There is a certain ambiguity present in the solar system.
After the formation of the solar system there was a lot of leftover material.
This material is still around in the form of the asteroid belt located largely between
the orbits of Mars and Jupiter, though that’s just where a lot of them congregate, they
really wander all over the solar system, and the comets, which are outer solar system objects
that tend to be different enough from asteroids to warrant their own classification as comets
or oort cloud objects, but if subjected to similar processes end up eventually as asteroids.
Asteroids proper show their histories in meteorites found on earth.
We see varying degrees of melting and shock in meteorites that show that asteroids are
not particularly pristine, but rather host melting and shock from various things that
happened to them in their histories, from exposure too close to the sun to impacts.
As a result, asteroids tend to be big conglomerates of rock that don’t form huge comet tails
if they pass closer to the sun.
Comets on the other hand are pristine material originating from the outer solar system, meteorites
from them tend to be very primitive material due to less collisions and madness in their
place of origin in the sparse outer solar system full of volatile ices that if they
get perturbed and sent into the inner solar system melt and form sometimes spectacular
tails.
But a comet on an orbit that brings it close to the sun relatively frequently will over
time deplete and the tail it forms will become lesser, and eventually non-existent and what’s
mostly left near the heatable surface is reduced to just plain rock.
It’s at that point that a comet essentially becomes an asteroid.
That’s one kind of ambiguity here, an exhausted comet isn’t really all that different from
an asteroid.
That said, there should still be a ready distinction.
Something sitting in the asteroid belt should not behave as a comet.
The asteroid belt has been subject to billions of years of heating.
Yet, lo and behold, hidden deeply within the history of modern astronomy we have an object
that did just that.
A seemingly perfectly normal asteroid belt object that should have behaved entirely like
a normal asteroid, suddenly became a comet with a tail, and it’s unclear just what
that tail was composed of.
Part of the problem here is that as humans, we like to categorize things.
This is a very human practice that helps our brains, such as they are, make sense of the
world around us.
We can look at the moon hanging in the sky, and when we see other objects orbiting planets
in a similar way, we can call them moons as well.
Similarly, we can take a myriad of dairy products and call them cheese, but we can go further
and call them cheddar, stilton, camembert, provolone and paneer.
We can even go further and certify them based on the specific regions of their origin.
Categories categories.
But they serve their purpose, they tell us certain information about the origin of something
that’s useful.
When at a sandwich shop, when prompted what cheese you want, strong feelings and unpleasantness
can result if the choice is misheard.
So we like categories as humans, but we also get discombobulated when we find things that
don’t quite fit into our system of categorization.
So let me spin you the tale of the comet that may have been, or may not have been.
It’s known as Elst-Pizarro and was first observed in 1979.
Initially, it looked like a normal asteroid belt object no different than anything else
and was just assigned a numerical designation.
Its orbit was such that it brought it to its closest point to the sun in 1996.
At that point it should have continued to look like a normal asteroid, it didn’t appear
to have any special attributes about it, just an asteroid in the main belt as it were.
Yet, it formed a detectable comet’s tail.
This was observed by Elst and Pizarro, so this object gained a name instead of a number.
It was unclear at the time however just what the tail was chemically made of.
They just saw that material was being ejected one way or another from the object.
It once again passed its closest point to the sun, called perihelion, in 2001.
And yet again, a comet's tail formed where it shouldn’t have.
This messed up the classification of the object, it has both an asteroid name and comet name
in the recognized cataloging systems in astronomy.
The initial working hypothesis was that the object had been recently hit by another object
and a cloud of debris was at fault for the observation.
But it didn’t work, subsequent observation showed that it wasn’t consistent due to
changes in brightness and dynamics, and it really just looked like a comet in the wrong
orbit.
There were also measurements that showed that the material Elst-pizarro was shedding was
more like smoke than pebbles as far as particle size, so taken as a whole the initial hypothesis
was discounted.
It really is a mass losing comet in the orbit of an asteroid.
The other issue is that in this orbit, a comet-like object isn’t going to last indefinitely.
It’s eventually going to exhaust all of its volatile ices and really become an asteroid.
So whatever happened with this object, it happened relatively recently.
One possibility here is the solar system’s elephant in the room, Jupiter.
It’s possible that Jupiter captured Elst-Pizarro as a comet and flung it into an orbit within
the asteroid belt.
This would mean that it’s essentially a coincidence, it just happened to end up in
an orbit that makes it look suspiciously like an asteroid, but it’s not, and is really
an object with an origin in the far outer solar system.
If that’s the case, then Else-Pizarro could be of great scientific interest in that it’s
essentially cometary material that may be more accessible than a normal comet is.
We can and have rendezvoused with comets before, Halley’s comet being an example, but those
are tricky missions that amount to flybys.
But for one behaving as an asteroid it may be far more readily studied over a long period
of time and even landed on.
This would open the way for the study of some potentially very primitive material leftover
from the very beginning of the solar system in an unaltered state, and even a sample return
mission might be feasible here.
But confounding this is another option.
It’s also possible that Elst-Pizarro really is just an asteroid and that some situational
weirdness occurred to allow for the observed behavior.
Given the fine line between asteroids and comets, it’s possible that asteroids can
retain volatile ices beneath their surfaces that indefinitely just sit there.
Ice hidden beneath a deep layer of rock.
So if an impact happens, another asteroid comes along and hits a volatile bearing asteroid,
it could expose that deposit of ice and make an asteroid appear as a comet, at least for
a time until the ice exhausts and the asteroid quiets down.
Ultimately, the pocket of ice within an asteroid getting exposed hypothesis might be the more
likely one.
Earth gets hit by meteorites all the time, and while asteroids are vastly smaller targets,
they do occasionally get hit as well.
So while it might be unlikely to catch an asteroid recovering from a recent impact,
it’s not that unlikely.
And it may be a better explanation than Jupiter just having happened to capture a comet and
place it into an eminently asteroid-like position as a mere coincidence.
And while there is no reason to suspect that Elst-Pizarro is in any way unnatural, it’s
something to do with volatile ice evaporating and escaping from a rock, there is actually
a potential technosignature hiding within this idea.
This is actually a very subtle technosignature, in that if it were to happen with just a single
object, it would be really ambiguous.
But it involves altering an asteroid to outgas in a very specific, timed way to create a
kind of road sign that announces that an alien civilization once passed through your star
system perhaps billions of years ago, noticed there was a suitable planet for intelligent
life to eventually arise on, and left a marker that long term would serve as a sign post
to inform that eventual civilization that they are not alone.
This could take the form of a depleted asteroid, where it’s missing some large part of its
original expected makeup as it should be in nature due to past mining of the asteroid.
That would be an unintentional technosignature in that it merely represents someone passing
through at sometime in the past depleting an asteroid of its iron and nicke or iridiuml.
But you could also do it intentionally, by placing volatile ices where they shouldn’t
be that periodically activate and emit an unnatural signature, but only if you monitor
the asteroid over a long period of time, hundreds or thousands of years.
This exposes a human bias ultimately in that there are technosignatures possible that work
on very long time scales that us impatient humans working on lifetimes of less than a
century might not notice until generations of scientists look at something and start
to notice patterns.
Think of it in terms of the Wow signal, the best candidate to date for a signal of artificial,
alien origin.
We only saw it once in 1977.
It looked technological to the point that it still has not been successfully discounted,
even after many attempts over the years, but what we look for is for it to repeat.
Again, many attempts at acquiring this signal again have failed.
But that assumes that the signal repeats on a time scale we’d recognize.
If you have an alien civilization where the average lifespan is a thousand years, more
than ten times longer than we live, then you might only repeat your signal once every 50
years and think that’s perfectly reasonable.
In other words, there could be alien civilizations out there that make the assumption that since
they live a thousand years, so does everyone else, and thus trickling out signals on long
time frames might make more sense.
Or they simply just view it as cost versus benefit, where they shoot out a signal periodically,
again say every 50 years, because to do so on shorter timescales would be uselessly expensive
as far as energy goes.
You could just assume that an alien civilization collects its knowledge over a long period
of time, which we actually do, generation after generation and will eventually notice
a pattern.
You could do this in a very controlled manner ultimately.
You could have an asteroid like Elst-Pizarro light up and emit a tail like a comet for
a period of time, say you’ve planted explosive charges to expose the ice, only for another
object to light up as Elst-Pizarro goes quiet again.
The pattern here would be asteroids behaving as they should not, but in a very controlled
manner eventually revealing that an alien civilization once altered your asteroid belt.
While a subtle way to do things, it pays to remember that we are not aliens.
We are homo sapiens native to planet earth, and we think in a very human manner, necessarily
so.
But that doesn’t mean there aren’t other ways to think, and that the collective mind
of an alien civilization may differ from the collective mind of our civilization, insofar
as we actually have one as a biological species.
Aliens may think on vastly longer timescales than we do.
We know that our lifespans are generally long for this planet, but there are earth species
that vastly outdo us.
There are olive trees that exceed a thousand years old, life can exist indefinitely if
it evolved to do so.
So let’s look at the longevity of life on earth.
Even an ancient olive tree isn’t all that impressive.
Microbial life on earth can go into metabolically inactive states and just sit in dormancy.
How long can that last?
The answer is shocking.
We have revived spores trapped in amber that have been dormant for 40 million years.
It’s even more so for spores in salt deposits, which have been revived after 250 million
years.
This technically means that there are bacteria on this planet that can situationally have
lifespans of hundreds of millions of years.
Scale that up to macroorganisms and it’s possible that there could be intelligent life
out there that lives very, very long lives working on very long timescales to contact
other species.
Maybe our thinking on technosignatures is flawed in that it’s not really a matter
of your ability to look for signs of other civilizations, but rather how long you look
and how diligently you collect your data.
Might it be that while the occasional tantalizing hits we see right now, might not be enough
yet?
We are at the very beginning of our technological monitoring of the cosmos and that may not
be sufficient to draw any conclusions from yet, and in 5000 years we may finally have
enough data to discern patterns that prove the existence of alien life.
Perhaps the real key in detecting aliens, is how much time you put into looking for
them.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently worried about plantlife
again.
Think of a sentient tree trying to build a radio transmitter.
It’s going to take a tree an awfully long time to do that, and once it does, what kind
of radio signal would it send, and on what timescale?
Tolkien thought of this with the Ents, which invoking the lord of the rings seems rather
odd in the context of astrobiology, but it works here.
Maybe the first message we receive from an alien civilization is “don’t be hasty”.
And then they explain that they’re a civilization of intelligent carnivorous plants and they’re
like “How you guys doin?”.
To which we respond “We’re a species of increasingly hairless apes and we eat a whole
lot of plants”.
That’s just a recipe for disaster if I’ve ever seen one, you just can’t cut it any
other way and be sure to check out my books at your favorite online book retailer and
subscribe to my channels for regular, in-depth explorations into the interesting, weird and
unknown aspects of this amazing universe in which we live.