton responsible for the renowned textiles that were traded throughout Mesoamerica.

“It was a much more complex market economy than the Maya are often given credit for,” Dunning said.

Local workers brought the Laguna de Terminos site to the attention of researchers about seven years ago.

“A forester working in the area said there seemed to be a network of ancient fields,” Dunning said. “I looked on Google Earth and was like, ‘Whoa!’ It was an area in the Maya Lowlands that I’d never paid any attention to. And obviously not a lot of other people had, either, from the perspective of looking at ancient agriculture.”

Satellite images revealed a patchwork quilt of blocks along drainage ditches that suggested they were built. Archaeologist also studied imagery NASA created of the region using a tool called Light Detection and Ranging, or LIDAR, that can depict the contours of the ground beneath the leafy canopy of trees and vegetation. Their review confirmed Dunning’s suspicions: the area was covered in ancient farm fields.

“It appears they developed fairly simply from modifications of existing drainage along the eastern edge of the wetlands,” Dunning said. “They probably deepened and straightened some channels or connected them in places, but then further expanded the fields with more sophisticated hydro-engineering.”

LIDAR gives scientists a never-before-seen picture of the Earth’s surface even after centuries of unchecked jungle growth conceals the remains of ancient structures. Researchers look for telltale signs of human activity: squares and rectangles indicating old foundations and circular pits from human-made reservoirs and quarries where the chert used in stone tools was mined. On the LIDAR maps, any hidden structures pop out, including ancient roads and former villages.

“That’s the magic of LIDAR,” UC assistant research professor Christopher Carr said.??Carr spent a career practicing engineering before returning to UC to study and eventually teach in the geography department. He approaches questions about the ancient Maya from an engineer’s perspective.

Carr pointed to a map of Yaxnohcah, Mexico, showing a small reservoir the ancient Maya apparently dug in a wetland far from cultivated fields or known settlements.

“What were my ancient counterparts thinking when they built that water reservoir? What did they want to accomplish?” he asked.

Carr also used the LIDAR imagery in the project to follow an ancient Maya road that perhaps hasn’t been traveled in more than 1,000 years. The road is perfectly visible on the LIDAR map but is virtually impossible to discern when you are standing right on it, Carr said.

“There’s vegetation everywhere. But when you’ve been doing this for a while, you notice little things,” Carr said. “I’ll have a LIDAR image on my smartphone that shows me where I am, but I don’t see anything but rainforest. You just walk back and forth until you can feel something underfoot and follow it.”

Identifying possible roads is important for another interest of the UC researchers: ancient Maya marketplaces. Dunning and Carr are working at Yaxnohcah with researchers such as Kathryn Reese-Taylor from the University of Calgary and Armando Anaya Hernandez from Universidad Autónoma de Campeche to unlock the mysteries of the ancient Maya economy. Additionally, they and graduate student Thomas Ruhl have been analyzing NASA’s LIDAR imagery across the Yucatan Peninsula to identify more ancient marketplaces.

Unlike pyramids or even many homes, marketplaces had no foundations or permanent structures, researchers said. They were built on low platforms or cleared areas, perhaps like a seasonal fair or flea market. But they were an important part of life in Maya culture

Dunning said the presence of roads between Maya cities would lend credence to the value the ancient Maya placed on trade with their neighbors. He thinks some of the larger squares identified on the LIDAR maps represent these open markets.

“In some areas, they have this very distinct physical signature,” Dunning said. “So far, we’ve identified several possible marketplaces. We don’t know for sure that they’re marketplaces, but they have an architectural layout that is suggestive of one.”

Soil analysis at other locations identified evidence of ancient butcher shops and stone masons. Dunning solicited the help of UC’s botanists who are conducting analyses that might shed light on his marketplace hypothesis. But the LIDAR maps themselves are instructive.

“I look at spatial patterns. If you look at these big structures and small pyramids, you can tell they’re important structures,” Carr said. “And then you have this ‘lightweight’ thing next to it. That’s what a marketplace looks like to me.”

Dunning said the ancient Maya likely sold perishable goods such as maize and a starchy tuber called manioc. And they traded “mantas,” or bolts of the ornate and richly patterned textiles made from the cotton they grew. These were prized by the Spaniards who arrived in the 1600s.

“We don’t have direct evidence of what the textiles look like in this area. But if you look at ancient paintings and sculptures, people were wearing very elaborate garments,” Dunning said.

Dunning first explored the historic sites of the Yucatan Peninsula at age 14 when he and his older brother drove down to Mexico from Illinois.

“We took a train to the Yucatan and used public transportation to get around to the sites,” Dunning said.

He applied to the University of Chicago partly because it offered a Mayan language class. Dunning returned to Mexico while in college to conduct his first field research. He’s been back many times since.

“My interest in archaeology is in human-environment interactions, including agriculture,” Dunning said.

Dunning is learning more about how ancient Maya people shaped their world to overcome challenges and take advantage of natural opportunities. Dunning’s work also took him to a place called Acalan near the Gulf of Mexico.

“Roughly translated, Acalan means ‘place of canoes’ because it’s very watery,” Dunning said. “And getting around by water is far easier than any other means in that area.”

Then as now the region is covered in thick tropical rainforest. Researchers have to be wary of cheeky monkeys that will throw fruit or worse from the treetops. Carr said one encounter left him sore for days.

“There was this aggressive spider monkey. He’d seen me a couple days earlier. And he’s back shaking the trees,” Carr said. “And all of a sudden, I’m lying flat on the ground. A branch hit me in the shoulder and knocked me to the ground.”

Visiting archaeologists at Yaxnohcah stay at a former Army outpost that was converted into a staffed research station.

“Living conditions are actually luxurious by camping standards. You’re in the field all day and you’re dirty and tired. But you can take a shower. And when you’re finished, someone has cooked you a meal,” Carr said.

At Laguna de Terminos, UC researchers are working to collect clues about the ancient Maya before they are lost to development. Many of the wetlands are being drained or plowed up for grazing pasture.?

Dunning said ironically these low-yield pastures provide far less economic value to today’s farmers than the seeming bounty of crops the ancient Maya derived from them more than 1,000 years ago. Their study warns the land-use practices are causing environmental damage to some of these valuable wetlands.

“It’s a shame because the grazing isn’t particularly good. The economic production from that land use is minuscule compared to what was produced by the Maya,” Dunning said.

Huge Explosion at Popocatepetl Volcano Spews Lave and Ash

Mexican authorities have raised the alert level for the Popocatepetl volcano near Mexico City to indicate increasing intensity after it started spewing steam and gas and ejected burning fragments that caused fires in surrounding pastures.

Mexico’s National Center for Disaster Prevention warned people to stay away from Popocatepetl, saying that in the previous 24 hours it had observed more than 200 discharges from the volcano, some 50 miles to the southeast.

The center raised the volcano’s alert level to yellow phase three from yellow phase two, indicating possible magma expulsion and explosions of increasing intensity. It is the third-highest warning on the center’s seven-step scale, according to the Mexican Civil Protection agency.

An eruption late on Tuesday generated a 3 kilometer (1.9 mile) column that released fragments of burning rock up to 2 km (1.24 miles) away in a northeasterly direction, setting fires to nearby pastures. Several municipalities reported ash falling on them from the explosion, the center said.

Popocatepetl has spewed smoke and ash over the last few years, and a major eruption in 2000 forced the evacuation of nearly 50,000 residents in three states surrounding the peak.

The agency has previously said that similar intensification of activity in the 5,450 meter (17,900 foot) volcano could provoke big explosions capable of sending incandescent fragments out over considerable distances, as well as ash showers.

Van Allen Probes Prepare for Final Descent into Earth’s Atmosphere

Two tough, resilient NASA spacecraft have been orbiting Earth for the past six and a half years, flying repeatedly through a hazardous zone of charged particles known as the Van Allen radiation belts. The twin Van Allen Probes have confirmed scientific theories and revealed new structures, compositions, and processes at work in these dynamic regions.

In February, the Van Allen Probes mission operations team at the Johns Hopkins Applied Physics Laboratory—where the probes were designed and built—began a series of orbit descent maneuvers that will position the satellites for an eventual re-entry into Earth’s atmosphere in approximately 15 years.

“At the new altitude, aerodynamic drag will bring down the satellites and eventually burn them up in the upper atmosphere,” said Nelli Mosavi, project manager for the Van Allen Probes at APL. “Our mission is to obtain great science data and also to ensure that we prevent more space debris so the next generations have the opportunity to explore space as well.”

Originally designated as a two-year mission because no one believed that a spacecraft could survive longer in the harsh radiation belts that surround Earth, these rugged spacecraft have operated without incident since 2012 and continue to enable groundbreaking discoveries about the Van Allen belts.

“The spacecraft and instruments have given us incredible insight into spacecraft operations in a high-radiation environment,” Mosavi said. “Everyone on the mission feels a real sense of pride and accomplishment in the work we’ve done and the science we’ve provided to the world—even as we begin the de-orbiting maneuvers.”

“We know that other planets in our solar system with magnetic fields have radiation belts,” said Sasha Ukhorskiy, a project scientist at APL. “We can assume that other bodies throughout the universe do too. By studying the belts and the physics associated with them here at Earth, and using our world as a natural laboratory, we can learn about how these structures function around other objects in the universe with magnetic fields.”

The magnetic field surrounding Earth creates a bubble known as the magnetosphere, which protects the planet from plasma blasts sent out by the sun. But it also serves to capture particles and can eventually settle these high-energy particle populations into radiation belts around Earth.

A complex chain of processes occurs in this near-Earth environment, acting like a giant particle accelerator and speeding some particles up to nearly the speed of light—more than 670 million miles an hour. These highly energized particles in the radiation belts can pose a number of hazards to space operations, as they can damage sensitive electronics.

During solar storms, conditions worsen, and the belts can swell in size, threatening nearby spacecraft.

“Our magnetic field does a pretty good job of shielding us from these solar blasts,” said David Sibeck, a mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But some of their energy penetrates deep into the Earth’s field and, through a variety of mechanisms, powers up the radiation belts. When that happens, spacecraft in the belts had better look out: Trouble lies ahead in the form of short circuits, disrupted computer memory, and instrument failure.”
The Van Allen Probes were designed and built to be resilient in this extreme environment—and even their builders were surprised by their ability to withstand such harsh conditions.

“Over the past six and a half years, the Van Allen Probes have completed three full circuits around the magnetosphere, and measured more than 100 geomagnetic storms,” Ukhorskiy said. “The Van Allen Probes verified and quantified previously suggested theories, discovered new mechanisms that can sculpt near-Earth energetic particle populations, and used uniquely capable instruments to unveil unexpected features that were all but invisible to previous sensors.”

The information on particles and waves delivered by the Van Allen Probes has proved to be a treasure trove for space physics research. Findings and observations include multiple belt structures, including a third belt observed shortly after launch; definitive answers about particle acceleration processes; and the discovery of a nearly impenetrable barrier region that prevents the fastest and most energetic electrons from reaching Earth.

Unusual Galaxies Defy Dark Matter Theory

After drawing both praise and skepticism, the team of astronomers who discovered NGC 1052-DF2 – the very first known galaxy to contain little to no dark matter – are back with stronger evidence about its bizarre nature.

Dark matter is a mysterious, invisible substance that typically dominates the makeup of galaxies; finding an object that’s missing dark matter is unprecedented, and came as a complete surprise.

“If there’s one object, you always have a little voice in the back of your mind saying, ‘but what if you’re wrong?’ Even though we did all the checks we could think of, we were worried that nature had thrown us for a loop and had conspired to make something look really special whereas it was really something more mundane,” said team leader Pieter van Dokkum, Sol Goldman Family Professor of Astronomy at Yale University.

Now, van Dokkum’s team has not one, but two, new studies supporting their initial observations, demonstrating that dark matter is in fact separable from galaxies.

Team members include Roberto Abraham, Professor of Astronomy and Astrophysics at the University of Toronto, Aaron Romanowsky, Associate Professor of Physics and Astronomy at San Jose State University, Charlie Conroy, Professor of Astronomy at Harvard University, and Shany Danieli, a graduate student at Yale University.

“The fact that we’re seeing something that’s just completely new is what’s so fascinating,” said Danieli, who first spotted the galaxy about two years ago. “No one knew that such galaxies existed, and the best thing in the world for an astronomy student is to discover an object, whether it’s a planet, a star, or a galaxy, that no one knew about or even thought about.”

Hubble Watches Asteroid Coming Apart

A small asteroid has been caught in the process of spinning so fast it’s throwing off material, according to new data from NASA’s Hubble Space Telescope and other observatories.

Images from Hubble show two narrow, comet-like tails of dusty debris streaming from the asteroid (6478) Gault. Each tail represents an episode in which the asteroid gently shed its material—key evidence that Gault is beginning to come apart.

Discovered in 1988, the 2.5-mile-wide (4-kilometer-wide) asteroid has been observed repeatedly, but the debris tails are the first evidence of disintegration. Gault is located 214 million miles (344 million kilometers) from the Sun. Of the roughly 800,000 known asteroids between Mars and Jupiter, astronomers estimate that this type of event in the asteroid belt is rare, occurring roughly once a year.

Watching an asteroid become unglued gives astronomers the opportunity to study the makeup of these space rocks without sending a spacecraft to sample them.

“We didn’t have to go to Gault,” explained Olivier Hainaut of the European Southern Observatory in Germany, a member of the Gault observing team. “We just had to look at the image of the streamers, and we can see all of the dust grains well-sorted by size. All the large grains (about the size of sand particles) are close to the object and the smallest grains (about the size of flour grains) are the farthest away because they are being pushed fastest by pressure from sunlight.”

Gault is only the second asteroid whose disintegration has been strongly linked to a process known as a YORP effect. (YORP stands for “Yarkovsky-O’Keefe-Radzievskii-Paddack,” the names of four scientists who contributed to the concept.) When sunlight heats an asteroid, infrared radiation escaping from its warmed surface carries off angular momentum as well as heat. This process creates a tiny torque that can cause the asteroid to continually spin faster. When the resulting centrifugal force starts to overcome gravity, the asteroid’s surface becomes unstable, and landslides may send dust and rubble drifting into space at a couple miles per hour, or the speed of a strolling human. The researchers estimate that Gault could have been slowly spinning up for more than 100 million years.

Piecing together Gault’s recent activity is an astronomical forensics investigation involving telescopes and astronomers around the world. All-sky surveys, ground-based telescopes, and space-based facilities like the Hubble Space Telescope pooled their efforts to make this discovery possible.

The initial clue was the fortuitous detection of the first debris tail, observed on Jan. 5, 2019, by the NASA-funded Asteroid Terrestrial-Impact Last Alert System (ATLAS) telescope in Hawaii. The tail also turned up in archival data from December 2018 from ATLAS and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) telescopes in Hawaii. In mid-January, a second shorter tail was spied by the Canada-France-Hawaii Telescope in Hawaii and the Isaac Newton Telescope in Spain, as well as by other observers. An analysis of both tails suggests the two dust events occurred around Oct. 28 and Dec. 30, 2018.

Follow-up observations with the William Herschel Telescope and ESA’s (European Space Agency) Optical Ground Station in La Palma and Tenerife, Spain, and the Himalayan Chandra Telescope in India measured a two-hour rotation period for the object, close to the critical speed at which a loose “rubble-pile” asteroid begins to break up.

New Evidence of Deep Groundwater on Mars

In mid-2018, researchers supported by the Italian Space Agency detected the presence of a deep-water lake on Mars under its south polar ice caps. Now, researchers at the USC Arid Climate and Water Research Center (AWARE) have published a study that suggests deep groundwater could still be active on Mars and could originate surface streams in some near-equatorial areas on Mars.

The researchers at USC have determined that groundwater likely exists in a broader geographical area than just the poles of Mars and that there is an active system, as deep as 750 meters, from which groundwater comes to the surface through cracks in the specific craters they analyzed.

Heggy, who is a member of the Mars Express Sounding radar experiment MARSIS probing Mars subsurface, and co-author Abotalib Z. Abotalib, a postdoctoral research associate at USC, studied the characteristics of Mars Recurrent Slope Linea, which are akin to dried, short streams of water that appear on some crater walls on Mars.

Scientists previously thought these features were affiliated with surface water flow or close subsurface water flow, says Heggy.

“We suggest that this may not be true. We propose an alternative hypothesis that they originate from a deep pressurized groundwater source which comes to the surface moving upward along ground cracks,” Heggy says.

“The experience we gained from our research in desert hydrology was the cornerstone in reaching this conclusion. We have seen the same mechanisms in the North African Sahara and in the Arabian Peninsula, and it helped us explore the same mechanism on Mars,” said Abotalib Z. Abotalib, the paper’s first author.

The two scientists concluded that fractures within some of Mars’ craters, enabled water springs to rise up to the surface as a result of pressure deep below. These springs leaked onto the surface, generating the sharp and distinct linear features found on the walls of these craters. The scientists also provide an explanation on how these water features fluctuate with seasonality on Mars.

The study, to be published on March 28, 2018, in Nature Geoscience, suggests that groundwater might be deeper than previously thought in areas where such streams are observed on Mars. The findings suggest that the exposed part of these ground fractures associated with these springs as the primary location candidates to explore Mars’ habitability. Their work suggests that new probing methods should be developed to study these fractures.

Method:
Previous research to explore groundwater on Mars relied on interpreting the returned electromagnetic echoes sent from the radar-probing experiments from orbit onboard Mars Express and Mars Reconnaissance Orbiter. These experiments measured the reflection of the waves from both the surface and the subsurface whenever penetration was possible. However, this earlier method did not yet provide evidence of groundwater occurrence beyond the 2018 South Pole detection.

The authors of this current Nature Geoscience study used hi-resolution optical images and modeling to study the walls of large impact craters on Mars. The goal was to correlate the presence of fractures with the sources of streams that generate short water flows.

Heggy and Abotalib, who have long studied subsurface aquifers and groundwater flow movement on Earth and in desert environments, found similarities between the groundwater moving mechanisms in the Sahara and on Mars.

“Groundwater is strong evidence for the past similarity between Mars and Earth—it suggest they have a similar evolution, to some extent,” says Heggy.

He says this deep source of groundwater is the most convincing evidence of similarities between the two planets—it suggest both may have had wet periods long enough to create such an active groundwater system.

For Heggy, an advocate for water science and water science education in arid areas, this particular study is not about colonization. But he says these rare and puzzling water flows on Mars are of big interest to the science community.

“Understanding how groundwater has formed on Mars, where it is today and how it is moving helps us constrain ambiguities on the evolution of climatic conditions on Mars for the last three billion years and how these conditions formed this groundwater system. It helps us to understand the similarities to our own planet and if we are going through the same climate evolution and the same path that Mars is going. Understanding Mars’ evolution is crucial for understanding our own Earth’s long-term evolution and groundwater is a key element in this process. ”

The new study suggests that the groundwater that is the source of these water flows could be at depths starting at 750 meters deep. “Such depth requires us to consider more deep-probing techniques to look for the source of this groundwater versus looking for shallow sources of water, ” says Heggy.

What Happened Before the Big Bang?

A team of scientists has proposed a powerful new test for inflation, the theory that the universe dramatically expanded in size in a fleeting fraction of a second right after the Big Bang. Their goal is to give insight into a long-standing question: what was the universe like before the Big Bang?

Although cosmic inflation is well known for resolving some important mysteries about the structure and evolution of the universe, other very different theories can also explain these mysteries. In some of these theories, the state of the universe preceding the Big Bang – the so-called primordial universe – was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.

To help decide between inflation and these other ideas, the issue of falsifiability – that is, whether a theory can be tested to potentially show it is false – has inevitably arisen. Some researchers, including Avi Loeb of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Mass., have raised concerns about inflation, suggesting that its seemingly endless adaptability makes it all but impossible to properly test.

“Falsifiability should be a hallmark of any scientific theory. The current situation for inflation is that it’s such a flexible idea, it cannot be falsified experimentally,” Loeb said. “No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it.”

Now, a team of scientists led by the CfA’s Xingang Chen, along with Loeb, and Zhong-Zhi Xianyu of the Physics Department of Harvard University, have applied an idea they call a “primordial standard clock” to the non-inflationary theories, and laid out a method that may be used to falsify inflation experimentally. The study will appear in Physical Review Letters as an Editors’ Suggestion.

In an effort to find some characteristic that can separate inflation from other theories, the team began by identifying the defining property of the various theories – the evolution of the size of the primordial universe.

“For example, during inflation, the size of the universe grows exponentially,” Xianyu said. “In some alternative theories, the size of the universe contracts. Some do it very slowly, while others do it very fast.

“The attributes people have proposed so far to measure usually have trouble distinguishing between the different theories because they are not directly related to the evolution of the size of the primordial universe,” he continued. “So, we wanted to find what the observable attributes are that can be directly linked to that defining property.”

The signals generated by the primordial standard clock can serve such a purpose. That clock is any type of heavy elementary particle in the primordial universe. Such particles should exist in any theory and their positions should oscillate at some regular frequency, much like the ticking of a clock’s pendulum.

The primordial universe was not entirely uniform. There were tiny irregularities in density on minuscule scales that became the seeds of the large-scale structure observed in today’s universe. This is the primary source of information physicists rely on to learn about what happened before the Big Bang. The ticks of the standard clock generated signals that were imprinted into the structure of those irregularities. Standard clocks in different theories of the primordial universe predict different patterns of signals, because the evolutionary histories of the universe are different.

“If we imagine all of the information we learned so far about what happened before the Big Bang is in a roll of film frames, then the standard clock tells us how these frames should be played,” Chen explained. “Without any clock information, we don’t know if the film should be played forward or backward, fast or slow, just like we are not sure if the primordial universe was inflating or contracting, and how fast it did so. This is where the problem lies. The standard clock put time stamps on each of these frames when the film was shot before the Big Bang, and tells us how to play the film.”

The team calculated how these standard clock signals should look in non-inflationary theories, and suggested how they should be searched for in astrophysical observations. “If a pattern of signals representing a contracting universe were found, it would falsify the entire inflationary theory,” Xianyu said.

The success of this idea lies with experimentation. “These signals will be very subtle to detect,” Chen said, “and so we may have to search in many different places. The cosmic microwave background radiation is one such place, and the distribution of galaxies is another. We have already started to search for these signals and there are some interesting candidates already, but we need more data.”

Many future galaxy surveys, such as US-lead LSST, European’s Euclid and the newly approved project by NASA, SphereX, are expected to provide high quality data that can be used toward the goal.

Read more at: https://phys.org/news/2019-03-big.html#jCp