mercury
it is of course the solar system's
closest planet to the sun
stick with me on this video and you'll
learn everything you need to know about
mercury everything i'll show you today
will be actual picture or video images
of mercury we'll be talking about the
orbit and rotation of mercury its
physical characteristics its surface
conditions and the magnetic field and
magnetosphere of the planet
now when you think about the physical
characteristics of mercury i'm sure you
imagine it being the closest planet to
the sun and its giant rock just floating
in space you wouldn't be too far wrong
with that but it is much more
interesting than what you may first
think for example when i look at mercury
i do think of our moon the mercury
actually is visually more appealing than
our moon look at it in its true color
the first thing that i notice is that it
actually does have a color it's not just
different shades of gray and what else
well did you know for example that
mercury consists of approximately 70
metallic and 30 silicon materials
because of this mercury's density is the
second highest in the solar system at
5.427 grams per centimeter cubed only
slightly less than the planet with the
greatest density that of earth
5.515 grams per centimeter cubed if
mercury happened to be the same size as
earth that would mean it would have
pretty much the same gravitational pull
as its surface but being the size that
it is its surface gravity is only 3.7
meters per second squared if you would
compare it to earth it would look
something like this this means the
surface gravity of mercury is only
slightly less than what it is on mars
and considering mars is a much bigger
planet that just says something about
the density of mercury
before we leave the subject of mercury
in its size i want to show you one last
comparison
that of ganymede and titan against
mercury now ganymede is the solar
system's biggest moon and also the
biggest moon of jupiter while titan is
saturn's biggest moon is the second
biggest moon in the solar system these
two giant moons are bigger than mercury
as you can see here but their masses are
less
if you look closely at mercury's surface
you'll see its appearance is similar to
that of the moon it shows extensive
mar-like planes and heavy cratering
indicating that it has been geologically
inactive for billions of years but it
obviously was geologically active at one
point because one of the distinctive
features of mercury's surface is the
presence of many narrow ridges extending
up to several hundred kilometers in
length it's believed that these were
formed as mercury's core and mantle
cooled and contracted over time when the
crust had already solidified
and one distinctive thing you'll notice
about mercury is this huge crater on its
surface caloris basin with a diameter of
1550 kilometers the impact that created
calories based in was so powerful it
caused lava eruptions and left a
concentric ring over two kilometers tall
surrounding the impact crater at the
antipode of the colorado's basin is a
large region of unusual hilly terrain
known as the weird terrain if you would
compare it to the rest of mercury you
would see why it would have this name
so what's it like on the surface of
mercury
well to start with the surface
temperature is hugely different all over
it can range from
-173 degrees centigrade to over 400
degrees centigrade it never rises above
minus 93 degrees of the pole because
there's no atmosphere retaining the heat
and so there's quite a big difference
between the equator and the poles but is
also due to its orbiting rotation which
we'll get back to later the sub solar
point reaches about 400 degrees while on
the dark side of the planet the
temperatures average minus 163 degrees
because mercury is too small and hot for
its gravity to retain any significant
atmosphere over long periods of time
it's not able to retain any of the heat
it gets from being so close to the sun
which is why the dark side of the planet
is so much colder than the side facing
the sun mercury though does have an
exosphere which is like a very very thin
atmosphere like volume surrounding the
planet where molecules are
gravitationally bound to that planet but
the density is so low that it can't
behave as a gas because these molecules
don't collide with each other in this
picture you can see proof of the
exosphere when solar winds hit the
planet they rip off certain atoms out of
the exosphere and what's left is this
trail of atoms going into space we call
this the planet's tail and every planet
has this to a certain extent earth does
have an exosphere but it's 600
kilometers above the surface it's really
the point where space and the atmosphere
meet now in the case of mercury this
exosphere is not at all stable atoms are
continuously lost and replenished from a
variety of sources
very recently nasa has been able to
confirm that craters at the north pole
contain water ice mercury also has
something which mars lacks an actual
magnetosphere or a magnetic field all
around the planet now it is only about
1.1 percent as strong as earth's but
it's still strong enough to deflect a
lot of the solar wind around the planet
and now finally we're going to get to
one of the things which i find the most
interesting about mercury its orbit and
its rotation mercury has the most
eccentric orbits of all the planets with
its distance from the sun ranging from
46 million kilometers to 70 million
kilometers now this is something a bit
hard to imagine mercury takes about 88
earth days to complete an orbit around
the sun it also has a 3-2 spin orbit
resonance of the planet's rotation
around its axis this means it spins
three times around its axis for every
two times that it orbits around the sun
so although it takes about 59 earth days
for mercury to rotate on its axis but
with this 3-2 orbital resonance actually
standing on mercury it would appear that
one day from sunrise to sunrise is two
mercurian years standing on mercury that
would look something like this you see
the sun rise quite fast and then as it
approaches midday it slows down and even
starts going backwards before continuing
on again to sunset as you can see that
took a whole year which means a night
time on mercury also takes a year the
sun starts going backwards in the sky
because approximately four earth days
before period the speed in which mercury
rotates around its orbit equals the
speed in which it's rotating so that the
sun's apparent motion stays stationary
at perillion itself mercury's orbital
speed exceeds its rotational speed so to
a person actually standing on mercury
the sun appears to move backwards four
days after perillion the sun's normal
motion resumes
you can see this even clearer from a
top-down perspective of mercury on one
of its poles twice a day the sun seems
to pause and then continue on again
something else to note about mercury's
orbit is it's inclined by seven degrees
to the plane of earth's orbit as a
result of this we can only see mercury
in front of the sun when it's directly
between us on earth and the sun itself
and because its orbit is inclined by
seven degrees this only happens about
once every seven years
and finally about the rotation of
mercury its axial tilt is almost zero
with the best measured value as low as
0.027 degrees this is even smaller than
that of jupiter which has been measured
at 3.1 degrees
and finally do you want to see earth
from mercury well here we are just a
couple of pixels across this picture was
taken from the messenger probe a couple
of years ago and every single one of us
was in this picture well thank you so
much for watching this video i hope you
learned something today about mercury
and that it seems more interesting to
you now than when you started this video
i'm really grateful as well for everyone
who watched the mars video on my channel
which seems to have really taken off and
for the positive feedback i've got from
it if you do want to learn more about
our solar system i do plan to do a video
on every single one of our planets and
more would you like to join me on this
journey then subscribe like and share
and i'll see you in the next video
you