среда, 29 апреля 2020 г.

Promising signs for Perseverance rover in its quest for past Martian life

New research indicates river delta deposits within Mars' Jezero crater - the destination of NASA' Perseverance rover on the Red Planet - formed over time scales that promoted habitability and enhanced preservation of evidence. Undulating streaks of land visible from space reveal rivers once coursed across the Martian surface - but for how long did the water flow? Enough time to record evidence of ancient life, according to a new Stanford study.

Promising signs for Perseverance rover in its quest for past Martian life
NASA's Mars Perseverance Rover, expected to launch in July 2020, will land in Jezero crater, pictured here. The image was taken
by instruments on NASA's Mars Reconnaissance Orbiter, which regularly captures potential landing sites for future missions
[Credit: NASA/JPL-Caltech/ASU]

Scientists have speculated that the Jezero crater on Mars - the site of the next NASA rover mission to the Red Planet - could be a good place to look for markers of life. A new analysis of satellite imagery supports that hypothesis. By modeling the length of time it took to form the layers of sediment in a delta deposited by an ancient river as it poured into the crater, researchers have concluded that if life once existed near the Martian surface, traces of it could have been captured within the delta layers.

"There probably was water for a significant duration on Mars and that environment was most certainly habitable, even if it may have been arid," according to lead author Mathieu Lapotre, an assistant professor of geological sciences at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "We showed that sediments were deposited rapidly and that if there were organics, they would have been buried rapidly, which means that they would likely have been preserved and protected."

Jezero crater was selected for NASA's next rover mission partly because the site contains a river delta, which on Earth are known to effectively preserve organic molecules associated with life. But without an understanding of the rates and durations of delta-building events, the analogy remained speculative. The new research, published online in AGU Advances, offers guidance for sample recovery in order to better understand the ancient Martian climate and duration of the delta formation for NASA's Perseverance Rover to Mars, which is expected to launch in July 2020 as part of the first Mars sample return mission.

Extrapolating from Earth

The study incorporates a recent discovery the researchers made about Earth: Single-threaded sinuous rivers that don't have plants growing over their banks move sideways about ten times faster than those with vegetation. Based on the strength of Mars' gravity, and assuming the Red Planet did not have plants, the scientists estimate that the delta in Jezero crater took at least 20 to 40 years to form, but that formation was likely discontinuous and spread out across about 400,000 years.

Promising signs for Perseverance rover in its quest for past Martian life
An unvegetated meandering river at the McLeod Springs Wash in the Toiyabe basin of Nevada is an example of what
researchers think is analogous to the ancient streams of Jezero crater on Mars [Credit: Alessandro Ielpi]

"This is useful because one of the big unknowns on Mars is time," Lapotre said. "By finding a way to calculate rate for the process, we can start gaining that dimension of time."

Because single-threaded, meandering rivers are most often found with vegetation on Earth, their occurrence without plants remained largely undetected until recently. It was thought that before the appearance of plants, only braided rivers, made up of multiple interlaced channels, existed. Now that researchers know to look for them, they have found meandering rivers on Earth today where there are no plants, such as in the McLeod Springs Wash in the Toiyabe basin of Nevada.

"This specifically hadn't been done before because single-threaded rivers without plants were not really on anyone's radar," Lapotre said. "It also has cool implications for how rivers might have worked on Earth before there were plants."

The researchers also estimated that wet spells conducive to significant delta buildup were about 20 times less frequent on ancient Mars than they are on Earth today.

"People have been thinking more and more about the fact that flows on Mars probably were not continuous and that there have been times when you had flows and other times when you had dry spells," Lapotre said. "This is a novel way of putting quantitative constraints on how frequently flows probably happened on Mars."

Promising signs for Perseverance rover in its quest for past Martian life
This illustration depicts NASA's Perseverance rover operating on the surface of Mars
[Credit: NASA/JPL-Caltech]

Findings from Jezero crater could aid our understanding of how life evolved on Earth. If life once existed there, it likely didn't evolve beyond the single-cell stage, scientists say. That's because Jezero crater formed over 3.5 billion years ago, long before organisms on Earth became multicellular. If life once existed at the surface, its evolution was stalled by some unknown event that sterilized the planet. That means the Martian crater could serve as a kind of time capsule preserving signs of life as it might once have existed on Earth.

"Being able to use another planet as a lab experiment for how life could have started somewhere else or where there's a better record of how life started in the first place - that could actually teach us a lot about what life is," Lapotre said. "These will be the first samples that we've seen as a rock on Mars and then brought back to Earth, so it's pretty exciting."

* This article was originally published here

вторник, 28 апреля 2020 г.

1,000-year-old church walls discovered in Ethiopia

The walls of a 1,000-year-old church in Ethiopia have been discovered by archaeologists from the Polish Centre of Mediterranean Archaeology at the University of Warsaw.

1,000-year-old church walls discovered in Ethiopia
Credit: M. Mackiewicz/CAS UW

After being forced to abandon their excavation in March after just eight days because of coronavirus, the team led by the Centre’s Dr. Michela Gaudiello decided to use a drone to help with their research. Today, only large, several-meter stone pillars on the top of the hill towering over the surrounding area remain on the surface after the medieval church in Debre Gergis ('Georgios Monastery').

Dr. Gaudiello said: “The locals know that there was once a Christian temple in this place, but due to the poor condition it is not known exactly in which period it was built and what its layout was. We are the first archaeological research team in the world to regularly use a drone for the needs of archaeological documentation in Ethiopia.”

1,000-year-old church walls discovered in Ethiopia
Credit: M. Mackiewicz/CAS UW

In two archaeological excavations, researchers noticed damaged walls probably constituting the outer part of a medieval church. One of them still contained wooden piles. In addition, a fragment of the apse was discovered, in the form of stone floor blocks with a semicircular layout.

The researchers also noticed a block with engraved inscription in Ethiopic. A preliminary analysis of its age based on the fragments of ceramic vessels discovered next to the block suggests that it dates back to 700-1100 AD. Works on translation are underway.

1,000-year-old church walls discovered in Ethiopia
Credit: M. Mackiewicz/CAS UW

Debre Gergis was an important point on trade routes leading from Africa inland to Axum, the capital of a Christian state that existed in the first centuries AD. As part of their latest project, researchers also did reconnaissance around Debra Gergis, because the region is poorly recognized in terms of archaeology and little is known about its ancient history.

Dr. Gaudiello who is from Italy has extensive experience in conducting excavations in Ethiopia. She was appointed project leader in an international competition announced by the Polish Centre of Mediterranean Archaeology UW.

* This article was originally published here

понедельник, 27 апреля 2020 г.

Cyprus accuses British company of illegally excavating ancient shipwrecks

The Cypriot authorities have accused a private British company of illegally excavating ancient shipwrecks in the eastern Mediterranean and “violently extracting objects, causing destruction to their context”.

Cyprus accuses British company of illegally excavating ancient shipwrecks
Chinese Ming porcelain from the Ottoman ‘colossus’ merchant ship, lost around 1630 in the Mediterranean
[Credit: Enigma Recoveries]

The strongly worded statement issued by the antiquities department on Friday comes less than a week after the company, Enigma Recoveries, unveiled news of spectacular treasures including Chinese Ming dynasty bowls found in a dozen wrecks in the waters between Cyprus and Lebanon. The fleet of Hellenistic, Roman, early Islamic and Ottoman wrecks were lost some two kilometres below the waves of the Levantine Basin.

One British archaeologist likened the “once in a generation” finds to discovering a new planet.

But Enigma’s revelations were as enigmatic as the company’s name, with its initial press release raising many questions such as who owned the finds and what would happen to them. The artefacts are at present impounded by the customs department.

Enigma, which used Limassol as its base for the marine excavations which ended in 2015, says the fascinating collection of 588 artefacts found in one vessel dating from 1630 could be in a museum by now, to be appreciated by a wide audience. It has accused the antiquities department of planning to sell the finds one by one at auctions.

Cyprus accuses British company of illegally excavating ancient shipwrecks
Chinese Ming porcelain tea cups on the Ottoman colossus lost around 1630
[Credit: Enigma Recoveries]

The department of antiquities hit back on Friday, denying the accusations and saying the company is well known for its illicit underwater excavations and their intention to sell objects.

“The company is well known both to Cyprus and other countries, as well as international organisations, including UNESCO, for its activities in illicit underwater excavations and their intention to sell objects is evident in the documents filed with the United States Securities and Exchange Commission,” the department said in a written announcement.

“The Cypriot authorities will not, under any circumstances, be auctioning the objects as erroneously reported, since this does not only contravene the ethical code, but it is also prohibited by the antiquities law of Cyprus.”

Engima insists its actions were not illegal and says that while the research ship was entering and departing Cyprus multiple times, the ship’s crew was not aware Cyprus required the cultural artefacts recovered to be listed as ‘cargo’ – which prompted the local customs department to seize the objects.

Cyprus accuses British company of illegally excavating ancient shipwrecks
The Ottoman colossus was stocked with 12 Ottoman ibrik copper coffee pots
[Credit: Enigma Recoveries]

No feedback received during former visits, or when the same ship departed the same port, flagged up any concerns at the time, the company said.

“Enigma Recoveries has consistently reached out to Cypriot authorities to resolve this unfortunate misunderstanding,” the company told the Cyprus Mail.

There is a lot at stake. The star of Enigma’s discoveries is an Ottoman colossus which sunk around 1630, containing goods of 14 cultures and nations from the Levant and as far away as Italy, Spain, Yemen, Iran, India and China.

On the ship the scientists found glass and ceramics from Belgium, Spain, Italy, Yemen and the Persian Gulf alongside Arabian incense and Indian peppercorns. The vessel sank in the reign of the sultan Murad IV (r. 1623-1640).

Cyprus accuses British company of illegally excavating ancient shipwrecks
Camel and rider stone tobacco pipe from the Ottoman colossus
[Credit: Enigma Recoveries]

In the hold was also the earliest Chinese porcelain found on a Mediterranean wreck and the first discovered in the Near East. The 360 cups, dishes and a bottle were made in the kilns of Jingdezhen during the reign of Chongzhen, the last Ming emperor. Decorated with idyllic rural scenes, figures and floral motifs, and designed for sipping tea, in Ottoman hands the 51 styles of blue-and-white cups were adapted to a new fashion sweeping the East, coffee drinking.

“The Enigma colossus is a once in a generation find,” said Tim McKechnie, co-director of Enigma Recoveries. “Imagine, it was so big that two normal-sized ships could have fitted on its deck. Despite being attacked by shipworms, silent assassins of the seas, the ship is richly preserved with a dizzying mix of goods from the ends of the world. The 3D photogrammetry mapping of the Ottoman colossus was a first for this technology in the East Mediterranean.”

However, according to the company it has not been able to do the research as planned, as the artefacts were confiscated by the customs department. Instead the British scientists had to focus on interpreting the shipwrecked discoveries using “the project’s comprehensive records and databases”.

Even who did the recording of the artefacts and their preservation is hotly disputed. The company says all 588 artefacts collected from the ship were carefully recorded using a suite of digital photography, HD video, photomosaics and multibeams.

Cyprus accuses British company of illegally excavating ancient shipwrecks
An iron sword and copper shield submerged in the mud to the top left of the image, taken from
an Ottoman wreck of 1650 to 1700 [Credit: Enigma Recoveries]

The antiquities department insists their staff did the recording and has overseen their conservation.

“Their conservation was undertaken by a specialist conservator under the supervision of the Department of Antiquities, which is still monitoring their state of preservation,” the department said, adding that the digital records show “show the violent extraction of objects causing destruction to their context”.

Engima, meanwhile, says it is concerned over the condition of the artefacts.

“Some of the wooden artefacts are extremely delicate. The glazes on jars and Chinese porcelain left too long in buckets of water are likely to fragment. We are unable to comment on the artefacts’ current state of preservation or damage under Cypriot control,” the company told the Cyprus Mail.

Cyprus accuses British company of illegally excavating ancient shipwrecks
A huge 13-foot iron anchor in the bows of the Ottoman colossus lost around 1630,
 surrounded by green-tinted storage jars [Credit: Enigma Recoveries]

The company says the wreck was discovered in the Levantine Basin of the East Mediterranean, outside the territorial waters of any country and the antiquities department accepts the the artefacts had been excavated in the EEZ/contiguous zone of Lebanon but says as the items were transported into Cyprus waters to Limassol harbour they had to be declared as cargo. As they were not, they had to be seized as they came under the jurisdiction of the customs department.

The company says it is hopeful it will be able to return to the Ottoman wreck to continue the work left in December 2015 “under more favourable conditions”.

“We will continue to make every effort to reach an amicable agreement with Cyprus customs that will lead to the return of the artefacts,” Aladar Nesser, Enigma Recoveries’ international relations representative told the Cyprus Mail.

If the antiquities department has its way, this will not be any time soon.

“A series of measures [have been] undertaken, including, primarily, the recent amendment of the antiquities law, so as to enhance the protection of the underwater cultural heritage in all the sea-zones of the Republic of Cyprus,” its statement on Friday said.

* This article was originally published here

5700 year old settlement unearthed in Upper Valais, Switzerland

As part of the expansion of the senior citizens' centre in Naters, in the canton of Valais in Switzerland, archaeologists have excavated a settlement from the Middle Neolithic period, dating from 3700 to 3550 BC. This is the largest site from this period in the Upper Valais to date. 

5700 year old settlement unearthed in Upper Valais, Switzerland
Credit: Archeodunum/KAA

The site was actually discovered in 2004 during the excavation for the new development. However, due to a weather-related rise in groundwater levels, it could only be briefly examined. At that time, the archaeologists uncovered 33 pits, two fireplaces and 29 postholes, as well as well-preserved ceramic shards and organic material such as charred acorns.

5700 year old settlement unearthed in Upper Valais, Switzerland
Credit: Archeodunum/KAA

In February and March of this year, the expansion of the Naters Senior Citizens' Centre, which had been put on hold, offered the archaeologists another opportunity to uncover an area of 100 square metres in order to excavate the continuation of the settlement consisting of several buildings from the Middle Neolithic period.

5700 year old settlement unearthed in Upper Valais, Switzerland
Credit: Archeodunum/KAA

These investigations yielded significant finds, including decorated pottery, various flint objects and tools such as blades or rock crystal drills: "These rich finds are all characteristic evidence of the period in question, as we expected after the preliminary investigations," says Corinne Juon, archaeologist with the canton.

5700 year old settlement unearthed in Upper Valais, Switzerland
Credit: Archeodunum/KAA

"The remains of the settlement ecompasses an area of no less than 2500 square metres and consists of aligned rows of posts, hearths and pits for waste disposal or storage", explains Juon.

5700 year old settlement unearthed in Upper Valais, Switzerland
Credit: Archeodunum/KAA

The total cost of the archaeological work - including evaluation and publication - amounts to around eight million Swiss francs, according to a statement from the Cantonal Archaeological Service. 

"Thanks to these discoveries and the excavations planned as part of the construction of the A9 motorway between Sierre and Susten, the Upper Valais is set to become one of the favourite areas for archaeologists, particularly for the study of Neolithic societies" the statement added.

* This article was originally published here

воскресенье, 26 апреля 2020 г.

Icelandic DNA jigsaw-puzzle brings new knowledge about Neanderthals

An international team of researchers has put together a new image of Neanderthals based on the genes Neanderthals left in the DNA of modern humans when they had children with them about 50,000 years ago. The researchers found the new pieces of the puzzle by trawling the genomes of more than 27,000 Icelanders. Among other things, they discovered that Neanderthal women gave birth when they were older than the Homo-Sapien women at that time, and Neanderthal men became fathers when they were younger.

Icelandic DNA jigsaw-puzzle brings new knowledge about Neanderthals
DNA of Icelanders provides new knowledge about extinct human species 
[Credit: Arhuus University]

It is well-known that a group of our ancestors left Africa and, about 50,000 years ago, met Neanderthals in Europe, and then had children with them.

Now, a new analysis shows that the Neanderthals may have had children with another extinct species of human (Denisovans), before they met Homo Sapiens, and that these children have been fertile and transferred genes from both species further on to modern people.

The analysis also shows that the Neanderthal women living 100,000 - 500,000 years ago on average became mothers at a later age than the contemporary Homo-Sapien women living in Africa. On the other hand, Neanderthal men fathered at a younger age than their Homo-Sapien cousins in Africa.

How can an analysis show all that?

Neanderthals may well be extinct, but small pieces of their DNA live on in us. All living people outside Africa have up to two per cent Neanderthal genes in their DNA.

However, this two per cent is scattered as small fragments in our genomes, and not all individuals have inherited the same fragments. The fragments are like pieces of a jigsaw puzzle, and if they are put together correctly, they will show a picture of the genome in the Neanderthal population that the modern Homo Sapiens had children with.

New method to find the pieces

First, of course, we have to find these pieces. And this is precisely what the group of researchers from Denmark, Iceland and Germany did to produce their results, published in the scientific journal Nature.

One of them, Laurits Skov, postdoc from the Bioinformatics Research Centre (BiRC) at Aarhus University, has developed a method for tracing Neanderthal fragments in our DNA. Laurits and PhD student Moises Coll Macia took the method to Iceland, where the genetics firm deCODE has amassed genetic data and health information for more than half of the Icelandic population.

"We spent several months at deCODE in Reykjavik on what can be called field studies for a computational biologist. By combining my method with deCODE's data and expertise, we have analysed 27,566 genomes, and this makes our study 10-times larger than previous studies of Neanderthal genes in human DNA," says Laurits Skov.

Together, the many fragments account for approximately half of a complete Neanderthal genome.

Denisovan genes gone astray?

However, the researchers also found significant fragments of genetic material from another archaic species of human, Denisovans, in the DNA of the Icelanders, and this was something of a surprise. Up to now, Denisovan genes have primarily been found in Australian Aborigines, East Asians and people in Papua New Guinea. So how did these genes end up in Islanders' DNA? And when?

Based on the distribution of genes and mutations, the researchers came up with two possible explanations.

Either Neanderthals had children with Denisovans before they met the Homo Sapiens. This would mean that the Neanderthals with whom Homo Sapiens had children were already hybrids, who transferred both Neanderthal and Denisovan genes to the children.

"Up to now, we believed that the Neanderthals modern people have had children with were "pure" Neanderthals. It's true that researchers have found the remnants of a hybrid between Denisovans and Neanderthals in a cave in East Asia, but we have not known whether there were more of these hybrids and whether, thousands of years later, they had children with modern humans," explains Professor Mikkel Heide Schierup from BiRC.

Or Homo Sapiens met Denisovans long before they met Neanderthals. So far, it has been thought that modern humans met Neanderthals and had children with them first, and not until tens of thousands of years later did they have children with Denisovans.

"Both explanations are equally likely, and both explanations will be scientific news," says Mikkel Heide Schierup.

Neanderthal genes of little importance

The study also shows that the Neanderthal DNA has no great importance for modern humans.

"We have previously thought that many of the Neanderthal variants previously been found in modern human DNA were associated with an increased risk of diseases. However, our study shows that the human gene variants located directly beside the Neanderthal genes are better explanations for the risk. We have also found something that can only be explained by Neanderthal genes, but this doesn't mean that much," says Mikkel Heide Schierup.

The properties and risks of diseases that can be linked to Neanderthal DNA are: slightly lower risk of prostate cancer, lower levels of haemoglobin, lower body length (one millimetre) and slightly faster blood plasma clotting.

* This article was originally published here

пятница, 24 апреля 2020 г.

New study reveals life's earliest evolution was more complicated than previously suspected

Biologists have long hoped to understand the nature of the earliest living organisms on Earth. If they could, they might then be able to say something about how, when, and where life arose on Earth, and perhaps by extension, whether life is common in the Universe.

New study reveals life's earliest evolution was more complicated than previously suspected
Phylogenetic tree diagrams form the basis of understanding microbial evolution. Long branches
 between the two domains in some trees may reflect a period of very rapid evolution,
billions of years ago [Credit: S. Shiobara, S. McGlynn]

Previous studies have suggested this information can be obtained by comparing the genes present in modern organisms. New research indicates that only limited information can be derived using this approach.

Biologists classify all living organisms into three major groups they call 'domains.' Two of these domains--the Bacteria and the Archaebacteria--consist of single-celled organisms, while the third--the Eukaryota--includes most of the larger, multicellular organisms we are all familiar with: fungi, plants and animals including ourselves. Of the three domains, the Eukaryota almost certainly evolved the most recently, but questions remain about which of the two single-celled domains arose first in the history of life.

Over forty years ago, American biologists Carl Woese and George Fox suggested that these two domains both emerged from a more primitive organism or group of organisms scientists now call LUCA, or the Last Universal Common Ancestor. Scientists would love to be able to say something concrete about what LUCA was like, what types of environment it lived in, and how it made its living.

New research from Tokyo Tech and the Max Planck Institute suggests understanding early life may be trickier than previously thought.

The research, published in the advanced access edition of the journal Molecular Biology and Evolution, was carried out by Sarah Berkemer, based at the Max Planck Institute for Mathematics in the Sciences in Leipzig, Germany, and Shawn McGlynn from the Earth-Life Science Institute at the Tokyo Institute of Technology in Japan comes in. Their analyses confirm other work which suggested that only a limited understanding of the lifestyle of the most ancient cells can be derived from DNA comparison. 

Although this is a disappointing result for evolutionary biologists, it is important to understand what can and cannot be known from the data that scientists are able to gather from modern organisms. Berkemer and McGlynn's work does supply one silver lining however; while it is clear that we don't know what the first organisms metabolised or where they lived, their work provides insight into how quickly they may have evolved billions of years ago.

New study reveals life's earliest evolution was more complicated than previously suspected
Phylogenetic tree of a protein which is evolutionarily 'mixed' between the archaeal and bacterial domains, precluding assignment
in the LUCA. Other proteins separate the domains onto different branches, suggesting they are ancient
[Credit: Berkemer & McGlynn, 2020]

To do so, Berkemer and McGlynn analyzed thousands of phylogenetic trees derived from the comparison of DNA similarity data from thousands of microorganisms to try to identify the oldest genes and when they might have evolved, and to understand how genes move between organisms to shed light on the nature of LUCA. 

Their careful analysis showed that early in life's history, different gene types changed at different rates. This suggests that early mutation rates were much higher than at present and there has been a significant contribution of 'gene jumping' over time which makes a simple interpretation of the early 'family tree' of life misleading. They concluded that previous studies sometimes vastly under-sampled the available data and that the data cannot resolve these questions, but that it does show that early evolution was wildly different from what it is at present.

Professor McGlynn explains, "A fundamental question in biology is what were the first life forms on Earth. There are two basic ways to try and address this. First, we can use the comparison of gene sequences to try and understand which ones seem most ancient. Second, we can look for evidence biology may have left in the geological record." 

McGlynn says this work shows that although it is clear there is a fuzzy yet remarkable general outline of a family tree of life in the available DNA sequence data, there has been so much evolutionary change that it is still as of yet impossible to say how the earliest organisms made their living or in what types of environments they lived. This is because the signal is simply too noisy due to this early genetic scrambling. As a result, we are still a long way from understanding what the most primitive organisms on Earth were like or the sorts of environments they lived in.

Importantly, however, this study marks the first time scientists have been able to say something about the pace of early evolution. This work shows there is a detectable signal of very rapid early evolution, thus, while we may not know exactly what early organisms were like, it seems likely life was mutating and evolving very quickly early on. Nevertheless, McGlynn believes it is still amazing that this limited information can be understood at all, that it still tells us important things about the evolution of life on Earth, and suggests we need to develop new ways of looking at available DNA data to find novel techniques of learning what Earth's earliest life was like.

* This article was originally published here

четверг, 23 апреля 2020 г.

Earth Day: Taking the pulse of our planet

Today marks the 50th anniversary of Earth Day. For Earth-observing satellites, every day is Earth Day. While news of COVID-19 dominates headlines and many of us practice social distancing, there still remains the need for action on climate change—and satellites are vital in providing the key facts on this global issue.

Earth Day: Taking the pulse of our planet
Today marks the 50th anniversary of Earth Day. For Earth-observing satellites, every day is Earth Day
[Credit: Pixabay]

First celebrated in 1970, Earth Day sparked a wave of international action. In 2016, the United Nations chose this very day—22 April—as the day when the landmark Paris Agreement was signed. Recognised as International Mother Earth Day by the United Nations, today reflects a day committed to understanding our planet's health—protecting it for future generations to come.

The scientific evidence of global climate change is irrefutable. International organizations, such as the Intergovernmental Panel on Climate Change, have warned of the consequences of a warming climate—affecting fresh water resources, global food production, sea level and triggering an increase in extreme-weather events.

In order to tackle climate change, scientists and governments need reliable data in order to understand how our planet is changing. For more than 30 years, Earth observation satellites have gathered valuable data to meet the challenges of our world.

We are all facing the consequences of a rapidly changing world, but thanks to the satellite era we are better placed to understand the 
complexities of our planet, particularly with respect to global change. Today’s satellites are used to forecast the weather, answer 
important Earth-science questions, provide essential information to improve agricultural practices, maritime safety, help when
 disaster strikes, and all manner of everyday applications. The need for information from satellites is growing at an ever-
increasing rate. ESA is a world-leader in Earth observation and remains dedicated to developing cutting-edge
 spaceborne technology to further understand the planet, improve daily lives, support effect policy-making
 for a more sustainable future, and benefit businesses and the economy [Credit: ESA]

Satellites provide unequivocal evidence of the changes taking place on Earth and provide the big picture, collecting long-term series of data, in order to understand its effects. ESA and their partners have recently tracked rapidly melting ice in Greenland and Antarctica, discovered unusual ozone holes, mapped wildfires from space and monitored air pollution in our atmosphere.

With four EU Copernicus Sentinel missions and four Earth Explorer missions in orbit, the satellites cover a vast array of areas, such as ice thickness coverage, deforestation, soil moisture, sea level and ocean surface temperature, as well as other essential climate variables.

The observations provide us with a global coverage, revisiting the same region every few days and proving a good understanding of the health and behavior of our planet—and how it is affected by climate change. Through ESA's Climate Change Initiative, long-term datasets on key indicators of climate change are being systematically generated and preserved.

Earth Day: Taking the pulse of our planet
ESA has been dedicated to observing Earth from space ever since the launch of its first Meteosat weather satellite back in 1977.
With the launch of a range of different types of satellites over the last 40 years, we are better placed to understand the
complexities of our planet, particularly with respect to global change. Today’s satellites are used to forecast the
weather, answer important Earth-science questions, provide essential information to improve agricultural practices,
maritime safety, help when disaster strikes, and all manner of everyday applications. The need for information
from satellites is growing at an ever-increasing rate. With ESA as world-leader in Earth observation, the
Agency remains dedicated to developing cutting-edge spaceborne technology to further understand the
planet, improve daily lives and support effect policy-making for a more sustainable future
[Credit: ESA]

ESA's Director of Earth Observation Programmes, Josef Aschbacher, says, "Earth observation has changed the way we comprehend our profound impact on the environment. Thanks to these sophisticated missions, we have an abundance of data that allows us to take the pulse of our planet.

"ESA is ready to deliver the hard facts required to tackle and address important environmental issues. For us in It is important we take some time today—Earth Day—to appreciate the beauty of our planet and learn more about the impact we have on our changing climate."

There are many ways to actively participate in Earth Day 2020 online. Join the Earth Day live discussion, learn more about what ESA does to combat climate change or explore our gallery of selected images from space.

* This article was originally published here

среда, 22 апреля 2020 г.

Simulations reveal Milky Way could be catapulting stars into its outer halo

Though mighty, the Milky Way and galaxies of similar mass are not without scars chronicling turbulent histories. University of California, Irvine astronomers and others have shown that clusters of supernovas can cause the birth of scattered, eccentrically orbiting suns in outer stellar halos, upending commonly held notions of how star systems have formed and evolved over billions of years.

Simulations reveal Milky Way could be catapulting stars into its outer halo
A simulated galaxy image from the FIRE-2 project, representing a structure spanning more than 200,000 light years,
shows the prominent plumes of young blue stars born in gas that was originally rotating
and then blown radially outward by supernova explosions [Credit: Sijie Yu/UCI]

Hyper-realistic, cosmologically self-consistent computer simulations from the Feedback in Realistic Environments 2 project enabled the scientists to model the disruptions in otherwise orderly galactic rotations. The team's work is the subject of a study published in the Monthly Notices of the Royal Astronomical Society.

"These highly accurate numerical simulations have shown us that it's likely the Milky Way has been launching stars in circumgalactic space in outflows triggered by supernova explosions," said senior author James Bullock, dean of UCI's School of Physical Sciences and a professor of physics & astronomy. "It's fascinating, because when multiple big stars die, the resulting energy can expel gas from the galaxy, which in turn cools, causing new stars to be born."

Bullock said the diffuse distribution of stars in the stellar halo that extends far outside the classical disk of a galaxy is where the "archeological record" of the system exists. Astronomers have long assumed that galaxies are assembled over lengthy periods of time as smaller star groupings come in and are dismembered by the larger body, a process that ejects some stars into distant orbits. But the UCI team is proposing "supernova feedback" as a different source for as many as 40 percent of these outer-halo stars.

Lead author Sijie Yu, a UCI Ph.D. candidate in physics, said the findings were made possible partly by the availability of a powerful new set of tools.

"The FIRE-2 simulations allow us to generate movies that make it seem as though you're observing a real galaxy," she noted. "They show us that as the galaxy center is rotating, a bubble driven by supernova feedback is developing with stars forming at its edge. It looks as though the stars are being kicked out from the center."

Simulations reveal Milky Way could be catapulting stars into its outer halo
This mock Hubble Space Telescope image shows how star formation happens at the edges of a supernova bubble.
The portion highlighted in pink shows the stellar birth region. Blue shaded areas show young stars; red/brown
 shows where dust has obscured the starlight. The simulation shows clearly where stellar
outflow shells are being generated [Credit: Sijie Yu/UCI]

Bullock said he did not expect to see such an arrangement because stars are such tight, incredibly dense balls that are generally not subject to being moved relative to the background of space. "Instead, what we're witnessing is gas being pushed around," he said, "and that gas subsequently cools and makes stars on its way out."

The researchers said that while their conclusions have been drawn from simulations of galaxies forming, growing and evolving to the present day, there is actually a fair amount of observational evidence that stars are forming in outflows from galactic centers to their halos.

"In plots that compare data from the European Space Agency's Gaia mission - which provides a 3D velocity chart of stars in the Milky Way - with other maps that show stellar density and metallicity, we can see structures similar to those produced by outflow stars in our simulations," Yu said.

Bullock added that mature, heavier, metal-rich stars like our sun rotate around the center of the galaxy at a predictable speed and trajectory. But the low-metallicity stars, which have been subjected to fewer generations of fusion than our sun, can be seen rotating in the opposite direction.

He said that over the lifespan of a galaxy, the number of stars produced in supernova bubble outflows is small, around 2 percent. But during the parts of galaxies' histories when starburst events are booming, as many as 20 percent of stars are being formed this way.

"There are some current projects looking at galaxies that are considered to be very 'starbursting' right now," Yu said. "Some of the stars in these observations also look suspiciously like they're getting ejected from the center."

* This article was originally published here


During the early 3rd Millennium BC much of Central and Northern Europe was being infiltrated by pioneer herders, often young men, from the east associated with the Corded Ware culture (CWC). In some important ways, this expansion may have been very similar to the European colonization of the more remote parts of the Americas during the 16th and 17th centuries. For instance, the European

* This article was originally published here

понедельник, 20 апреля 2020 г.

'A bad time to be alive': Study links ocean deoxygenation to ancient die-off

In a new study, Stanford researchers have strongly bolstered the theory that a lack of oxygen in Earth's oceans contributed to a devastating die-off approximately 444 million years ago. The new results further indicate that these anoxic (little- to no-oxygen) conditions lasted over 3 million years - significantly longer than similar biodiversity-crushing spells in our planet's history.

'A bad time to be alive': Study links ocean deoxygenation to ancient die-off
Laminated black shales and cherts exposed on the Peel River, Yukon, Canada, that were deposited during the late Ordovician
and earliest Silurian. These sediments show no evidence of organisms living on the seafloor due to anoxic conditions
at the seabed. Researchers estimated the global extent of low-oxygen conditions during this time period using new
 trace metal isotope data and uncertainty modeling [Credit: Erik Sperling]

Beyond deepening understandings of ancient mass extinction events, the findings have relevance for today: Global climate change is contributing to declining oxygen levels in the open ocean and coastal waters, a process that likely spells doom for a variety of species.

"Our study has squeezed out a lot of the remaining uncertainty over the extent and intensity of the anoxic conditions during a mass die-off that occurred hundreds of millions of years ago," said lead author Richard George Stockey, a graduate student in the lab of study co-author Erik Sperling, an assistant professor of geological sciences at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "But the findings are not limited to that one biological cataclysm."

The study, published in Nature Communications, centered on an event known as the Late Ordovician Mass Extinction. It is recognized as one of the "Big Five" great dyings in Earth's history, with the most famous being the Cretaceous-Paleogene event that wiped out all non-avian dinosaurs some 65 million years ago.

Water world

At the outset of the Late Ordovician event about 450 million years ago, the world was a very different place than it is today or was even in the age of the dinosaurs. The vast majority of life occurred exclusively in the oceans, with plants having just begun to appear on land. Most of the modern-day continents were jammed together as a single super-continent, dubbed Gondwana.

An initial pulse of extinctions began due to global cooling that gripped much of Gondwana under glaciers. By approximately 444 million year ago, a second pulse of extinction then set in at the boundary between the Hirnantian and Rhuddanian geological stages largely - albeit inconclusively - attributed to ocean anoxia. Around 85 percent of marine species vanished from the fossil record by the time the Late Ordovician event ultimately passed.

The Stanford researchers and their study colleagues looked specifically at the second pulse of extinction. The team sought to constrain uncertainty regarding where in Earth's seas a dearth of dissolved oxygen - as critical for oceanic biology then as it is now - occurred, as well as to what extent and for how long. Prior studies have inferred ocean oxygen concentrations through analyses of ancient sediments containing isotopes of metals such as uranium and molybdenum, which undergo different chemical reactions in anoxic versus well-oxygenated conditions.

Elemental evidence

Stockey led the construction of a novel model that incorporated previously published metal isotope data, as well as new data from samples of black shale hailing from the Murzuq Basin in Libya, deposited in the geological record during the mass extinction. The model cast a wide net, taking into account 31 different variables related to the metals, including the amounts of uranium and molybdenum that leach off land and reach the oceans via rivers to settle into the seafloor.

The model's conclusion: In any reasonable scenario, severe and prolonged ocean anoxia must have occurred across large volumes of Earth's ocean bottoms. "Thanks to this model, we can confidently say a long and profound global anoxic event is linked to the second pulse of mass extinction in the Late Ordovician," Sperling said. "For most ocean life, the Hirnantian-Rhuddanian boundary was indeed a really bad time to be alive."

Effects on biodiversity

The lessons of the past suggest that the deoxygenation increasingly documented in the modern oceans, particularly in the upper slopes of the continental shelves that bracket major landmasses, will put strain on many organism types - possibly to the brink of extinction. "There is no way that low oxygen conditions are not going to have a severe effect on diversity," Stockey said.

In this way, in addition to shedding light on Earth of a distant yester-eon, the study's findings could help researchers better model the planet as it is now.

"We actually have a big problem modeling oxygenation in the modern ocean," Sperling said. "And by expanding our thinking of how oceans have behaved in the past, we could gain some insights into the oceans today."

* This article was originally published here

воскресенье, 19 апреля 2020 г.

Volcanic CO2 emissions helped trigger Triassic climate change

A new study finds volcanic activity played a direct role in triggering extreme climate change at the end of the Triassic period 201 million year ago, wiping out almost half of all existing species. The amount of carbon dioxide released into the atmosphere from these volcanic eruptions is comparable to the amount of CO2 expected to be produced by all human activity in the 21st century.

Volcanic CO2 emissions helped trigger Triassic climate change
Credit: McGill University

The end-Triassic extinction has long been thought to have been caused by dramatic climate change and rising sea levels. While there was large-scale volcanic activity at the time, known as the Central Atlantic Magmatic Province eruptions, the role it played in directly contributing to the extinction event is debated. In a study for Nature Communications, an international team of researchers, including McGill professor Don Baker, found evidence of bubbles of carbon dioxide trapped in volcanic rocks dating to the end of the Triassic, supporting the theory that volcanic activity contributed to the devastating climate change believed to cause the mass extinction.

The researchers suggest that the end-Triassic environmental changes driven by volcanic carbon dioxide emissions may have been similar to those predicted for the near future. By analysing tiny gas exsolution bubbles preserved within the rocks, the team estimates that the amount of carbon emissions released in a single eruption - comparable to 100,000 km3 of lava spewed over 500 years - is likely equivalent to the total produced by all human activity during the 21st century, assuming a 2C rise in global temperature above pre-industrial levels.

"Although we cannot precisely determine the total amount of carbon dioxide released into the atmosphere when these volcanoes erupted, the correlation between this natural injection of carbon dioxide and the end-Triassic extinction should be a warning to us. Even a slight possibility that the carbon dioxide we are now putting into the atmosphere could cause a major extinction event is enough to make me worried," says professor of earth and planetary sciences Don Baker.

* This article was originally published here

суббота, 18 апреля 2020 г.

Corded Ware cultural and genetic complexity (Linderholm et al. 2020)

Open access at Scientific Reports at this LINK. Although very useful and broadly accurate, I'm really not sure what to make of this paper yet, especially in regards to its more nuanced inferences. I'll need to look at the genotype data at some point. Worthy of note is that most of the Corded Ware males sampled by the authors belong to Y-haplogroup R1b-M269, rather than R1a-M417, which is the

* This article was originally published here

пятница, 17 апреля 2020 г.

Climate change and the collapse of Angkor Wat

Built using a thousand elephants and 300,000 laborers, the opulent temple city of Angkor has been near-deserted for centuries, yet its grandeur and mystery now attract a million visitors each year. The question is, why was it deserted at all? An answer is finally emerging.

Climate change and the collapse of Angkor Wat
On a floating platform, Penny and team take a drill core sample from an overgrown reservoir.
The 12th century tower S1, of the Prasat Suor Prat group, looms in the background
[Credit: Louise M Cooper]

In the basement of the University's Madsen Building are archives of Cambodia's environmental history, including dozens of drill cores in a cool room, that were extracted from the city of Angkor. These drill cores have seen scientists reconsider the downfall of the world's largest pre-industrial city.

Taken from just two meters beneath the earth's surface, the cores tell the story of how land at Angkor has been used over thousands of years. "Their layers are like pages in a book," says Associate Professor Dan Penny from the School of Geosciences.

"Once we bring a core home from Angkor and split it open, going back through each of those pages is like going back through time," he says, his detailed descriptions conveying a deep knowledge of this ancient city, one he has explored for more than 18 years.

A wonder of the ancient world

Over five centuries, Angkor grew to cover more than a thousand square kilometers, comparable in size to modern day Los Angeles, though with a much lower population density.

The accepted view has been that Angkor collapsed suddenly in 1431, following an invasion by inhabitants of the powerful city of Ayutthaya, in modern day Thailand. Penny and his colleagues put this theory to the test when, in 2016, they took a dozen drill cores from the earth beneath Angkor's temple moats.

From these cores Penny extracted microscopic evidence of past environmental change. In particular, he examined pollen grains from plants and charcoal derived from residential fires, while also measuring rates of erosion and sedimentation.

"We were looking for what people were doing in the landscape. How they used fire, how plants were changing, when occupation was intense and when it decreased," he says. "We certainly didn't find evidence of the sacking in 1431, and a sudden abandonment of the city. It was instead a very prolonged diminution in the commercial and ritual core of the city."

Penny's findings suggest the central city elite left Angkor gradually, attracted, perhaps, to the better located and more profitable trading centers on the Mekong Delta.
That word again: climate

Additional evidence provided by ancient tree rings suggests climatic variation may have been the nail in the coffin. Tree ring cross-sections taken from long-lived conifers indicate a major drought in Angkor towards the middle of the 14th century, followed by intense monsoons and then another big drought.

Climate change and the collapse of Angkor Wat
Split sediment cores reveal layers of history. In the petri dish are ceramic fragments,
sometimes found in these environmental archives [Credit: Louise M Cooper]

"The problem was not drought or flood, but variability between both," Penny says. The collapse of the water network—due to a combination of intense summer monsoon rains and lack of maintenance—likely hastened the city's desertion.

Penny began looking at Angkor as a postdoctoral researcher in 1999, and soon began collaborating with archaeologist Roland Fletcher. Now a professor, Fletcher was at Angkor exploring questions about urbanism and the demise of cities. Penny was researching environmental change at pre-Angkor sites along the Mekong Delta. Their skills were perfectly matched to explore the rise and fall of Angkor.

"It's not a purely urban story, nor is it a purely environmental one," says Penny. "It's a mixture of the two."

Penny returned from Edinburgh University to join the University of Sydney in 2001. Along with Fletcher, he is now a director of the Angkor Research Program, which brings together academics from across the University to better understand this once great city. Rather than focus on the monuments, the program delves into "the stuff that's no longer there."

"We're interested in what goes on between the monuments. We're interested in water, in forests, in soils," all of which draws on Penny's skills in paleo-botany and sedimentology.

Knowing the past to save the future

Why is this important? There are a number of cases, particularly in the tropics, where large, low-density cities failed at least partly because of stress generated by climate variability, Angkor among them.

"That rings quite significant alarm bells because we are moving into a century full of climate variability and more frequent climate extremes," says Penny. "More than half of humanity lives in cities, so understanding the fundamentals of urban resilience in the context of climate change is very important."

Penny points out that when we talk about the collapse of societies, we see it as an end point.

"But it isn't an end point for its people," he says. "It's part of a transformation as populations adapt to changing environments or circumstances. In the case of the Khmer people, the decline of Angkor saw their society transform from one huge agrarian kingdom to become much smaller trading cities along the Mekong Delta."

As Penny's work continues on these so-called middle period cities on the Mekong Delta, his team is also exploring the collapse of civilizations in the Maya territories of Belize, Mexico and Guatemala. Happening at the end of the first millennium, the collapse of the Maya was also triggered by drought. In his Central American work, the focus is on cities that survived.

"What is it about these cities that makes them able to survive the profound changes in climate, whereas cities only tens of kilometers away were destroyed or abandoned?" he asks.

Small-picture thinking

Penny does field work in the tropics of Asia and America every year to collect drill cores. Back in Sydney, he spends much of his time in the laboratory or at the microscope set up on his desk, surrounded by slide boxes, methodically examining every sample. While this kind of scientific work takes patience, what Penny does is laced with moments of pure satisfaction, like finding a pollen grain from a crop plant that someone tended 900 years ago.

"Those connections to places and peoples that are long gone are really exciting."

* This article was originally published here

Mahogany tree family dates back to last hurrah of the dinosaurs

Mahogany is a commercially important wood, valued for its hardness and beauty. The United States is the world's top importer of the tropical timber from leading producers like Peru and Brazil. Unfortunately, mahogany is harvested illegally a lot of the time.

Mahogany tree family dates back to last hurrah of the dinosaurs
The holotype of Manchestercarpa vancouverensis is a section of fruit showing fleshy mesocarp,
leathery meso- carp, thick-walled endocarp, and subapically attached seed
[Credit: University of Kansas]

For science, mahogany is important, too -- the fossil presence of the mahogany family is a telltale of where tropical forests once stood. Until recently, paleobotanists had only found evidence the mahogany family extended back to the Paleocene (about 60 million years ago).

Now, a new paper written by University of Kansas researcher Brian Atkinson in the American Journal of Botany shows the mahogany family goes back millions of years more, to the last hurrah of the dinosaurs, the Cretaceous.

"For understanding when many of the different branches of the tree of life evolved, we're primarily dependent on the fossil record," said Atkinson, an assistant professor of ecology & evolutionary biology and curator in the Biodiversity Institute's Division of Paleobotany. "In this case, Meliaceae, the mahogany family, is an ecologically and economically important group of trees. A lot of researchers have used this group as a study system to better understand the evolution of tropical rainforests. This work is the first definitive evidence that the tropically important trees were around during the Cretaceous period, when we first start to see the modernization of ecosystems and modern groups of plants."

Atkinson's new work pushes back the fossil record for Meliaceae by 15 to 20 million years, the Campanian stage of the Late Cretaceous, from between 72-79 million years ago. The well-preserved mahogany specimen Atkinson analyzed was discovered just off Vancouver Island in Canada.

"The rock that contained the specimen was collected by a local fossil collector, Graham Beard, who is the director of the Qualicum Beach Museum of Natural History," Atkinson said. "He collected it years ago, but I was actually interested in the rock that has this fossil in it for something else. And as I kept preparing this rock, more for the other fossils were in there, this thing showed up by surprise. So, it was kind of found by accident."

To pinpoint the fossil's identity, Atkinson carefully studied the structure of the fossilized fruit and also analyzed phylogenetic information to figure out its relationship to other species in the mahogany family.

"I combined the molecular data from living representatives of the mahogany family with the morphology of the fossil, as well as the morphology of living species," he said. "And then I subjugated that combined dataset to phylogenetic analyses, which allows us to reconstruct evolutionary relationships. Based on this analysis, we found the fossil is closely related to this genus called Melia, which is living today."

The KU researcher gave the oldest-known mahogany fossil the scientific name Manchestercarpa vancouverensis -- the species name signifies where the specimen was discovered, and the genus is named after an esteemed colleague in the field.

"I named it after a prolific paleobotanist who's really improved our understanding of the evolution of flowering plants through the fossil record," Atkinson said. "So, I named it in honor of Steve Manchester, who's at the University of Florida Museum of Natural History."

While it's noteworthy that Atkinson has pushed back the origin story of mahogany, he stressed it also helps improve our understanding of the rate of early flowering plant evolution and, in turn, our grasp of larger modern ecosystems.

"They're our most diverse group of plants on Earth, and so there's a whole lot to explore," he said. "And there are some cool things you can do methodologically that you might not be able to do with other groups of plants. I can really ask some exciting paleontological and general evolutionary questions with this group."

* This article was originally published here


https://t.co/hvL60wwELQ — XissUFOtoday Space (@xufospace) August 3, 2021 Жаждущий ежик наслаждается пресной водой после нескольких дней в о...