The Moonless Skies of Mercury and Venus

Moons are a popular accessory for the outer planets in our solar system, but Mercury and Venus are suspiciously unadorned. In this episode of Stuff to Blow Your Mind, Robert and Joe discuss why the two most inner planets have no moons today and whether they might have had moons in the past.

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Episode Transcript

Speaker 1 (00:03):
Welcome to Stuff to Blow your Mind, the production of
My Heart Radio. Hey you welcome to Stuff to Blow
your Mind. My name is Robert Lamb and I'm Joe McCormick,
and its moons once again. That's right, The Stuff to
Blow your Mind tour of moons continues. We've over the years,

(00:24):
we've previously covered the moons of Saturn, the moons of Jupiter,
more recently the moons of Mars, and we intend to
move on to the other moons out there, the other
lunar systems. But in today's episode, we're going to consider
the moons of the two innermost worlds, Mercury and Venus.
I see a flaw on your plan immediately, Yes, because
here's the thing. Mercury and Venus do not have any moons. Well,

(00:48):
that can't stop us, can it. I mean, we we
could stop right there. We could just we could just
call the episode. But no, we're gonna keep going because
instead we're going to consider some additional questions and hypotheses
as so aated with these two moonless worlds. Yeah, we're
gonna look at the question where, you know, why are
they moonless? Were they always moonless? Did we ever think
they might have moons and um and so forth, and

(01:11):
you know what is also what is this moonless aspect
of Mercury and Venus seemed to tell us about the
uh the the neighborhood, the orbital neighborhood more immediately surrounding
the Sun. All right, well, maybe before we get into
the specifics of these two planets, we should do a
little bit of general moon review or revision as the
Brits would say, Yes, so yes, as a refresher, how

(01:35):
does any moon tend to uh form or arrive or
what have you? How does it how do you get
a moon established in orbit? Well, as we've discussed in
past episodes, uh, there seemed to be a few different ways.
One of the big ones is the the impact hypothesis. Now,
this is basically a situation where something large collides with

(01:55):
a given planet, knocking debris into orbit and beyond orbit,
and there is alting orbital debris forms into a moon. Yeah,
and this seems to be the leading contender to explain
the origin of our moon, Earth's moon. And the theory
goes something like this. Very early after the Earth formed,
so roughly four and a half billion years ago, it

(02:15):
had a collision with another rocky planet, which was a
Mars sized object hypothetically named THEA. And after this giant crash,
most of Earth and THEA after they crashed together, melted
and then reformed together into a new sphere that is
now the Earth we live on today. But a small
amount of the mass of that crash turned into debris uh,

(02:39):
and that debris coalesced in orbit around the newly formed
Earth and became the Moon. And the collision hypothesis seems
to be consistent with a lot of the available evidence
when it comes to Earth in its moon, including analysis
of lunar material brought back by the Apollo missions. Uh.
In fact, I just dug up a NASA press release
about new research from providing further support for the giant

(03:04):
impacts hypothesis on the basis of different levels of light
versus heavy chlorine and that are found on on the
Earth in the Moon. So we don't know for sure,
but giant impacts looks like the best explanation for how
we got our moon. But there are other ways for
moons to come to exist, that's right. Another way of
looking at it is the hypothesis of coformation. So basically,

(03:26):
the Moon forms along with the planet out of the
same material that long ago accreed it into a planet.
And I think this is often used to explain the
likely origin of say, the moons of Saturn, like the
gas giants. I think also the moons of Jupiter. Yeah,
kind of a garlic knots and crazy bread situation here
where a little that was left over and the making

(03:47):
of the great pizza. Uh, and it becomes the moon
in this case, I like the way you think. Now.
The next hypothesis is the capture hypothesis. And this one,
of course, is when we talked about a good deal
in our Mars episode. Uh, the moon. In this case,
the moon itself is an object like an asteroid that
is captured by the planet's gravity and drawn into orbit. Right, So,

(04:11):
as you say, capture is one of the proposed explanations
for the moons of Mars. It fits some characteristics of
those moons, but not others. We go into more depth
about this in the episodes on phobos and demos, but
the short version is Uh. In terms of physical characteristics
and composition, the moons of Mars look a lot like
asteroids that would support the idea that they were originally

(04:33):
orbiting the Sun, they were part of the asteroid belt.
They they somehow slipped into what's known as the hill
sphere of Mars, the sort of the area around Mars
where an object can fall into a stable orbit around
the planet, and then they got stuck there. But there
are other things about the moons of Mars, such as
their orbital characteristics, which are near circular and near equatorial,

(04:56):
that don't really look like capture, because when an object
is haptured originally going on its own trajectory, you'd expected
to have a sort of more elongated elliptical orbit and
also to be offset from the equator. So they're outstanding
mysteries about the moons of Mars that their characteristics seem
to be a little from column A and a little
from column B, and maybe future missions to those moons

(05:19):
can can tell us something that will help solve that mystery.
But there is one moon in the Solar System that
looks absolutely like it was captured, and that is Neptune's
moon Triton. Now how would we really know this moon
was captured, Well, one very big clue is that its
circles Neptune in a retrograde orbit, so it orbits the

(05:40):
planet opposite the direction of the planet's rotation. That does
not look like something that would naturally happen if say
a moon co formed with a planet as an accretion disk. Yeah.
Like I said, my my main analogy that I made
in the Mars episode, it's like cats. You know, if
you raise a cat from a kitten, you know there's
going to be it's maybe gonna be a little more
orderly situation. But if you have have brought a a

(06:03):
feral cat into your house, Uh, it's gonna be a
bit wilder. The orbit of that cat is going to
be wilder. That's the way I like to think of it. Anyway,
Oh I I think that's exactly right now. Hopefully in
the cat's situation, it's not as doomed as the Triton
capture situation, because one thing I was reading about is
how Neptune's gravity is actually sort of dragging on Triton

(06:25):
the fact that Triton is orbiting in retrograde to the
rotation of Neptune means the gravity is slowing down the
orbit of Triton over time because they're going across purposes,
and this is making Triton spiral a little bit closer
to the planet every time it goes around, and in
a few million years I'm not sure exactly how long,
but some number of million years from now, Triton will

(06:47):
get close enough to start to get tidally broken up
by Neptune's gravity and maybe turn into a ring. Yeah. Interesting.
And then on the cat front, I mean all cats
will eventually explode. That's just now. These are three of
the major explanations for where moons of the Solar System
come from. You've got yeah, like you say, impacts co

(07:08):
formation and capture. But there is actually one more major
theory that has been used to explain at least the
origins of Earth's moon. I don't know if it's been
proposed for any other object in the Solar System, but
this was the fission hypothesis, the idea that the Moon
is originally a mass of molten material that somehow was

(07:30):
ejected from a rapidly rotating Earth at some point in
its early history. This hypothesis, weird trivia, was actually advanced
by the astronomer George Howard Darwin, the son of Charles Darwin. Now,
I don't think this is a widely held theory at
this point. If I recall correctly. It makes some assumptions
that are kind of hard to square with other facts,

(07:52):
like I think it predicts an extremely high original rotation
speed for the Earth, but it is at least conceivable
in theory. And it does connect to one very eye
popping paper that I came across years ago that has
stuck in my mind ever since, not necessarily because it's
very likely to be true, but just because it's a

(08:12):
captivating image. And this is an idea that's explored in
a paper published in the journal Chemical Geology by R. J. Demeyer.
At All and the authors here argue that the fission hypothesis,
the idea that the Moon was somehow flung out of
the Earth or spun out of the Earth, would help
explain some of the isotopic similarity between Earth material and

(08:36):
Moon material. Of course, this would make sense if they
originally came from the same ball. But the question is
how does the ejection of the Moon actually happen? Like,
how do you fling off a moon sized chunk of
a planet? Well, they've got a guest to explain this,
and I want to read from their abstract quote. We
showed that the dynamics of this scenario requires on the

(08:57):
order of ten to the twenty nine to tend the
thirty jewels almost instantaneously generated additional energy if the angular
momentum of the proto Earth was similar to that of
the Earth Moon system. Today, the only known source for
this additional energy is nuclear fission. We showed that it
is feasible to form the Moon through the ejection of

(09:19):
terrestrial silicate material triggered by a nuclear explosion at Earth's
core mantle boundary or CMB, causing a shock wave of
propagating through the Earth. So I'm definitely not convinced it's correct,
but that is a memorable take a naturally forming nuclear
geo reactor that went supercritical and blew up the planet. Yeah,

(09:43):
still as best I can tell, I think most scientists
in the relevant fields would tell you that the giant
impact hypothesis is currently the best at explaining the most
Now there's another. This one this was a moon formation hypothesis.
It's it's closely related to examples one and two that
we aid here, and that is, uh, the idea of
a ring of debris consolidating into a rough moon. And

(10:05):
this is one of the hypotheses concerning the Martian moan
Phobos that we discussed, and um, you know, while it's
it's not something to to jump to with moons, you
know that there is also the concept of an advanced
civilization establishing an artificial moon in a planet's orbit. Again,
that was one briefly held hypothesis regarding Phobos. There's no

(10:25):
evidence for this now that concerning Phobos, there's no evidence
that an artificial moon exists or has ever existed, But
some scientists have considered it as the sort of thing
we could someday, you know, look for, we could look
for in other systems. Uh, you know, it's the kind
of thing that we might do in the future if

(10:46):
we reach the point where we have uh that level
of scientific power. Um. But but again, no artificial moons
are known to exist. I don't think any any moon
in our Solar system is currently um a thought to
be artificial in form But it's one of those things
you have to sort of keep on the table, you know,
and the towards the back of the table. But it's

(11:08):
it's technically on the table, all right. So let's get
to the question, then, why wouldn't any of these various
processes result in moons For mercury or venus. So, first
of all, here's some more general stats about moons in
our Solar system. Our Solar system has a current known
total of around two hundred and fourteen moons is according
to NASA, that entails both a hundred and fifty eight

(11:29):
confirmed moons and fifty six provisional moons and all told,
if you go planet by planet in order, uh you know,
from the Sun outward, the moon count goes like this zero,
that's mercury, zero, that's venus. One, that's Earth, and then
it goes to two seventy nine eight, two fourteen, and

(11:51):
those bigger numbers in the middle are of course the
gas giants. Now the rest of the moons out there,
and that that that two fourteen total. Those are a
tree did to the dwarf planets Pluto, Airishmia, Maki, Maki,
and Series with only Series boasting zero moons. H Pluto
has five. Series will remind you is the largest object

(12:13):
in the asteroid belt, but it's quite small. Pluto, which
has five moons again is fourteen times the size of Series,
and Series is the smallest recognized dwarf planet, so Series
has none, but the larger actual planets of Mercury and
Venus also have none. Yeah. Now, yeah, I mean the
reason I'm rolling through all this, I guess, is just
to make the point that it's like, you can't just

(12:34):
look at Mercury and say, okay, well, Mercury is the
smallest of the recognized planets, so maybe that's why it
doesn't have have a moon. Because again, Pluto Um, which
we don't consider one of the core planets anymore. Uh,
you know it it has five moons, but it is
smaller than Mercurys. So you know, something else other than
just the the absolute mass of the world is in

(12:55):
play here. Now, there is something that Mercury and Venus
haven't common, which, even without knowing much about how the
Solar system was formed, you could probably just guess is
a major reason that they don't have moons, and it's
that they are the closest to the Sun. Yeah, and
this basically relates to the short form simple answer to
this question. This is the the answer that you'll find

(13:16):
across NASA's web presence, especially in various short form and
q A articles. Uh. Yeah, they're just simply too close
to the Sun. If a moon were to orbit one
of these worlds there would be two major risks in play.
If we were to venture too far from the planet
it's orbiting, it would venture into an unstable orbit and
the Sun would capture it. And if it was too

(13:38):
close to the planet, they'd be destroyed by tidal gravitational forces.
And while there is a stable orbital zone around these
planets that could remain viable for billions of years, it's
likely so narrow that nothing has ever been captured by
it or created within that stable zone. Yes, and so
this does apply to some extent to both of these planets,
but especially to Mercury. It would be really hard for

(14:01):
Mercury to have a moon. Uh, and it would be
and it looks like it would be somewhat difficult for
Venus to have a moon, though, though not as difficult
as for Mercury. Right right, So, you know, we don't
know for certain. Um, we know there are no moons
orbiting either world now, but scientists have wondered if there
if there have been moons in times past. So we'll
get into some of these questions as as we go,

(14:23):
Planet by planet. Now, brief throwback to a past episode. Uh,
there's the hypothetical planet Vulcan that was once thought to
exist between mercury and the Sun, and we actually call
such hypothetical bodies, especially asteroids between mercury and the Sun, vulcanoids. Now,
vulcan was proposed by French a mathematician or Bann la

(14:43):
Verier during the nineteenth century to account for irregularities and
Mercury's orbit there are now explained by general relativity. Uh,
but occasionally you'll see some you know, people talking about
the possibility of vulcanoids. No evidence of a vulcanoid has
ever been reported. Granted, it's difficult to or of things
that close to the Sun, but it's it's interesting because

(15:04):
we've discussed the shadowy world of potential mysteries in the
transplutony and outer reaches of the Solar System. But it's
also interesting interesting how the bright inner realm of the
Solar System can also be shrouded in mysteries. Yeah, and
this is one of the major themes we talked about
in in that previous episode. If you want to go
look that up. It might have been a two parter
or I don't recall, but it was called The Lost

(15:25):
Daughters of Otten, where we talked about multiple hypothetical planets
or other planets that were believed to exist at one
time or another, and and we're later discovered not to exist.
And and it was cool, yeah, that the idea of
vulcan and inner planet that would explain the precession of
Mercury's orbit was in fact done away with by not
by an observation, but by a new theory, which, as

(15:46):
you say, was general relativity. But it makes me wonder
if we still have kind of a geocentric impulse in
our understanding of the Solar system. Like we know the
Earth is not the center of the universe. We know
our son is not the center of the universe. We
know our planet orbits the Sun, and yet we kind
of we think about our Sun. We kind of think
of that is like the center of things like and

(16:06):
therefore it should be the center of knowledge. It should
be the bright inner part of the city that we
know the most about. And yeah, the outskirts are dark
and mysterious, but but surely the inner area that place
right next to the light, we shouldn't have any any
mysteries or outstanding questions about that, but but we do
because we don't. We don't live there. We live we're
more in the suburbs, the Goldilocks suburbs. Yeah, yeah, yeah.

(16:30):
I mean another way you can think about it is
when we're looking for stuff way out in the in
the dark, that's the problem is too little signal. We're
when we're looking for things really close to the sun,
there's too much noise. Yeah, all right, well let's let's
talk some more about mercury here. So again, Mercury has

(16:52):
no moons, and this knowledge is based on observation, number crunching,
and two previous admissions to Mercury Mariner In which launched
in nineteen seventy three, which conducted one fly by of
Venus and three fly bys of Mercury, and the other
is Messenger, launched in two thousand four, which did two
Venus fly bys, three Mercury fly bys, and an orbital insertion,

(17:14):
achieving a quote unquote perfect orbit before it ran out
of fuel for for alterations and its orbit decayed and
it crashed into mercury surface. So it didn't see any moons. Correct, No,
no moons were observed, And I don't think there are
any serious scientific arguments for the existence of of of
of a mercur in moon today. But this hasn't always

(17:37):
been the case, so I thought we might go back
in time to nineteen seventy four. And before we get
into this, I need to drive home something I've probably
said before and and related before, and that is that
I do not like April fools Day. It's it's abominable.
It should be illegal. I regret every time I've done
in April fools Day thing in the past. I resent

(17:57):
everybody who does April Fool's Day things to day, especially
given I just earlier, earlier this morning, was reading about
an article in a respectable but I'm not going to
name names, but an article in a respectable publication that,
in a hugely embarrassing mistake, UH extensively referred to as
a source an April fools Day article, an interview with

(18:20):
an author that didn't actually take place and was posted
originally as an April Fool's hoax. And I live in
constant fear that this is going to happen to me,
that I'm just not going to notice that something was
an April Fool's joke and I'll think it was real
and refer to it on this show and just die. Yeah,
it's I mean, it's a celebration of low hanging fruit

(18:41):
and so and like sheep got you humor and and
it's it's often used by like reputable like reputable people
and sources engage in it, and yeah, it makes it
confusing later on when you're like going back through the
archives of something and then you're like, wait, all right,
this is this is April one, this is or this
is you know, the day before, the day after April first,
and you know it's it's if we're going to celebrate

(19:03):
April Fool's Day, we can't we can't like not do
other news on that day. You know, It's that's ridiculous.
Uh So, anyway, I'm we we mentioned all this because, uh,
the the the the incident they were discussing in nineteen
seventy four. Uh, it was covered in the New York
Times on April one, nineteen seventy four. But this is

(19:26):
a legitimate news article by Walter Sullivan and not an
April Fool's Day joke. But really part of me wishes
they could have just held on it this when published
it on April two. And this was confounded by the
I mean, our confusion was confounded anyway, when you found
an actual April fools Day joke by Uh was this
by NASA? Um? That came out many years later? Yeah? Yeah,

(19:49):
I think this was posted on April Fool's Day twelve.
It's now labeled April fools Day. I don't know if
it was at the time. And it was the announcement
of a discovery of a moon of mercury. Imagine our confusion. Yeah, so, um,
I think it was posted maybe as NASA's Astronomy Picture
of the Day that they do. Uh. And it's called

(20:11):
Mooning Mercury t he and it says that there's a
moon that it's approximately seventy meters or two hundred and
thirty feet in diameter that orbits mercury at a mean
distance of fourteen thousand, three hundred kilometers. The proposed name
for the moon is Caducius, named after the staff that's
carried by the Roman god mercury. Uh. And and this

(20:32):
it just it reads like a real piece of of
NASA copy, you know, it's not just like an obvious
wet joke. So imagine my irritation and reading about this
and then trying to figure out if this is somehow
related to the April first news article you're talking about
from decades previous. Yeah, because the link you shared here

(20:53):
for this, uh, for this, aside from the tag April
Fool's Day, there's no punchline in this, or at least
none that resonates with with with me or or certainly
the casual reader. Um, Like, there needs to be some
in my opinion that you need to get to that
like ridiculous point where it's clear that they're messing with us.
But but at any rate, yes, so I did a

(21:14):
little research on this just to be sure, because it
made me nervous as well, according to David Dickinson Dickinson
in Universe Today in the article Astronomical Pranks of April
Fool's Past, Dickinson writes that quote, spurious moons are apparently
the low hanging fruit of astronomical April Fool's pranks, and
so he mentions this one specifically, but does point out

(21:36):
that there was, indeed, Yeah, there was indeed a two
twelve April Fool's Day joke about Mercury having a moon,
but that the nineteen seventy four confusion uh, and subsequent
you know, press coverage of it was legitimate. So again,
maybe we're making too big a deal out of this.
But I want to be clear, like this is not
an April fool's joke. Uh, the nineteen seventy four publication here. Okay,

(21:59):
So the seventy four article was about something that they
thought had been discovered perhaps by the mirror in er ten. Yes,
and I'm going to read from part of it here. Uh, Pasadena, California,
March thirty one. That's refreshing that the it's actually tagged.
The day before um quote, an ultra violent scanner aboard
the mirror in er Tin spacecraft is detected what seems

(22:20):
to be a small moon in orbit around Mercury. It
would be the first moon discovered orbiting either Venus or Mercury,
the two planets between the Sun and the orbit of Earth.
Then it goes on for a bid. It comes back
Mayor in er Tin flew by Mercury Friday for the
first close up reconnaissance of that planet. The mysterious object
that maybe in orbit around Mercury was reported by Dr

(22:41):
Lyle Broadfoot of kit Peak National Observatory in Arizona and
Dr Michael McElroy of Harvard University. From the observation so far,
it appears to be moving at about ten thousand miles
an hour relative to the planet in rather eccentric or
egg shaped orbit, roughly fifteen thousand miles above mercury surface
and more or less in the planet's equatorial plane. It

(23:02):
is thought to be far enough from Mercury to be
spare destruction from stresses induced by the planet's gravity. However,
as noted by Dr Bruce C. Murray of the California
Institute of Technology, the head of the picture interpreting team,
any moon of Mercury would be subject to a quote
title tug of war between that planet and the Sun.
All Right, So it seems like some of the same
concerns we've already talked about are being stressed as as

(23:26):
possible reasons to be skeptical of this discovery at the time.
And it would turn out that this discovery at the
time was a false one, right. And I should also
point out the article, which you can read in full
in the New York Times Archives. It goes on to
speculate that this might be an asteroid captured by the
planet's gravity, but then also goes on to just talk
about a number of other interesting additional findings that were

(23:47):
coming in from the Mariner ten spacecraft at that point.
But yeah, looking at it especially, you know, with knowing
what we know now, so that this is what occurred.
The details of this seemed to be that one of
Mariner ten's instruments registered a bright UV emission what we
would call now a far UV that seemed out of place.

(24:10):
Then it was gone the next day. Then three days
later it was back and seemed to be coming from
an object that, as Swedish astronomy author Paul Schleiter explains
in in in Hypothetical Planets quote, seemingly detached itself from Mercury.
So one idea was, well that maybe we're looking at
a star. Uh, you know, we're just watching, you know,

(24:31):
we're seeing the light of a star as it as
the planet is moving between us and the light of
that star. But then it was it was observed that
the emissions were in two directions, and they thought, well,
maybe it's a great it's a great deal closer to us,
like something orbiting Mercury. But subsequent data indicated that it
was not in fact something orbiting Mercury. It was not
a moon. It seemed to move, then it seemed to

(24:52):
move beyond Mercury, and then it was determined that this
actually was not a moon, was not something orbiting Mercury.
It was bright UV light stemming from the binary star
system thirty one. Criteris located three thousand, one sixty six
point sixty three light years away from Earth. But this
finding itself ended up proving very useful because it was

(25:14):
the realization that extreme UV could travel UH this well
across interstellar space. Interesting. So, despite what you may have
read April fool stay or otherwise, Mercury has no moon.
It's probably not ever gonna have a moon. Just this
is not a happy place for moons to live, right,
But for a brief moment there, it apparently seemed possible.

(25:35):
But it seemed possible because there was UH because of
the information we were receiving, and we didn't know quite
how to analyze it and how to understand it. But
then subsequently we did. And this is not the only
example of far UV there are. There are other examples
that have subsequently been UH have been detected, so that
it's not that this alone is not an anomaly. Right, Well,

(25:57):
are you ready to talk about the planet van Us?
Let's do it. So Venus is as we said earlier,
another planet without a moon, though it wouldn't be as
surprising to find a moon orbiting Venus as it would
be to find one orbiting Mercury. Observation of Venus through
a telescope actually has a very interesting history with a
lot of cool controversies and mysteries in it. One example

(26:20):
that we've talked about on the show before I Know
is that the observation of Venus was one of the
lines of evidence offered by Galileo in support of the
heliocentric model of the Solar System. Now, there are a
number of arguments he offered. One was based on observations
of the surface of the Moon through a telescope. You know,
when you look at the surface of the Moon, it
appears cratered and to have terrain, going against the idea

(26:44):
that these objects in the heavens are just sort of
like perfectly smooth ideal bodies. Instead, it looks like the
Moon is made of rock, much like the Earth is.
And then the other things where he saw the the
Galilean moons named for him of Jupiter, and so the
obs ovation that there could be things orbiting another planet
like Jupiter made it seem like, well, then maybe not

(27:05):
everything orbits the Earth, maybe just things orbit other things,
and so it seems more plausible that the Earth could
be orbiting the Sun. But then also one of the
lines of evidence he produced what had to do with
the observation of the phases of Venus. Of course, Venus
from our perspective has phases just like our moon, And

(27:25):
the question is why, why why does our moon have
phases to begin with it? Well, the moon is full
when it's on the opposite side of the Earth from
the Sun, allowing sunlight to reflect off of the full
disk back in our direction. So the phases of a
spherical object that we see in the sky are determined
by our viewing angle of the day side of that object.

(27:49):
You know, the sun is always shining on half of
that sphere. What is our viewing angle on the on
the brightly lit half. And Galileo observed that Venus also
went through phases like this that would be consistent with
it orbiting the Sun rather than the Earth, for example,
appearing more as a half disc when it's further away
from the Sun, but growing full when it neared alignment

(28:12):
with the Sun. So if you try to picture that
when Venus is on the opposite side of the Sun
from Us. Roughly we're gonna get the best view of
its full day side. But another one we've talked about
before was the interesting issue of the ashen light. You
remember this one. Yeah, So this is a supposed faint
glow emanating from the shaded regions of the surface of Venus,

(28:34):
which has been observed or at least claimed by a
bunch of astronomers over the years. You can go back
and listen to our full episode on that if you
want to know more. But the planet Venus has also
been subject to spurious satellite sightings, and uh, I figured
we should talk about a few. So one of the
Venusian moon sightings, and this is probably the first ever,

(28:55):
was by a seventeenth century Neapolitan astronomer named Francesco Fontana.
And Rob, I've attached a picture for you to look
at of this guy. I don't know how accurate this
drawing of him is. Actually it's an engraving from the
seventeenth century, I guess, or actually I'm not sure when
this was produced. But in this picture, he looks like
he's up to no good. He looks like he's thinking

(29:17):
about I don't know, going through your trash or something. Yeah,
he looks kind of like a like kind of like
a cabbage patch doll, a little bit like a slightly
sinister cabbage patch doll with a with a mustache and goatee.
Fontana was actually originally a lawyer by training. He studied
law at the University of Naples, but apparently at some

(29:37):
point his interests shifted and he became more interested in
the study of mathematics and astronomy, and so Fontana actually
became one of the early telescope makers of the telescope revolution.
Now another thing you'll recall that we've talked about before.
I think this was actually in an invention episode we
did on the telescope. Um, it's difficult to say, really

(30:01):
with with confidence, who should get credit for inventing the telescope,
because you can make arguments, uh, you know, like what
really counts as the invention? And when did they first
have it? You know, was it Galileo, was it lip
or shy Uh? Something was sort of in the air
in the early sixteen hundreds, and a lot of people
were experimenting with lenses and magnification. In this first decade

(30:23):
of the sixteen hundreds. Galileo's famous initial observations were in
sixteen o nine, but Francesco Fontana was part of this
movement also. He was making telescopes right around the same time,
and according to the Danish historian of science science Helga
Krog in his book The Moon That Wasn't, Fontana was

(30:43):
one of the most respected early telescope makers in Italy,
and he achieved high levels of magnification at the time
by pairing together two convex ocular lenses in in alignment.
But this reputation for making high magnification telescopes did not
necessary fairly translate into a reputation for being a good
astronomer or being a good scientist. But try he did

(31:07):
crowd rights that by using a telescope of his own design,
Fontana was able to produce the first known drawings of
Mars in the sixteen thirties, though unfortunately his drawings appear
to be based mostly on optical illusions rather than genuine
surface detail, and so to read from Krog here quote
in observations of sixteen thirty six and sixteen thirty eight,

(31:28):
Fontana saw in the middle of Mars quote a black
cone like a very dark little globule, but he was
uncertain quote whether it was separate from the planet itself
and a satellite of it, or rather a big hollow
on its disk. So so here's a good pitch for you, right,
the black Cone of Mars. Yeah, this is you know,

(31:51):
we've discussed this phase of of of the telescope and
and looking for things and how and how you know,
ultimately we have to remind usel this one. In a
situation where you're taking a photograph, taking some getting some
sort of like a high um you know, high detail um,
you know, objective imagery. You know, there's it's it's someone,

(32:12):
it's a human observing something. And so all the various
optical illusions and illusions of perception, uh that are that
are there just you know in our everyday life are
also present through the telescope. Right. So for the first
few hundred years of astronomy, there are a lot of
cases where somebody says they saw something and somebody else
looks for it and they can't see it, and then

(32:33):
they just argue back and forth and other people chime
into yeah I saw it. No I I didn't see it.
I don't think it's there. So there's a lot that
can go on there. You know, you can you can
you can just be straining to see something and think
you see something and then reinforce that idea that you
saw something. You may you know, you may be picking
up on some sort of momentary um you know, you

(32:53):
know illusion that is, you know, due to the physical
structure of the eye. Uh, something to do with the
lens is perhaps, UH have to mention you get into
atmospheric phenomena as well, like there's so many things that
could interfere with it. Yeah, totally, and a minute ago
I should at just to clarify, I think I said
the first few hundred years of astronomy, I mean the
first few hundred years of telescope astronomy. Obviously people have
been doing naked eye astronomy for a long long time.

(33:15):
But so yeah, so Fontana was, as we say, a
respected telescope maker, but his astronomical observations were not similarly
respected by his peers. In fact, Uh, this book I'm
talking about by by Helga Kroc uh just catalogs a
bunch of people talking trash about Fontana. A lot of

(33:36):
them are like, this guy is not smart, he is
not good and Galileo was apparently somewhat contemptuous of anything
Fontana reported seeing. Uh, sort of like, yeah, he makes
pretty good telescopes, or at least high magnification telescopes. I'll
give him that, but don't believe him if he says
he saw something that was essentially Galileo's attitude. And there's

(33:57):
a great quote in this book where Galileo's assistant Evangelie
sta Toricelli, was writing a letter in sixteen forty seven, uh,
and he was writing about Fontana's observations. He writes, quote,
I have the book of Foolishness observed rather dreamed by
Fontana in the Heavens. If you want to see insane things,
that is, absurdities, fictions, effronteries, and a thousand similar outrages,

(34:20):
I will send you the book. Oh man, yeah, yeah,
they should print that on the back. But in the
sixteen forties Fontana made observations of Venus, and looks like
here he also got a lot of things incorrect. So,
for example, one thing he thought he saw was so

(34:43):
when he's when you're looking at Venus, he is seeing
the phase of Venus, right, So it's partially illuminated and
he thought, based on the partially illuminated circle that he
was seeing, that Venus must actually not be spherical but
more of an oval shape. The way he through it
makes it look like it's sort of elongated from pole
to pole, which I guess a lot of planets actually are,

(35:05):
but not to the point they would see it as
an oval like this. This is definitely exaggerated. This looks
like more like a lima bean or something. Yeah, and
then and I'm just a straight up bean. It looks
like a great being in the sky. Yes, it is
very bean or almost banana like. To be fair to him,
he is. He's drawing I guess the illuminated portion of it,
but it's still it's it's stretched out. He also drew

(35:27):
fringes around the planet. Crowd rights that this is this
is not something that's actually there. This is an optical effect. Um.
But here is where we get to the moon or
moonlike observation. Uh so here here to read from crag
crowd rights. Quote on the evening of eleven November, Fontana
observed near the center of Venus of the Venus crescent

(35:51):
quote a certain spot of subdued reddish color, noting that
this was quote a new discovery, hitherto unknown. He did
not report the size of the spot, but from his
drawing it appears that it had a radius of about
one fifth of that of Venus. The Neapolitan telescope maker
further reported, and this is a block quote from Fontana

(36:12):
himself in translation. Obviously, two small dots were seen to
accompany Venus, which I would suppose to be her courtiers
and attendants, as we shall also call those of Jupiter
and Saturn. This is a new discovery, not yet published,
in my opinion. But it is true that they do
not always appear, but only when Venus is shimmering, as

(36:32):
will be revealed in the diagrams, and these little dots
were always seen to be of a more reddish color.
These little dots were, however, not always seen in the
same situation on Venus, but they moved back and forth
like fish in the sea. From this, it can be
deduced that Venus itself moves in the same way and
is not attached to any part of the sky. Okay,

(36:55):
so moving around like little fish in the sea, he
sees at least one dot, maybe sometimes multiple dots, though
it might be notable that he he only notices that
when Venus is shimmering. Now Fontana's claims. He went on
to say that he saw the globes or the globe
I think it. At one point he sort of resolved
it to say, well, maybe there's just one of them.

(37:16):
But he claimed to see them on multiple subsequent occasions,
and his claimed observations immediately caught people's attention. A number
of other astronomers expressed skepticism about Fontana's claims, though, and
reported having independently searched for these moons and found nothing.
So I just wanted to mention a couple of examples
of his contemporaries who were not impressed by these claims.

(37:37):
One was an anti Copernican astronomer named Giambatista Riccioli uh,
and I a couple of notes on him. Number one,
I think this was actually the guy who was the
first observer, or one of the early observers of the
so called ash and light on Venus. But if he's
an anti Copernican astronomer, I think that means he is

(37:58):
holding out for geocentrism, which is cool. But he described
Fontana's observation of a possible moon of Venus to be fair.
I don't think Fontana said it was a moon or
said he was certain it was a moon. He just
saw a dot whatever this globule was. And so Ricchieoli
he called this observation very ungraceful, which I thought was

(38:20):
really funny. It's like, you know, oh, you saw a
moon of Venus. Gross dude. The Crag quotes Ricchieoli in
his in his writings on this, and Richie Ali says
that you know, whatever it was Fontana was looking at
was quote, either something like a meteor or a little
cloud in the evening, or something like sun spots in
front of Venus, or the lunar image of a cave

(38:43):
and of mountains. And then he added quote I have
never and neither has Francesco Maria Grimaldi, nor Pierre Casindi
other astronomers of the time, as seen in book three
of his Institutionists astronomic A admitted ever to have observed
at Venus or close to Venus any globules in any telescope.
So no globules. And I almost feel kind of bad

(39:06):
for Fontana because it seems like, of all these contemporaries,
it's like nobody likes him. He's got Helio centrists and geocentrists,
both insulting him constantly. I don't know, maybe the selection
of quotations that that I've come across in this book
are are especially bad. Maybe people were saying nice things
about him elsewhere, But um, he would definitely not be

(39:28):
the last to believe that he had seen a moon
or some other kind of object near Venus, because here
we're going to get to a much more celebrated and
well remembered astronomer, Giovanni Domenico Cassini, who also saw the
moon that supposedly didn't exist, though I think he also
never said it was a moon. Cassini lives six to
seventeen twelve, and he was in Italo, French astronomer and

(39:51):
mathematician who was known for having discovered multiple moons of Saturn.
The Cassini space probe, which visited those moons of Saturn,
was named after him, and Cassini believed that he observed
a small object in orbit around Venus or near Venus
multiple times, once in sixteen seventy two and then again
in sixteen eighty six. He thought that the object was

(40:14):
about one quarter the diameter of Venus, and he says
he observed it in one case for about fifteen minutes,
and then lost track of it. But then he has
a In one of his writings he has a full
description of his observations, and this is from the observation
on January sixteen, seventy two. He says, quote, Venus was

(40:37):
then horned, and this object, which was of diameter almost
one quarter that of Venus, was of the same shape.
It was distant from the southern horn of Venus a
diameter of Venus on the western side. In these two
observations I was in doubt whether it was or was
not a satellite of Venus, of such a consistence as
not to be very well fitted to reflect the light

(40:58):
of the Sun, and which in magnitude born nearly the
same proportion to Venus as the Moon does to Earth,
being at the same distance from the Sun and Earth
as was Venus the phases of which it resembled. But
in spite of some research I have done from time
to time after these two observations in order to complete
a discovery of such great importance, I have never succeeded

(41:20):
to see it except these two times. And this is
why I suspend my judgment. So Cassini's holding off a
little more. He says, I thought I saw something a
couple of times separated by many years, but I'm gonna
reserve judgment because I'm not sure what I saw, if
I saw anything, and uh, and I'm not sure it
was a moon if I did see it. But in
the decades that followed this, many other astronomers, I think

(41:42):
probably dozens, based on what I was reading, at some
point claim to see a satellite or companion to Venus.
But then many others looked for it and failed, And
of course the observations of a moon of Venus were
all wrong. We know now Venus has no moon. A
number of reasons for these faulty observations have been have
been advanced as possible explanations, many involving optical illusions caused

(42:07):
by problems with telescope lenses or interference between the telescope
lens in the eye, as well as the mistaken observation
of stars in the background for objects in the foreground.
But there is one interesting variation on explaining these observations
that was put forward by a Belgian astronomer named Jean
Charles Huzzo, who was once a director of the Royal

(42:29):
observatory in Brussels. Huzo tried to square the circle of
all these conflicting observations by suggesting that the object being
observed was not a moon of Venus, but another planet
which often appeared near Venus, often appeared in conjunction with
it at certain times of year when their orbits lined up,

(42:49):
And this also proved to be incorrect. But it's a
very interesting idea, and he gave the hypothetical planet a
very cool name, ninth. Yes, ninth. Ninth is interesting because
this is the name of an Egyptian goddess. Uh So
I had to look. I had to look a knife
up in the book on Egyptian mythology by Geraldine Pinch

(43:10):
that I've really enjoyed this year. And Pinch describes Um
nine as quote a formidable creator goddess who could be
called the Great Mother, and the name literally means the
terrifying One, an imposing goddess who wore the red crown
of the North, and whose curious symbol Um may have
originally represented the click beetle. Uh. Click beetle is found

(43:34):
near water, so there would be linked to the Nile.
And in addition, we talked about that in previous episode
and then it's importance in Egyptian mythology, but the same
symbol was later interpreted to be two arrows crossing a shield.
She can be considered the mother of both Raw and Horace,
but also sometimes so Back as well. She has goddess
of all things linked to the quote fertile primeval waters.

(43:58):
She's the mother of snakes in the mother of crocodiles
creatures quote who are in the Abyss. She is sometimes
depicted as a crocodile headed goddess nursing young crocodiles, and
so Back is of course linked to crocodiles as well.
Um and when she spat into the Abyss, the chaos
god Apophus is said to have been born, and so

(44:19):
she's also the mistress of the bow, which she uses
to shoot down the enemies of Raw, as well as
the offspring of the chaotic Apophus, who is uh, at
least in some accounts, her own offspring. So anyway, really
cool goddess to to to draw your name from. In
coming up with potential names for hypothetical planets. Oh yeah,

(44:40):
I'm all in favor of more Egyptian naming of celestial objects.
I mean, you obviously we love Greek and Roman mythology,
but you know there's plenty of Greek and Roman mythology
already in the heavens. I yeah, get Egyptian mythology more
up in there, and all all the mythologies. Yeah, I mean,
we're doing it to to a certain extent that I
feel like we keep drawing names from from other cultures

(45:02):
and other deities and other pantheons, and certainly there's no
there's no shortage of things out there to to give
fancy names too. So we'll we'll probably run out of
gods and goddesses first. Eventually we'll reach, you know, the
point in our culture's future where we're having to name
stars stuff like Gozer. We'll have to draw on fictional pantheons.

(45:24):
Very good, but I kind of dread the day we
get like asteroid Relord, the Lord of Light. Now, there's
one more thing I wanted to mention about Venus, which
is an idea I came across in an astronomy paper
from two thousand six. I'm not sure how well this

(45:47):
is held up in the years since, but it's a
suggestion that Venus could have possibly had a moon or
even multiple moons in the past. And it also connects
to an interesting fact about Venus which concerns it's rotation.
The rotation of Venus is unusual. First of all, it's
very slow. In fact, it's so slow that on Venus

(46:09):
a day is actually longer than a year, So the
planet goes all the way around the Sun before it
completes a single full rotation. And the second fact is
that its rotation goes in the opposite direction from most
of the other planets. So the standard rotation orientation in
our Solar System is counterclockwise from the north pole, but

(46:32):
Venus spends clockwise at this creeping pace. So what would
these facts potentially have to do with a hypothetical moon
of Venus. Well, in the year two thousand six, at
the a S Division for Planetary Sciences meeting, there was
a presentation given by a couple of cal Tech researchers
named Alex Ellimi and David Stevenson called why Venus has

(46:55):
no moon? Now, given our best theories about how the
early Solar System worms, it's pretty likely that most inner
planets planets like Earth and like Venus, would undergo heavy
bombardment in their early years. Including at least one large
collision at some point. Uh now, like we already talked about,
a large collision between Earth and a Mars sized object

(47:18):
probably created our moon. And in this study, the authors
argue that the same type of catastrophic impact happened to
Venus at least twice. So according to their model, the
sequence goes like this. Venus suffers a massive collision early
in formation, and the resulting debris in orbit around Venus
becomes its first moon. Because of tidal interactions with Venus,

(47:43):
this moon gains momentum over time and drifts farther and
farther away from the planet. And actually, as a side note,
the same thing is gradually happening to Earth's moon today,
but at a very slow pace, so as the Moon
raises tides on Earth, the Earth contributes back to the
Moon's orbital energy, and the Moon's orbit becomes wider and

(48:03):
wider all the time. Alami and Stevenson are proposing the
same thing happened to Venus and its first moon that
formed here. But then, according to their model, about ten
million years later, so Venus gets hit by a giant
impact again. The second impact happens at an angle in
velocity that ends up reversing the planet spin, and this

(48:25):
would account for why Venus spins in the opposite direction
from the other planets and why its rate of rotation
is so sluggish. But now because the planet is rotating
in the opposite direction, tidal interactions drag on the Moon
rather than adding energy to its orbit, so the Moon's
spirals in instead of spiraling out, and it ends up

(48:46):
merging into Venus. Uh and uh. And if there was
another moon created by this second collision, it would have
also fallen down and been absorbed into the planet as well.
So again this is just a model, just a hypothetical proposal,
but if they are correct, Venus would have had at
least one moon in the past, possibly multiple moons, but

(49:08):
catastrophic impacts made it eat its own satellite, the violent
formation of of of a moon and then the violent
destruction of the moon as well. One strange trivia effect
I came across that I wanted to mention one of
the main writers who was an astronomer who dispelled with
the notions of a satellite for Venus and explain them

(49:29):
away in terms of various other possible explanations for the sightings.
Was a guy named Maximilian Hell, also known as Father Hell.
Oh wow, there's any version of that name is cool.
Maximilian Hell, max Hell, Father Hell, oh man, Mr Hell.
It's very good. He will set you straight about the
super hot, high pressure world. All right, Well that does

(49:53):
it for me? Yeah, I guess that about rounds it up.
I mean, I think a sizeable episode about the moons
of two planets that have no moons, So I think
it bodes well for the future when we moved back
to planets that actually have moons and discuss the details
of those those actual actual lunar bodies. UM. So I
look forward to and I guess the one thing I

(50:14):
would like to hear from everyone, like, where do you
want us to go next? Do we do we just
keep going in order? Do we look to uh to
Uranus and Neptune do we go? Or do we just
shoot straight to Pluto and go there? Or do we
start looking at at the dwarf planet? Yeah, other dwarf
planets and there their various moons. Uh. Let us know.
There's also the just the whole topic of of um

(50:36):
you know, talking about hypothetical moons and all is like
the subject of of of exo moons, of moons around
exo planets, and uh, what what we what we expect
to see, uh, and what we have seen or haven't
seen in particular, this is an interesting topic as well.
Or maybe you're sick of moons. I don't know, let
us know about that as well. We we cover kind
of wide variety of topics here, and we know that

(50:58):
you know some topics or not for for all listeners.
But you know that's just part of trying to to
cast a wide net and you know, to stay curious
about reality. We promise here and now that we will
never do in April Fool's Day episode where we report
the existence of a spurious moon. Yes, that's the that's
that's the stuff to blow your mind promise. All right,

(51:20):
we're gonna go and close it up here then, but yeah,
we'd love to hear from you. Let us know what
you thought about this episode, possible future episodes, anything else.
It's just right in let us know. In the meantime,
you can find stuff to blow your mind wherever you
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(51:41):
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(52:02):
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(52:25):
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