One of our greatest technical achievements in space has been the launch and deployment
of the James Webb Space Telescope.
As a small update, the mirror alignment phase of the mission has completed and the results
are simply stunning.
The telescope is now fully focused in all instruments and, get this, its optical performance
is exceeding expectations.
This telescope is better than it was designed to be.
Now comes the final stage before beginning its science mission, which appears may happen
slightly earlier than expected given that everything has basically gone flawlessly,
a testament to the engineering that went into it.
The next step is calibrating the instruments and preparing for the main mission, which
could begin as early as June but the good stuff will start coming down in July, in which
case we should have stunning images very quickly, though even the test images are absolutely
stunning.
While JWST’s main mission is to study the universe and its beginnings, also on the table
is to try to characterize exoplanets.
And while not a SETI instrument, JWST has the power to detect certain anomalies that
could be technosignatures.
Also on the table is trying to characterize the make up of exoplanet atmospheres, which
if successful may show the strange disequilibrium of atmospheric gasses like oxygen on earth
that could indicate a biosphere on an exoplanet.
If anything is found, then the debate begins as scientists eliminate any non-biological
scenarios that could be responsible.
But there are also unambiguous biosignatures that JWST could search for that really would
have no other explanation than life, or a civilization, such as certain atmospheric
gasses that to be present in any detectable concentration would need an industrial civilization
producing them.
One of these would be CFCs in the atmosphere, but also things like phoshine and some nonstandard
gasses would not be biosignatures on their own, but in certain combinations could be.
But beyond that, it would be very difficult to detect a pre-industrial civilization on
an exoplanet.
In other words, if aliens were looking at earth from a distance of 2000 light-years
whether through a giant telescope or a technique like gravitational lensing, they would see
the obvious biosignature of the oxygen and methane in our atmosphere and know that was
due to a biosphere, but they would have no idea that the Roman Empire, the Mayans, China’s
empire etc. were flourishing on this world.
But there are a few possibilities for detecting and learning at least something about us,
if they had an instrument like the JWST.
The first is the vegetative red edge.
JWST is uniquely suited for detecting this biosignature, and also monitoring it to see
if it were being moderated by a civilization.
The red edge is an infrared signature that earth plants exhibit, where in certain IR
frequencies the plants become highly reflective, like mirrors.
The effect has to do with the structure of their cell walls and how light is handled,
but it’s a very distinctive feature and should be detectable at a distance if the
analogue of plant life on an exoplanet works on similar rules to our own, or a close enough
variation for some kind of effect to be seen.
If this is ever detected, by monitoring it, such as regular repeating variations in the
signal indicating seasonal changes or even some common lifecycle that also shows a periodic
methane signature as the vegetation rots, only to see it peak and disappear as the new
life cycle begins.
But there may be variations in the signal that appear unnatural, such as an abrupt drop
in the signal that could indicate a harvest on a planet with global agriculture covering
most of its surface.
In this regard, we’d be hard to detect, because during the days of Rome while agriculture
was widespread, the population was lower, and much of the planet was still covered in
vast amounts of natural forest.
You probably couldn’t tease the agriculture signatures out due to the overwhelming “noise”
of the forests.
Even if the civilization were close, say at proxima centauri, it would still to this day
be difficult to detect the agriculture using this method, but it’s not out of the realm
of possibility with a large enough version of an alien JWST.
But there is another method that while the Romans wouldn’t have been detectable using
it, we very well might.
And it’s a brand new technosignature, which highlights that we haven’t thought of all
the possible technosignatures we might see in the universe, much less looked for them.
In a paper by Jacob Haqq-Misra and colleagues, link in the description below, they detail
that it may be possible to detect alien agriculture through a disruption of an exoplanet’s nitrogen
cycle.
Nitrogen is of key importance to plant life on earth.
It’s basically fertilizer, and must be fixed in the soil for plants to live.
In nature, this is mostly accomplished by the microbes, but ultraviolet light from the
sun and even lightning also contribute in producing it in a form that can make it into
the soil.
But then there’s artificially applied fertilizer.
One of the most used nitrogen containing fertilizers in modern agriculture is anhydrous ammonia.
Ammonia is NH3 and it’s usage maybe a common feature among all analogues of plant life
in the universe, and thus could conceivably be a basis for alien agriculture.
But here’s the thing, there is a difference between a natural nitrogen cycle and one that’s
being affected by the use of fertilizer.
Specifically, you see rises in the levels of ammonia and nitrous oxide and even N2 that
may be unexplainable without widespread agriculture when coupled with the usual suspects such
as oxygen, water vapor, methane etc.
It also implies advanced chemistry on the part of the aliens because without industrial
chemistry, this form of fertilization is difficult.
We create ammonia through the Haber-Bosch process, which allows us to create plenty
of it easily and cheaply for our agriculture.
Aliens may well know of this process as well.
Specifically, there is one juxtaposition of chemicals that might be an obvious technosignature
that the authors detail.
If you see unusual abundances of nitrous oxide and ammonia, it could indicate industrial
scale agriculture is being practiced on an exoplanet.
But there’s a catch, you need a really huge population to see it.
As huge of a population as earth has, coming up on 8 billion, it’s actually not that
close to what earth could support.
This is termed the carrying capacity of a planet, and we’re not sure what earth’s
is.
The number ranges from us already having passed it, to as high as 14 billion.
But there’s a problem here, people have been making carrying capacity predictions
for earth since Thomas Malthus in the early 19th century, and not a single prediction
has held up, especially the now infamous 1960’s prediction that we would run out of aluminum
by the 90s, which was made despite aluminum being infinitely recyclable and the most abundant
metal in the earth’s crust.
The reason those predictions haven’t ever panned out is largely due to either an underestimation
of the resources available like aluminum or just plain technological advancement.
Malthus couldn’t have predicted the dramatic leaps agricultural technology would make,
and just how efficient it would become.
Likewise, it’s difficult to predict what’s in the future, especially in regards to genetic
modification of crops.
So it could easily be that carrying capacity is far larger than we currently envision for
an earth-like world.
And that’s where the nitrogen cycle disruption becomes visible.
The authors estimate that a population of 30 to 100 billion on a planet should make
the technosignature detectable.
This technosignature has an additional benefit that so long as the civilization survives,
which could be millions of years or more, the technosignature of their active agriculture
would likewise be visible long term increasing the chances of detection.
And there are other agriculture related potential technosignatures that could potentially be
detected.
One of these might involve a tidally locked exoplanet orbiting a red dwarf that has a
zone of habitability at the twilight point of that world.
This is a so-called eyeball world, and might be something like the planets in the habitable
zone of a star like Trappist-1.
Here the civilization might expand habitability to the dark side of their world using orbital
mirrors reflecting sunlight onto the surface, and thus extend agriculture as their population
grows, since any such eyeball planet would have a much more limited carrying capacity
than a planet like Earth.
But as with any technosignatures, certain assumptions have to be made.
In this case, you have to assume that aliens would practice agriculture at all, or do it
on a level that could be detected.
This would be a problem if the alien population eats completely differently than we do, such
as entirely carnivorous, or some other method of ingesting nutrients that only involves
geology, or they may be rare aliens and not maintain a large enough population to practice
detectable agriculture.
But in the end, the opposite could be true and that in addition to being one of the earliest
technologies civilizations across the universe discover, agriculture might be the most universal
of all technologies in the universe.
Even locked in civilizations that live in oceanic environments on global ocean worlds
might even practice some form of aquaculture if they hit upon intelligence and have suitable
physiology for it.
The universe could be chocked full of exofarms.
Thanks for listening!
I am futurist and science fiction author John Michael Godier in addition to currently pondering
the existence of exocarrots, im also pondering 300 thousand subscribers.
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