On this channel we often wander the universe distantly, at least with our imaginations
if not physically going there.
But this time, let’s look closer to home, but not too close.
It’s somewhere we’ve actually visited in person.
It’s the moon, and like most objects in the universe, it is no stranger to mysteries
and oddness.
So here are 10 strange aspects of our own moon.
Number 10.
Human Impact On the Moon Will Last A Very Long Time
We live on a very, very dynamic planet.
The forces of nature on earth are constantly at work reshaping our world.
Rocks weather, volcanoes deposit new rock, the winds and water erode.
Not so on the moon, where erosion, provided by micrometeoroids impacting the surface over
immense amounts of time and to some degree the solar wind, is so slow that any change
introduced by human activity will last almost indefinitely.
Take this footprint from the Apollo missions.
It’s estimated that it could last at least several million years at current rates of
erosion, but the equipment itself such as the descent stage could last 100 million years.
That’s if a bigger meteorite doesn’t come along and entirely obliterate a landing site.
But there is one type of object left on the moon that almost certainly is no longer there.
It’s the American flags.
Due to the intense ultraviolet radiation from the sun, earth has some protection there,
and things still fade and degrade, the moon has no protection at all and the nylon flags
would have completely degraded and disintegrated over the decades.
By now, nothing likely remains other than the poles.
Number 9.
The Moon … has a smell
During the Apollo missions to the moon, it was noted by the astronauts that the moon’s
dust was not easy stuff to deal with.
No matter how well they tried to brush off their suits before going back into the lander,
they could not eliminate the lunar dust that clung to them.
Upon getting back into the lander and taking off their helmets, they noticed that the lunar
dust smelled very strongly.
Described as smelling something like spent gunpowder, the reason for this smell remains
a mystery because gunpowder and lunar dust have very different compositions.
Ideas include ions from the solar wind, along with the very dry lunar dust coming into contact
with humidity creating the odor.
Presumably, this will be an issue for any lunar colony we found, and I would imagine
good air filtration will be a must.
But there’s another aspect to this, astronaut Jack Schmitt even had some kind of allergic
reaction to the dust the first time he smelled it, though he later acclimated in later incidents.
Number 8.
The Moon May Have Water … and Sparks
The lunar surface is a very, very dry place.
Desert doesn’t describe how dry it actually is.
Water does not survive on the surface long term due to the action of the intense sunlight.
But, there are areas on the moon where sunlight never reaches.
In the 1960’s it was first conjectured that certain craters on the moon, near the poles,
that were deep enough to never receive any sunlight and thus could still contain water
ice, deposited there long ago by comets.
Evidence mounts that this is indeed the case, with NASA’s Lunar reconaissance orbiter
discovering that the floor of Shackleton Crater near the Moon’s south pole could have as
much as 22 percent of its surface covered in ice.
This is important for any hopes of founding a human colony on the moon.
Water is heavy, and launching it from Earth is expensive, so having as much water natively
available to a colony is a great thing, not only for drinking and growing food, but also
making oxygen and fuel.
That’s one less problem facing those with the intent of colonizing the moon.
But that’s not the only thing to be found in the permanently shadowed regions of the
moon.
Scientists have found that the soil in these regions shows evidence that it has been partially
melted.
That’s not too surprising for a surface being bombarded by micrometeoroids, but there
may be something else going on here melting the soil.
A recent NASA study found that during powerful solar storms, the moon’s surface might become
electrically charged in the very cold permanently shadowed polar regions.
That charge would build up over time, and then discharge causing the soil to literally
spark, and slightly melt.
Imagine how alien that might seem, walking on the lunar surface in pitch black conditions,
the only sources of light being the stars blazing overhead with no atmosphere or light
pollution to mute them, and tiny flashes from the sparking soil beneath your feet.
Number 7.
The Moon May Have Once been Part of Earth
A great mystery within planetary science is just how the moon formed.
The best explanation yet, though not universally accepted in the scientific community, is that
early in the earth’s history, so early it’s best to call it proto-earth at that point,
a Mars sized objected impacted proto-earth and blew out the materials that would become
the moon into space.
Given the name Theia, this Mars sized object is thought to have been a glancing blow where
it hit at a certain angle sufficient to toss enough material out of the collision that
could coalesce and become the moon.
This is backed up with chemical similarities between the moon and earth’s geology, which
is not consistent with objects that formed in different areas of the solar nebula.
But this creates a problem.
The moon is responsible for earth’s tides.
That in turn is suspected to have played a role in the genesis of life on earth, tidal
pools are a possibility for the solvent where the chemistry of life first occured.
So if the moon hadn’t existed, then tidal pools couldn’t have occured as described.
So are we here because of the existence of the moon?
And, does that apply to the rest of the universe?
If terrestrial planets like Earth do not have moons can they host life?
Unknown.
But if that’s the case and the natural chemical laboritory for the genesis of life relies
on the existence of a terrestrial planet with a large moon, then how often does that happen?
We don’t know, but Mars only has tiny inconsequential moons, and Mercury’s got nothing, and Venus,
which is effectively earth’s twin doesn’t have anything … does this mean that terrestrial
planets within the inner parts of star systems don’t form moons unless an accident happens
like the glancing blow?
We do not yet know the answer to the question.
But it could solve the Fermi Paradox in coming years as we figure out what the deal is with
earth-like planets and exomoons.
Number 6.
Moonquakes
We always think of the moon’s tidal effects on earth as a phenomenon of our ocean that’s
caused by the moon, but only affects us.
But it’s very much a two way street, earth too has tidal effects on the moon, and it
causes one major effect.
Moonquakes.
During the Apollo missions the astronauts set up seismometers on the moon.
This was essentially to see if there was anything happening, but expectations of the time were
that they might not pick anything up and moonquakes do not regularly occur.
This is because the moon does not have plate tectonics, which is one of the main driving
forces behind earthquakes on earth.
But the seismometers did pick up moonquakes, and there were several different types.
One obvious cause were those created by meteorite impacts.
Another type were thermal in nature, as the crust of the moon contracts and expands when
sunlight is either present or isn’t, then small quakes occur.
But very deep quakes were also found, as much as 700 kilometers below the surface.
These appear to be created by earth’s tidal forces acting on the moon, as our planet pulls
on the moon, it has to adjust and when it does it creates a moonquake.
These quakes are significantly weaker than what we experience on earth but the final
type detected by the Apollo missions is a bit more mysterious in origin, and a bit more
powerful.
These were shallow moonquakes.
The cause of these more powerful moonquakes is still a mystery, but it may involve movement
in fracture zones in the rock underlying the surface of the moon.
Only more study, and more seismometers on the moon will shed light on these more powerful
earthquakes.
Number 5.
Why is the far side of the moon so different from the face we see?
The moon is tidally locked to earth and always presents the same face to us, in fact, until
1959 when the soviets sent a probe, no human had ever seen the far side of the moon.
Before then it had been expected that we could reasonably assume that the far side would
look much like the part we see.
This was most certainly not the case.
The near side of the moon is covered in dark regions, the familiar lunar maria that we
look up at in the night sky.
The far side is nearly devoid of these, instead showing a dramatically mountainous and cratered
surface.
And it’s not just visually different.
It’s been found that the moon’s crust on the far side is apparently significantly
thicker than the near side.
The reason for this is not known, but it does explain the differences between the near and
far side.
The thinner side was simply more prone to allow for molten mantle material from the
moon to flow out after an impact, forming the maria.
But it doesn’t answer the question as to why the far side’s crust is so thick.
One possibility is that when the moon formed after the collision with theia, the coalescing
material may have formed two moons, a large one and a small one in a similar orbit.
At some point they collided, but not in a huge explosive event, but rather something
like a slow splash, where the object basically flowed out onto the far side of the moon,
causing the thicker crust on one side.
But, there’s a problem.
If this is what happened, we would expect to find differences in composition on either
side of the moon.
We don’t, the variations within the composition of the lunar surface appear continuous between
both sides.
A second idea is particularly interesting to imagine.
After the formation of the moon after the impact with Theia, the moon would have been
seriously close, as close as 20,000 kilometers.
And both earth and the moon would have been in a molten or semi-molten state at this time.
Given how close they were, the tidal effects on both bodies would have been severe.
During this time, the tidal locking of the moon might have occurred, with the near side
facing a very hot earth, and the far side cooling faster.
This could have allowed vaporized materials migrate to the cooler far side of the moon,
and condense and build up, building up a thicker crust over time.
4.
The Moon is Receding into Space
While the moon was once closer to earth, the process of it receding has never stopped and
each year the moon moves about 4 centimeters further away.
This leads to an odd coincidence, that the moon’s apparent size in the sky is nearly
identical to the sun, it allows for total solar eclipses and a nearly complete view
of the sun’s corona.
This is rare, while eclipsing bodies in the solar system aren’t rare, it is rare that
our moon can so exactly block the sun’s disk.
This was not always so, and in 600 million years, it won’t be possible and only annular
eclipses will be visible from earth.
As the moon moves further away, things are eventually going to get chaotic here on earth.
Sometime around 3 billion years from now, it will so distant that it no longer regulates
earth’s rotation.
This means that earth will undergo serious changes in its axial tilt, and the whole thing
will become highly irregular.
But, at least it’s better than what’s going to happen with Mars.
It’s moon Phobos is set to collide with Mars in only about 50 million years.
It’s too small to destroy Mars, but if we have colonies there at that time, it’ll
be a problem to tackle for sure.
3.
Without the Moon, we May Never have Evolved
One of the biggest questions within the subject of the origin of life on earth is the role
of the moon.
One possibility is that life first arose here in oceanic tidal pools.
Water accumulates in a pool, essentially becomes stagnant, and that allows for the chemistry
of the beginnings of life might occur.
If this is the case, then the moon causes the tides, and without it, life on earth might
not have been able to arise.
While speculative, the actual conditions for which life to come from abiotic chemistry
are poorly understood at best, and there are other ways for water to pool than tides, it
does raise an interesting possibility.
If indeed a large moon around a terrestrial planet is required for life to arise, then
look at the inner solar system.
Venus has no moon, and Mars just has very tiny ones.
It would mean that they had no chance for life.
And Earth only had it because of a chance collision with a Mars sized object.
Therein is a question, do large moons indeed form around terrestrial planets in most circumstances?
We’ve never seen that with exoplanets, small planets like earth are very difficult to detect,
and even smaller moons around them, even less so.
So it may be that we live in a very unusual system.
The Earth-moon arrangement may be quite rare in the universe, and if it turns out that
this arrangement is a requirement for life to arise, then we live in a very lifeless
universe.
But, again, that’s speculation.
We don’t know.
But it’s certainly ominous as far as life in the universe goes.
2.
The End of the Moon
The slow estrangement from the moon as it spirals out has a happy ending of sorts.
The moon’s attempted escape faces an insurmountable problem.
That is the sun’s evolution to become a red giant.
As it does so in the far future, at some point during the expansion, the gases from the sun
will cause drag on the moon, and cause it to start falling in towards earth again.
As it approaches closer, it will hit the Roche limit, which means that the gravitational
forces holding the moon together will be overcome by tidal forces from Earth.
This means that the moon will predecease earth, and be torn apart to form a ring system.
The dying Earth, for a time, will resemble Saturn as it is today.
But not for long.
This ring will fall to earth, and then the earth itself will be consumed by the sun.
And that will be it.
Or will it?
Other models suggest that the moon might actually be tossed away from earth, with earth being
destroyed, and then spend it’s lonely eternity without its former companion.
Or it could be that the earth and moon system isn’t consumed at all, the process of a
star losing mass as it swells to a red giant stage isn’t well understood, so it might
be that the scorched earth and moon will still spend eternity together, much as they are
now, orbiting, in a probably very changed way, a cooling white dwarf cinder remnant
of the sun.
Number 1.The Moon Is Being Bombarded By Life
Orbiting a planet with an enormous biosphere and even a civilization living on it is going
to expose a moon to life, in a number of different ways.
Most obviously is when that civilization lands on its surface and plants a flag on it.
But that’s not the only way life from earth could end up on the moon.
Now, ending up on the moon and living on it are two different things, the moon is far
to harsh for anything to survive there for long.
But, just as meteorites of lunar origin are found here on earth, it may also be the case
that rocks from earth have transported life to the moon through panspermia.
It’s safe to say that life didn’t last long, but it’s possible that even tardigrades,
which are not microbial, might have made it to the moon in some form, and of course travelling
with Apollo would have been bacteria, and even within the astronauts themselves in their
intestinal tracts.
But humans aren’t the only macroscopic life from earth to have been to the moon, there
is another seemingly unlikely visitor to the moon that greatly outnumbers the number of
humans that have visited the moon.
And, if you know where to find one, you can meet one of these alternative astronauts yourself,
and even talk to it for hours if you’re so inclined.
It’s a group of trees.
During the Apollo 14 mission astronaut Stuart Roosa used his small amount of space allotted
to carry personal items to carry tree seeds.
Roosa had once been involved with the US forest service in suppressing wildfires, and wanted
to pay tribute to the US Forest Service.
What better way than to bring along some seeds.
And, there was science to this.
Scientists used the opportunity to see what would happen to the seeds after being on the
moon.
Turns out, the seeds were resilient, and most of them germinated.
And the seedlings were distributed.
And cuttings were made and distributed, meaning that there are a lot of moon trees out there.
Unfortunately, the record keeping was poor so for the most part we don’t actually know
where most of the moon trees are currently located.
Efforts are ongoing to find the moon trees.
Many of them have plaques from when the trees were distributed in the 1970’s, but some
of them will never be known and could be anywhere.
Known examples are growing at Goddard Space Flight Center, a Girl Scout camp in Indiana,
(find more).
And, trees generally are long lived.
For example, some of the redwood trees from the experiment could live for centuries.
Perhaps their seeds will be brought back to the moon in a new round of exploration.
Thanks for listening!
I am science fiction author and futurist John Michael Godier currently angry at the garden
weeds.
They’re everywhere and we wouldn’t have this problem if we’d never developed agriculture.
Technology.
So I’m currently living primitively.
Yesterday I painted a picture of an antelope on a cave wall, and today I’m grinding up
cornmeal, but I’m not using rocks.
I’m using old cell phones.
And it’s not working out well.
Primitive sucks!
O’neill cylinder time!
And now I’m going to the grocery store and be sure to check out my books at your favorite
online book retailer and subscribe to my channel for regular, in-depth explorations into the
interesting, weird and unknown aspects of this amazing universe in which we live.