Artist's evidence-based portrayion of the blast that had the power to destroy 1,000 Hiroshimas
This article was first published by The Conversation. Space.com's Expert voices: Op-Ed and Insights was contributed by the publication.
Christopher R. Moore, Archaeologist and Director of Special Projects at the Savannah River Archaeological Research Program and South Carolina Institute for Archaeology and Anthropology (University of South Carolina).
Tall el-Hammam, an ancient Middle Eastern city, was going about its daily business as usual 3600 years ago. They didn't know that an unknown icy space rock was speeding towards them at approximately 38,000 mph (61,000 kph) when they saw it.
The rock flashed through the atmosphere and exploded in a huge fireball at about 2.5 miles (4 km) above the ground. It was 1,000 times stronger than the Hiroshima nuclear bomb. It blinded the stunned city dwellers as they stared at it. Air temperatures rapidly rose above 3,600 degrees Fahrenheit (2,000 degrees Celsius). Wood and clothing immediately caught fire. The entire city was on fire. The entire city caught fire almost immediately.
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A massive shockwave struck the city just seconds later. It moved at 740 mph (1.200 km/h), and was stronger than any tornado ever recorded. The powerful winds decimated every building in the city. They tore off the top 40ft (12m) of the palace's four-story tower and blew the debris into the next valley. The city was destroyed and the bodies of all 8,000 residents and animals were torn into tiny pieces.
A minute later, the blast winds struck the biblical city Jericho, located 14 miles (22km) west of Tall el-Hammam. The walls of Jericho fell and the city was set on fire.
This sounds exactly like the end of a Hollywood disaster movie. How can we be sure that this all happened in Jordan near the Dead Sea a millennia back?
The city, now called Tall el-Hammam is situated 7 miles northeast from the Dead Sea in what is now Jordan. Image credit: NASA
Nearly 15 years of hard work by hundreds of people was required to find the answers. The detailed analysis of excavated material was done by over two dozen scientists from the U.S. and Canada. Our 21 co-authors were archaeologists and geochemists, geomorphologists as well as mineralogists, paleobotanists and sedimentologists. They also served as cosmic-impact experts, medical doctors, and geochemists when the evidence was published in Scientific Reports.
This is how we created this image of destruction in the past.
All over the city, firestorm
An archaeologist looked out at the city's ruins years ago and saw a dark layer of charcoal, ash, and melted mudbricks. This city had been destroyed by an intense firestorm long ago. This dark layer was later called the destruction layer.
Researchers are standing near the ruin of ancient walls. The destruction layer is about halfway down each wall. (Image credit to Phil Silvia. CC BY ND).
Although no one knew exactly what caused the layer, it was not due to an earthquake, volcano, or war. They are incapable of melting metals, mudbricks, and pottery.
Our group used the Online Impact Calculator in order to determine what scenarios could be created. This calculator was created by impact experts and allows researchers to calculate the details of a cosmic event based on nuclear detonations and known impact events.
Tall el-Hammam is believed to have been caused by a small asteroid that was similar in size to the one that decimated 80 million trees in Tunguska (Russia) in 1908. It would have been much smaller than the massive rock measuring miles in width that drove the dinosaurs to extinction 65 millions years ago.
We knew the likely suspect. We needed evidence of what had happened at Tall el-Hammam that day.
Find 'diamonds in the dirt'
Our research revealed an astonishingly wide range of evidence.
Images of many small cracks in shocked Quartz grains taken with an electron microscope (Image credit: Allen West, CC BY-ND)
There are finely fractured quartz sand grains at the site. They only form at 725,000 lbs per square inch of pressure (5 gigapascals). Imagine six Abrams military tanks, each weighing 68 tons, stacked on your thumb.
Also, the destruction layer contains tiny diamondoids, which, as their name suggests, are as hard and as durable as diamonds. Each one is about the size of a flu virus. The fireball's high temperatures and pressures instantly transformed the wood and plants of the area into the diamond-like material.
The fireball's high temperatures, pressures on woods and plants caused the formation of diamonoids (center), inside a crater. (Image credit: Malcolm LeCompte, CC BY-ND)
Laboratory furnace experiments showed that bubbled pottery and mudbricks from Tall el-Hammam liquefied at temperatures higher than 2,700 F (1.500 C). This is hot enough to melt an automobile in minutes.
Spherules made from melted sand (upperleft), palace plaster (upperright) and melted steel (bottom two). (Image credit: Malcolm LeCompte, CC BY-ND)
Also, the destruction layer contains small balls of melted material that are smaller than airborne dust particles. They are also known as spherules and are made from vaporized iron or sand, which were melted at around 2,900 F (1.590 C).
Additionally, the surface of the pottery or meltglass is speckled with small melted metallic grains. These include iridium, which has a melting point at 4,435 F (2.4666 C), platinum, which melts at 3,215 F (1.768 C), and zirconium silicate, which melts at 2,800 F (1.540 C).
All of this evidence together shows that the temperatures rose faster than normal city fires, war, and volcanoes. Only a cosmic effect is the only natural process that remains.
Similar evidence can be found at other known impact sites such as Tunguska or the Chicxulub Crater, which were created by an asteroid that caused the dinosaur extinction.
The mystery remains as to why the city and more than 100 nearby settlements were abandoned several centuries later after this disaster. High salt levels may have made it difficult to grow crops due to the impact event. Although we aren't sure, we believe that the explosion may have vaporized salt water from the Dead Sea and sprayed it across the valley. The valley would have no crops for 600 years, unless the desert-like climate and minimal rainfall wiped out the salt.
Did anyone survive the blast?
It is possible that a written description of the destruction of the city was passed down through generations, and eventually became the Biblical Sodom story. The Bible describes the destruction of an urban center close to the Dead Sea stones. Fire fell from the heavens, multiple cities were destroyed, thick smoke rose out of the fires, and many city residents were killed.
This could be an account by an ancient eyewitness. Tall el-Hammam's destruction may have been caused by a cosmic event. It is likely that this was the second-oldest human settlement to be destroyed, following Abu Hureyra in Syria, which occurred about 12,800 years ago. It may also be the first documented record of such a devastating event.
It's almost certain that this is not the last time that a human-populated city will suffer such a fate.
Animation showing the positions of near-Earth objects at different points in time during the 20 year period ending January 2018. (Image credit: NASA/JPL-Caltech)
Tunguska-sized, or even large-scale, airbursts like the one at Tall el-Hammam can cause massive destruction in entire areas and cities. They are a serious modern-day danger. There are over 26,000 near-Earth asteroids, and more than 100 short-period Near-Earth comets. One of them will eventually crash into Earth. There are millions more that have not been detected and may be heading toward the Earth.
These rogue objects may not be detected by ground-based or orbiting telescopes, so the world may not have any warning.
This article was co-authored with research collaborators, archaeologist Phil Silvia and geophysicist Allen West. Ted Bunch, Ted Bunch, Malcolm LeCompte, and geologist Ted Bunch.
This article was republished by The Conversation under Creative Commons. You can read the original article.
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