Leonard David's INSIDE OUTER SPACE

A concept image illustrating various types of technosignatures, including atmospheric, optical, and radio technosignatures.
Credit: Jacob Haqq-Misra, et al.

On the lookout for evidence of extraterrestrial technology? For one, keep an eye out for city lights as a “technosignature.”

Technosignatures refer to observational manifestations of technology that could be detected through astronomical means. Various types of technosignatures include atmospheric, optical, and radio technosignatures.

A new research paper – “Searching for technosignatures in exoplanetary systems with current and future missions” presents a number of conclusions of a TechnoClimes 2020 workshop sponsored by NASA and Blue Marble Space Institute of Science.

Credit: ESA/Hubble & NASA

Takeaway messages in the paper include the fact that current and future astronomical facilities can place constraints on the prevalence of technosignatures. Also, technosignature searches can be included in mission science justification without added cost.

That said, there’s need to engage the broader astronomical community in thinking seriously about the possibility of detecting technosignatures. Furthermore, the tools to find technosignatures may already be available, “but it will require a community-wide effort to start looking,” the paper explains.

Renewed interest

“A logical extension to the search for extraterrestrial life through biosignatures is the search for evidence of extraterrestrial technology,” the paper explains.

Capabilities for detecting technosignatures with recent, ongoing, and future missions and facilities.
Credit: Jacob Haqq-Misra, et al.

“The idea of searching for ‘technosignatures’ has been considered by astronomers for more than half a century, with initial efforts focused on the possibility of detecting extraterrestrial radio transmissions.”

On one hand, funding remains a limiting factor in advancing technosignature science. But recent years have shown a renewed interest in technosignatures by public and private funding agencies.

Atmospherics

According to the paper, atmospheric technosignatures are gases that are produced by artificial means either as an incidental byproduct of industrial civilization or for a specific purpose, perhaps to manage planetary climate.

An example of an atmospheric technosignature is nitrogen dioxide (NO). “The production of NO on Earth today includes biogenic and anthropogenic sources, in addition to lightning. However, human generated NO2 dominates by three times the amount from non-human sources. “Detecting high levels of NO at levels above that of non-technological emissions found on Earth could be a sign that the planet may host active industrial processes,” the paper notes.

Cross-sections for a subset of potential atmospheric technosignature molecules including Ammonia (NF3), Carbon Tetrafluoride (CF4), and Sulfur hexafluoride (SF6).
Credit: Jacob Haqq-Misra, et al.

Nightside city lights

One of the strongest spectroscopic technosignatures present on Earth’s nightside is the emission from nightside city lights, but on Earth this emission is relatively concentrated.

It may be that advanced civilizations on exoplanets have built cities over significantly more of their planets’ surface, the research paper suggests. “These more urbanized planets would have a higher nightside brightness from city lights, and be correspondingly easier to detect.”

To gain free access to the research paper – “Searching for technosignatures in exoplanetary systems with current and future missions” by lead author Jacob Haqq-Misra of Blue Marble Space Institute of Science in Seattle, Washington, go to:

https://doi.org/10.1016/j.actaastro.2022.05.040

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