Chinese researchers have made another new discovery while studying data acquired from China's Zhurong Mars rover, confirming that wind and sand activities on the Martian surface have recorded changes in the ancient Martian environment. The discovery, scientists said, may shed light on predicting future climate changes on Earth.
The research findings have been published online in the science journal Nature on Thursday, the China Lunar Exploration Project (CLEP) said on its official WeChat account on Monday.
Among planets in the solar system, Mars is considered to be the most similar to Earth. Scientists believe that the current state and evolutionary history of Mars may represent the "future of Earth." Therefore, the study of Martian climate evolution has long been a topic of great interest, and wind and sand activity have shaped the extensive distribution of sand dune features on the Martian surface.
"Wind and sand activities can be said to have recorded the characteristics of the late evolution and recent climate environment of Mars, as well as the process of its climate change. However, due to the lack of detailed and systematic scientific observations in situ and at close range, we still know very little about the process," said Li Chunlai, a research fellow at the National Astronomical Observatory of China, Chinese Academy of Sciences.
In order to address this scientific question, researchers used high-resolution cameras, navigation terrain cameras and multispectral cameras among others on the Zhurong rover to conduct joint remote sensing and close-range investigations in the landing area on the Red Planet.
Through in-depth analysis, the researchers discovered significant evidence of changes in the wind regime in the Zhurong landing area.
The evidence shows good consistency with the ice-dust cover layers found in high latitudes on Mars, indicating that the Zhurong landing area may have experienced two major climate stages marked by changes in wind direction, with a nearly 70-degree shift from northeast to northwest.
The wind-sand accumulation transformed from crescent-shaped bright dunes to longitudinal dark sand ridges.
This climate change occurred approximately 400,000 years ago, at the end of the last ice age on Mars, scientists said, according to the CLEP. It is believed to have been caused by variations in the axial tilt of Mars, which resulted in a global climate transition from an ice age to an interglacial period.
Li said that this research has contributed to our understanding of the ancient climate history of Mars, providing a new perspective for the study of Mars' ancient climate and important constraints for global climate simulations on Mars. It may even provide insights for the future climate evolution of Earth, Li said.
The Chinese Embassy in Pakistan and the Chinese Consulate General in Karachi have strongly condemned an attack on a convoy of Chinese engineers working on a project at Gwadar port, Pakistan on Sunday morning.
The convoy was ambushed by bombs and gunshots on their way from the airport to the port at 9:17 am Sunday local time, according to a statement released by the Chinese Consulate General in Karachi on Sunday. No injuries or casualties were reported in the attack.
The convoy of three SUVs and a van, all bulletproof, carried 23 Chinese personnel, the Global Times learned from one of the Chinese personnel.
An IED exploded during the attack and the van was shot at. A picture obtained by the Global Times shows the bulletproof glass on the window of a van belonging to the Chinese convoy cracked from the attack, and there were bullet holes on the windows.
All the personnel concerned have been properly relocated, according to the Chinese Embassy in Pakistan.
The Embassy and the Chinese Consulate General in Karachi on Sunday night strongly condemned the act of terrorism, and asked the Pakistani side to severely punish the attackers and to take practical and effective measures to ensure the safety of Chinese nationals, institutions and projects.
The Consulate General activated the emergency response plan immediately, reminding local Chinese nationals, enterprises and projects to be more vigilant, upgrade security initiatives, prevent security risks, closely monitor the security situation and ensure safety.
The Chinese Embassy and Consulate General urged Chinese nationals in Pakistan to maintain high vigilance, safeguard life and property safety, and strictly control large-scale gathering activities due to the severe security situation.
China will continue to work with Pakistan to jointly address the threat of terrorism and effectively protect the security of Chinese personnel, institutions and projects in Pakistan, said the embassy in a statement.
Pakistani security forces killed one terrorist and three others were injured during a security clearance operation in Gwadar, local media outlet Daily Pakistan reported Sunday. After getting intelligence about the presence of militants, security forces cordoned off the area and started a search operation to find other militants, according to Daily Pakistan.
The Balochistan Liberation Army (BLA), a militant separatist group, claimed responsibility for the attack, according to media reports.
Chinese personnel have been targeted by terror attacks by Baloch militant groups many times.
In April 2022, a terror attack against the shuttle bus used by Karachi's Confucius Institute killed three Chinese teachers and their local driver, for which the BLA took responsibility.
In August 2021, two children were killed and three were wounded in an attack targeting Chinese nationals in Gwadar.
In July 2021, a shuttle bus blast in Pakistan that killed nine Chinese and four Pakistanis was confirmed to be a terrorist attack.
In April 2021, a deadly car bomb explosion that rocked a hotel which was hosting the Chinese ambassador in Quetta, Bolochistan province killed five people, for which Pakistan Taliban claimed responsibility.
In 2018, the BLA attacked the Chinese Consulate-General in Karachi in south Pakistan, during which two police officers were killed. In May 2017, 10 workers were killed by two gunmen on motorbikes, which the BLA claimed was a response to the development of the China-Pakistan Economic Corridor (CPEC).
The purpose of this BLA-planned terrorist attack is no different from the previous terror attacks against Chinese personnel, mainly because it wants to impact China-Pakistan cooperation, especially the CPEC, Qian Feng, director of the research department at the National Strategy Institute at Tsinghua University, told the Global Times.
The terrorist group deliberately set the attack in August as the CPEC had just celebrated the 10th anniversary of its cooperation in July and was hoping to take advantage of a period of change in the administration in the country.
Qian noted that although the ongoing unrest in Balochistan has limited the Pakistani government's presence in the province, the Pakistani government managed to protect Chinese personnel from being harmed in this attack, which demonstrates the strength of their protection. The attack will not affect the continued construction of CPEC in the future, he said.
Together with other nine departments, the National Health Commission (NHC) has launched a one-year campaign to crack down on corruption in the healthcare sector across the country, focusing on "key few" and key positions in the pharmaceutical industry to ensure high-quality development of the medical and healthcare sector, the NHC announced on Tuesday.
Since China started the sweeping anti-corruption drive in the public health sector in mid-July, at least 176 Party secretaries or heads of hospitals had been put under investigation as of Saturday, according to media estimates.
Strengthening the anti-corruption work in the healthcare field is an important content of promoting the high-quality development of the pharmaceutical industry, and an important part of improving the construction of the pharmaceutical governance system.
In recent years, some people in key positions have been guilty of accepting kickbacks, bribery and profiteering, among other crimes, thereby seriously diluting the dividends gained from the reform and development of the pharmaceutical industry and eroding the rights and interests of the people. This not only hinders the reform and development of medical, insurance and pharmaceutical undertakings, but also jeopardizes the interests of the vast majority of people in the field of medicine and health, the NHC said on Tuesday.
The one-year campaign covers the entire chain of production, circulation, sales, use and reimbursement in the pharmaceutical industry, as well as pharmaceutical administrative departments, industry associations, medical and health institutions, pharmaceutical production and operation enterprises, and medical insurance funds, according to the NHC.
This concentrated campaign will focus on six aspects: administrative departments in the field of medicine using power for profiteering; the "key few" and major key positions in medical and health institutions; sales representatives for drugs, equipment, and consumables; social organizations that accept the management and guidance of administrative departments that use their position for self benefit; illegal acts by pharmaceutical enterprises during purchases and sales; and medical staff in violation of the standards for integrity, the NHC said.
Recently, some media outlets have reported on the suspension and postponement of some academic conferences due to the anti-corruption campaign. However, the NHC responded that what needs to be remedied is the illegal behavior of fabricating academic conferences out of thin air, carrying out illegal benefits transmission, or illegally sharing the sponsorship fees of academic conferences.
Medical experts said that the anti-corruption campaign in the sector this year is different from previous campaigns, as it is sweeping and more vigorous than ever.
Corruption in the medical sector is a serious issue that affects the credibility of the healthcare system and the interest of patients, said Zhong Chongming, an expert from the China Health Culture Association.
As the medical anti-corruption campaign has received widespread attention, some social platforms have exposed several corruption cases. In one case, Xu Bo, the director of the cardiac catheterization room at Fuwai Hospital, the Chinese Academy of Medical Sciences, was investigated by the discipline inspection team of the Central Commission for Discipline Inspection and the NHC of the State Supervisory Commission for suspected serious violations of discipline and law. At present, the case is still under investigation.
After confirming with related departments, the NHC said that online rumors about Xu using the opportunity of surgeries, consumables, and participation in the procurement of medical equipment bidding to accept bribes of up to 1.2 billion yuan ($165.6 million) are seriously inconsistent with the current investigation of the case.
China's top cyberspace regulator announced on Monday the launch of a two-month nationwide special campaign to regulate the network environment for the 19th Asian Games in Hangzhou, East China's Zhejiang Province, addressing problems such as fan conflicts involving insults and comment manipulation.
According to the notice released by the secretary bureau of the Cyberspace Administration of China, the Copyright Management Bureau of the Central Publicity Department and the office of the Organizing Committee of the 19th Asian Games in Hangzhou, the campaign kicked off on Monday and will run through October 29. The campaign will focus on eight categories of prominent problems.
Issues to be addressed include the incitement of insults among fans and the manipulation of comments.
The cyberspace regulator will also rectify the problem of excessive sensationalism and "fan circle culture" in the sports event coverage.
The campaign will target "human flesh search" activities that deliberately expose personal information of athletes, referees and coaches, leading to online violence, as well as the release of unlawful and harmful information that spreads insults, defamatory, abusive and attacking content, causing harm to individuals' physical and mental health.
The authority will also regulate internet news and information service activities without authorization or permission, as well as activities that create and disseminate fake sports event videos with generative artificial intelligence (AI) technology.
Other behaviors that will be rectified during the campaign include spreading false information about the Hangzhou Asian Games and Asian Para Games, the related regional public policies and social and livelihood issues, fabricating rumors about disasters and accidents, illegal activities, food and product quality issues, and other false information that could cause panic.
Besides, unlawful marketing activities that promote commodities and services or collect personal information, private identification or biometric information in the name of the sports events will also be targeted.
The notoriously intricate strategy game Go has a new champion.
AlphaGo, Google’s Go-playing computer program, has topped Lee Sedol, the world’s reigning player, in a five-game match played over a week in South Korea.
The program, a breakthrough in artificial intelligence, learned to play Go by watching human experts and by playing millions of games against itself. It stepped into the world spotlight in January, when it beat Fan Hui, the European champion, 5 games to 0. Victory wasn’t certain against Sedol, though, a player often described as “legendary.”
But by March 12, Sedol was officially sunk. AlphaGo had defeated the human in three consecutive games. The only question left was whether the program would sweep the match. In game 4, however, Sedol defied expectations and pulled out a win. In game 5, AlphaGo made a big mistake early on, but clawed its way back in a match that Google DeepMind’s Demis Hassabis tweeted was “nail-biting.”
Google DeepMind, the artificial intelligence company that developed AlphaGo, will give away the $1 million in prize money, splitting it amongst UNICEF, science, technology, engineering and math charities, and Go organizations.
For Wisconsin’s snowshoe hares, climate change now ranks as an even bigger menace than the bulldozing, paving and other destructive things people have done to northern forests.
Habitat loss as humans reshape landscapes has loomed for decades as the main conservation problem for a lot of wildlife. It’s still important, says climate change ecologist Benjamin Zuckerberg of the University of Wisconsin‒Madison. But along the southern boundary of the snowshoe hares’ range, climate change bringing skimpy snow covers has surpassed direct habitat loss as a threat, Zuckerberg and his colleagues say March 30 in Proceedings of the Royal Society B. North America’s Lepus americanus hares may be especially sensitive to climate change. “Almost everything about them screams adaptation to seasons of extensive snow cover,” says study coauthor Jonathan Pauli, also at Wisconsin‒Madison. The hares have outsized snowshoe feet, thick fur and an annual molt from brown to snow-white. Getting out of sync with the snow turns camouflage into a come-on for predators (SN Online: 1/26/16). In bad years, “there’s a lot of white hares on brown backgrounds,” Pauli says.
To see how the hares have fared, the researchers looked for signs of the animals at 199 sites during the winters of 2012‒2013 and 2013‒2014. Many of these locations were mentioned in a rather anecdotal 1945 study and in a more systematic one in 1979 to 1980. Satellite images showed not much change in the overall amount of hare-suitable forest since the 1980s, but snow cover averages have declined. When researchers put all their information into a computer simulation, the climate-related changes — particularly the length of the snow-cover season — did a better job of explaining the ups and downs of hare populations than just the forest changes did. Snow cover has powerful effects on hares. For each 7.41 days that snow blankets the landscape, snowshoe hare populations become four times as likely to survive, the researchers found.
If the hares dwindle from a place, the loss may ripple through the ecosystem. “Snowshoe hares are central, really central, to prey species,” Pauli says. Lynx, great horned owls, coyotes and many more species dine on them. And regardless of any ecosystem role, hares are remarkable creatures in their own right. “It’s hard for me, a person living in Wisconsin, to imagine these northern conifer forests without snowshoe hares,” Pauli says. To prevent such a loss, reducing greenhouse gases is important, but so is creating “climate-resilient landscapes,” Zuckerberg says. For snowshoe hares, that landscape might bristle and tangle with abundant, thick young growth, full of hiding places for too conspicuous, out-of-season-sync hares, he suggests.
White furry animals may not be the only ones that will have to cope with a shift in the balance of threats. “In a number of cold-associated butterflies, and also birds, it is becoming clear that climate change is beginning to surpass land use as the primary driver of extinction at the trailing edges of the species’ range,” says ecologist Tom Oliver of the University of Reading in England. And the threats of climate change and land-use upsets can intensify each other. “We appear to be entering a worrying time,” Oliver says.
NEW YORK — Sometimes forgetting can be harder than remembering. When people forced themselves to forget a recently seen image, select brain activity was higher than when they tried to remember that image.
Forgetting is often a passive process, one in which the memory slips out of the brain, Tracy Wang of the University of Texas at Austin said April 2 at the annual meeting of the Cognitive Neuroscience Society. But in some cases, forgetting can be deliberate. Twenty adults saw images of faces, scenes and objects while an fMRI scanner recorded their brains’ reactions to the images. If instructed to forget the preceding image, people were less likely to remember that image later. Researchers used the scan data to build a computer model that could infer how strongly the brain responds to each particular kind of image. In the ventral temporal cortex, a part of the brain above the ear, brain patterns elicited by a particular image were stronger when a participant was told to forget the sight than when instructed to remember it.
Of course, everyone knows that it’s easy to forget something without even trying. But these results show that intentional forgetting isn’t a passive process — the brain has to actively work to wipe out a memory on purpose.
Tadpoles don’t cry to get their way. But some of them sure can beg.
Each bout of hungry-baby drama among mimic poison frogs (Ranitomeya imitator) occupies both parents for hours. The tadpoles get so crazy-frantic that researchers wanted to know whether the begging is an honest call for help or a histrionic scam.
Frogs can lay globs of eggs by the thousands and leave them to fend for themselves. But the two-to three-egg clutches of mimic poison frogs (the only known monogamous frogs) get coddled, says Kyle Summers of East Carolina University in Greenville, N.C. Dad repeatedly checks in, sitting on the eggs and shedding some paternal pee if they’re drying out. When the eggs hatch, dad gives each tadpole a piggyback ride to its own private pool. To find a little rainfall cupped between a leaf and stem, he’ll haul youngsters four meters or so. “A bit of a hike,” Summers says, since dad is only about a centimeter or two long himself.
These baby pools are pretty empty: home to only some algae, maybe some small insects. “The good news is that your offspring are not likely to get eaten; the bad side is that they don’t have anything to eat,” Summers says. This is where the begging comes in. Frogs can’t make milk like mammals or regurgitate bugs like birds. But this species is one of the rare frogs whose moms, after considerable persuading, will lay an unfertilized egg for the tadpoles’ breakfast. When parents show up on their weekly visit, a youngster stops regular swimming, noses up to a parent and goes into a frenzy of vibrating its tail. “The parent cannot miss a hungry tadpole,” Summers says.
Bouts of persuasion go on for several hours as the tadpole begs, stops, begs more and then more. Mom often makes several false starts, entering the pool but leaving it without any egg action. During all this, “dad will be the cheerleader,” calling in trills and stroking her, Summers says.
Analyzing tadpole frenzies in the lab, Summers’ then-student Miho Yoshioka found that tadpoles on short rations begged more as hungry weeks dragged on. Parents fed these hungrier tadpoles more reliably than the babies that researchers slipped treats to, Yoshioka, Summers and Casey Meeks report in the March Animal Behaviour. Overall, the researchers conclude, the relentless frenzy shows honest need, not tadpole greed.
A mushroom whose genes have been edited with molecular scissors known as CRISPR/Cas9 doesn’t need to be regulated like other genetically modified crops, the U.S. Department of Agriculture said April 13 in a letter to the mushroom’s creator. The edible fungus is the first CRISPR-edited crop to clear USDA regulation.
Yinong Yang, a plant pathologist at Penn State University, used CRISPR/Cas9 to snip out a tiny bit of one gene from the mushroom Agaricus bisporus. The edit reduces browning when the mushroom is sliced.
Because the gene editing left no foreign DNA behind, the USDA’s Animal and Plant Health Inspection Service determined that the mushroom poses no risk to other plants and is not likely to become a weed.
Yang says he plans to submit data about the mushroom to the U.S. Food and Drug Administration. FDA clearance isn’t required but, says Yang, “we’re not just going to start marketing these mushrooms without FDA approval.”
Smartphone-toting pilgrims regularly stream into northern Cambodia from all over the world. Their destination: Angkor Wat, a medieval temple that’s famous for massive towers and majestic stone carvings of Hindu gods, spirits and mythological battle scenes. The site, considered the world’s largest religious monument, drew more than 2.3 million visitors in 2014.
Angkor Wat’s sightseers encounter a study in contrasts. This architectural wonder of human civilization ascends skyward, on the verge of being engulfed by nature below. Tourists walk along a path that crosses over a moat and through the temple’s western side, the one entrance cleared of vegetation. Lush forest stops just short of the rest of the structure. Outside the moat, trees, thick ground cover and ponds dominate the landscape. While adventurous visitors snap pictures, scientists are using high-tech approaches to uncover Angkor Wat’s hidden side, long obscured by all that vegetation. After more than a century of research on the parts of Angkor Wat that are visible with the naked eye, many scientists assumed that the site was a sacred city contained within the bounds of a square moat. But even though its name roughly translates as “temple city,” new finds show that Angkor Wat was not a sacred city at all. It was a gigantic temple connected to residential districts, canals and other structures that stretched beyond the moat and blended into a sprawling city called Greater Angkor, which covered about the same area as Berlin or Columbus, Ohio. Angkor Wat’s unveiling by modern laser technology began in April 2012. Archaeologist Damian Evans of Cambodia’s Siem Reap Center and several colleagues made daily helicopter flights for almost two weeks over a 370-square-kilometer area around the temple. The helicopter carried $250,000 worth of special equipment that fired millions of laser pulses every few seconds at the forest below. A small percentage of those pulses zipped in between trees and foliage to the forest floor. The Earth’s hard surface bounced those laser shots back to a sensor on the helicopter. This technique, known as light detection and ranging, or lidar for short, picked up differences in the contours of the land now obscured by jungle. With the findings, researchers could draw a picture of city blocks, residential areas, dried-out ponds and other archaeological remains. Results gleaned from lidar and from new ground-based investigations appeared in the December 2015 Antiquity.
Lidar has been around since the early 1960s. Scientists have used it to measure pollutants in the atmosphere, map shorelines and guide robotic and manned vehicles around obstacles. Lower costs over the last decade have made the technology accessible to archaeologists.
With their laser eye in the sky, Evans and colleagues uncovered big surprises at Angkor Wat. Just beyond one side of the roughly 1.3-kilometer-square moat surrounding the temple, the researchers found six massive and mysterious lines of earth arranged in precise coils — as well as adjacent areas where later canal construction had apparently destroyed two more coiled mounds. These Khmer creations resemble the spiraling paths of labyrinths. Lidar-guided excavations within the moat’s boundary upended ideas about who lived on temple grounds. Rather than religious or political bigwigs, residents were workers who kept the place running. And on-the-ground research found evidence of unexplained towers, built and then demolished during Angkor Wat’s construction, as well as defensive platforms used, perhaps, to fight off invaders. SUBSCRIBE “It’s an embarrassingly exciting time for archaeologists who study Angkor Wat,” says University of Sydney archaeologist Roland Fletcher. “Researchers have driven and walked over many of these new discoveries for a century.” Fletcher directs the Greater Angkor Project, which combines remote sensing technology with archaeological digs.
If Angkor Wat blended into Greater Angkor’s 1,000 square kilometers of urban sprawl, so did hundreds of other temples and shrines of lesser grandeur built by rulers of Southeast Asia’s Khmer Empire from the ninth to 15th centuries, he says.
“There was nothing like Greater Angkor until the advent of 19th century industrial cities,” says Fletcher, who estimates it held about 750,000 residents in the 12th and 13th centuries. Cities of around 1 million people arose in China by the ninth century, but those metropolises covered one-half or less the area of Greater Angkor. Spread-out cities in the mold of Greater Angkor became more common in the 1800s as trains and cars made long-distance travel easier. But discoveries at Greater Angkor shatter a long-standing assumption that urban sprawl was impossible without mechanical forms of transportation, he says. City sprawl Lidar technology revealed new structures in and around the Angkor Wat temple complex. Tap red dots for details Big grids Carved inscriptions at Angkor Wat describe the structure as the pet project of Suryavarman II, who ruled the Khmer Empire from 1113 until his death in 1149. Serving first as a temple dedicated to the Hindu god Vishnu, Angkor Wat also became a mausoleum for Suryavarman II when he died.
The temple hosted Hindu ceremonies into the 13th century. In the 14th or 15th century, it became a Buddhist temple. Like tourists and scientists, Angkor Wat’s modern-day Buddhist monks had no idea that the site was once so extensive.
Lidar revealed a grid of pathways forming four rectangular blocks, each the size of a small town, that encircle the main temple inside the moat. Earthen mounds and an estimated 250 to 300 ponds — now dried-out depressions on the forest floor — dotted these gridded areas.
Excavations in 2010 and 2013, the latter guided by lidar findings, uncovered remains of modest wooden dwellings and household goods, such as pots and a ceramic cooking device, in the mounds. Archaeologist Miriam Stark of the University of Hawaii at Manoa in Honolulu led that work.
Radiocarbon dating conducted by Stark’s team indicates that houses situated around the ponds appeared at least as early as the sixth century near the eventual site of Angkor Wat. Other residences date to after the 15th century, supporting evidence — including a 17th century Japanese map of the Angkor Wat temple — of the structure becoming a Buddhist religious center. No more than 4,500 people lived within Angkor Wat’s moated boundary in the 12th century, Fletcher estimates. His calculation is based on the account of a 13th century Chinese emissary to Greater Angkor, who wrote that one to three families shared each pond in the area around the tample.
Stone inscriptions at nearby Ta Prohm, a late–12th century Greater Angkor temple, record a workforce of 12,640 people that included only about 2,000 on-site residents. Another 66,625 people were described as being “in service” to the temple, delivering food and other supplies.
At roughly twice the size of Ta Prohm, Angkor Wat probably relied on a workforce of about 25,000, Fletcher suspects. An additional 125,000 people must have shuttled in supplies. Each Greater Angkor temple apparently supported a vast economy.
If that’s true, it makes sense that crisscrossing roads forming residential blocks fan out far beyond Angkor Wat’s moat on the 2012 lidar map. “Urban grids stretched beyond temple walls into the hinterlands,” Evans says.
Lidar data showed a comparable street network at a nearby 12th century temple, Angkor Thom. Here too, “to our complete surprise, the layout of houses and streets continues beyond the moated confines of the temple,” says archaeologist Charles Higham of the University of Otago in New Zealand. He studies Greater Angkor and is familiar with the lidar results.
Religious and political big shots lived somewhere in the urban sprawl outside Angkor Wat and other temples, Fletcher suspects. Why they did so is unclear.
Mystery coils Finding that Angkor Wat extended far beyond its moat was unexpected. But a discovery just south of the temple’s moat was unprecedented.
Lidar unveiled long banks of earth that formed six well-preserved coiled or spiral-shaped patterns. Each formation is roughly 1 kilometer long and 0.5 kilometers wide, or about 10 times the length and width of a football field. The precise alignment of these earthworks with the moat suggests they were assembled around the time of Angkor Wat’s construction. A ground survey in late 2012 and early 2013 determined that the coils consisted of 18-meter-wide sandbanks separated by 12-meter-wide channels. After using laser maps to locate the spirals on the ground, investigators walked through the channels searching for signs of human activity. They found no pottery or other artifacts to suggest that anyone had lived or worked there.
“Nothing like the shape and design of these spirals has been seen anywhere else,” Fletcher says.
Suryavarman II’s reasons for building the coils are unknown. These mounds might have served as raised fields for growing herbs used in temple rituals. Or the coils might have been sites of formal gardens that would have been unrivaled in size and complexity until the construction of 18th century palace gardens in Europe, Evans suggests.
Rainwater could have flowed through channels between the coils. Evans doubts, however, that enough water collected to support farming.
It’s also possible that Angkor Wat’s spiral structures held special spiritual meaning for Khmer people and had no practical use. Yet Fletcher says that nothing resembling these coiled forms appears in Hindu writings and art. After what must have been several decades of construction coinciding with work on the temple, “the spirals may never have been completed and might never have become operational,” Evans says.
Researchers are now examining fossilized pollen recovered from the coils for signs of cultivation or gardening.
Buried towers Another surprising discovery at Angkor Wat comes not from lidar but from ground-penetrating radar. While lidar reveals characteristics of the ground’s surface covered by vegetation, ground-penetrating radar can detect objects buried deep under several dozen meters or more of soil.
In December 2009, a team led by archaeologist Till Sonnemann of Leiden University in the Netherlands dragged a wheeled device reminiscent of a lawn mower over Angkor Wat’s vast outer section for two weeks. High-frequency radio waves emitted by the contraption bounced off buried objects, signaling locations of possible archaeological remains.
Sonnemann was looking for remnants of houses or administrative buildings from the 12th century or later. Something far more intriguing turned up.
At Angkor Wat’s western entrance, where visitors enter the grounds of the temple, the radar machine identified what looked like the foundations of eight towers. Excavations in 2010 and 2012 confirmed their existence. Foundation remains lie roughly 21 meters belowground, about 10 times as deep as an Olympic swimming pool.
Each cross-shaped foundation, held in place by walls made of a reddish rock called laterite, had a square central section bound by porches jutting out on each side. Intact shrine towers from other Khmer Empire sites, which were dedicated to various gods, feature side porches.
Angkor Wat’s former towers were intentionally destroyed, Sonnemann says. Radiocarbon dating of burned wood from the foundations suggests the towers were built around the time that work started on Angkor Wat. Demolition occurred when Angkor Wat’s outer wall and western gate were completed, Sonnemann suspects.
Perhaps 12th century residents of Greater Angkor used the gateway towers as a temporary religious shrine to the Hindu god Vishnu while erecting Suryavarman II’s temple, which was dedicated to the same deity, Sonnemann says. Of the eight towers, four formed a square that stood within a larger square formed by the four others. Angkor Wat itself features four towers arranged in a square around a central tower.
The gateway towers may have served as an outline of Angkor Wat’s permanent towers, Sonnemann speculates. But they were not identical. Remote sensing identified no remnants of a central tower at the western entrance. Wall defenses Tourists and researchers have long gazed at Angkor Wat’s impressive stone outer wall without realizing it holds clues to warfare between the Khmer Empire and regional foes, says archaeologist David Brotherson of the University of Sydney.
Archaeologist Christophe Pottier of the Bangkok Center in Thailand first noticed holes that had been intentionally carved in parts of the wall constructed later. When Brotherson took a closer look, he speculated that those openings once supported wooden platforms and fences.
Angkor Wat’s defenders stood on the platforms and positioned themselves between the fences to repel attacks by nearby Thai kingdoms, Brotherson proposes. Those confrontations probably took place sometime between the late 13th and early 17th centuries.
Brotherson studied 6,257 wall cavities. Most consist of groups of seven square holes, at the same height, running across the inside of the wall near its top. Sets of holes, notches and grooves also run across adjacent areas on top of the wall. These alterations appear at spots where six nearly 20-meter-wide gaps in the wall — which probably framed wooden gates — were later filled in with stone blocks. Differences in detailing and finish distinguish original masonry from filled-in sections.
Holes on the inner part of the wall held wooden beams that supported platforms about 3.5 to 4 meters above the ground that must have had stairs at each end, Brotherson says. Angkor Wat’s fighters would have stood on platforms while raining down arrows or other weapons on attackers. Wall-top holes probably held fence posts for additional protection, he suspects. Yet researchers have found no arrowheads or other weapons and no evidence of military damage to Angkor Wat, such as wall marks from catapulted boulders or remnants of torched wooden buildings.
Still, it’s more likely that the wall’s inside holes held platforms for temple defenders to stand on than wooden roofs that sheltered people or animals underneath, Brotherson says. Gateway spaces would not have been filled in simply to construct shelter roofs, he contends. And roofs would not have required holes carved on top of the wall.
“There are no historical references to defensive fortifications at Angkor Wat,” Fletcher says. “Sometimes archaeology tells us things that history cannot.”
Tropical trajectories Lidar’s bird’s-eye view of forest floors has guided archaeologists not only to lost parts of Angkor Wat, but to a greater appreciation of similarities between Greater Angkor and other ancient tropical cities.
Lidar surveys of west-central Belize in 2009 and 2013 showed that the ancient Maya city of Caracol sprawled across now-forested landscape much as Greater Angkor did. A dense urban area, incorporating agricultural fields into a planned city, spread 10 kilometers in all directions from central Caracol in 650. Researchers estimate that more than 140,000 people lived at Caracol (SN: 12/15/12, p. 14).
Laser maps revealed farming terraces, housing tracts and roads leading to public plazas that ranged far beyond Caracol’s urban center. Anthropologists Arlen and Diane Chase of the University of Central Florida in Orlando directed lidar research at Caracol.
At 1,000 square kilometers, Greater Angkor covered a much larger area than Caracol. “Lidar surveying has just begun, but we now know that Maya cities were shrimps compared with mighty Angkor,” says Yale University anthropologist Michael Coe, a long-time investigator of the Maya and other ancient American civilizations. Nothing like Angkor’s street grids stretching with geometric precision toward the horizon appears at Caracol, adds Coe, who is familiar with work at both sites.
Still, common factors inspired the rise and fall of Greater Angkor, Maya urban centers such as Caracol and the tropical city of Anuradhapura in Sri Lanka between the ninth and 16th centuries, Fletcher and two colleagues concluded in the October 2015 Antiquity.
Rulers in each region directed the construction of reservoirs and canals that allowed spread-out cities to flourish. Effective water management cemented the power of kings by enabling masses of farmers to make a steady living.
Severe periods of drought, indicated by analyses of tree rings and lake sediments, strained water supplies in each tropical setting, Fletcher says. Periodic monsoon rains in Southeast Asia and Sri Lanka added insult to injury, overwhelming reservoirs and damaging canals.
Unable to supply enough water, political systems at Greater Angkor and other tropical cities crumbled, Fletcher argues. But societies didn’t vanish. Farmers reorganized into smaller communities based near coasts and along major rivers. Cultivation continued in fields that had once been part of massive cities.
Laser quest Fletcher’s rise-and-disperse scenario for ancient tropical cities is being put to a broader test. From March to May 2015, a second set of lidar flights expanded laser mapping of northern Cambodia to a total area of 2,000 square kilometers. Researchers want to see if, like Angkor Wat, other ancient temples in the region sat in the center of dispersed settlements tied together by reservoirs, canals and ponds. Archaeological investigations based on the new lidar data are under way. Evans plans to announce initial findings in June.
Over the next 10 to 15 years, lidar technology will become smaller and cheaper, Evans predicts. Laser-wielding drones will replace lidar-toting helicopters. But laser mapping is already a game changer for tropical archaeology.
Around Angkor, “the impact of lidar data is like turning on a light after groping in the dark for over a century,” says archaeologist John Miksic of the National University of Singapore.
Suryavarman II, a politically ambitious warrior who tried to expand his kingdom by launching wars and allying himself with Imperial China, would surely celebrate Angkor Wat’s laser revival if he was around today. It’s a revival of sorts for the once-mighty king, as well.
