On June 18,1178 several monks at an abbey in Canterbury, England saw something very
odd happen to the moon.
The chronicler Gervase of Canterbury wrote that he and the other monks saw a "flaming
torch" spring up from the moon's limb.
He goes on to say that the phenomenon repeated several times over a short period of time.
Ancient and medieval accounts are vague by nature when it comes to a scientific phenomena
no matter what culture they come from, but it could be said that this particular one
might be something close to what a person might see if they watched the moon get struck
by a crater forming meteorite.
In fact, we might have indications of which specific crater was formed.
While the moon is covered with craters, it's been collecting them since volcanism ended
there long ago, it's not often that someone actually observes the formation of one.
In 1976 geologist Jack Hartung proposed that right about in the area where the monks saw
their flaming torch coming from there is a rather fresh looking crater now named after
Giordano Bruno.
Surrounding it is a prominent rayed pattern of material that could suggest that it's fresh
enough to have been laid out in 1178 AD.
People tend to think of the moon's surface as unchanging, but in reality the moon is
subject to a constant rain of micrometeorites.
Over time, these sort of garden the surface and erode things.
Giordano Bruno's rays do not appear to be very eroded and the idea of a sizeable crater
forming on the moon within recorded history suggests that earth got lucky in 1178.
We could have just as easily been hit by this object.
While it's by no means impossible that a large meteorite would hit the moon and form a 22
kilometer crater within recorded human history, we'll no doubt see this happen again at some
point, there's a problem with the 1178 event.
It's thought that the creation of such a large crater on the moon would throw a lot of debris
into space and earth would then be subject to spectacular meteor showers for some time
afterwards.
But those showers do not seem to have happened, or at least no one recorded them if they did
and this was at a time when astronomers across the globe were recording whatever oddness
they saw in the skies.
No one in Europe, Arabia, China, the New World, India etc. seems to have seen anything.
That opens up the possibility that the Canterbury monks merely happened to see a head on meteorite
entry that just happened to be within their line of sight of the moon.
That also might explain why they seem to have been the only people on earth who recorded
the phenomenon.
They were merely lined up just right.
But this is one lunar mystery that some day we probably will have an answer for.
Whenever we colonize the moon, no doubt geologists will study the Giordano Bruno crater up close
and determine just when it formed.
But all of this does relate to a group of papers that, if correct, could have broad
implications on the future safety of our world.
Some of these papers link Gervase of Canterbury's account with remnants of a large periodic
comet that's been disintegrating for the last 20 or 30 thousand years, perhaps brought on
by too close of a pass to earth.
The biggest remaining fragment from this original comet is thought to be comet Encke, a fairly
low key short period comet that enters the inner solar system every 3.3 years.
This comet and the disintegration process has created trails of debris that earth periodically
passes through, in fact one such cloud left by comet Encke is responsible for the main
Taurid meteor shower in October and November of each year.
The Taurids are unusual for meteor showers, which typically consist of sand-like grains
of dust entering the atmosphere.
The Taurids however produce occasional fireballs from pebble-sized material.
Also, this meteor shower is not usually that great as far as meteor showers go, typically
if you go out you'll see five or so meteors per hour radiating from the constellation
of Taurus.
But, occasionally the Taurids can go crazy when earth passes through denser areas of
the meteor stream.
This actually has a cycle.
About every 3000 years we go through the core of the material and intense showers are seen.
In fact, it's been suggested that the construction of Stonehenge might be linked to ancient people
seeing such a shower, though I find that a pretty hard sell for something that was an
evolving religious and burial site for centuries.
But there are other cases of the main Taurids going crazy, and there are other meteor shower
streams associated with this material.
In 1975 seismometers placed on the lunar surface during the Apollo missions detected a swarm
of small impacts hitting the moon.
This swarm began pelting the lunar surface on June 22 and is associated with another
section of the swarm which is responsible for the Beta Taurid and Zeta Perseid meteor
showers which we don't see much of due to them peaking while the daylight side of the
planet passes through the swarm.
But note that date, June 22, and note that Gervase of Canterbury's impact was on June
18th.
On November 7, 2005, within the timeframe of the main Taurid meteor shower, another
impact on the moon was witnessed, though this one smaller than whatever Gervase of Canterbury
saw.
NASA scientists Rob Suggs and Bill Cooke observed a small impact on the moon, link to the paper
below.
They concluded, once again, that it was probably part of the Taurid meteor stream.
But just how big can these Taurid chunks be?
No one really knows, but a theory put forth by Kenneth Brecher of Boston University in
the 1980's, link in the description below, suggested that maybe Gervase of Canterbury's
lunar impact might have been related to another subset swarm, called the Canterbury swarm,
of this cometary debris field.
If true, this is a problem because if what those monks saw was the creation of an impact
crater, and the Giordano Bruno crater is the result of that, it was not a small object
and other such objects could pose a threat to earth, as noted by Victor Clube of Oxford
in a 1992 paper, link in the description below.
But remember June 18th and 22nd coinciding with the Beta Taurids?
Well, it just so happens that on June 30, 1908 the Tunguska event occurred and astronomers
Duncan Steele and Bill Napier have suggested that the Beta Taurids could have been responsible
for it, link to their paper in the description.
Tunguska is a well-known event and the subject of many YouTube videos, some good, some not
so good.
But it did happen and it really was huge, airbursting and flattening 2000 square kilometers
of the Russian tiaga.
Had this happened over a populated area the devastation and loss of life would have been
unimaginable.
The explosion's estimates, in terms of tons TNT or how we calculate nuclear weapons yields,
varies wildly from 3 to 30 megatons.
This was a meteoroid not a nuclear weapon, so there's a lot of debate there, but in terms
of scale, no matter what it was many, many times greater than the atomic bombs of World
War II, though actually smaller than some of the hydrogen bomb tests of the cold war
era.
Despite its size though, little material was found remaining of the Tunguska object.
There was no meteorite strewnfield as you have with craters like Barringer crater in
Arizona or Australia's Henbury craters.
There have been, among the thousand scientific papers written about Tunguska, reports of
finding material that might be solidified vapor from the object.
It's long been pointed out by scientists that this would be consistent with material from
a comet entering the atmosphere rather than an asteroid fragment.
Asteroid material can be rather dense, such as nickel-iron meteorites show.
Comet material is loose and icy, which means it does not last long passing through an atmosphere
like earth's and is likely to vaporize and leave very little behind.
But a fragment of a comet is still an object, so lots of energy would be released when it
fell as what happened at Tunguska.
Today a Tunguska-like event over populated land on earth would be far worse in effect.
How much of a threat the Taurid streams pose to earth is still an open question and comparatively
little work has been done on the subject in recent years, or at least I couldn't find
it if there is ongoing work.
If anyone knows of anything, do let me know.
But for now, we probably should be on the look out when it comes to the Taurid meteor
streams.
Thanks for listening!
I am science fiction author and futurist John Michael Godier currently with an imminent
book release, Supermind is coming soon and be sure to check out my other books at your
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into the interesting, weird and unknown aspects of this amazing universe in which we live.