We tend to think of the moon as something that never changes.
A long dead place that’s static.
After all, the moon we see when we look up at the night sky looks, for all intents and
purposes, exactly the same as it was when early humans first looked up at it many thousands
of years ago.
You could even say that it’s appearance is almost a constant across human history
and existence, While our planet changes constantly, the moon sort of doesn’t.
And while the moon does change from our perspective over geologic time scales, or very rapidly
should it get hit by an asteroid, generally speaking when something does appear to change
regarding the moon short term, it seems more than a bit odd.
And, surprisingly, anomalies do occur with regularity, often spotted by credible observers
studying the moon.
In fact, credible observations of mysterious changes in the moon’s appearance number
in the thousands.
Regarding change, the moon is an alien world, and it is in many respects, not like earth
at all.
For example, the Apollo astronauts were disoriented by just how dark things in shadow are on that
moon.
They even found that the shadow of their own hand, being so dark, made work difficult because
they just couldn’t see.
This is due to the lack of raleigh scattering that we have here on earth, atmospheric scattering,
which the moon doesn’t have, allows for things in shadow to be easily seen.
All the moon has are things like is the meager light reflected off of nearby hills.
Yet, when the astronauts looked down at their own shadows, they noticed a luminous halo
surrounding them.
This was due to, or so it’s thought, to the opposition effect, essentially a trick
of light due to retroreflection and it’s seen in other areas of astronomy.
But it was rather disconcerting to the astronauts, and if it happens here on earth it tends to
get lost in the glare from our blue luminous sky.
Point is, the moon is a very alien place and change there takes on a different form than
it does here on earth.
But sometimes, apparently, some of this strangeness can be seen from earth.
Termed Transient Lunar Phenomena, people that study the moon see changes, typically very
short term, such as clouds that appear on the moon, or discolorations or brightening
and darkening.
The reason for these transient lunar phenomena that we see from our vantage point is still
a mystery.
But accounts of something seemingly wrong with the moon’s appearance on a short term
basis go back for a very long time, possibly as early as the sixth century and persists
to this day with surprising regularity of reports.
One early one is from the year 1178 when monks in Canterbury England saw what might have
been a small asteroid impacting the moon.
They described it as a flaming torch, and spoke of the appearance of hot coals and sparks.
Then, apparently the whole moon throbbed like a wounded snake, in their words.
Then it simply returned to normal.
This could in principle have been an asteroid impacting the moon, and evidence exists that
it may have been responsible for the formation of the crater Giordano Bruno on the moon.
But it might be more likely they instead saw a meteor entering the earth’s atmosphere
head on from their line of site, since no other accounts of this are known from this
period, and several groups, such as the Chinese astronomers, were observing and reliably recording
astronomical events at this time.
They apparently didn’t see this event.
Accounts from the middle ages aside, some very credible people within science have observed
these phenomena.
On April 19, 1787, none other than Sir William Herschel, the discoverer of Uranus, saw what
he described as three glowing spots on the moon.
This one’s weird, since he described it as the moon being in a phase, and the lights
were coming from the dark part.
Herschel thought they were volcanic eruptions, a reasonable conclusion at the time, but now
we know that the moon is cooling and isn’t regularly volcanically active, the most recent
evidence of activity on the moon was 18 million years ago, so it couldn’t have been that.
One possibility for Herschel’s sighting is that it may have had something to do with
an aurora borealis, which were noted to be occurring at the time.
But three glowing dots seems rather odd for that, so whatever he saw remains a mystery
to this day.
Since that time, several thousand reports of lunar transient phenomena have been reported.
This is a problem, because while the moon does change over geologic time, it shouldn’t
be doing much over human scales of time.
And, even stranger, about a third of these events cluster over a specific region of the
moon.
Aristarchus plateau.
More seemingly credible observations include Russian astronomer Nikolai Kozyrev seeing
some kind of eruption in Alphonsus crater.
This one was particularly interesting, as he was using a 48 inch telescope with a spectrometer
attached.
He was able to detect chemical changes in the spectra, presumably due to whatever he
was observing.
And then the light disappeared and the spectra returned to normal.
Yet another observation came from professional, very respected cartographers, James Greenacre
and Edward Barr, observing at the Lowell observatory.
It occurred at Aristarchus crater, again, on the Aristarchus plateau, in 1963.
They saw bright reddish lights near the rim of the crater.
Days later another group of astronomers saw a wider general rise in luminescence on the
moon.
But perhaps the strangest account comes from an incident that occurred during the Apollo
11 mission to the moon in 1969.
There was an observation here on earth of transient events once again in the region
of Aristarchus.
Houston asked Michael Collins to take a look, and lo and behold he reported an area that
was unusually illuminated in the aristarchus region; he described it as fluorescence.
So what exactly is going on here?
In a paper by Winifred Cameron, link below, she detailed that there appear to be five
different types of lunar transient phenomena.
The first is gaseous, meaning that some kind of mist appears to obscure a small portion
of the moon.
Another are variations in color, green, blue or violet.
Reddish colorations are also noted as a separate category, and then there are darkenings, and
brightings, all temporary.
One possibility is that at least some of these phenomena are caused by outgassing from deep
within the moon’s interior.
There are some pieces of evidence to back this up.
When the Apollo 15 mission passed over aristarchus plateau, they detected a rise in alpha particles.
These were believed to be due to the decay of radon gas.
Years later, the lunar prospector mission then confirmed that radon-222 was emanating
from this crater.
The problem is, we don’t know how this gas is escaping.
It could be that it’s seeping out slowly and wouldn’t cause a visual phenomenon.
But if these events are explosive, it might.
But, there is another clue.
A feature on the moon known as the Ina structure appears to be consistent with a relatively
recent explosive gas release, thought to have occurred about a million years ago.
That suggests that it can happen, but these features aren’t common on the moon so that
would suggest that they are rare and happen on geologic time scales, unlike the frequent
lunar transient phenomena.
Another potential explanation for the phenomena is electrostatic charging or discharging.
It may be that solar wind near the moon, or gases seeping from cracks might become electrically
charged, and that when a discharge occurs, it might be visible as a lunar transient phenomena.
Another possibility is that areas of lunar dust might become charged, causing it to levitate,
and take on the appearance of a cloud as some reports of the phenomena describe.
Levitating dust is a thing on the moon, and while it might sound very alien, we do live
on a planet that experiences dust storms, and well, everyone has to occasionally dust
the house.
But that’s our atmosphere.
But on the moon it’s different, it has no atmosphere.
There, it’s levitating because of an electrostatic effect.
But it gets weirder,
When you see the moon in one of its phases, you see a black area, and an illuminated one.
The dividing line between the two is called the terminator.
Ominous name aside, this area is home to something really weird discovered during the Apollo
missions.
It’s home to a sunrise dust storm of sorts.
This was not expected at the time, but a 1972 Apollo experiment known as LEAM, or Lunar
Ejecta and Meteorites detected something strange.
It was looking for dust kicked up by micrometeoroids hitting the surface of the moon.
Every time the lunar morning occurred the experiment detected a rise in particle matter
around the terminator.
This wasn’t likely to be dust kicked up by meteoroids.
The thinking is that the day side of the moon is positively charged, and the night is negatively
charged.
So the electrostatic phenomenon that’s present on the moon causes levitating lunar dust to
get pushed along the terminator, forming a permanent dust storm of sorts, though a very
weak one by our standards here on earth.
Even stranger, the LEAM instrument itself was found to heat up a few hours after the
sun rose quite a bit more than it should have.
Apparently the dark electrostatically charged dust was sticking to it, and absorbing heat,
bringing it up to something on level with the boiling point of water, ultimately causing
the mission controllers to shut it off to keep the instrument from damaging itself.
And, astronauts may have seen this effect directly.
Several Apollo crews noted bands of sunlight behaving strangely from orbit near the terminator,
along with one of the unmanned spacecraft that also recorded the phenomena.
It could be that the moon has what amounts to a dust atmosphere of sorts.
And that brings us back to the lunar transient phenomena, perhaps some of them were due to
this effect.
But it’s worth noting that most of the observations of the phenomena, other than notably Apollo,
were done from the surface of the earth looking through our atmosphere.
This introduces a different dimension, and it could simply be that some of the phenomena
are simply due to disturbances in our own atmosphere.
As any amateur astronomer knows, earth’s atmosphere can and does distort astronomical
objects, opening the way for at least some of the phenomena just being an effect of bad
seeing that night.
And there are other issues, such as what may have happened with the monks at Canterbury,
and seeing a meteor head on that just happens to have the moon as a backdrop could be mistaken
for the lunar transient phenomena, or satellites crossing between the vantage point of earth
and the moon is another option.
But we may soon have answers for the phenomena.
Scientists in Germany are configuring a telescope that will observe and automatically identify
the phenomena, which can then be studied to determine their origin.
It should then be possible to figure out if it’s due to one single cause, or a multitude
of causes.
Given that the phenomena may happen as frequently as several times a week, it seems that we
will soon demystify at least one of the mysteries of our natural satellite.
As we visit and colonize it though, no doubt new mysteries will arise.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently feeling sorry for
the janitorial staff of a future lunar colony.
The charged dust didn’t just stick to equipment, the astronauts complained that it stuck to
everything, and couldn’t even be easily brushed off their suits before getting back
in the lander.
And, once inside, the dust smelled.
Hopefully, dusting a lunar colony isn’t ever going to be added to my resume, so to
make sure that doesn’t happen ... 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.