Cycloidal Ridges on Europa: A Xenoarchaeological Analogue

7 05 2012

Jovian moon Europa. (Credit: NASA NSSDC)

When seriously considering the possibility of xenoarchaeology as a practicable science, I’ve proposed (as have others) the endeavor to be deeply interdisciplinary.

Solid archaeological methodologies will need to be complemented with and modified by a strong foundation in planetary science.

I also often suggest that the practice of xenoarchaeology will find its most frequent utility in “debunking” rushed, biased, or outright pseudoscientific claims.  In many cases, it seems sensible to presume this may appear strictly as planetary science applied in a feature-analysis context.

So, with this in mind, I’d like to look at the mysterious case of “cycloids,” or specifically, “cycloidal ridges” on Jupiter’s second moon, Europa:

Cycloidal double ridges viewed in the northern hemisphere of Europa (60°N, 80°W): Striking evidence that nature can produce apparently-artifical features on other worlds. (Modified from Hoppa et al., 1999)

Jovian Cycloids

Found across both hemispheres of the barren, fractured ice world, these double-ridges are vast – nearly half a mile tall and half-again as wide – and shockingly symmetric, with apparently perfect vertices connecting each sweeping arc.  They exhibit a puzzling nature to parallel nearby ridges, as though “drawn” on the surface of the world in series, yet they then suddenly conflict with ridges curving the opposite direction.

The features were, at the time, truly bizarre, with no understood natural process to account for them.

While due to their immense size and their relatively-obscure nature, no one (to my knowledge) actually suggested them to be the result of Extraterrestrial Intelligence (ETI).

However, due to the cycloids’ striking geometry, I feel them to be a perfect example of an analogue scenario where a scientific xenoarchaeological hypothesis might be entertained.

Still don’t see them?  Look at the features highlighted here in red.

Icy Geoglyphs?

So, let’s say for the sake of argument that a popular case had been made that these were “Europan geoglyphs” – symbols or markers left behind by an ancient extraterrestrial civilization.

While it is often difficult to explain to non-scientists the ultimate importance of seeking to disprove a working hypothesis, in this context the utility of taking such a stance becomes clear.  With any potential xenoarchaeological site or artifact, the first order of business will be to characterize the planetary environment in order to rule out natural causes.  Only then would an archaeological-style investigation proceed, evaluating site context, invoking potential inference-by-analogy, etc.

In the case of Europan Cycloids, given a thorough and persistent site evaluation, a principal xenoarchaeologist, (being interdisciplinary and a capable planetary scientist by necessity,) would have identified that these features could have been caused by tidal forces from Jupiter.  Therefore, the ETI hypothesis is unnecessary, and with no other supporting evidence to suggest the presence of extraterrestrial life, should be refuted.  (To verify the more prosaic explanation from a more archaeological perspective, one might then investigate possible astronomical alignments with respect to the cycloids, [see: archaeoastronomy,] yet these would all point – literally and figuratively – to Jupiter itself, leading to the aforementioned cause.)

Case closed.

Avoiding the Tendency to Cherry-Pick

Why take this approach?  Why be so eager to rule out the “fun” option?  Simple:

In order to challenge the innate predisposition toward bias common to us all, one must work against the preferred hypothesis, not toward it.  (See also: cherry-picking fallacy.)

Now, had the features been discovered on a moon experiencing much less tidal stress, the story might be different…  (One might investigate in-situ geochemistry or seek more up-close imagery to search for detailed evidence of possible machining.)

-But one simply cannot go there first because the implications are possibly thrilling.  It is, in fact, because the ETI hypothesis is fantastic that one must work to rule it out.

This is the fundamental consideration that separates science from pseudoscience, which cannot be overemphasized when proposing something new, (i.e., xenoarchaeology.)


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