Beyond Angkor: How lasers revealed a lost city

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Deep in the Cambodian jungle lie the remains of a vast medieval city, which was hidden for centuries. New archaeological techniques are now revealing its secrets – including an elaborate network of temples and boulevards, and sophisticated engineering.

In April 1858 a young French explorer, Henri Mouhot, sailed from London to south-east Asia. For the next three years he travelled widely, discovering exotic jungle insects that still bear his name.

Today he would be all but forgotten were it not for his journal, published in 1863, two years after he died of fever in Laos, aged just 35.

Mouhot’s account captured the public imagination, but not because of the beetles and spiders he found.

Readers were gripped by his vivid descriptions of vast temples consumed by the jungle: Mouhot introduced the world to the lost medieval city of Angkor in Cambodia and its romantic, awe-inspiring splendour.

“One of these temples, a rival to that of Solomon, and erected by some ancient Michelangelo, might take an honourable place beside our most beautiful buildings. It is grander than anything left to us by Greece or Rome,” he wrote.

 

His descriptions firmly established in popular culture the beguiling fantasy of swashbuckling explorers finding forgotten temples.

Today Cambodia is famous for these buildings. The largest, Angkor Wat, constructed around 1150, remains the biggest religious complex on Earth, covering an area four times larger than Vatican City.

It attracts two million tourists a year and takes pride of place on Cambodia’s flag.

But back in the 1860s Angkor Wat was virtually unheard of beyond local monks and villagers. The notion that this great temple was once surrounded by a city of nearly a million people was entirely unknown.

It took over a century of gruelling archaeological fieldwork to fill in the map. The lost city of Angkor slowly began to reappear, street by street. But even then significant blanks remained.

Then, last year, archaeologists announced a series of new discoveries – about Angkor, and an even older city hidden deep in the jungle beyond.

An international team, led by the University of Sydney’s Dr Damian Evans, had mapped 370 sq km around Angkor in unprecedented detail – no mean feat given the density of the jungle and the prevalence of landmines from Cambodia’s civil war. Yet the entire survey took less than two weeks.

Their secret?

Lidar – a sophisticated remote sensing technology that is revolutionising archaeology, especially in the tropics.

Mounted on a helicopter criss-crossing the countryside, the team’s lidar device fired a million laser beams every four seconds through the jungle canopy, recording minute variations in ground surface topography.

The findings were staggering.

Lidar technology has revealed the original city of Angkor - red lines indicate modern features including roads and canals

Lidar technology has revealed the original city of Angkor – red lines indicate modern features including roads and canals

The archaeologists found undocumented cityscapes etched on to the forest floor, with temples, highways and elaborate waterways spreading across the landscape.

“You have this kind of sudden eureka moment where you bring the data up on screen the first time and there it is – this ancient city very clearly in front of you,” says Dr Evans.

These new discoveries have profoundly transformed our understanding of Angkor, the greatest medieval city on Earth.

Phra Sav Ling Povn, palace of the leprous king, near Angkor Wat, circa 1930

Phra Sav Ling Povn, palace of the leprous king, near Angkor Wat, circa 1930

At its peak, in the late 12th Century, Angkor was a bustling metropolis covering 1,000 sq km. (It would be another 700 years before London reached a similar size.)

Angkor was once the capital of the mighty Khmer empire which, ruled by warrior kings, dominated the region for centuries – covering all of present-day Cambodia and much of Vietnam, Laos, Thailand and Myanmar. But its origins and birthplace have long been shrouded in mystery.

A few meagre inscriptions suggested the empire was founded in the early 9th Century by a great king, Jayavarman II, and that his original capital, Mahendraparvata, was somewhere in the Kulen hills, a forested plateau north-east of the site on which Angkor would later be built.

But no-one knew for sure – until the lidar team arrived.

The lidar survey of the hills revealed ghostly outlines on the forest floor of unknown temples and an elaborate and utterly unexpected grid of ceremonial boulevards, dykes and man-made ponds – a lost city, found.

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Most striking of all was evidence of large-scale hydraulic engineering, the defining signature of the Khmer empire.

By the time the royal capital moved south to Angkor around the end of the 9th Century, Khmer engineers were storing and distributing vast quantities of precious seasonal monsoon water using a complex network of huge canals and reservoirs.

Harnessing the monsoon provided food security – and made the ruling elite fantastically rich. For the next three centuries they channelled their wealth into the greatest concentration of temples on Earth.

One temple, Preah Khan, constructed in 1191, contained 60t of gold. Its value today would be about £2bn ($3.3bn).

But despite the city’s immense wealth, trouble was brewing.

At the same time that Angkor’s temple-building programme peaked, its vital hydraulic network was falling into disrepair – at the worst possible moment.

The end of the medieval period saw dramatic shifts in climate across south-east Asia.

Tree ring samples record sudden fluctuations between extreme dry and wet conditions – and the lidar map reveals catastrophic flood damage to the city’s vital water network.

With this lifeline in tatters, Angkor entered a spiral of decline from which it never recovered.

In the 15th Century, the Khmer kings abandoned their city and moved to the coast. They built a new city, Phnom Penh, the present-day capital of Cambodia.

Life in Angkor slowly ebbed away.

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When Mouhot arrived he found only the great stone temples, many of them in a perilous state of disrepair.

Nearly everything else – from common houses to royal palaces, all of which were constructed of wood – had rotted away.

The vast metropolis that once surrounded the temples had been all but devoured by the jungle.

 

Source: BBC

Image credit: David Lazar

Cassini Watches Mysterious Feature Evolve in Titan Sea

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September 29, 2014

NASA’s Cassini spacecraft is monitoring the evolution of a mysterious feature in a large hydrocarbon sea on Saturn’s moon Titan. The feature covers an area of about 100 square miles (260 square kilometers) in Ligeia Mare, one of the largest seas on Titan. It has now been observed twice by Cassini’s radar experiment, but its appearance changed between the two apparitions.

Images of the feature taken during the Cassini flybys are available at:

http://photojournal.jpl.nasa.gov/catalog/PIA18430

The mysterious feature, which appears bright in radar images against the dark background of the liquid sea, was first spotted during Cassini’s July 2013 Titan flyby. Previous observations showed no sign of bright features in that part of Ligeia Mare. Scientists were perplexed to find the feature had vanished when they looked again, over several months, with low-resolution radar and Cassini’s infrared imager. This led some team members to suggest it might have been a transient feature. But during Cassini’s flyby on August 21, 2014, the feature was again visible, and its appearance had changed during the 11 months since it was last seen.

Scientists on the radar team are confident that the feature is not an artifact, or flaw, in their data, which would have been one of the simplest explanations. They also do not see evidence that its appearance results from evaporation in the sea, as the overall shoreline of Ligeia Mare has not changed noticeably.

The team has suggested the feature could be surface waves, rising bubbles, floating solids, solids suspended just below the surface, or perhaps something more exotic.

The researchers suspect that the appearance of this feature could be related to changing seasons on Titan, as summer draws near in the moon’s northern hemisphere. Monitoring such changes is a major goal for Cassini’s current extended mission.

“Science loves a mystery, and with this enigmatic feature, we have a thrilling example of ongoing change on Titan,” said Stephen Wall, the deputy team lead of Cassini’s radar team, based at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re hopeful that we’ll be able to continue watching the changes unfold and gain insights about what’s going on in that alien sea.”

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.

For more information about Cassini and its mission, visit:

http://www.nasa.gov/cassini

http://saturn.jpl.nasa.gov

Source: NASA news

Traces of Neanderthal Virus DNA Found in Modern Human Genomes

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Even though the last common ancestor of Homo sapiens and Neanderthals lived at least 400,000 years ago, traces of our cousins can still be found in our DNA. Fragments of DNA from viruses that affected Neanderthals have been found in modern human genomes according to new research led by Emanuele Marchi from the University of Oxford’s Department of Zoology, which was was published online this month in Current Biology.

Marchi’s results show that humans today have traces of Neanderthal viruses in portions of our DNA that don’t code for protein. DNA from Denisovan bone fragments was compared with genetic samples from Neanderthals and cancer patients today. The results showed that viruses that infected Neanderthals nearly half a million years ago can still be found in our genomes today, and researchers aren’t sure yet what implications that DNA may have for modern diseases like HIV and cancer.

Viral DNA that gets passed down though DNA is known as endogenous retroviruses (ERVs). While ERVs make up almost a tenth of our genomes, it is found in regions that we don’t really understand. There are hints that some of these ERVs can team up to cause disease, but it requires a lot more study. Future research will seek to understand ERVs better to determine if it still has pathogenic properties and if those ancient genetic sequences can possibly be used to target treatments.

As genetic sequencing techniques continue to improve, we will continue to understand our evolutionary history more completely. By learning more about what makes us who we are, we will be able to exploit those processes to improve our quality of life while we’re here and will make it better for those who come after.

Found on: ifl science

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