By Alexandra Innanen
The North Pole of Mars is a pretty cool place – pun absolutely intended. This summer I’ve joined Giang in looking for patterns in the Martian ice cap, something he talked about in a previous post. I have looked through a truly astronomical number of HiRISE images, nearly 1000 at this point. While many of them do showcase those beautiful patterns we’re looking for (I have been known to punch the air at a particularly uniform set of dunes), a number are what I lovingly refer to as ‘garbage’. Some of these are just flat nothingness, with no distinguishing features to recommend it. Some are more visually interesting, but without any sense or uniformity. These are fairly useless in terms of patterns, but can be fun to look at, and sometimes have neat stories behind them.
I have a folder on my laptop called “Space Stuff” which I could easily rename “Nifty Pictures of Mars” at this point. It’s full of HiRISE images that I looked at and went “well, there’s no pattern there but boy is that cool!” I’m going to show off my top five images here.
Okay, the one at the top of this article is probably the coolest. Should I have ended with it? Is everyone going to leave now? Anyway, this is an avalanche at the edge of the layered deposits of the north pole, which fall off in steep cliffs (reminding me a bit of the Scarborough Bluffs near where I live). You can see the layering in the escarpment, and the edge of the ice in the lower left corner. Here’s some perspective: the dust cloud you can see is about 200 m across. That’s nearly two football fields long. This led me to another image taken in 2008 showing FOUR avalanches, which readers are encouraged to peruse at their leisure.
Colours are exciting! The RGB colouring in this is especially stunning, the blue ice contrasting with the bright red terrain. This shows a crater near the Olympia Planum. Most of the ice has gone from the surroundings, but the patch in the crater is still really bright, as it’s shielded by the crater walls. This also plays some fun perspective tricks: the crater might appear as though it’s above the surroundings, but it is in fact sunken into the terrain. Craters like this are used to estimate the age of the landscape; a younger landscape will have fewer craters whereas an older one will have more. However, surface looks can be deceiving. Based on the number of craters around the pole, the ice cap could be around 100 000 years old, a relative baby in geological terms. Yet because the surface is constantly reshaped by ice, the oldest craters get destroyed.
Here is another boundary (what geologists would call a contact) between the layered deposits of the ice cap and the surroundings. You can really see all the different layers in here, and the boundary between the ice and the surrounding terrain is incredibly clear. This was taken in the Martian spring, when most of the ground is still covered in frost (carbon dioxide, not water). Also hidden in this image are some avalanche deposits. In fact, this is the same region as the image with four avalanches that I mentioned earlier, this image being taken just over two years later.
While there is something to be said for lovely, uniform dunes, the ones above are certainly more exciting to look at. These are some dunes in a region known as Abalos Undae, tucked between two chasms to the west of the Chasma Boreale. This is an enhanced colour image, and the different colours show differences in composition. The blue indicates the basaltic nature of the dunes, while the more creamy-reddish areas are likely dust. Looking closer you can see grooves and ripples carved into the dunes by winds. It has been suggested that the dunes are no longer migrating, and that these smaller features are the only ones remaining active here. Though dunes do move elsewhere on Mars.
You don’t have to have colour to make a striking image, as this one above clearly demonstrates. The nearly perfectly circular edge led me first to believe that this was another crater, but it is in fact another escarpment dropping off from the ice cap. Again, the layering is very clear in the scarp – the brighter white area – and there is a vast difference between the relative uniformity of the ice cap, lower in the image, and the terrain at the bottom of the scarp (confusingly situated at the top of the image). This is one of a number of regions that are being monitored for avalanches.
There are so many more fascinating images I could share, just of the Martain north pole, but that would probably devolve into a lot of exclamation marks and excited capital letters. So I’ll leave a link to the HiRISE special releases page. There’s some really neat stuff there, and it is well worth anyone’s while to check out.