The Mars Reconnaissance Orbiter has been orbiting Mars for 10 years already.
On board the orbiter is a very special scientific instrument called the HiRise camera.
It turns the spaceship into a scanner, imaging the surface of Mars in incredible high definition
and detail.
The camera it uses is not like a conventional camera, which captures everything in a set
frame.
Instead, it is like a photocopier that scans an image line by line.
This is especially convenient for an orbiter, as it is moving around the planet anyway.
HiRise has taken some of the most stunning images of another celestial object I have
ever seen, and so I wanted to do a bit of a different video, investigating HiRise’s
true colour images while explaining what it is you are looking at.
Today’s video will focus on the polar regions of Mars.
I’m using Google Earth to help you see where each image was taken.
Google Earth surprisingly also has the Moon and Mars included.
This first image is found near the North Pole, near a group of sand dunes.
Coating these sand dunes are the closest thing to snow you are going to see on Mars.
This is actually a frost made of carbon dioxide.
You see, most of Mars’ atmosphere consists of Carbon Dioxide, and because Mars can get
much colder than Earth with a much lower air pressure, it means during the winter on Mars,
this atmosphere condenses on the surface.
It is very similar to how water vapour freezes as frost on a cold night on Earth.
However, the frost on Mars is seasonal, and when spring comes around, the co2 will sublime
back into the atmosphere.
This is the process of a solid turning straight back into a gas.
This next image is found in a crater near the South Pole.
Craters near the poles tend to be a bit more protected against sunlight than flatter surfaces,
which means the frost lasts a bit longer into the spring than normal.
You can still see the frost in this image, although you will notice these dark blobs
too.
These are called seasonal haloes, as they appear in the spring.
What is happening here is sunlight passes through the couple of meters thick ice sheet,
heating the dusty surface beneath.
The ice near the surface sublimes, creating an air pocket of increasingly pressurised
carbon dioxide.
Soon, cracks form in the ice sheet, releasing the carbon dioxide as gas jets into the atmosphere.
These jets also kick up a lot of dust hundreds of meters into the air, which is what causes
these dark deposits all over.
These jets are thought to look something like this, and must be quite the spectacle up close.
Researchers theorise that the ground would rumble while standing on these meters thick
dry ice sheets while the jets go off all around you.
What I find really interesting about this image is some of these deposits have veins
coming from them.
That is thought to be the finest and lightest dust pulled out by the sudden release of gas
once the crack forms.
This leads us nicely on to our next image, which is again found near the South Pole.
I’m using a height elevation map this time so you can see how this next image is in the
middle of a big dune.
In this image, you can clearly see there was a prevailing wind as these jets were going
off.
This is why all the dark deposits are in fan shapes.
Further across in the image however, you can see how the jets on this side of the dune
were going off at a different time and so there was a direction prevailing wind direction.
The shape of the dune could have also impacted the wind direction for this other side.
The dark spots are between 20m-100m wide.
In this image, we are in the southern hemisphere again, but this time a little higher north.
Because we are further away from the pole, there is not as much of a permanent frost
throughout the year.
When the ice is present, it looks very thick, even appearing blue at some points.
Contrast that to the same crater, but about 2 Earth years later, and you can see the sand
dunes that were hidden under the ice.
With both images overlapping each other, you can really see what seasonal variations do
to the surface of Mars.
And what video about the polar regions of Mars would be complete without a look at the
polar ice caps?
These permanent features are here for the whole Martian year, and are extremely thick,
a few kms thick in some places.
These patterns form with sublimation of the dry ice during the pole’s summer.
Under the dry ice is the much more stable water ice, which does not melt all year long.
Well thanks for watching!
Mars is an incredibly interesting planet and I could do many more subjects from the HiRise
images.
If you enjoyed this video, please give it a thumbs up so I can know if you want more
of this type of video or not.
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All the best, and I will see you next time.