Neither bio- nor technosignature: New method for searching for extraterrestrials
The search for extraterrestrials has so far focused on individual exoplanets. Now a team proposes searching for patterns in their distribution.
(Image: NASA)
When searching for extraterrestrial civilizations, we should focus less on individual exoplanets and more on scanning celestial bodies close to each other for statistically significant patterns and similarities. At least, that's what a research group from Japan suggests, which has now presented its alternative method. It is based on exactly two assumptions: if extraterrestrials travel between star systems and can alter planets away from their home worlds according to their preferences, then we should find striking groupings of similar exoplanets. A connection between the properties and positions of exoplanets that emerges in this way would be “a reliable indicator of life,” only slightly falsified by a few false positives.
An “agnostic biosignature”
As Harrison Smith from the Institute of Science Tokyo and Lana Sinapayen from the Sony Computer Science Laboratories in Kyoto explain, the search for extraterrestrial life has so far primarily relied on so-called bio- or technosignatures. The former are, for example, traces of chemical substances that can only be produced biologically. However, this is enormously difficult, not least because there are often non-biological formation processes. Technosignatures are described as traces of extraterrestrial technology, but they rely heavily on our assumptions about the nature and behavior of intelligent life. And those may not be correct.
If life does not spread between different worlds, there is no connection between position and composition – otherwise there is (right).
(Image:Â Smith et.al)
To circumvent these limitations, they have pursued a “fundamentally different idea.” Instead of searching for traces of life on individual exoplanets, life might possibly be detected “through its collective effects across many planets.” The two speak of an “agnostic biosignature,” for which it is not necessary “to know in detail what life consists of or how it functions.” Instead, they only assume that life can spread between planets – for example, through so-called panspermia – and that intelligent life should be capable of altering planetary environments over time. This involves so-called terraforming.
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Should extraterrestrial life exist and spread beyond its home planet, there would be “detectable statistical correlations between planet locations and their observable traits.” Specifically, this means that exoplanets close to each other must be more similar to each other than would be the case if they had all developed completely independently of each other. This is not about all of them having, for example, an oxygen-rich atmosphere. Thus, this method does not rely on modeling biological processes but only on statistics: “Life could be detectable even without understanding its chemistry.” Such an analysis does not yet exist; the two present their work in The Astrophysical Journal.
(mho)
