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Science

Mural shows earliest known record of salt being sold at a marketplace in the Maya region

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The first documented record of salt as an ancient Maya commodity at a marketplace is depicted in a mural painted more than 2,500 years ago at Calakmul, a UNESCO World Heritage site in the Yucatan Peninsula in Mexico. Credit: Rogelio Valencia, Proyecto Arqueológico Calakmul

The first documented record of salt as an ancient Maya commodity at a marketplace is depicted in a mural painted more than 2,500 years ago at Calakmul, a UNESCO World Heritage site in the Yucatan Peninsula in Mexico. In the mural that portrays daily life, a salt vendor shows what appears to be a salt cake wrapped in leaves to another person, who holds a large spoon over a basket, presumably of loose, granular salt. This is the earliest known record of salt being sold at a marketplace in the Maya region. Salt is a basic biological necessity and is also useful for preserving food. Salt also was valued in the Maya area because of its restricted distribution.

Salt cakes could have been easily transported in canoes along the coast and up rivers in southern Belize, writes LSU archaeologist Heather McKillop in a new paper published in the Journal of Anthropological Archaeology. She discovered in 2004 the first remnants of ancient Maya salt kitchen buildings made of pole and thatch that had been submerged and preserved in a saltwater lagoon in a mangrove forest in Belize. Since then, she and her team of LSU graduate and undergraduate students and colleagues have mapped 70 sites that comprise an extensive network of rooms and buildings of the Paynes Creek Salt Works.

“It’s like a blueprint for what happened in the past,” McKillop said. “They were boiling brine in pots over fires to make salt.”

Her research team has discovered at the Paynes Creek Salt Works, 4,042 submerged architectural wooden posts, a canoe, an oar, a high-quality jadeite tool, stone tools used to salt fish and meat and hundreds of pieces of pottery.

LSU archaeologists discovered in 2004 the first remnants of ancient Maya salt kitchen buildings made of pole and thatch that had been submerged and preserved in a saltwater lagoon in a mangrove forest in Belize. Credit: Heather McKillop, LSU

“I think the ancient Maya who worked here were producer-vendors and they would take the salt by canoe up the river. They were making large quantities of salt, much more than they needed for their immediate families. This was their living,” said McKillop, who is the Thomas & Lillian Landrum Alumni Professor in the LSU Department of Geography & Anthropology.

She investigated hundreds of pieces of pottery including 449 rims of ceramic vessels used to make salt. Two of her graduate students were able to replicate the pottery on a 3D printer in McKillop’s Digital Imaging Visualization in Archaeology lab at LSU based on scans taken in Belize at the study site. She discovered that the ceramic jars used to boil the brine were standardized in volume; thus, the salt producers were making standardized units of salt.

“Produced as homogeneous units, salt may have been used as money in exchanges,” McKillop said.

LSU archeologist Heather McKillop’s research team has discovered at the Paynes Creek Salt Works, 4,042 submerged architectural wooden posts, a canoe, an oar, a high-quality jadeite tool, stone tools used to salt fish and meat and hundreds of pieces of pottery. Credit: Heather McKillop, LSU

An ethnographic interview with a modern day salt producer in Sacapulas, Guatemala collected in 1981 supports the idea that the ancient Maya also may have viewed salt as a valuable commodity:

“The kitchen is a bank with money for us…So when we need money at any time during the year we come to the kitchen and make money, salt.”

Salt: Mover and shaker in ancient Maya society

More information:
Heather McKillop, Salt as a commodity or money in the Classic Maya economy, Journal of Anthropological Archaeology (2021). DOI: 10.1016/j.jaa.2021.101277
Provided by
Louisiana State University

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Mural shows earliest known record of salt being sold at a marketplace in the Maya region (2021, March 22)
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Entertainment

Robin Thicke Takes Criticism of “Blurred Lines” With a “Grain of Salt”

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Since releasing “Blurred Lines” in 2013, Robin Thicke and Pharrell Williams have faced controversy for all sorts of reasons.

In 2015, the two musicians were ordered to posthumously award Marvin Gaye a songwriting credit on the song, after a federal jury found them responsible for copyright infringement. 

The songwriting process was also a topic of debate, with Robin claiming that he played a large role in creating the single, something he later admitted was untrue.

According to The Hollywood Reporter, he confessed to lying about his contributions to the song during the copyright infringement trial, saying, “I was jealous and I wanted some of the credit … I tried to take credit for it later because [Williams] wrote the whole thing pretty much by himself and I was envious of that.”

Then, there are the controversial lyrics, which got the song banned at official events for more than 20 British universities. Critics of the song argued that the lyrics promoted a culture of date rape, citing lines such as, “But you’re a good girl/The way you grab me/Must wanna get nasty.”

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Science

A Previously Unseen Chemical Reaction Has Been Detected on Mars

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The giant Martian sandstorm of 2018 wasn’t just a wild ride – it also gave us a previously undetected gas in the planet’s atmosphere. For the first time, the ExoMars orbiter sampled traces of hydrogen chloride, composed of a hydrogen and a chlorine atom.

 

This gas presents Mars scientists with a new mystery to solve: how it got there.

“We’ve discovered hydrogen chloride for the first time on Mars,” said physicist Kevin Olsen of the University of Oxford in the UK.

“This is the first detection of a halogen gas in the atmosphere of Mars, and represents a new chemical cycle to understand.”

Scientists have been keeping an eye out for gases that contain chlorine in the atmosphere of Mars, since they could confirm that the planet is volcanically active. However, if hydrogen chloride was produced by volcanic activity, it should only spike very regionally, and be accompanied by other volcanic gases.

The hydrogen chloride detected by ExoMars did not, and was not. It was sniffed out in both the northern and southern hemispheres of Mars during the dust storm, and the absence of other volcanic gases was glaring. 

This suggests that the gas was being produced by some other process; luckily, we have similar processes here on Earth that can help us understand what it could be.

It’s a several-step process that requires a few key ingredients. First, you need sodium chloride (that’s regular salt), left over from evaporative processes. There’s plenty of that on Mars, thought to be the remnants of ancient salt lakes. When a dust storm stirs up the surface, the sodium chloride gets kicked up into the atmosphere.

Then there’s the Martian polar ice caps which, when warmed during the summer, sublimate. When the resulting water vapour mingles with the salt, the resulting reaction releases chlorine, which then reacts further to form hydrogen chloride.

Graphic showing the potentially new chemistry cycle detected on Mars. (ESA)

“You need water vapour to free chlorine and you need the by-products of water – hydrogen ­- to form hydrogen chloride. Water is critical in this chemistry,” Olsen said.

“We also observe a correlation to dust: we see more hydrogen chloride when dust activity ramps up, a process linked to the seasonal heating of the southern hemisphere.”

 

This model is supported by a detection of hydrogen chloride during the following 2019 dusty season, which the team is still analysing.

However, confirmation is still pending. Future and ongoing observations will help put together a more comprehensive picture of the process’s cycles.

Meanwhile, laboratory experiments, modelling and simulations will help scientists rule out or confirm potential mechanisms behind the release of hydrogen chloride in the Martian atmosphere.

The research has been published in Science Advances.

 

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Science

Could Mars’ Landslides Be Caused by Underground Salt And Melting Ice?

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Changes in Mars’ geography always attract significant scientific and even public attention.  A hope for signs of liquid water (and therefore life) is likely one of the primary driving forces behind this interest. 

 

One particularly striking changing feature is the Recurring Slope Lineae (RSL) originally found by the Mars Reconnaissance Orbiter (MRO).

Now, scientists at the SETI Institute have a modified theory for where those RSLs might develop – a combination of water ice and salt just under the Martian surface.

According to the SETI team, led by Senior Research Scientist Janice Bishop, there is a two-step process going on that creates these RSLs. 

First, underground water ice must mix with a combination of chlorine salts and sulfates to create a type of slurry that destabilizes the regolith in the area. 

Then, the dry wind and dust storms of Mars take over, blowing the destabilized material into new patterns across the Martian surface.

Krupac Crater also shows RSL development. (NASA/JPL/University of Arizona)

This is not the first time that researchers have suggested that chlorine salts might be involved in the creation of RSL.  As with much good science, this theory has now been fleshed out more through data gathered in both field and lab experiments.

Unfortunately, the field experiments were not able to be carried out on Mars itself (at least not yet). 

 

However, there are several places on our home planet that are considered “Mars analogs”, including the Dead Sea in Israel, Salar de Pajonales in the Atacama Desert, and the Dry Valleys in Antarctica.

The SETI team collected data at some of those locations and noted that surface destabilization has already been observed when salt interacted with gypsum, a type of sulfate. 

For this project, the team collected data in the Dry Valleys, where the soil geology and temperature are remarkably similar to those found on Mars by the Phoenix lander and MRO.

Fieldwork was then followed by lab work, as the team subjected Mars analog regolith to tests using colored indicators that would show how the regolith simulant would react when subjects to the same kind of chemical reactions that were taking place in Antarctica.

All this data collecting resulted in a geological model involving sulfates, chlorides, and water that can account for the appearance of the RSLs seen on Mars’ surface. 

The model also has implications of the habitability of sub-surface Mars and how the presence of this slurry might affect any biosphere the red planet might have. 

Until there are some further on-site tests this model will be hard to prove, but there are plenty of those planned for Mars in the near future.

This article was originally published by Universe Today. Read the original article.

 

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Science

Martian landslides may be caused by melting ice and salt under the surface

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The NASA InSight mission has helped researchers determine that the planet experiences Marsquakes, making it seismically active.

And then there is the mystery of Recurring Slope Lineae, known as RSL, that have intrigued scientists for years. These RSL are a form of landslide on Mars, but no one knows what causes them, said Janice Bishop, author of a new study on the phenomena.

“We see them from orbit by the dark streaks they produce on the ground and they tend to always occur on sun-facing slopes, which led geologists to think they were related to melting ice early on,” said Bishop, senior research scientist at the SETI Institute in California.

“The interesting thing is that they increase over months following dust storms and then fade away, and they appear to form repeatedly in the same regions. Also, a large number of these are forming in the equatorial part of Mars, where there is very little ice.”

Any ice in these regions would have to be in tiny frozen particles that exist between grains of soil below the surface.

These puzzling landslides have never been seen up close by a rover or lander, and until they can be investigated by a robotic explorer, scientists are using lab experiments and Martian analogs on Earth to try and understand them.

Some of the strange environments on Earth that are similar to that of Mars include the Atacama desert in Chile, parts of Antarctica and even the Dead Sea. These places show that surface collapse and landslides occur when salt interacts with sulfates or water underground.

“Antarctica and the Atacama are excellent analogs for Mars because they are ultra dry environments,” Bishop said. “Antarctica has the added benefit that it is super cold. Parts of Antarctica including Beacon Valley are actually on par with Mars for temperature and aridity.”

While water may have once been plentiful on the Martian surface billions of years ago, when the planet was warmer and still retained most of its atmosphere, the current surface of Mars is a freezing cold and barren landscape.

What lies beneath

However, Mars missions and imaging by orbiters have revealed that frozen salty water is below the surface — and that water could be driving activity that appears on the Martian surface, like the landslides.

Bishop and her colleagues collected samples from some similar environments on Earth, including Wright Valley in Antarctica, to test how salts and melting ice underground could cause chemical reactions that trigger these seasonal landslides on Mars. The researchers wanted to test if processes observed in places like Antarctica, where salty sediments can have an effect on surface soil, could be happening on Mars.

The scientists modeled the briny water beneath the surface of Mars in a lab by taking the collected soil samples and exposing them to water and chlorine salts and sulfates — all of which could exist beneath the Martian surface. This experiment resulted in the creation of thin, moving films of slushy water.

To model Martian temperatures where ice exists beneath the surface at the planet’s mid-latitudes, the researchers found slushy ice formed near negative 58 degrees Fahrenheit and a slow, gradual melting of the ice between negative 40 degrees Fahrenheit and negative 4 degrees Fahrenheit.

These temperatures may sound cold, but on Mars, they’re actually considered to be slightly warmer temperatures found near the equator — which could support briny water beneath the surface in the Martian spring and summer.

If this subsurface brine on Mars expands and contracts over time on Mars, it could weaken the surface and cause sinkholes, ground collapse and landslides.

Previously, scientists believed that flows of liquid debris or dry grainy material could be causing the landslides, but neither completely matched up with what scientists saw in the RSL.

However, if ice is melting just beneath the surface, that change would also alter the surface itself. The Martian surface is also at the mercy of wind and seasonal dust storms, which could also play a part in this phenomenon.

“During my fieldwork at Salar de Pajonales, a dry salt bed in Northern Chile, I have observed numerous examples of the action of salts on the local geology. It’s gratifying to find that it could play a role in shaping Mars as well,” said study coauthor Nancy Hinman, a professor of geosciences at the University of Montana, in a statement.

The study published Wednesday in the journal Science Advances.

Chemical activity

“If our hypothesis is correct, then RSL could be indicators for salts on Mars and for near-surface active chemistry,” Bishop said. “Most of us Mars scientists have considered modern Mars as a cold and dry and dormant place, shaped mostly by dust storms. This is certainly true of the surface, but our work shows that the subsurface could be much more chemically active than realized before.”

Bishop noted that this underground process that could result in landslides on the surface would be a slow and limited one.

While this brine would be too salty to support life, the experiments in the study support the idea that this subsurface liquid water can actually move around the salt and mineral grains. If that’s the case, water on Mars 4 billion years ago could have filtered down into the subsurface as a type of permafrost soil. This ice could have thawed and refrozen over time.

“It could be that more of this early water on Mars persisted longer than we realized below the surface,” Bishop said. “If true, this could indicate that the subsurface of Mars was habitable longer than the surface environment. It is difficult to estimate how long, but perhaps liquid water was present around soil grains below the surface until 3 or 2 billion years ago or even more recently.”

Previous research has also suggested that the most habitable part of Mars actually lies beneath its surface.
Future robotic explorers, like the European Space Agency’s Rosalind Franklin rover scheduled to launch in 2022, can drill beneath the surface and investigate what’s going on.

“Once we send rovers to Mars that can drill down into the surface, I think we will see signs of salt reactions below the surface — especially if we investigate some of the equatorial regions where RSL are occurring,” Bishop said.

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