Greetings and welcome to the
introduction to astronomy.
In this lecture, we're going
to talk about the planet
Mars and more specifically
its geology and atmosphere.
Now Mars is one of
the primary planets
that we look at for a
possibility of having life.
And that's because it is the
only planet other than Earth
that has been known
to have liquid water
on its surface in the past.
The conditions on Mars no
longer allow liquid water.
But because that possibility
existed in the past
it gives us the hope
perhaps that we're able
someday we'll be able to
find some kind of either life
or fossilized remnants
of Martian life
that might have
existed at one time.
So let's start off
looking at some
of the exploration of Mars.
Mars has been probably
the best explored planet
with probably two dozen
craft that have visited
over the last 50 years or so.
So we can go back to some
of the earliest ones, which
would be the Mariner
spacecraft Mariner 4 in 1965
was the first
successful Mars flyby.
So it flew by Mars giving
us our closest images of it
to date Mariner 9 -
6 years later in 1971
was the first spacecraft
to orbit another planet.
So the first time
we had actually
orbited another planet
in the solar system.
Now a little later, a
little later in the 1970s,
we had the Viking craft
- the Viking 1 craft
was the Viking 1 craft was the
first of a good lander on Mars
and the first successful
landing on Mars.
And you can see it here.
This is part of one of the
feet of the craft as it landed.
And you can see some
of the Martian rocks
there close to where
it landed and that
was a chance to be able to
explore and look for life.
The Viking Lander drilled
into Mars looking for samples
and trying to test those
samples for any signs of life.
Now more recently, we
have the Curiosity Rover,
which has been on
Mars since 2012
and is currently
exploring Mars today.
So here we can see an image
taken of it by itself actually
a number of different images,
then stitched together
to show us an image
of the Rover itself.
There on Mars.
And it explores the entire
part of the surface of Mars
within the crater
that it was landed on.
So that is one way to be
able to explore in the rovers
in a way are better than things
like the Viking craft which
landed.
But could not move
the Curiosity Rover
can move around and
travel to explore
slightly different areas.
So if something
interesting would
be just out of reach
for Viking it's
possible to direct the
Curiosity Rover there
to be able to explore it.
Now what kind of samples
of Mars can we explore.
Well, we actually do have some
samples of Mars here on Earth.
Certainly the Landers
and the rovers
have been able to
study samples on Mars.
But we have not yet had any
samples returned to Earth.
So we have not yet sent
a craft that went to Mars
picked up samples
and brought them back
from Earth here to earth
to study in the laboratory.
However, we do have
meteorites from Mars.
There are meteorites that
we have detected here
on earth that show features that
relate to them being from Mars.
Now how can we get a
piece of Mars here?
Well, as with all
other objects there
have been large impacts on
all of the other planets
not just here on earth
or just on the moon.
But we have seen
those on Mars as well.
And in a very large
massive impact
material could be thrown
off with the escape velocity
of Mars meaning that it
can then escape from Mars
and head off into space.
And some of those would
eventually make their way here
to Earth.
Interestingly, we find that
these are relatively young
only 1.3 billion years old.
So they are relatively young.
So something that would have
had to have happened in the more
recent past, not
dating back to the very
early history of the solar
system four billion years ago.
But only 1.3 billion years old.
But those are samples of
Mars that we could actually
study here on Earth.
Now let's look in a
little more detail at Mars
and some of its
surface features.
So what do we see?
Well, here is a nice image
of Mars that we can see.
We see some of
the major features
we do see some craters
not so much in this image,
you can see a few
scattered around there are
some cratering that does occur.
So Mars has kind of intermediate
between everything else.
It has far more craters
than the Earth and Venus.
But far fewer than
Mercury and the moon
putting its age in
between those two.
So Mercury and the moon would
be the two oldest objects -
Venus and Earth would be
the two youngest and Mars
would be in between.
We do see volcanoes
on Mars and you
can see several of those
off to the side here.
There are three of
them in this case.
And there is another
even larger one
that we'll look at in a
minute - that's off kind
of off the edge of this image.
These are massive volcanoes
compared to anything
we have on Earth.
And again, look at those in
a little bit more detail.
But they are incredibly
massive volcanoes.
One of the reasons for
that is that Mars does not
have plate activity and
therefore, the volcanoes
keep occurring in the same
spot over and over again.
So unlike the Hawaiian region
on Earth the Hawaiian Islands,
where the chain of
islands is formed
because the plate is moving here
on Mars, the plate didn't move.
And the volcano erupted
in the same place.
We also see great canyons -
not like canyons on the earth.
But the great tectonic
features and we
can see what is called
Valles Marineris here.
And that is a gigantic
tectonic feature that has since
been eroded away
this would stretch
across the entire United States.
So it's a gigantic one you could
put Washington D.C. on one side
and the other side would be
out towards San Francisco.
That is how large this
tectonic feature is.
So it is more like some
of the Great Rift Valley
that we see here on
earth, than things
like the Grand Canyon,
which would be negligible
compared to this size.
We also see flowing
water features on Mars
not current but
enough that water
has to know that water has
flowed on Mars in the past.
So let's look at some of these
in a little bit more detail.
First of all volcanoes we
have things like Olympus Mons.
Olympus Mons is
the largest volcano
in the entire solar system.
It is three times
the height of Mt.
Everest.
So were you to climb Mt.
Everest.
That is the equivalent of
getting one third of the way
up Olympus Mons.
We can see it here how it
stretches out the peak here
is the caldera that's where
lava would have flowed out
and then lava would have
flowed down the sides
again over billions of years ago
and spread out on the surface.
How big to get an idea of how
big this is a let's compare it
its about the size of France.
So if we put the two here there
is Olympus Mons in the inset
here.
So this is just about
the size of France
would cover most of France.
And this little section here is
the caldera where the material
would have erupted from.
So this is an
incredibly big volcano.
Now the whole region actually
around it is volcanic
and we saw on a
previous slide, we
were able to see
three of the volcanoes
and let's look at
them here again.
Here are those three
volcanoes that I
looked noted on the
original map of Mars.
And here is Olympus Mons.
This entire region is
called the Tharsis region.
And that is a hotspot region
on Mars very similar to Hawaii
here on the Earth.
However, the chain is not
because of plate motions.
It's because of just
three separate hotspots.
So one hotspot here and one
for each of these volcanoes.
And then they would
have continually
erupted in the same spot
over and over again, because
of massive pressures underneath.
Actually this entire region is
pushed up by seven kilometers.
So not only are there
the high mountains.
But this entire region
here on Mars as noted here
has been pushed up much higher
above the regular surface
level of Mars.
Now Mars is not all volcanic.
We have other features as well.
Let's take a look
at Valles Marineris.
So let's take a look at
Valles Marineris here.
It is a very long canyon
- 4,000 kilometers long.
Much, much larger than the
Grand Canyon here on Earth.
So as I said, this would stretch
across the entire United States
you can imagine some of
these little side canyons
would be similar in size to
the Grand Canyon here on earth.
It is formed by a
different process.
The Grand Canyon on earth
is formed by running water.
So water in the river that
has eaten away at the ground
and caused it to
erode away here.
This is actually
a tectonic feature
that has crack essentially
a big crack in the crust
that where the crust
was separating.
So very similar to a
Rift Valley here on Earth
where the plates
may maybe plates
that were starting to form
were actually separating.
However Mars was much smaller
and cooled off too fast
for all the plates to form.
And so this region is
kind of locked in place.
Now, one thing we notice
that the Tharsis region
is to the left of this image.
So that would be
over on this side.
So is that could that be
the cause of this rift.
Is the volcanic
region there part
of the reason that
the rift happened
to form at this specific point.
But Valles Marineris again,
one of these very large
features that we see on Mars.
Now Mars does have an
atmosphere as well.
So we can take a look at that.
Here it is an extremely
thin atmosphere less than 1%
of the Earth's so we can see
it a little bit in the image
here off at the edge
where it's a little bit
hazy that is looking
through with the atmosphere.
But it is very thin.
So even if it had
the same composition
is the Earth's you would
then be unable to breathe
because the pressure
would just be too low.
However, its composition is
also nothing like the Earth.
It is 95% carbon dioxide.
It is 3% nitrogen and 2% argon.
So no, no sign of
things like water.
No sign of things like
oxygen in the atmosphere.
The thin atmosphere does have
some very high winds and dust
storms High winds
will pick up dust
from the surface that
result in dust storms that
engulf the entire planet.
So they don't just
cover part of Mars
as a large dust storm might
cover part of the Earth.
However, they do cover - they
can cover the entire planet.
So very extreme dust storms
that occur here on Mars.
But it's a very, very thin
atmosphere thick enough
to have to worry about
if you're landing
if you're trying to
go through it to where
it would cause friction.
But not enough to begin
to be able to breathe.
So the last thing we
want to look at it Mars.
Here are the moons of Mars.
We didn't have any moons to
talk about with Mercury or Venus
because they don't
have any however,
Mars does have two small moons.
We have Phobos which
is the doomed moon.
And we see that one
here on the left.
And we see Deimos which
is the other moon of Mars
here on the right.
Phobos is only about 6,000
kilometers from the surface.
That's very close to the
surface of Mars actually.
So close that it orbits
faster than Mars rotates.
So that means that
it moves faster.
That means it's
moving through the sky
and will end up rising in the
West and setting in the east
because it is moving faster
than Mars is rotating
and it's its motion dominates
its rising and setting.
It is being torn
apart by tidal forces.
So when will it be gone?
Well, you can see
some of the stress
stresses here these lines
that occur are actually
some of the stresses that are
pulled beginning to slowly pull
it apart.
That doesn't mean it will be
gone tomorrow or next year
or even in a decade.
But in millions or Tens
of millions of years,
likely it will have
been ripped apart
and probably crashed
into the surface of Mars
and then Mars will be
down to just one moon.
Deimos is the
smaller of the two.
And we can see on both of
these, we do see impact craters.
So they have been hit by
smaller objects as well.
We don't believe that they
formed through a giant impact
like the Earth's moon.
We feel more likely that
these have been captured.
These are asteroids
that have been captured
by Mars likely Mars being so
close to our asteroid belt had
lots of asteroids
passed near it.
And these two happen
to pass just right
to be able to be captured.
So let's finish up
with our summary
as to what we've
covered on Mars here.
First of all, a large
number of spacecraft
have visited Mars
and more are planned.
So lots of exploration
of Mars coming up.
We do see large volcanoes
and large canyons
on the surface of Mars.
So very large features
compared to what
we see on the earth especially
for such a small planet.
The atmosphere of
Mars is very thin
and is primarily carbon dioxide
much like Venus's atmosphere.
And we did note that Mars
has two small moons, which
perhaps have asteroids that
Mars captured in the past.
So that concludes our
lecture on the geology
and the atmosphere of Mars.
We'll be back again next time
for another topic in astronomy.
So until then, have
a great day everyone.
And I will see you in class.
