The search for techno-signatures has always taken a back seat in the broad search for extraterrestrial life forms. Biosignatures, such as methane in the atmosphere of an exoplanet, have long been at the center. But while we look for signs of biology, signs of technology can hide in clairvoyance. According to a new report from members of the TechnoClimes conference, humanity could potentially find evidence of technology by simply using data that will already be collected for other purposes. To prove their point, they came up with a list of possible techno signatures and cross-referenced them with a list of observatories that could potentially find them. The result is a framework for how to best search for techno signatures and a wealth of references for those who search for them.
Although the report was just released in May 2022, the actual conference took place in August 2020. TechnoClimes considered itself “an online workshop to develop a research agenda for non-radio technology signatures.” The report is the result of one of the four goals of the workshop – to “encourage a wider range of astronomers to consider the relevance of techno-signatures for their research by acting as a resource describing the detectability of various non-radio-techno-signatures with current and future missions.”
The second goal focused on developing mission concepts that could specifically look for techno signatures, which are much lacking so far, although we reported on some last year. The third goal focused on a framework for evaluating “non-canonical astrophysical phenomena” – in fact data that we cannot otherwise explain and which in itself can be a techno-signature. The ultimate goal is to recruit more researchers to the goal by “broadening international participation” in searches with techno signatures.
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With the overwhelming amount of data it already has to sift through, the field will need all the help it can get. And that amount of data will only grow when more competent observatories come online. To understand what these observatories are capable of, the TechnoClimes participants’ framework broke both the observatories themselves and the techno signatures they could find in three main categories each.
The first category of observatories is the current and recently completed missions, such as JWST, Gaia and TESS. Next are “near future” missions that are expected to start in the next five years, such as the Roman Space Telescope and PLATO. The last category is “future” assignments that are still five or more years away and are largely still concept studies at this time. These include LUVOIR, HabEx and Nautilus.
Techno-signature categories are also divided into three main areas, with subcategories for each. This report focuses in particular on non-radio-based techno-signatures, as the authors point out that radio-based techno-signatures have already received a great deal of attention in the form of SETI and other efforts to detect them in recent decades.
The first techno-signature category is optical beacons. These can usually be seen as lasers, which can be used for communication, or as a light sail, such as those developed by Breakthrough Starshot. But they can also be translated into things like fusion devices, whose exhaust gases can potentially be seen for hundreds of light years around. A wide range of observatories, ranging from existing ground-based telescopes through LUVOIR, could probably detect powerful optical beacons.
Next on the list of potential techno signatures is planetary technology. This is divided into two subcategories, which are then broken down into additional subcategories. Atmospheric Technosignature is the first subcategory, and it is further divided into a category for UV, visible light and near-infrared, as well as a medium-infrared category. Atmospheric techno-signatures can be considered as gases emitted into a planet’s atmosphere from industrial or non-biological processes.
Humans produce abundant amounts of these gases, such as chlorofluorocarbons and sulfur hexafluoride, every year. Some gases, such as nitrogen dioxide, could be detected in visible light. Although this gas has certain biological causes, the amount produced by them is less than that produced by industrial processes. It should be visible around planets orbiting sun-like stars for observatories such as LUVOIR.
Other gases, such as carbon tetrafluoride, are more likely to be captured in the medium infrared wavelengths by observatories such as James Webb. In fact, JWST may be able to find Earth-like levels of certain atmospheric techno-signatures simply on one of the TRAPPIST planets. Lots of other atmospheric observations may prove to be a way to search for techno signatures, but as the authors point out, this is still an area for ongoing research.
The following subcategory of planetary technologies are artificial surface modifications. The most obvious of these would be to see the city lights on an exoplanet. Parts of the earth are brightly lit during the night, and even lights that are only slightly brighter can be visible to any future generation of observatories, such as LUVOIR. They may even be visible to the Roman space telescope, although this has not yet been proven.
Other potential surface modifications would include large portions of solar panels, which may be visible from far, far away, and their dimming effect on the reflected light from an exoplanet could be potentially noticeable. Alternatively, a “heat island” effect, as a more pronounced version of the effect seen around many modern cities on earth, may be visible in the middle-infrared region.
Taking a step up from planetary surface modifications, the last category of potential techno signatures is known as system megastructures. These are engineered objects, such as a Dyson sphere or swarm, that may be large enough to have their own passage of their host star that could be detected in visible to near-infrared light. Another way to find them would be to look for the waste heat that they would inevitably produce, which should be visible in the middle infrared area. Passages of such a megastructure should be visible to almost all currently launched and future missions. At the same time, their waste heat could be detected by Spitzer or NeoWISE, two aging infrared observatories.
The fact that they have not yet been seen in NeoWISE or Spitzer data is not proof that they do not exist – just proof that no one has found a sustainable search criterion for them in that data. As the authors are quick to point out – even not finding any potential techno signatures is still a very valuable scientific endeavor as it allows researchers to put statistical constraints on the probability of the occurrence of these techno signatures elsewhere.
For example, there are 74 “bright” stars within 10 parsecs (~ 33 light-years) from Earth – most of them probably have planets. Assume that no techno signatures are found on any of them after an exhaustive search. In that case, there is more data to feed into a statistical model of the probability of intelligent life evolving elsewhere in the galaxy. But finding a potential techno-signature can fundamentally change our understanding of life as we know it. It seems worth the investment, right?
Haqq-Misra et al. – Searching for techno signatures in exoplanetary systems with current and future missions
UT – The next generation of telescopes can search for intelligent civilizations directly
UT – NASA’s Technosignatures report is out. All ways to find evidence of an intelligent civilization
UT – Techno signatures are NASA’s new targets for discovering other civilizations in space. Wait. What is a techno signature?
Concept image showing different types of possible techno signature signals.
Credit – Haqq-Misra et al.
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