Earth is fantastically beautiful.
On this channel, we have mainly focused
on planets in our solar system and have
seen spectacular flyovers of the moon
and Mars. But our endeavor to discover
and understand new worlds may have meant
that we have neglected what is probably
the most beautiful planet that we know
of,
our home.
And after some of the views I'm about to
show you, I'm a little worried that you
may never want to look at another planet
again.
I'm Alex Mccoan and you're watching
Astramm. And in this first episode, we
will look at some of the most
spectacular mountains in the Middle East
with real time-lapses seen from the
perspective of the International Space
Station. And I will explain the context
to these images to give you a true
appreciation for what it is you are
looking at.
Let's start with an impressive look at
some of the mountain ranges either side
of the Red Sea.
We are orbiting Earth at an altitude of
roughly 350 km. Currently heading in a
southwardly direction with Egypt to our
left and Saudi Arabia to our right.
It may seem like we are only looking at
a small area but in reality this view is
400 km across.
The mountains to our right are the Sowat
mountains, a large range that covers
over 180,000 square kilometers and rises
well above 3,000 m.
You'll notice river beds running down
the mountains. Although these river beds
are dry in this video,
this range sees the most rain in the
whole Arabian Peninsula. They just tend
to get it all in one go.
Have a look at this enormous crater
here.
This is not an impact crater, but rather
the remnants of a volcanic crater.
This whole region is actually formed
from volcanic activity with some
volcanoes still being active today.
These white dots here are not a city,
but rather a huge cement factory.
Just under these clouds is the famous
city of Mecca.
And just overlooking it are some
fantastic mountains and winding roads.
As you can see, this area is extremely
arid. Although in other parts of the
mountains, vegetation can be found.
Let's speed up our journey a bit now.
Heading towards the tip of the peninsula
on the far right is the edge of the
Arabian desert with its famous seif or
longitudinal dunes.
These dunes stretch for hundreds of
kilome around the Arabian Peninsula
following the direction of the wind
which is a constant in this area.
seen just at the border of the desert
and the mountains seems to be a scar in
the landscape. This is not a valley as
it may appear, but a raised ridge with a
sandjune following along the side of it.
You can just about see a dam with its
reservoir by here and to the east of the
dam in the middle of the sand is a
farming town.
The harsh environments humans can grow
crops astounds me.
Also found in this region is Jabal and
Nabi Shu, the tallest mountain on the
Arabian Peninsula,
reaching 3,700 m tall.
Let's start heading west from here. Now
underneath us is the east side of the
Arabian desert. individual seafunes just
about visible from this angle.
The Euphrates and the Tigress rivers are
flowing from the north towards the
Persian Gulf in the south. You can see
how these rivers visibly nourish the
ground of Iraq with most of Iraq's towns
and settlements found within this
region. This is known as an aluvial
plane, a flat region of land where these
rivers have flooded over time, creating
fertile soil
beyond Iraq. And to the left, you see
the mountain range running through
Georgia and Aabaijan,
separating Europe and Asia called the
Caucasus mountains.
These mountains are the result of a
tectonic plate collision between the
Arabian plate moving northwards into the
Iranian plate, folding the ground
upwards into the peaks you see today
under the pressure.
found in this range is the highest peak
in Europe,
Mount Elberus, which reaches 5,642
m tall.
Unlike most of what we've seen today,
this area is lush in vegetation, and the
mountains feed hundreds of glaciers into
the valleys below.
In stark contrast to these green
mountains all in a line in Iran to our
right we have an almost surreal looking
set of mountains. Surreal because the
peaks are poking out of the cloud cover
or fog.
These are all part of the same range
called the Zagros mountains. As you can
see they are vast spanning 1,600 km in
length. Let's have a closer look at what
makes these mountains so interesting.
These mountains were also formed due to
plate tectonics, although in a different
process to the Caucus' mountains we
looked at earlier.
One big visible difference you'll notice
is that the vast region has linear
mountains, but not just in a single row,
but rather it has many peaks and troughs
like corrugated iron.
The fault that these mountains formed on
is called a fold and thrust belt through
collisions with the Arabian plate moving
into the Iranian plate.
But let's zoom out to the wide-angled
view again. If this is all the Zagros
mountains, then why do these mountains
in the south look so different to the
ones in the north? This is due to it
being comprised of different types of
rock.
In the south, sedimentary layers are
deforming over a rock salt layer,
meaning folding happens a lot easier in
this type of rock. Whereas to the north,
the rock salt layer is either very thin
or missing altogether.
The rock layer that does exist here is
not as ductile or plastic as the rock
salt, meaning the landscape is only
deformed along a much narrower band
along the fault line.
Interestingly, it is around the parts of
the exposed rock salt layer that most of
Iran's oil reserve is found. As the salt
structures are impermeable, meaning vast
pockets of oil can be retained.
Salt domes and glacias can be exposed to
the surface. And I must say, they form
some of the most bizarre landscapes I've
ever seen of Earth.
They are visible from space. Here is a
giant dome 14 km across.
And here are some salt glaciers.
Yes, these structures flow down into the
valley in a similar fashion to a water
ice glacia on Earth.
A close-up inspection of the salt shows
layering and erosion from the rain.
And looking out over the landscape shows
an otherworldly view.
The Zagros mountains to the north are a
lot more normal looking, but that's not
to say they aren't beautiful in their
own right.
Beyond the Zagros Mountains, but just
before the coast of the Caspian Sea, we
can see a lake called Lake.
This lake used to be the largest lake in
the Middle East and the sixth largest
saltwater lake in the world with a
surface area of 5,200
km.
However, since the 1980s, it has shrunk
to only 10% of its former size as dams
have stopped the flow of rivers into the
lake.
If the lake ever dries up completely,
this could adversely affect the climate
in the area and plans are in motion to
refill it.
Next to the lake though is an old
volcano which is easily visible against
the lighter colored ground.
But zooming out a bit, we see that this
volcano is tiny in comparison to this
mammoth known as Sahan at 3,77
m tall.
This means that even though it is found
in the Middle East, it's tall enough for
there to be a ski resort on it during
the winter.
Heading further east, we come to another
range of mountains bordering the Caspian
Sea called the Albor Mountains. As you
can see, Iran is actually a very
mountainous country. And although we
have such a wide field of view from this
shot, the largest mountain in Iran,
Damavand is easily visible.
Just south of it is the capital of Iran,
Tehran.
But let's have a closer look at
Damavand.
This impressive volcano is the tallest
in Asia at 5,609
m.
and it is still active, although it
hasn't seen an eruption in an estimated
8,000 years.
Although it hasn't erupted for so long,
it's considered active because it emits
sulfur regularly.
It even has a volcanic crater at the
top.
And what's really impressive about this
volcano is how high it rises in
comparison to anything around it.
The Albor's mountains make an impressive
sight for those living in Tran too.
Rising high above the city with snowcap
peaks.
Moving beyond Iran, we start to leave
the Middle East and also the scope of
this video.
Earth, of course, has storms. Some to us
appear massive and can cause millions of
dollars worth of damage. In the grand
scheme of things though, they're not
that big. Compared to the biggest storms
we know about, out of the great red spot
on Jupiter, they're pretty tiny. But for
us mere mortals, we need to understand
these storms in order to protect people
and property as best we can. Right now,
we're going to look at a notorious hot
spot for cyclones, the Bay of Bengal
near India, and at a cyclone Fiin that
ran its course from the 8th to the 14th
of October in 2013.
The cyclone started off as a depression
but very rapidly intensified over the
course of two days.
By the 10th of October, it had properly
become a very severe cyclonic storm
equal to a category 1 hurricane.
The next day it became category 5 and
the second strongest system to ever make
landfall in India.
But because of frictional forces over
land by the 12th it started to weaken
and by the 13th and 14th shows it
returning again to an area of low
pressure.
If we zoom out a bit, I find it very
interesting that while this is all going
on, there seem to be other cyclonic
systems going on over the Pacific. This
typhoon season was one of the most
active and most destructive for many
years, as you can see by the amount of
what's happening over such a short
period of time.
The first typhoon you see is the
categories 3 typhoon Nari or Santi.
It began over the Philippines and made
its way over to Vietnam before fizzling
out.
The next typhoon you see is Typhoon
Whipper or Tino.
It got as strong as a category 4
hurricane.
Heat. Heat.
Earth is a beautiful planet and to me
visually it's my favorite. You might
also be wondering what the difference is
between typhoons, cyclones and
hurricanes and also how they are formed.
Short version is that tropical cyclones
in the West Pacific are called typhoons.
Those in the Indian Ocean are cyclones
and those in the Atlantic and East
Pacific Ocean are called hurricanes.
It's the longitude that makes the
difference. When in the northern
hemisphere,
they will both spin antio
counterclockwise. And in the southern
hemisphere, they will spin clockwise.
And how do they form? Well, tropical
cyclones are like giant engines that use
warm, moist air as fuel. That's why they
only form over warm ocean waters near
the equator. The warm moist air over the
ocean rises upwards near the surface.
Because this air moves up and away from
the surface, there's less air left near
the surface, and then air from
surrounding areas with higher air
pressure pushes into the low pressure
area. And that new air becomes warm and
moist and rises too.
As the warm moist air rises and cools
off, the water in the air forms clouds.
The whole system of clouds and wind
spins and grows, fed by the ocean's heat
and water evaporated from the surface.
And because the Pacific is so warm, it's
the ocean that will see the most
tropical cyclones.
Above our planet's poles, an invisible
force is at work. Hypothesized decades
before we were able to measure it
directly, this global energy force is
responsible for sculpting our atmosphere
and driving charged particles into
space. It's also why some planets end up
uninhabitable altogether. It's called
the ambiolar field and it's a force as
fundamental to our Earth as gravity or
magnetic fields. Although for the sake
of life on Earth, it's a good thing it
isn't too strong. Recent breakthroughs
from NASA's Endurance mission have
finally allowed scientists to solve a
60-year-old mystery by measuring the
ambipolar field for the first time,
proving once and for all that our planet
has a third global energy field.
I'm Alex Mccoan and you're watching
Astramm. Join me today as we unravel the
mystery of our planet's ambipolar
electric field. A phenomenon that not
only powers the polar wind, but also has
an enormous impact on our planet's
habitability.
Earth's magnetic field depicted in this
video as onion-like layers of lines
helps to shield our atmosphere from
dangerous solar energy and damaging
cosmic rays. And the gravitational field
shown here as the white glow around our
planet not only keeps us planted on
Earth's surface and stops our atmosphere
from drifting away but also provides
valuable information in the study of
Earth's changing climate sea level rise,
ocean circulation, and much more. As you
can see, our magnetic and gravity fields
are critical features that help make our
planet habitable. And with the recent
publication of a 2024 paper in the
journal Nature, direct evidence has been
found for a third energy field, the
ambiolar field.
To understand this energy field, we need
to talk about plasma.
Like a solid, liquid or gas, plasma is
another state of matter which happens to
make up 99% of all visible matter in the
universe. Plasma is made of ionized
particles and is responsible for several
well-known phenomena on Earth like the
aurora borealis and lightning.
Plasma can form where atmospheric gas
density becomes low enough to support
the conditions for it and around 90 km
above Earth's surface. This plasma is
made up of very lightweight, fastm
moving particles which get trapped along
the Earth's magnetic field lines as they
move away from the surface. Around the
majority of our planet, plasma
encounters a barrier that limits its
escape into space known as the plasma
pores. Here, plasma co-rotates along
with Earth along its closed magnetic
field lines.
Until the mid 1960s, the prevailing
model of our planet's magnetic field
theorized that all of the magnetic field
lines were closed and the plasma
remained trapped. So what changed? We
went to space.
In the 1960s, the first spacecraft
flying over our planet's north and south
poles could actually detect a supersonic
wind of charged particles or plasma
flowing out to space, including
positively charged hydrogen and oxygen
ions. This observation led scientists to
start wondering whether the Earth's
magnetic field model should have an open
rather than a closed tail.
At the time, scientists already knew
that our atmosphere lost some particles
to space due to thermal escape. This is
a type of atmospheric escape that
typically happens when the energy from
sunlight heats up particles in our
atmosphere, allowing them to reach
escape velocity and break free of our
planet's gravitational pull. Kind of
like when a pot of water boils and steam
evaporates. So, it was no surprise that
some particles would be escaping into
space. But something didn't quite add
up.
If energy from the sun were the only
cause of atmospheric escape, one would
expect the particles that were escaping
into space to be heated. However, many
in the stream were actually cold with no
signs of being heated. And yet, they
were traveling at supersonic speeds.
Scientists hypothesized that there must
be another invisible force driving this
phenomenon. And in 1968, the term polar
wind was coined to describe it, leading
to more research and theories into its
cause and effects.
The idea of a planetwide electric field
was developed to explain the polar wind.
But when this was theorized in the
1960s, it was thought that the force was
too weak to detect. And at the time,
scientists were correct. The electric
potential was so weak, it would require
very sensitive instruments to measure,
and that technology wouldn't be invented
for several more decades.
Enthusiasm to measure our planet's
ambipolar field was spurred again in
2016 after a clue came from the European
Space Ay's Venus Express mission.
One of the reasons that Earth is
hospitable for life is because of its
water. While Venus today is dry and
barren. However, billions of years ago,
evidence suggests that Venus might have
had abundant water like our own world
does now. This raises the intriguing
question, if Venus once had water, where
did it all go?
The issa's Venus Express mission offered
a potential explanation when it detected
a 10V electric potential around Venus,
at least five times larger than
expected. This marked the first
successful measurement of an electric
field on any planet, including Earth.
The electric field surrounding Venus
could pull positively charged ions like
oxygen out of the atmosphere, draining
it of the essential ingredients of
water, like a vacuum cleaner siphoning
particles out to space. Over time, this
could have played a role in draining the
planet of its once abundant water. This
prompted a question much closer to home.
Does Earth have a similar electric
field? And if so, why has our planet
managed to hold onto its water?
The electric potential measured around
Venus was around 10 V. For comparison, a
standard car battery is 12 V, but
scientists expected our planet's
electric potential to be as little as
0.3 V, similar to a button battery you
might find in a watch, and some 25 times
weaker than the electric potential on
Venus. It's this difference that may be
a key reason why our Earth has been able
to keep its water. And that's what
inspired NASA's Endurance team to
develop a new type of scientific
instrument called a photo electron
spectrometer to find Earth's weak
electric field. The instrument is
designed to measure the speed of
electrons escaping from Earth's
atmosphere as a way to reveal our
planet's electric potential.
Earlier I explained thermal escape and I
mentioned that particles are able to
escape from our atmosphere when they
reach escape velocity. That escape
velocity is a very specific predictable
speed. But this speed should be ever so
slightly slowed by Earth's electric
potential.
And so by measuring that slowing effect
at apogee or the furthest point in
Endurance's orbit from Earth, the
instrument would be able to measure the
strength of the electric potential
around our planet. Such a sensitive
instrument would need to be launched at
precisely the right location and time.
In order to ensure a chance at making
the observation successful, the Swalbard
rocket range was selected for the job.
is the northernmost range in the world
located in Swalbad, Norway, a group of
islands in the Arctic Ocean. Here, the
NASA Endurance team would be able to
launch the instrument on a suborbital
rocket through Earth's magnetic north
pole. And on the 11th of May, 2022, the
team of international scientists did
just that.
Named after the ship that carried Ernest
Shackleton's crew in their 1914 attempt
to reach the South Pole and cross
Antarctica, the Endurance mission
launched its suborbital rocket to an
altitude of 768 km, collecting data over
518 of those kilm before splashing down
19 minutes later in the Greenland Sea.
During its flight, the instrument
measured a change of 0.55 volts in
electric potential between 250 km and
768 km. Space scientist Glen Collinsson,
the principal investigator for NASA's
Endurance mission, said even though half
a vault is almost nothing, again almost
about the strength of a watch battery,
it's just the right amount to explain
Earth's polar wind.
This first ever direct measurement of
Earth's electric field marked a pivotal
moment in our understanding of this
fundamental planetwide energy force.
The ambiolar field exists in what's
called the ionosphere, a region that
stretches across three out of five of
our atmospheric layers. Our atmosphere
is divided into five main layers. The
troposphere, also known as the lower
atmosphere, only reaches about 20 km
above Earth's surface and is where the
majority of weather occurs. Next is the
stratosphere, which extends up to about
50 km and contains most of our planet's
ozone that protects us from ultraviolet
radiation from the sun. This layer has
very little circulation and is where
commercial airlines usually fly. Above
the stratosphere is the messosphere,
extending up to about 85 km. This is
where meteors burn up near the bottom of
the meosphere layer are thick enough to
slow them down. It's within the upper
reaches of the meosphere that the
ionosphere begins, but its influence
stretches far beyond that. Starting
around 80 km above the surface in the
meosphere, the ionosphere continues
outward through the entire thermosphere
layer from about 85 to 600 km. This is
where auroras happen and high energy
ultraviolet and x-ray radiation are
absorbed creating charged particles.
And finally, the ionosphere ends in the
lower exosphere, which begins around 600
km and continues out to about 10,000 km
from Earth's surface, where it fades
into outer space. The exosphere is where
many satellites orbit around our planet.
As you can see, the ionosphere starts
around 80 km above sea level and
stretches hundreds of kilome into space
where it overlaps with Earth's
magnetosphere, a region of space
surrounding Earth. Within this massive
region of the ionosphere is where we
find the ambipolar field, which is
theorized to begin at around 250 km.
While most of our atmosphere is composed
of nitrogen, the upper region of our
ionosphere is home to lighter elements
like oxygen, hydrogen, and helium. When
photons from the sun collide with these
elements in the upper atmosphere, they
can knock electrons loose from the
elements in a process called ionization,
leaving positively charged particles
called ions and negatively charged
electrons.
Because of the opposite charges of the
negative electrons and positive ions,
they are attracted to each other and
become tethered together by an electric
field. It's this electric field that
constitutes a major part of the ambiolar
field. The electrons within the electric
field are so light that the slightest
push could send them flying out to
space. While the ions are more than
1,800 times heavier than the electrons
and sink toward the ground due to
gravity, the subatomic tug of war works
in both directions. But the upward tug
from the energized electrons is able to
just slightly overwhelm the force of
gravity on the ions. This outward
pressure of ionospheric electrons is
what creates the ambipolar field
depicted here as the sparkling blue glow
around our planet. The upward lift
inflates our planet's ionosphere and
accelerate some ions enough to escape
from the atmosphere, creating the polar
wind along our poles magnetic field
lines. What's more, the ambipolar field
can achieve this acceleration of plasmas
without heating them, providing an
explanation for the cold plasma
scientists have detected escaping from
the ionosphere. It's the birectional
nature of the interaction between ions
and electrons that gives the ambipolar
field its name. The Latin prefix ambi
means both and polar refers to the polar
regions where the electric fields
effects are felt the strongest.
Collinsson, the Endurance Mission's
primary investigator, called the
Ambiolar Field an agent of chaos,
stripping particles from our atmosphere
away into space.
Hydrogen ions make up the majority of
the polar wind. They are so light the
ambipolar fields upward force of these
electron ions is 10.6 six times stronger
than the force of gravity, leading the
ions to accelerate up at supersonic
speeds and escape from our atmosphere
above the Earth's magnetic poles.
Scientists have found that our planet
loses about 3 kg of hydrogen gas every
second or 95,000 tons per year.
Additionally, the Earth also loses about
50 g of helium per second or 1,600 tons
of helium gas per year. a smaller but
still measurable amount and a much
smaller amount of other gases like
oxygen. However, not all of this is due
to polar winds. It occurs through a
combination of factors including thermal
escape and non-therrmal escape
mechanisms such as polar wind. But don't
worry, despite our planet losing several
thousand tons of its atmosphere to space
every day, we are nowhere near running
out of air. The planet won't run out of
oxygen for a billion years. It will be
another billion years after that before
our oceans will have been depleted of
most of their hydrogen. Around 4 billion
years from now, our planet may look very
similar to how Venus looks now. All of
our water will have evaporated and the
greenhouse effect will have become
strong enough to melt rock, leaving our
planet a dry, lifeless world.
Keep in mind that modern humans have
only existed on this planet for around
300,000 years. Our species would need to
exist more than 3,300 times that length
to be around in 1 billion years.
While not really important on human time
scales, it is still interesting to think
about though. And while hydrogen ions
may be the lightest and most common type
of ion to escape in a polar wind,
heavier particles also get a boost from
the ambipolar electric field, helping to
shape our atmosphere's structure and
dynamics. How exactly? Well, now that
we've measured the ambipolar field,
scientists can delve into all the ways
the ambipolar field shapes our
atmosphere. Take oxygen ions for
example. These heavy ions weigh half as
much when they're immersed in the 0.55V
ambiolar field. This effect increases
the ionosphere's scale height by 271%
which means our atmosphere can remain
denser at greater heights than it would
otherwise be able to. Endurance's
discovery and measurement of the
ambipolar field also provided an
important key to understanding why Earth
has been able to hold on to much of its
water up until this point. While our
neighboring planet Venus was not able to
do the same. It's theorized that any
planet with an atmosphere may also have
an electric field. And you may recall
that earlier I said Venus's electric
potential was measured to be around 10
volts, roughly 18 times stronger than
the ambiolar field on our own planet.
While Earth does lose a constant flow of
particles to space, both through the
polar wind as well as other types of
atmospheric escape, this effect would
have likely been much more pronounced on
Venus because of its stronger electric
potential, leading to the loss of
heavier particles like the ones that
make up water. The fact that our
ambipolar field is so weak may be an
important part of why our planet has
been able to hold onto its water. We've
only just started to explore the depths
of how the ambipolar field has
influenced our planet and life on Earth.
And the Endurance scientists have said
there are already plans for additional
measurements of our planet's ambipolar
field in the future. Like its
predecessor, the new rocket will also
carry the legacy of a long past Arctic
explorer named after the Resolute, a
ship that set off to explore the Arctic
in 1850.
And now that we've finally been able to
confirm and measure the ambipolar field
strength and with a follow-up mission
already planned to take more
measurements, scientists can start
asking some of the bigger and more
exciting questions like what it means
for Earth's complex atmospheric dynamics
and how it helps to govern planetary
evolution. And doesn't the potential
insights we stand to gain from this
research feel electric?
In 1977,
two pioneers embarked on what might be
one of the most epic feats of
exploration ever undertaken.
Their goal to unravel the cosmic mystery
surrounding the solar system and our
place in it. Not only did they provide
us with some of the first and best
imagery of our solar systems outer
planets, but they continue to send us
incredible new information about our
universe from interstellar space some 47
years and 24 billion km later. The
Voyager 1 and 2 probes are more than
just instruments and circuitry. They are
a symbol of humanity at its best.
Curious, audacious, ambitious, and
resilient,
Voyager didn't just capture dazzling
photos of our gas giants and their
moons. It captured the hearts and minds
of generations back home on Earth. "When
I look back, I realize how little we
actually knew about the solar system
before Voyager," says Voyager mission
project scientist Edward Stone. "We
discovered things we didn't know were
there to be discovered time after time.
I'm Alex Mccoan and you're watching
Astramm. Join me today as we trace
Voyager's iconic journey in pictures.
From the splendor of Jupiter to Saturn's
icy rings to the topsyturvy world of
Uranus to the mighty storms of Neptune,
we explore what this mission taught us
about our planetary neighborhood.
On the 20th of August 1977, NASA
launched the Voyager 2 space probe from
Cape Canaveral, Florida. Its partner in
crime, Voyager 1 was launched 2 weeks
later on the 5th of September. Even
though both probes were Jupiter bound,
Voyager 1 was set on a shorter, faster
trajectory, so taking off second made
sense.
It overtook Voyager 2 on the 15th of
December 1977 and exited the asteroid
belt first.
Together, this dynamic duo was set to
take advantage of a once in 176-year
planetary alignment. Jupiter, Saturn,
Uranus, and Neptune were going to be
aligned in a way that would allow one
mission to explore all four gas giants.
An opportunity NASA simply refused to
miss.
After some back and forth with the US
Congress, a few hurdles surrounding
budget approvals, and a decade of hard
work, the Voyager probes finally made it
to the launchpad, heralding a new era of
space exploration. The dazzling parade
of pictures Voyager would send back were
absolutely revolutionary at the time.
But don't take my word for it. Let's
jump in and you'll see for yourself.
13 days after launch, Voyager 1 sent
this photo back to Earth. The first of
tens of thousands it would send back
over the next 5 years. Taken 11.6
million km from Earth. It's a
sentimental place to start our journey.
It might remind you of the Earthrise
photo taken by the Apollo 11 crew from
the moon just 8 years prior. We can see
our blue marble and its moon in the
distance. I don't know about you, but I
find this photo so hauntingly beautiful,
especially knowing how far this probe
traveled and how much it's seen since
then.
NASA's Mars Reconnaissance Orbiter has
been imaging the surface of Mars for
over 10 years now with its powerful
high-rise camera.
10 years of taking photos every day
means that its catalog is huge and we
can pick out pretty much any part of
Mars that we want to have a closer look
at.
Today, I thought it would be really
interesting to investigate the sandjunes
on Mars and see how they compare to the
wonderful sandjunes we have on Earth.
You may have already seen imagery of the
Sahara Desert with dunes hundreds of
meters tall or the Namib Desert with
rolling sandjunes as far as the eye can
see.
Did you know though that there are five
different types of sandjunes and that
Mars has a type of June Earth doesn't
have? And also what are the biggest
Junes on Mars?
The most common type of sanjune on earth
is the cresant or the bakan sanjune.
While not always as distinctive as these
dunes in this image, they are plentiful
and found in most sand deserts. They are
defined by this kind of cresant shape
with arms and they are usually wider
than they are long. Like you can see
here, they form like this because in
these places there is only one dominant
wind direction. They have a shallow
slope on one side that faces the wind
and a slip face on the other side. They
are a type of transverse dune as they
move gradually over time as the wind
blows, whipping sand from the front over
the top and down the slip face.
When many of them merge, they can create
an almost wave of sand smooth on the
side facing the wind with a slip face
away from the wind, moving gradually
over time with the wind's direction.
They are also in plentiful supply on
Mars. All of the ones I'm about to show
you can be found at the base of various
large craters. Going to this old crater
near Mars's equator. Barkan dunes can be
seen lumped together somewhat here in
this plane. This happens when there is a
plentiful amount of sand and the dunes
merge together into a big lumpy
transverse dune.
But individual dunes are really evident
a bit higher up where the sand is
contrasted against the bedrock.
Here are some more found in Arangolski
crater.
When there is a smaller amount of sand,
the dunes tend to stay separate, which
looks really peculiar from above.
These dunes do move, although very
slowly. Here's a couple of examples of
dunes on Mars moving slowly over the
course of 2 to 3 years. Scientists
originally thought the sandunes would
stay pretty motionless on Mars as
sandunes require wind to move them and
Mars only has about 1% of the
atmospheric pressure at the surface
compared to Earth whose winds can easily
move sand.
We knew the wind on Mars could pick up
tiny dust particles, but it would
require extremely strong winds to move
sand.
This could be helped though by the fact
that sand on Mars is not exactly the
same as Earth sand. In my Opportunity
video, I mentioned that the sand
particles Opportunity analyzed were far
smaller than what we're used to on
Earth, which may aid the movement of
these dunes.
But what happens if the wind is
birectional?
Going back to Earth, a beautiful type of
June which can easily be seen all the
way from the International Space Station
is the longitudinal or seif
is the Arabic word for sword which
describes these dunes nicely as they are
long and narrow.
These linear dunes can be hundreds of
kilome long and are often found in
parallel sets separated by gravel or
rocky corridors.
These occur where wind directions can
flip over meaning that these ridges have
a slip face on either side of the dune
making them appear quite sharp.
Seafunes also appear on Mars. And in my
opinion, the most beautiful example of
it can be found here.
Again, found at the bottom of a crater.
These tunes look remarkably similar to
each other, including this dusty band
found on each one.
Although we're not totally sure how they
form. One leading theory is that they
are the result of wind directions
changing around Barkan dunes.
In this image, some Barkan dunes seem to
be mid-process of forming into seafunes.
It's a really pretty image that
seemingly tells a story. To our right
here, we have a meer being eroded,
feeding sand into the valley below.
Then you have these beautiful examples
of barkan junes which show the
stepbystep process of becoming seafunes.
Another spectacular example of this a
bit further into the process can be
found here.
The contrasts of the different materials
in the image are stunning
and the dark sections are the sandjunes
merging together.
The third type of June is the dome June.
Typically these are not very big on
Earth, usually only a few feet high.
They have no slip face. They are smooth
all over, hence the name.
They are quite rare and usually found in
and around other types of dunes.
And yes, these are also found on Mars.
Here's a field full of domes, a few of
which can be seen starting to cross over
into Barkan Junes.
And in this impressive expanse of dunes,
and I really do mean an expanse, as
these dunes continue on way beyond this
image, you have wobbly lines of dunes
with domes on the end of them. These
domes seem to be much bigger here than
they are on Earth. The domes here, tens
of meters across.
This field is indicative of a change in
wind direction as the lines are nowhere
near as straight as in some of these
previous images.
The fourth type of June is a parabolic
June which is the opposite of a
baranjune meaning the slip face is on
the other side compared to a baranjune.
These occur near coastal regions and
form the way they do because something
often vegetation anchors the arms of the
June in place. Lack of vegetation on
Mars means it's a bit tricky to find
parabolic dunes.
The closest thing I found is this
beautiful image. A dune wrapped around a
large mound in the middle.
The June is clearly moving from left to
right in this image. And you can even
see the shadow of the slip face just by
here on this side.
The existence of this June is heavily
influenced by the size and shape of this
mound funneling wind along its walls.
The fifth and last type of June is the
biggest type, the starjune.
This is a dune where wind direction
changes frequently, meaning the dunes in
this region have three or more arms and
are often stationary, just building up
over time.
This impressive image is the Sahara
Desert as seen from the ISS, and it is
full of star dunes.
The scale of these dunes truly is
impressive. Zooming in, you'll realize
that these dots are people.
And of course, we have star dunes on
Mars.
Some are small, a collection of dunes
merged together,
but others are massive, like these found
in Russell Crater, which reach far
beyond this image. As this image is
found nearer the poles, carbon dioxide
ice can form on these dunes. During the
Martian spring, the carbon dioxide
sublimates, which dislodges loose
material, leaving these streaks.
Moving to another image, again near
Mars's pole,
we find one of the most beautiful images
of Mars I have ever seen. This image was
taken just as the sun was either rising
or setting, meaning a lot of the image
is shadows cast by dunes.
I love this as it provides a sense of
depth to the image. These again are big
star dunes with their individual arms
reaching out for kilometers.
There's one last thing I want to talk
about the dunes of Mars. Have you ever
been to the beach and seen sand ripples
like these? These are actually a type of
transverse June forming perpendicular to
the direction of the water waves as they
flow over the sand.
Much like larger scale transverse dunes
caused by the wind.
Mars has these ripples too, but they are
much much bigger than what you would
find on Earth with a meter or two
between the ripples. This size makes it
difficult to see from space. But luckily
we have another rover on hand. Curiosity
seen here in this image
to take this remarkable photo of them.
Scientists didn't even know this type of
June existed. And it is a fitting
reminder that although Mars may appear
quite familiar to us, it is still a
world full of secrets and unexplored
facts. And there is still so much we can
learn from it.
Space is a desolate void, a vacuum where
no sound can travel. So you might think
that space is extremely quiet.
You would be right, but only because you
don't have the capability to hear
anything with your natural ears. Turn
your ears into radio wave receivers and
suddenly space is a constant symphony of
strange and interesting sounds.
I'm Alex Mccoan and you're watching
Astramm and together we will find out
what the sources of these radio waves
are and what they sound like.
We don't have to go too high above Earth
to already be in space only60 km up and
sound can't be heard anymore because
there aren't enough particles for sound
waves to travel.
But even here in space, there are plenty
of other waves to be found.
The ones particularly interesting to us
are electromagnetic waves, which don't
require other particles to travel like
sound, but rather travel by themselves
through photons.
You are witnessing a form of
electromagnetic radiation right now in
the form of visible light by watching
this video.
However, visible light is just a tiny
section of the total spectrum of
electromagnetic radiation. It stretches
from waves with extremely high
frequencies
to radio waves
which have waves sometimes kilome long.
There are observatories that look at all
these different wavelengths. And this
channel has focused normally on
frequencies higher than infrared as they
can easily be converted and visualized
in visible light.
But there are also radio observatories,
some orbiting Earth right now.
And we're going to check out what they
have picked up in the way you are most
used to witnessing radio waves at audio
frequencies converted to sound.
being in Earth's Van Allen belt or its
large band of radiation surrounding the
planet and you'll already start to hear
some very interesting sounds.
These sounds are generated by energetic
particles in Earth's plasmosphere which
are being tugged to and fro by the
rotation of Earth's magnetic field.
You see, there is a plasmosphere around
Earth containing clumps of ions and
electrons. As Earth and its
magneettosphere rotate, the magnetic
fields push through these particles,
accelerating them in a wave called a
plasma wave. Similar in a way to how
disturbances in Earth's oceans can cause
waves to form.
You are hearing these disturbances in
the form of radio waves as they pass by
one of NASA's Van Allen probes.
These are called chorus waves and are
often heard during Earth's dawn, which
is why they are found on this side of
the planet.
An amazing type of chorus wave closer to
Earth is the whistler mode plasma wave,
which sounds like space battles and
laser fire.
These exist in the cold and denser part
of the plasmosphere and are caused by
electromagnetic radiation released by
lightning striking in the atmosph.
atmosphere.
These waves generated by these strikes
can bounce around within the magnetic
field of the earth.
And because higher frequencies travel
faster than lower frequencies, that's
why these chorus waves sound like they
have a fall in pitch. like whistle.
Going further out from the plasmosphere,
an opposite effect can be heard.
This time there is a rising tone almost
like a conversation between songbirds.
It is thought to be caused by electrons
moving towards the night side of the
earth because of magnetic reconnection
in Earth's magneto tail
transferring their energy to the plasma
as they collide with it.
As can be seen in this simulation,
in another region within the
plasmosphere, we can find something
called hiss waves.
These are thought to be chorus waves
which have leaked out from the inner
plasmosphere. It sounds much more
menacing and cold than the other sounds
we've heard so far.
I find these clips very interesting as
it's sometimes hard to comprehend waves
you can't see. But sound adds a new
layer of understanding when combining it
with a visualization.
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