I would like to share with you our new paper that just got published in January volume of Icarus journal.
The most exciting part of this paper is that HiRISE detected some new troughs in Martian polar areas. The troughs were not visible when the HiRISE observed those locations for the first time in Martian Years (MY) 28 and 29. But when we have commanded HiRISE to take repeated observations in MY 30 and 32, we were rewarded with images of new features that you can see in the animated image below.
The troughs are really small: the whole image is less than 200 m across, while the new troughs are only up to 1 m wide. The total length of them reaches 582 m thanks to their multiple branches.
The new troughs, large enough for HiRISE to detect, are created under the current climate condition – and this is really a big deal. They do look much like spiders: they have different tributaries and resemble the dendritic nature of the large spiders. And they are developing. In turn this means that the large spiders might be developing right now as well. We are still waiting to see topographical changes on the large and fully developed spiders, but we know now that the process is able to erode away quite some ground material. For example, the volume of the material that was moved to create the troughs in the image above is 24 m², they were created over 3 MY, meaning, the process moved 8 m² yearly only in this one example.
The erosion rates like this lets us evaluate the age of the large spiders. They take amazing 1.3 thousands Martian years! It is a long time for a human being, but it is really just a blink of an eye for a geological feature.
We are continuing to monitor these locations to check if these troughs will not be erased in the next years. It well may happen because the new spiders are located very close to the dune fields, and moving sand is capable to cover or sand-blast these small topographical features barely in a year.
We have recently started showing you data from a new location! Have you noticed?
This new place is called Ithaca. It is located at lat =-85.2, lon = 181.401. Unlike Inca City (our most recent focus), this is a flat area, no considerable slopes are present here. Ithaca is located in the middle of this elevation map:
You see, that the red area has maximum elevation change of less than 80 meters. In the absence of slopes, we can say more confidently that the fans here are result of interaction of dusty CO2 jets with winds and not gravity simply pulling sand downhill. Winds direct dust and sand particles after they are lifted up into the atmosphere by the jets. It is very striking, that the fans look very similar in several consequent years of HiRISE observations. The usual year in Ithaca looks like this:
This is a mini-series of HiRISE images from early spring (a) progressing to late spring via (b) to (c) and finally to (d). Fist images that HiRISE returns each spring show large dark fans with the similar opening angles and similar directionality every year. This tells us that there is few variation in local weather from year to year.
When spring progresses, fans extend, later blue fans appear, and sometimes they take over most of the surface! Like in figure (c) – whole area is blue apart from really dark fans. This is one of the mysteries of Ithaca – we know from spectrometers, that those blue fans are fresh CO2 frost, but how comes fresh frost appears on the sides of the dark fans? Dark surface is warmer when exposed to sunlight and must prevent CO2 from forming there.
Another Ithaca mystery is its fan sizes. Here the fans grow to be huge: you see the scale bar on the first image? That is 100 m and the fans on the figure (d) are 2-3 times that long. It is larger then in most of other polar locations. For example Inca City, that must be familiar to you by now, has fans of only tens of meters. Currently scientist do not have models that is able to explain how such big fans form.
If you carefully compare left and right frames of the figure below, you can see quite some new fans appearing in the right frame.
Scientists would really like to know, how many of those appear each day and how big are they compared to the old fans. In this example new fans look small, but this is only one tiny area from Ithaca. To make a clear statement we really need to count them and outline their sizes. That is why Ithaca is now waiting for you to get marking!
Thanks to your help, we’ve been able to complete the set of Season 1 Manhattan images with 30 independent reviews. We’re now moving on to Inca City Season 1 images. You might notice bright light-colored small smooth circles and ovals in the images showing in the classification interface. Those features are actually boulders. HiRISE can resolve down to the size of a small coffee table on Mars, so those boulders aren’t so tiny!
It has been suggested from previous analysis that boulders may impact the prevalence of fans and blotches in Inca City. If you come across an image that has boulders, please discuss the image on Talk (hit the ‘Discuss’ button – it appears after you click the ‘Finish’ button once you’ve marked the fans and blotches in the images) and add the hashtag #boulders. This will mark the image as possibly having boulders, and the science team can look at these later to see if we can try and find any possible correlation with fan and blotch activity and morphology.
Below are some examples of images with boulders for reference. Click any of the images for a larger view and slide show:
Dear citizen scientists!
Back then I promised to get HiRISE to image this scene again when the ice is gone. The image is now here, very fresh from the production pipeline:
I framed this image exactly the same as the original “topic-starter”. This way everybody can see that we are talking about the same feature, as 2 months ago. The ice cover is not completely gone yet: one can still see small persistent leftovers in some shadowed places, mostly in small channels. But ice has cleared the feature in question. It happened to be a crater with an unusual inner surface. As often it is hard to see if it is a cone or a depression, but we know that the sunlight comes from bottom right-ish and this tells us it is a crater. To see it better, here is the best zoom HiRISE has to offer (appr. 30 cm/pix resolution):
Without the ice the crater floor looks smooth and its sides show very pronounced polygons. The ice in the trenches between these polygons created the illusion of a bright branching “crown” in our original image. And smooth blanketing on one side of the crater had smooth ice cover that tricked people into seeing Dalek or octagonal-based chimney. So sorry that neither of those are real!
When I saw the polygons inside the crater, I decided to ask my more knowledgeable colleague about them. Mike Mellon (from Southwest Research Institute in Boulder, CO) did a lot of research about polygons on Mars and Earth. He had a look at both, old and new, HiRISE images for us:
“I can see that there are loads of eroded polygons in the region. There are large ones with clear evidence of subdivision into smaller forms. Smaller polygons cover nearly all the surface (roughly 3 meters in diameter). In some areas they are clear and in others they are so small and flat they are a little hard to see. They are completely invisible at the old image because of its poor resolution. The polygons inside the crater are on the order of 5 meters with more deeply incised troughs, so they are easier to see. The crater floor looks featureless. I see these same larger polygons in the neighboring pits, the pits that appear arrayed N-S. The larger polygon size in the crater may be caused by sun light on the crater slopes.
The presence of polygons and their sizes are consistent with ice cemented soils about 2-5 meters deep. But it is not easy to interpret the details and especially hard to eliminate the seasonal effects from this discussion, as this location is very close to the polar cap and spider-related processes happens here and there.”
With this we came back to where we have started from: fans and spiders. The image made it to this project because it had them all. Now plus polygons, minus the chimney.
The project has only been running for one day, and you’re already finding interesting things in the images you’re classifying. We’d like you to help us study them more by marking them in the classification interface and in the Planet Four Talk discussion tool.
The majority of the fans and blotches that you mark will be completely dark. You may come across a fan that has bright blue or white streaks in it. Like these:
We believe that the bright stuff is carbon dioxide frost that has condensed from the gas coming out of the geyser and back onto the surface of the ice sheet. Observations have shown that the bright streaks are variable over time. Knowing where they are in the images will help us monitor them.
If you see a fan like those above, mark it with the fan tool as your normally would and but also mark it with the Interesting Feature tool. Please also highlight your discovery on our discussion tool (Planet Four Talk) by clicking on the Discuss button after submitting your classification and label the image with #frost.
The Interesting Feature drawing tool can be found below the Blotch drawing tool in the classification interface. (see the red arrows below in the screen shot).
You may have also spotted bright roundish small blobs in the images where there are dark fans or dark blotches. Like these:
These are bright roundish features are boulders and we think in on region on the South Pole they may have some role in the formation of fans. If see an image like above or below:
Please also mark these with an Interesting Feature Tool after marking blotches and fans in the images and highlight the boulders on Planet Four Talk with #boulder