For decades, the search for alien life often meant one thing: radio signals.

But today, the search has expanded into something far more interesting: technosignatures—detectable evidence of technology.

NASA describes technosignatures as potential signals or observational evidence of advanced civilizations, and frames them as part of the broader search for life.

In plain language:

A technosignature is any measurable sign that someone, somewhere, built something.

And if we find one, it may be the first undeniable proof that we are not alone.

Why Technosignatures Changed the Game

Biosignatures (like oxygen or methane) can suggest life—but not necessarily intelligence.

Technosignatures aim higher:

• cities (or their energy footprint)

• industrial chemistry

• artificial light

• engineered satellites

• megastructures

• unusual, narrowband signals

NASA emphasizes technosignatures as a subset within the continuum of evidence we can search for on exoplanets and beyond.

The 7 Most Promising Technosignatures (Ranked by Realistic Detectability)

1) Narrowband radio signals

This is classic SETI: a tight, artificial-looking frequency spike.

The problem: many human technologies create interference that can mimic signals—meaning verification is hard and requires strict follow-up.

2) Laser pulses and optical beacons

A civilization might use lasers for communications. Short, powerful pulses could stand out against natural astrophysical noise.

3) Atmospheric industrial pollution

This is one of the most compelling ideas because it doesn’t require aliens to “phone us.”

Certain compounds—especially those unlikely to exist naturally in large quantities—could indicate industry. NASA has discussed pollution as a possible technosignature approach.

4) Waste heat (the “Dyson” approach)

If a civilization uses enormous energy, thermodynamics demands waste heat. In theory, infrared surveys could detect anomalies consistent with large-scale energy use.

5) Artificial night-side illumination

City lights on the dark side of a planet are conceptually straightforward: artificial light has a distinct signature compared with reflected starlight.

6) Planet-scale engineering signals

Examples: unusual reflectance patterns (massive solar arrays), orbiting infrastructure, engineered rings.

NASA has addressed why certain “solar panel” technosignatures may be challenging to spot but scientifically meaningful.

7) “Anomaly hunting” in giant datasets

Instead of guessing what alien tech looks like, some researchers argue for data-driven approaches: scan huge surveys for things that simply do not fit known categories. This approach is increasingly discussed in modern technosignature strategy.

Why We Might Miss the Signal Even If It’s There

Three reasons:

1. We’ve barely looked (astronomically speaking)

2. Civilizations may be quiet (intentionally or by nature)

3. Our assumptions may be wrong (technology may not resemble ours)

What Would Count as “Proof”?

A single odd signal is not enough. Proof likely requires:

• repeatability

• independent detection

• elimination of human interference

• a pattern that cannot be explained naturally

Technosignatures are hard. But they are also one of the most exciting scientific frontiers because the upside is enormous.

FAQ

Are technosignatures officially part of NASA’s life search?
NASA has published multiple pieces framing technosignatures as a legitimate part of the broader search for life.

What’s the most likely technosignature to detect first?
If it exists nearby: radio or laser. If it exists at scale: atmospheric pollution or waste heat.