A look from heaven: how space and aero technologies are helping the study of history

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

To whom the inhabitants of the Nazca desert intended their gigantic drawings, which are visible only from a bird's eye view, is not known for certain. One thing is clear - unlike those spectators "from above", modern archaeologists manage to read much more mysterious and meaningful signs of the past. All the same look from heaven …

Any visitor to Venice, who has had enough of admiring the palaces, bridges and temples of the unique city, sooner or later asks himself the question - to whom and when it occurred to him to settle in such a completely unusual entourage. When instead of streets, solid water, and instead of wheels - sails and oars.

In response, the guides and guidebooks patiently explain to tourists that the founders of Venice arrived on the islands and began to build a city there not from a good life. In the V-VII centuries. AD, the Western Roman Empire turned into a memory, Italy was attacked by barbarians, in particular the Huns, and now, fleeing from the cruel conquerors, the inhabitants of the North

The Adriatic took refuge on the islands, where they began to build the future capital of the Republic of St. Mark.

You can see everything from above

In the arsenal of modern archaeologists conducting searches for ancient ruins from the air and from space, there are several technologies that allow you to literally look into the depths of time. Among them - aerial and space photography in the near infrared range on film with "false color". Used mainly in oceanography, "lidar" - a device that creates a relief map of the area (bottom) using laser scanning from the top point - is able to detect changes in the relief invisible from below. An artificial aperture locator (SAR) allows you to scan from space areas, even cloudy and covered with vegetation, revealing linear and geometric contours.

Also for these purposes, microwave location is used, which makes it possible to see what is in the ground at a shallow depth.

It would be logical to assume that the Romans, who took refuge in Torcello, Burano and other islands of the lagoon, left some other city on the coast, the experience of living in which, the skills of construction, crafts and trade, formed the basis for the prosperity of the pearl of the Adriatic. But where was this ancestor of Venice located? Oddly enough, the answer, more or less satisfying to modern science, was found quite recently. Thanks to the crops of soybeans and corn, as well as aerial photography.

Shade and color

The discovery happened in 2007, when professor of the University of Padua Paolo Mozzi, together with his colleagues, organized an aerial photograph of the area, where nothing reminded of any ancient ruins. No walls, no mounds, no bumps - just a field sown with useful crops. But in the picture, scientists were presented with a plan of the large ancient Roman city of Altina, which, as historians knew, was located somewhere in these parts. Actually, he is considered the ancestor of Venice.

On the photos obtained, we managed to make out the walls with gates, canals (yes, there were canals in the ancestral home of the Venetians - the coastal lands are very swampy here), houses, streets, an amphitheater. No excavation was required to find out where what was.

Transparent earth

In recent years, several major archaeological discoveries have been made using remote sensing of the surface. The famous Buddhist temple complex Angkor Wat (Cambodia, XII century) today stands surrounded by dense jungle. However, aerial surveys of the area with a synthetic aperture radar, recording microreliefs and changes in soil moisture, have yielded amazing results.

It turns out that Angkor Wat was once surrounded by an inhabited area the size of modern Los Angeles, built up with houses and covered with a network of roads and canals. In another part of the world - in Egypt - about 100 new archaeological sites have been found in the Nile Delta. A team of archaeologists led by Sarah Parsack (University of Alabama) studied images taken by the Landsat satellite in different bands of the electromagnetic spectrum. After processing these images, scientists saw that the places of the former settlements clearly differ from the untouched "virgin lands", since, thanks to organic remains, they otherwise absorb moisture.

Strictly speaking, the use of aerial photography for archaeological research is not at all yesterday's invention. It became known at the dawn of aeronautics that when looking at the earth from a bird's eye view, invisible from below, the contours of ancient walls and roads suddenly appear. In our country, the work of the Khorezm archaeological and ethnographic expedition of the Institute of Ethnography named after N. N. Miklukho-Maclay, who discovered, by means of aerial photography, hundreds of monuments of Central Asian civilizations buried under the sand in the lower reaches of the Amu Darya and Syr Darya.

Sometimes what is seen from the air can be present on the ground only in the form of a microrelief, a small one - a few centimeters of elevation. This is already a good thing, since at a certain angle of illumination, the elevation begins to cast shadows. But often there is no microrelief, and the contours of the structures "camouflaged" by the soil are only barely distinguished by a special shade of the soil. And if the territory of the ancient monument is covered with vegetation? Sometimes it becomes a hindrance for archaeologists, but sometimes it helps.

Life above an ancient stone

In 2016, in the area of the famous Stonehenge, when viewed from the air, crop circles were found, but not exactly those whose authorship is usually attributed to aliens or unknown earthly pranksters. Circles with "alien" overtones are geometrically verified ring-shaped areas with carefully crushed ears or stalks of grass. Here, the rings were distinguished by the fact that the grass on them did not grow well, that is, it was distinguished by a swishy yellow color against the background of the surrounding greenery.

The solution to this mystery turned out to be quite earthly and very joyful for archaeologists: the circles marked the outlines of burial mounds hidden underground, in which the ancient British, who lived about 6,000 years ago, found peace. The mechanism for the emergence of such important for science marks is very simple - in the dry season, plants feeding on a thin layer of soil that covers, for example, ancient walls, suffer from thirst and change color. At the same time, their fellow neighbors, who have the opportunity to run roots deeper into the ground without interference, still turn green happily.

In principle, the discovery of the contours of the ancient Altin by Professor Mozzi and his comrades happened due to the same phenomenon. It is especially worth noting that the Italians carried out aerial photography at a time when a dry summer happened on the shores of the Gulf of Venice and the habitually wet local soils became scarce. The subtlety at the same time lies in the fact that not always nature and soil give their secrets as easily as it happened with the British mounds.

In other words, traces of long-forgotten cities and temples inscribed on the soil may, even when shooting from a high point, not manifest themselves in the visible range. That is why the arsenal of modern archeology includes new means of searching for ancient monuments, allowing them to be discovered by observation in other ranges of the spectrum of electromagnetic radiation.

The photo shows a NASA Gulfstream III aircraft testing a synthetic aperture locator (SAR), intended in the future for installation on unmanned aerial vehicles. SAR is actively used by scientists, in particular, to search for ancient monuments in Central America and Southeast Asia. The picture on the right shows the IKONOS satellite, which began the active use of space imagery in archeology.

Spies to archaeologists

In particular, the aerial photograph of the soybean and corn fields, on which the Altin plan arose, was taken in the short wave (close to visible red) part of the infrared spectrum. The photographs were taken in the so-called false color, when areas with very different radiation intensity were not reproduced as shades of gray, but were marked with pink and green-bluish colors. Such a photo gave an unusually detailed and embossed picture of the city, in fact, erased from the face of the earth by time.

However, even more impressive results are achieved today in archeology not with the help of aerial photography, but with the help of observing the Earth's surface from space. There are two reasons for this: firstly, the satellites designed to monitor the earth's surface are equipped with a large number of diverse and effective equipment that makes it possible to carry out observations in different ranges of electromagnetic radiation, including in conditions of cloud cover over the territory. Secondly, spacecraft easily access those parts of the planet that are not so easy to equip archaeological expeditions to, especially if it is not known for sure whether there is something worthy of attention there.

Active work with satellite images in archeology began not so long ago - for a long time, photos from space did not have sufficient resolution to look out for the ghostly contours of ancient structures. Then such a resolution was achieved, but the military who owned the spy satellites were in no hurry to make their images available to civilians, including historians. True, Tom Siver, the only archaeologist who collaborated in this direction with NASA, since 1981 managed (with the help of a photo in the thermal range) to discover, for example, the oldest Indian trails in the state of New Mexico and even the exact location of the long-demolished hangar of the Wright brothers.

The real revolution came when on January 1, 2000, photos of the earth's surface, taken with a resolution of up to 1 m, appeared on the free market. These images came from the IKONOS satellite, manufactured by Lockheed Martin and launched in September 1999. The satellite is still in orbit and takes pictures both in panchromatic mode (black and white image formed by all rays of the visible spectrum, without filtering), and separately by spectral channels (near (shortwave) infrared, red, green, blue).

Jungle memory

In 2002, Daniel Irwin, Tom Seiver's NASA colleague, sent IKONOS maps of the earth to his new friend Bill Saturno. This American archaeologist is famous for his excavations in the department of Petén (Guatemala), where he discovered the Mayan pyramids, built in the pre-Columbian era. In the 8th-9th centuries, life was in full swing on the territory of Pétain. The Maya built cities, roads and temples, cutting down all the local forests along the way.

It is believed that the ensuing environmental disaster was one of the reasons for the collapse of the ancient Indian civilization. When man left nature alone, the humid equatorial jungle rose again over the remains of its former greatness.

Having examined the satellite images taken in different ranges, Bill Saturno suddenly realized that the outlines of structures that had long been covered with earth and dense forest vegetation were clearly visible in the space photos. This was clearly visible in the near-infrared images.

Saturno reported his findings to Siver, and although he was at first skeptical about the results of the analysis of the images, later both archaeologists began active cooperation in the use of remote sensing for archaeological research. After all, the conclusions of Bill Saturno turned out to be completely correct.

The fact is that the remnants of the lime plaster used by the Maya, once in the soil, changed its chemical characteristics for hundreds of years in advance. Because of this, on the site of former buildings and roads, the color of the soil and even the foliage of the trees has become slightly different. However, it was impossible to see this difference from Earth.

Into the monitor - beyond Atlantis

Today, Earth remote sensing techniques make it possible to see traces of roads, defensive ramparts and city walls even under layers of volcanic lava or under a layer of sea water. Of course, these searches include not only the production of images of the earth's surface from space or from the air, but also the processing of this data using sophisticated software. In general, this is the sphere of activity of high professionals, which does not mean at all that amateurs cannot join the search for hidden antiquities. With the universal availability of such popular network services as Google Maps and Google Earth, anyone can try to see on the surface what has escaped the eyes of everyone else.

Back in 2005, the Italian programmer Luca Mori, looking at the surroundings of his house on space maps from the Internet, saw a strange dark oval on the ground, and a rectangular outline nearby. It turned out that this is how the underground remains of a Roman villa appeared on the soil. So it is quite possible to find the ancient ruins without getting up from the computer. The main thing is sometimes still to curb your imagination and not rush with reports of the discovery of ancient ruins in Mozambique or Atlantis at the bottom of the ocean.