The Mars Reconnaissance Orbiter has been very busy during its 10 years in orbit around Mars.
One of its specialised instruments - called the HiRise camera – has been imaging huge
portions of the surface of Mars in incredible high definition.
I’m Alex McColgan, and you’re watching Astrum, and today we are going to be focusing
on what it has seen over Valles Marineres, Mars’ giant scar.
This canyon is seriously deep, 7km deep in some parts, and extremely long at over 4000km.
It starts with Noctis Labyrinthus to the west, a large maze of spectacular canyons, and ends
to the east in what appears to be an outflow channel, perhaps emptying into a once ocean.
This is especially evident with the MOLA altimetry map.
First of all, I want to give you some scale for these images, and also the size of the
canyon walls of Valles Marineris, as saying 7km deep off hand doesn’t really give you
a sense of how big this canyon really is.
This black and white image of the plains above the canyon wall is 5km across, and zooming
in, the colour image is 1km across.
That’s the scale I will be using throughout the video.
Now have a look at this.
Approaching the drop, we start rapidly descending down into the canyon.
Layers of bedrock can be seen extruding from the dust, notably a different colour indicting
they are made of different things.
The further down we go, the more colourful the bedrock gets.
Incredibly, the wind’s erosion at this point can be seen, as well as trails of boulders
that have fallen down and left a path in the dust.
And finally, the canyon levels off, although this isn’t actually the bottom.
Seeing this for the first pretty much floored me, it is unbelievably impressive.
Let’s have a look at what else Valles Marineris has in store for us.
Here is a cliff face along the side of Ganges Chasma, where weathering from wind erosion
can be seen acting on the cliff face, exposing the dark and hard lava flow layers sticking
out from the dust.
A mineral deposit can be seen on the plains here, on top of this section of the cliff
face that looks like it could fall at any moment.
Interestingly, we can compare these jagged and rough layers to some smooth yet resistant
layers further up in the image.
These could be sediments laid down by water activity that are more resistant to erosion
than the surrounding dust.
Going further along, we find a lot more of these lighter mineral deposits along the walls.
But what would you find at the bottom of the canyon?
Well you may have seen something similar to this on Earth.
Sand dunes sweep over the canyon floor, but not sand as we know it.
We are used to silica rich sand, which produces the light yellow or orange colour we know.
Martian sand in this area is rich in iron and magnesium, which makes it much darker.
Looking at another section of the canyon floor, this time in a region called Noctis Labyrinthus,
we find these patches of dunes, but everything has this odd green tint.
This isn’t just a funny angle of the Sun, but it is thought that the ground is made
of clay here.
It looks like the sand dunes have filled ditches in the ground here, this is particularly evident
when you see the little craters that are dotted around filled with sand.
Moving on to another region in Noctis Labyrinthus, we find dark minerals on light coloured sand
dunes, and even a small crater here, until we get to this curious looking oddity.
What we are looking at here, to help you visualise it, is a mesa, a raised bit of land with a
flat top.
This mesa is only small, at 400m wide, but quite a few are found at the bottom of Noctis
Labyrinthus.
Just to show how varied the landscape around here can be, have a look at this beautiful
view.
You’ll notice more clay around here, but you also have these much brighter patches
of ground.
This is thought to be hydrated material, or material that contains water.
To the west of this image are some old volcanoes, which during their more active days could
have melted ice found at the bottom of this trough which sunk into the ground.
Now this amazing image, found in Melas Chasma, gives a breath-taking example of folding on
the surface of Mars.
Usually this happens deep underground by high heat and pressure, so why is it apparent here?
A possibility is that these folded deposits were soft and deformable near the surface,
such as wet or icy sediments and wind erosion has exposed it.
It does remind me somewhat of a cliff or rock cross-section.
It’s very beautiful.
OK last one for today.
I wanted to show this small mountain range for no other reason other than it is spectacular
up close!
The shadows certainly give a sense of how towering the mountains are, elevated very
sharply above the rest of the canyon floor.
That is fantastic.
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