If astronomers see these chemicals in a planet’s atmosphere, there is likely an advanced civilization there | Albiseyler

If astronomers see these chemicals in a planet's atmosphere, there is likely an advanced civilization there

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An artist’s rendering of a potential water world exoplanet that could support advanced civilizations. Such life could advertise its existence through technosignatures from industrial or other activities. Credit: ESA / Hubble / M. Kornmesser

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An artist’s rendering of a potential water world exoplanet that could support advanced civilizations. Such life could advertise its existence through technosignatures from industrial or other activities. Credit: ESA / Hubble / M. Kornmesser

With the ever-increasing number of exoplanets orbiting other stars, it’s only natural that astronomers look for signatures of advanced civilizations. These signatures can be biological or technological in origin.

What if instead of looking for radio signals (as SETI and others did) we looked for something a little different? What do you think about the evidence of atmospheric pollution produced by technology companies? After all, we know it here on Earth. That’s a paper move Scientific reports by Sara Seager of MIT and an international team of scientists.

They suggest that technological civilizations could be detected through the hunt for chemicals not made by life. Specifically, the team proposes nitrogen fluoride (NF3) and sulfur fluoride (SF6). They are ideal technosignature gases to find because, as they state in the paper, “life on Earth is not known to produce any molecules with N–F or S–F bonds, and this includes fully fluorinated N and S compounds.”

In fact, the article states that fluorine is almost eliminated from the chemistry of life on Earth. Other natural processes also do not produce it in large quantities. So all that remains is artificial (read industrial) pollution. In other words, these gases would be atmospheric byproducts of industrial activity. Here on Earth, their abundance has increased rapidly (from almost nonexistent) since the beginning of the Industrial Revolution.

Not only are these gases specific to industrial processes (at least here on Earth), but they have very unique spectral properties. When they were found in the atmosphere of a distant planet, their spectral signatures would jump out from the background spectra. So if astronomers see these fingerprints in the atmosphere of an alien world, they may have been created by a reasonably advanced civilization.

Searching for the chemical fingerprints of advanced civilizations

As we recently learned, astronomers can now look in greater detail for gases in the atmospheres of exoplanets. And these searches have discovered gases that could indicate life. A possible JWST observation shows evidence of biologically derived gas. The telescope diffracted the light from the planet’s star as it passed through the world’s atmosphere, and the fingerprint of that gas appeared in the data.

Spectroscopy via JWST is a powerful tool that astronomers have been waiting decades for. But not all discoveries have to be about biologically derived gases. The same technique can be used to search for technologically derived ones. This includes those suggested by Seager’s team as technosignatures.

To find evidence for them in the atmospheres of exoplanets, Seager’s team created a new tool called the “spectra phalanx plot.” Essentially, it allows users to create a visual comparison of all the spectral peaks in the spectrum of gas molecules. Groups molecules with similar peaks. This allows further analysis of spectral clusters. In addition, the team uses its data to simulate model atmospheres. The result is an approximation of the atmospheric amount of gases that scientists want to detect on the target planet. The team also maintains a “natural products database” of compounds that are produced by natural biochemical processes. This helps them understand the unique properties of fully fluorinated compounds that are likely to originate from non-biological (industrial) processes.

What about other signatures of life?

Biological and industrial processes are not the key to life that astronomers might be looking for. There are a number of other technosignatures that could emerge. They could include artificial lights seen on the world, some kind of megastructures (either on or surrounding the planet, such as Dyson spheres), waste heat or other types of emissions, or some kind of radio signals.

The fields of astronomy and astrophysics are full of amazing data. It turns out that astronomers are sitting on a goldmine of information that could well include possible technosignatures from other civilizations. The data comes from all-wavelength sky surveys and solar system survey data streams. Combine such troves of information with machine learning algorithms and the rise of artificial intelligence, and we have sophisticated tools in the search for technosignatures. They can help identify anomalies in survey data that could indicate the presence of life and advanced civilizations.

Using big data to hunt advanced civilizations

In 2019, a group of astronomers led by George Djorgovsky convened a workshop entitled “Data-driven Approaches to Searches for the Technosignatures of Advanced Civilizations”. It was hosted by the Keck Institute for Space Studies. The goal was to revisit the search for evidence of extraterrestrial technology in light of advances in the hunt for other planets and the growth of data-driven astronomy. The final report from this workshop, although delayed due to pandemic shutdowns, remains an extremely interesting read. It outlines the background and motivation for the workshop and explores methodologies for using large databases of astronomical data.

In particular, the report focuses on machine learning to detect “outlier data” that could indicate a technological signature. He also talks about what to look for in large databases (including things like Dyson structures). Finally, he outlines other types of signals to look for in databases and some possible ideas for searching for artifacts within the solar system.

Interestingly, the report also suggests that unexpected discoveries in astronomy and astrophysics will result from the search for life elsewhere. It reads: “A key outcome of this workshop was that searches for technosignatures should be conducted in a manner consistent with Freeman Dyson’s ‘First Law of SETI Investigations’, namely ‘any search for extraterrestrial civilizations should be planned to produce interesting results, although no aliens This approach to searching for technological signatures is commensurate with NASA’s approach to biological signatures in that no single observation or measurement can be considered to provide full certainty for the detection of life.”

Public reception of “The Search”

However, one of the biggest factors in the search for life elsewhere is not scientific. It’s social. As both the Seager paper and the Keck report mention, we must examine our own biases in these searches. For a long time, people simply assumed that other civilizations were naturally just sending us a “cosmic hello”. Or they came to us in flying saucers. As both papers suggest, signals from other civilizations may be much more subtle and alien than we expect.

The other part of the “social” equation is that any search for life elsewhere needs considerable public support. Keck’s report states: “Currently, SETI and the search for technosignatures are met with mixed positive and negative reactions. Many past papers and claims have been erroneous and have led to others making outrageous claims that have not been scientifically verified. The same situation occurred when the the search for exoplanets. It took many verified detections to mainstream the exoplanet field. It is important to have financial support (ie public support) to seriously search for technosignatures.”

Keck’s report suggests that scientists approach audiences in ways that help them explain the science involved and the stakes of discovery. A message to the public will be quite different from a message intended to garner support for peer review within the community. And of course funding agencies need to see funding proposals from legitimate science teams doing what they can to advance astronomy, astrophysics and the search for life elsewhere. Such a combined approach to public education will be important, especially since scientists can now conduct detailed studies of exoplanets and their atmospheres in the search for life in space.

More information:
Sara Seager et al, Fully Fluorinated Non-Carbon Compounds NF3 and SF6 as Ideal Process Gases, Scientific reports (2023). DOI: 10.1038/s41598-023-39972-z

Information from the diary:
Scientific reports

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