Mysteriously bathed in a strange orange fog, Saturn’s moon Titan has shown itself through
the Cassini mission to Saturn to be a very unique object in our solar system.
It is the only moon known to have a dense atmosphere, and it’s the only other object
in the solar system known to have ponds on its surface.
But there’s much we do not know about this strange little world, so here are 10 strange
mysteries of Titan.
Number 10.
Why is Titan’s atmosphere so dense?
The moons of our solar system tend to share one thing in common, they have little to no
atmosphere.
This is typically due to them not having enough gravity to hold onto much of an atmosphere.
But there is an exception.
Titan.
And it’s atmosphere isn’t just some wispy tenuous gas barely holding onto that moon,
but rather a thick, very dynamic atmosphere more fitting of a planet like Earth.
Why Titan has this atmosphere is a mystery.
It’s helped by several factors however.
It’s actually quite large for a moon, being second only to Ganymede in the solar system
as far as size.
But it’s size isn’t the only factor, Mars is larger still, yet only retains a thin atmosphere.
Another factor at play is a magnetic field.
Titan doesn’t have one of its own, but it spends most of its time within Saturn’s
strong magnetic field.
This affords some protection from the solar wind, which would otherwise strip away Titan’s
atmosphere over time.
But again, that doesn’t appear to be sufficient for what we see.
And we’re not even certain how Titan acquired its atmosphere in the first place.
Also, Titan’s atmosphere is predominantly nitrogen, and shares that distinction in the
solar system only with earth.
Why Earth and Titan have such different atmospheres to the rest of the solar system is also unknown.
Number 9.
The Sand Dunes of Titan
One of the many surprises that came from NASA’s Cassini mission to the Saturn system was the
discovery of what appeared to be sand dunes on Titan.
This had not been predicted, it was previously thought that Titan’s wind speeds would not
be sufficient for it.
It turns out they are.
But this material is not sand as we know it here on earth.
Rather the material making up the dunes appears to be some kind of organic material, such
tholins.
The mechanism for how the sand is made on Titan is not well understood, but it may be
a situation where the sand is formed in the northern and southern regions where liquid
hydrocarbon lakes exist, and then is transported to the equatorial regions by wind.
There’s a problem with that idea, studies have shown that the material probably isn’t
strong enough to survive the trip leading to a competing view that the particles of
dust are somehow made on site.
This may happen in the atmosphere itself, where the particles may coagulate from organic
materials present in the atmosphere and then presumably rains out, for lack of a better
term.
8.
The Lakes of Titan
As the Huygens probe drifted down to land on the surface of Titan, it took a series
of aerial photographs on its way down.
It spotted what looked suspiciously like dry shorelines on the landscape below.
This had been anticipated for years, that Titan’s temperatures were such that hydrocarbons
could exist in liquid form on the surface.
The lakes on Titan are generally confined to the polar areas, and now that they are
confirmed there are some mysteries surrounding them.
One is that they appear to have a very low erosion rate, suggesting that either some
process wipes out older features on Titan, or that erosion is simply very slow for unknown
reasons.
While Titan is significantly drier than earth, some of the lakes are quite large, several
being larger than North America’s great lakes, but nothing so large as an ocean.
But liquid is liquid, and it even rains and snows on Titan.
Imagine a low gravity snow of benzene falling into the hydrocarbon lakes.
Eventually, it would saturate like the dead sea is saturated with salt, and would leave
benzene sludge building up on the shoreline.
Then a chemically different rain made up of ethane might slowly fall and erode the benzene
sludge away, perhaps forming voids and even caves on the landscape.
A very alien place indeed.
7.
The Labyrinths of Titan
Another strange feature of Titan are mysterious labyrinth like structures that stretch for
miles on some areas of the surface.
The formation of these structures likely has something to do with the liquid ethane and
methane that rains down upon the surface, but the exact mechanism for how they carve
these labyrinths out is a mystery.
Similar looking structures can be found on Earth, and the ultimate cause of the terrain
could be due to one cause, or even a mixed bag of wind, erosion by rain, and the dissolving
of underlying layers similar to a sink hole here on earth.
While little is known about rainfall rates on Titan, the upcoming Titan helicopter mission
being developed by NASA will go a long way in teaching us about this strange moon.
6.
Some of Titan’s Lakes May Have Been Formed by Explosions
In addition to having the distinction of liquids on its surface, the actual lakes on Titan
themselves are intriguing.
Some, but not all, show features such as steep rims that look more like filled volcanic craters
rather than typical lakes.
This has led some researchers to suspect they these lakes were formed by explosions.
Just how explosions happen on Titan is linked to subsurface liquid nitrogen warming up and
explosively releasing as expanded gas.
The problem is that there is no clear way for this to happen on Titan, and requires
some mechanism of heating.
What that mechanism is remains a mystery.
5.
We’re Going to Fly a Drone on Titan
Earlier this year NASA announced the dragonfly mission which will arrive at Titan in 2034.
This unique mission is effectively a drone, with eight rotor blades that will allow it
to fly in Titan’s atmosphere allowing for the investigation of multiple sites.
Intended specifically to look into pre-biotic chemistry at Titan, essentially looking for
the building blocks of life, that may yield clues on the origins of life here on earth.
It will also search for chemical clues of past, and possibly even present, life on that
world, and even look for some of the hypothetical biochemistries in this video.
Perhaps what might end up stealing the show however will be the images from the drone.
Panoramic imaging, and even a microscope, will be present on the mission and should
yield aerial images of Titan’s mountains and lakes.
If all goes well, the mission will spend 2 years flying on Titan, and depending on even
more luck, perhaps longer.
4.
Titan May be Habitable Some Day
As it stands right now, Titan’s current habitability is an open question.
It might be possible for life to exist there, or it may not be.
This is very much unlike earth where it’s quite obviously habitable, evidenced by all
the life inhabiting it.
But the Solar System changes, and long term Earth will cease to be habitable and Titan
may start resembling earth as it is today.
About 5 billion years from now, the sun is slated to expand into a red giant phase.
While this will at least scorch earth into a cinder, it may well swallow the planet entirely,
the habitable zone of the solar system will extend further out.
This could raise Titan’s surface temperature enough to melt it, and support liquid water.
This process will also change Titan’s atmosphere.
The sun’s ultraviolet output will drop, so this will have the effect of clearing the
atmosphere of the fog that’s currently the case.
This is interesting because it currently supports the opposite of a greenhouse effect, Titan’s
hazy upper atmosphere actually serves to chill the planet down rather than warm it.
With the haze lessened, the greenhouse gases present on that moon, such as methane, could
start to warm it up.
But this period of habitability won’t last long, just a few hundred million years.
But with Earth, we know that life arose here basically the first moment it could.
It may do so on an earth-like Titan, though the presence of chemicals such as ammonia
might interfere or slow down the process.
If Titan already has life, and that life adapts and evolves to those changing conditions,
who knows what might happen.
3.
Pre-Biotic Chemistry
Titan, while really strange in comparison to earth now, actually is a fairly good representation
in many ways to what earth is thought to have been like early on.
This is interesting because when an atmosphere like Titan’s is reproduced, and energy is
added, the building blocks of life are produced.
This chemistry is pre-biotic, meaning that it’s one of the steps needed to reach biology,
but opens up the way for life to exist, or have existed on Titan’s surface.
This got even more complicated in 2017.
Cassini scientists reported the presence of complex, large organic molecules in Titan’s
upper atmosphere, in much the same way that it seems to happen in the interstellar medium.
This may mean that complex organic chemistry is all over the universe.
Also in 2017, acrylonitrile was found on Titan, a key component to creating life there by
providing a means for forming cell membranes.
Titan seems to have the stuff of life.
2.
The Subsurface Oceans of Titan
And, it has a second chance for life.
Like many bodies in the outer solar system, the conditions of Titan’s interior are such
that it’s strongly suspected that starting at about 60 miles below the surface, it’s
warm enough to support a liquid water ocean.
This ocean’s floor might be punctuated by geothermal vents that could deliver energy
and nutrients to the water, allowing for the possibility of subsurface life on Titan, much
in the same way that the possibility exists for Europa and Enceladus, and quite a few
other bodies in the outer solar system.
The evidence for the existence of this ocean lies in how Titan behaves.
Saturn has a huge gravity well that deforms the moon tidally.
If it were solid all the way through, then the deformation would be much less than it
actually is.
This means that Titan is not made entirely of solid material, but also liquid.
But this may not be an ocean made entirely of water.
There could be significant amounts of ammonia present, and if so might provide a mechanism
for how Titan’s atmosphere manages to hold onto its methane.
In short, the methane, which would normally be destroyed relatively quickly, is being
liberated by ammonia-water liquids rising through the crust and releasing methane and
keeping the atmosphere replenished.
It’s also worth noting that the presence of ammonia seems to have been crucial in the
early history of life on earth.
Perhaps it was that way for Titan as well.
1.
Disappearing Hydrogen and Acetylene
One of the oddest mysteries of Titan has been one that’s not really received much attention
since the discoveries were made.
In 2010, several papers came out reporting findings that indicated that hydrogen molecules
filtering down through Titan’s atmosphere suddenly disappear just before they hit the
surface.
Then, to complicate things, it was found that acetylene also disappears in much the same
way, despite having been predicted to accumulate on the surface due to the breakdown of methane.
The missing acetylene is particularly interesting, since it would be an energy source for methane-based
low temperature hypothetical life that could exist on Titan, which incidentally could be
supported by hydrogen consumption as well, along with the liquid hydrocarbons standing
in for water.
I stress, this is only a hypothetical form of life based in chemistry, we have not seen
anything quite like this on earth, but it is at least plausible.
Adding to this mystery is that whatever is going on in Titan’s atmosphere, it’s producing
organic compounds that are accumulating on Titan’s surface as a sort of thin crust.
And it’s doing it quickly, as areas are washed clean by the liquid hydrocarbons, this
crust gets replenished rapidly.
Point is, organic chemistry is happening very quickly on this little world.
But it could also be non-biological processes happening that are producing these effects.
But one thing is clear, if this is life on the surface of Titan, it’s very different
from life on earth existing in an impossibly cold environment using chemistry that earth
life doesn’t really use.
If that’s the case, then it likely represents truly alien life distinct from that of earth.
The transfer of life from earth to contaminate other worlds is always a concern in astrobiology.
Take Mars as an example.
It was once very much like Earth, with liquid water and an environment still that might
still support microbes eeking out a living in some way.
But that life would probably be vaguely recognizable to us, and perhaps even related due to panspermia.
And indeed we look to visit, or even colonize Mars because it’s, very marginally, earth-like.
But Titan is not, and life there may well be totally independent of earth with no relation.
Microbial they may be, they may not be cousins and might offer us a glimpse of what the word
alien really means.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently puzzled about yet
another Titan mystery.
Around 2014 Cassini scientists noticed weird reflections in Titan’s lakes that they called
magic islands.
They’d be there in one image, and then disappear in the next.
The hypotheses ranged form reflections off of waves to icebergs, but the general consensus
ended up being that they were bubbles rising from beneath the surface.
Bubbly or wavy lakes of liquid hydrocarbons, can’t wait for the dragonfly to image that
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.