Technosignatures: Searching for Evidence with AI, Instead of Waiting for a Visit.

One possible approach to the question of extraterrestrial civilizations is simply to wait for a visit. Some scientists and astrophysics enthusiasts occasionally raise this possibility when discussing anomalies observed in interstellar objects such as 3I/ATLAS. A few have even proposed more dramatic scenarios. For example, an article recently published in Medium Digest by M. Popovic, titled “3I/ATLAS — Final Destination: Ganymede’s North Pole,” suggested that such an object might even have a destination within our solar system.

Alongside these ideas, however, another research approach has been gaining attention. Instead of waiting for a potential encounter, scientists can search for technosignatures — measurable traces left behind by technological activity.

In a universe that is about 13.5 billion years old, and in a solar system that has existed for roughly 4.5 billion years, many researchers assume that humanity is unlikely to be alone. Current estimates suggest that there may be trillions of planets in the universe, and more than a billion Earth-like planets in the Milky Way galaxy alone. To seriously examine the possibility of other civilizations, researchers look for biological, chemical, climatic, and even archaeological indicators — but particularly for technological signatures.

The key point is that the only known model of a technological civilization today is Earth itself.

Earth as a Laboratory for Technosignatures:

If we treat Earth as a “laboratory,” we can examine the kinds of traces a technological civilization leaves behind and how they might appear to a distant observer — or even to a cosmic archaeologist in the distant future.

Over the past century, Earth has become a source of several types of unusual astronomical signatures.

Radio leakage:

Radio, television, and radar transmissions create a bubble of artificial signals expanding into space at the speed of light. To a distant observer, such signals would appear as narrow spikes at specific frequencies — a pattern rarely produced by natural astrophysical sources.

Light pollution:

Artificial lighting alters Earth’s brightness on its night side. The possibility of detecting a brightly illuminated night side on exoplanets has already been discussed as a potential research goal for future telescopes.

Technofossils:

Industrial materials such as plastics, concrete, and refined aluminum are rare in nature. Over time they can leave geological signatures that may persist in rock layers for millions of years.

Atmospheric signatures:

The burning of fossil fuels alters the ratios of carbon isotopes in the atmosphere and oceans. In addition, industrial gases such as CFCs do not occur naturally and could therefore serve as clear indicators of technological activity.

Nuclear signatures:

Nuclear tests in the twentieth century produced global layers of radioactive isotopes such as plutonium-239, which are extremely rare in natural environments.

All of these examples illustrate an important point: technology leaves measurable traces, sometimes long after the activity itself has ended.

From a Laboratory to Historical Exploration: Mars.

If these are the kinds of signatures technology leaves on Earth, the question arises whether similar traces might be searched for on other worlds.

Mars is a natural target for such investigations. Geological evidence suggests that in the distant past, the planet once had flowing water and a much denser atmosphere.

Around the same time — roughly three billion years ago — microbial life already existed in Earth’s oceans, including in deep-sea environments such as the hydrothermal ecosystem known as the “Lost City” in the Atlantic Ocean.

Earth’s oceans are not merely reservoirs of water. They act as planetary stabilizers, regulating temperatures, supporting chemical cycles, and allowing life to adapt more easily to environmental changes — including variations related to gravity and atmospheric conditions. Large oceanic environments provide long-term climatic stability and protection from extreme surface conditions.

This understanding has also influenced research on the subsurface oceans believed to exist beneath the icy crusts of Jupiter’s moons, including Europa and Ganymede.

Around that same period, however, Mars began losing its global magnetic field and most of the atmosphere that had protected it from cosmic radiation. Mars also has only about 38% of Earth’s gravity, making it far more difficult to retain a stable atmosphere over geological timescales.

If life ever existed there — and possibly more than microbial life — it would have had to cope with far harsher conditions.

Some researchers have even raised a speculative possibility: if a civilization once existed on Mars in the distant past, it might have looked for a nearby environment capable of supporting long-term survival. In such a scenario, Earth would have been a natural candidate. If anything like this ever occurred, traces might remain — archaeological or technological — either on Mars or on Earth itself.

Earth’s Oceans as a Hidden Archive:

Earth is an extremely active planet geologically. Plate tectonics, erosion, and biological activity continuously recycle the surface, erasing many of the oldest traces of the planet’s past.

However, the deep ocean floor may function as a different kind of geological archive. Sediments accumulating in deep marine environments can preserve unusual chemical or structural signatures over long periods of time.

In recent decades, advances in sonar technology, autonomous underwater vehicles, and high-resolution seabed mapping have made it possible to explore regions that were previously almost inaccessible.

Space Debris and AI: The Method of Elimination:

Another domain where technosignatures might be searched for is Earth’s orbital environment.

Over the past decades, tens of thousands of objects have been launched into space, accompanied by millions of smaller fragments of debris. Most of these objects are carefully cataloged in international databases.

The challenge lies in identifying anomalies within this enormous dataset. This is where artificial intelligence becomes particularly useful.

AI systems can perform anomaly analysis by:

Comparing all cataloged objects across multiple orbital regimes.

Filtering out objects associated with known launches.

Identifying objects that do not match the profiles of known modern space debris.

Any object that does not correspond to existing databases and cannot easily be explained as a natural object may become a candidate for further investigation.

In this context, unusual images from planetary missions — for example, objects whose shapes cannot easily be explained as geological formations — may also serve as starting points for scientific examination. If such objects cannot be identified as known human equipment, anomaly-detection systems may classify them as targets for further research.

A Changing Research Approach:

In recent years, there has been a gradual shift in scientific thinking on this subject. Instead of focusing solely on the search for intentional radio messages, researchers are increasingly examining a broader spectrum of possible signatures — atmospheric, chemical, thermal, and even archaeological.

The combination of advanced telescopes, massive astronomical datasets, and artificial intelligence tools now makes it possible for the first time to conduct systematic searches for anomalies.

Conclusion:

In a world where more than tens of thousands of objects orbit Earth and more than a million smaller fragments of debris are present, no human observer can realistically find the proverbial needle in a haystack.

Artificial intelligence, however, is designed precisely for such anomaly-detection tasks.

The first evidence of another civilization may not arrive as a direct visit or a clear message. Instead, it may begin with the detection of a trace — a small anomaly in data, an unexpected chemical signature, or an object in orbit that does not fit known models.

Rather than waiting for a dramatic encounter, science may increasingly adopt another strategy: understanding how technology leaves traces, searching for them in multiple environments — from Earth to Mars — and using tools such as artificial intelligence to distinguish the known from the unexplained.

© The Times of Israel (Blogs)