Perusing Planet Four: Ridges Talk I came across the image below. I thought I’d say more about it in case you encounter similar types of images. What drew my eye was the large diffuse lighter streaker on the one side of the crater.
That’s called a wind streak. Wind streaks have been found not only on Mars but also on Venus and Earth. As their name implies, they are formed directly by the interactions of the surface wind with the soil. The wind is impacted by obstacles in its path on the surface like crater rims. As the wind moves around the crater rim either picks up dust particles pushing them together collecting them to create bright streaks visible from orbit or the wind excavates material exposing a darker material than the surrounding top surface layer. Wind streaks extend into into the direction the wind is moving towards, so they are also good indicators of past wind direction.
Today we have a guest post by Planet Four volunteer Peter Jalowiczor.
Why Ziggy Stardust and the Spiders from Mars? As we know Ziggy Stardust is David Bowie’s alter ego, a rock star who acts as a messenger for extraterrestrial beings. Unfortunately, no extraterrestrial beings have been found on Mars (at the time of writing, at least!). But spiders have definitely been discovered…
From this then, as a Planet Four contributor for a number of years now, I recently put together a talk about the P4 Project to be given at my local Astronomical Society: the MSAS (Mexborough and Swinton Astronomical Society). The society is based about 20km from Sheffield (pop. 570,000), England and was founded in 1978. Every Thursday evening is a social occasion centered around a talk. Members, such as myself are encouraged to give talks on different subjects. Usually once a month, an academic visits the society to lecture on an aspect of Astronomy. In March this year the MSAS held a ‘Back to Basics Workshop’ in conjunction with the BAA (British Astronomical Association).
Back to the talk: my initial presentation was to be a preliminary discussion about Mars in general, before focusing on the results (images) from the HiRISE (High Resolution Imaging Science Experiment).
After letting Meg know of my P4 talk, I was very kindly sent lecture materials over from Hawaii. and on June 1st did my best to interpret and present one of Meg’s lectures: ‘Exploring Mars with 150,000 Earthlings’. This was Meg’s lecture at the ‘Imiloa Astronomy Center of Hawaii from February. It was an introduction to the Planet Four Project and collaboration with over 150,000 citizen scientist volunteers worldwide. Describing how, by the power of the internet, volunteers map the fans and other surface features formed by carbon dioxide jets helping planetary scientists characterize surface features on Mars. There was also a discussion of the other Mars projects: Terrains and Ridges and how people can get involved in exploring Mars from the comfort of their own home.
Photos from just before start of the lecture are included here. On an evening where I was competing against the British weather – but this time it was a very beautiful, warm sunny evening (something to be cherished in the UK) so the turnout wasn’t that bad. The society was very interested in the research carried out by the team and is grateful to Meg for the material.
A quick update on the Planet Four: Terrains paper. For the past month or so the team has been working on making changes to the manuscript and creating new figures to address the concerns of the two independent referees who reviewed the paper. The referees are experts in the field who assess and critique the paper. Having an independent set of eyes give feedback is useful and makes the paper better. We’ve submitted the revised draft on May 16th with a list of each of the changes we made to address the points raised by the referees. We’re waiting to hear back from the journal. We hope that after this first round of review/edits that there will be only minor changes requested going forward. We’ll have to wait for the referees’ to read the revised manuscript and our report and send their assessment to the editor. Fingers crossed for a speedy review.
As a teaser, below is a new figure we made for the paper. The image is a subframe from a HiRISE observation of one of the regions targeted based on your classifications on Planet Four: Terrains. You can see that this area is like Inca City where we see fans emanating from a top the ice sheet where boulders are embedded/below the ice sheet. Not all the boulders exhibit seasonal fan/carbon dioxide jet activity when this image was taken
The science team is making great progress towards freezing developing of the Planet Four clustering algorithm. I reviewed some of the output from the pipeline Michael Aye has been writing. Basically the task was to check on the few issues we were working on addressing by having a two size regime clustering for blotches drawn by volunteeers and pick the parameters that seemed to work best for the data.The good news is we see an improvement.
I thought I’d share some of then plots so you so you can see how close we are to finalizing the pipeline. These plots are at the stage of clustering all the blotch markings alone and then clustering all the fan markings alone. We combine the fans and blotch markings into one later on in the process. For now we’ve just run the first part of the clustering pipeline and outputted the results to these figures. As you can see we’re doing pretty well at picking up all the fans and blotches marked by the majority of the classifiers who made a marking on the subject image.
We’ve got one or two more tweaks we brainstormed in the last science team call last week, and once we review those I think we’ll be freezing development on this part of the Planet Four analysis pipeline until after the first paper is submitted.
We wanted to give a quick update on the original Planet Four. Michael Aye has been leading the development of the data analysis pipeline. As previously mentioned, we’ve hit a major milestone with completing the fan clustering algorithm for combining your classifications together. We think we’ve now hit that point for finalizing the blotch clustering algorithm.
We think we’ve now got a decent solution for addressing how to cluster very large blotches that take up half the image and very small blotches that are the default blotch circle size. Currently how we’re tackling this is clustering with one linking radius for the center of the blotch markings, and then we run the analysis again using a much larger linking radius. Here’s an example output:
This blotch clustering strategy seems to be a good compromise for our science goals and needs. We’re going to review several more test cases and if all goes well with this step, we will freeze development on the clustering pipeline. That’s one of the last hurdles to applying the pipeline to all of your classifications and dive into what the shapes and sizes and directions of the fans and blotches tell us about the seasonal carbon dioxide jet process and the surface winds in the Martian South Polar region.
Thanks for everyone’s patience while we worked on getting new images on the Planet Four: Ridges website. The data is now live on the site. This set of images is the 2nd third of the new search region we’ve been focusing on. This search region includes two of the three remaining potential landing sites for the NASA’s next Mars rover, called Mars 2020. You can learn more about the region in this blog post. Dive in and search for polygonal ridges today on http://ridges.planetfour.org
We wanted to give a quick update on Planet Four. Our main focus has been to get a data reduction pipeline that robustly clusters all the volunteer drawn markings of each subject image together to identify the seasonal fans and blotches and based on the majority shape select decide if the feature is a fan or a blotch. Michael Aye has been leading this effort. We’re pleased to say that that the main fan identification portion of the analysis pipeline is complete. We still have a few more things Michael has been working on for the blotch identification part. We think we’ve come up with a decent solution for identifying small and very large blotches. We hope to have this part of the analysis pipeline finalized soon. Then we will be able to apply the pipeline to all of your classifications and dive into what the shapes and sizes and directions of the fans and blotches tell us about the seasonal carbon dioxide jet process and the surface winds in the Martian South Polar region.
A quick update on all things Mars or at least all things Planet Four.
We got the referees’ reports back from the Planet Four: Terrains paper. The journal set it to two experts in the field. The read the paper and provided a critique of the paper. The reviewers gave positive feedback and have questions and concerns for us to address as well as other more minor requested changes to the manuscript. These additions and changes will improve the paper. So over the coming weeks, the science team will make modifications additions to the paper draft over the coming weeks and we hope to have it back in to the journal as soon as possible. Then our written response to the referees’ report and the updated manuscript will go back to the referees for their second look. We’ll keep you posted as we make more progress. In the meantime, there are new images we have uploaed on the Planet Four: Terrains website in need of review.
In regards to Planet Four: Ridges, thank to your help we’re completed 100 CTX images of our second search area. We’re currently working on getting new images onto the site. The CTX images are being processed as we speak and cut up into the subimages we need for the website. The images should hopefully be uploaded over the next week or so. Stay tuned to this space for more updates.
For Planet Four, we’re really at the stage of making the last changes and tweaks to the data analysis pipeline and switching gears to working on finishing the paper draft. We’ll have a separate blog post on that in the coming weeks.
Today we have a guest blog by JPL research scientist Laura Kerber, one of our lead researchers on Planet Four: Ridges . Laura studies physical volcanology, aeolian geomorphology, wind over complex surfaces, and the ancient Martian climate,
Hello Ridge-Hunters! We have been finding lots of ridges in Nilosyrtis Mensae, and I wanted to give you a bit of an update on our progress. Here is a map showing the images that we have looked through (blue), the places where I thought there might be ridges before the project started (circled in orange), and the spots where you have actually found ridges (purple dots).
As you can see, most of the ridges were found in the southeast portion of the search area. I took a look at the outliers, and they aren’t the kind of polygonal ridges we are looking for—meaning that all of the polygonal ridges we found have been in a pretty restricted area. Here is a close-up of that area:
There are a couple of important things that we have already learned from what we’ve found so far. First, we can see that the ridges aren’t correlated with craters. One of the early theories about these ridges was that they were breccia dikes—that is, dikes of broken-up material that was forced through surrounding terrain during a violent impact event. The presence of polygonal ridges both in craters and on the inter-crater plains makes this hypothesis seem less likely.
Here are some great ridges that you found on the intercrater plains:
And an even closer close-up:
We also want to know whether or not the ridges are correlated with valley features. At first glance, it looks like valleys and ridges aren’t correlated, because there are plenty of ridges in the inter-valley plains, and valleys like Auqakuh Vallis that don’t have a lot of ridges near them:
Upon closer inspection, we can see that the ridges are correlated with what we call an “etched” terrain—terrain that has been heavily eroded, leaving bits and pieces of the terrain that came before it. The southern part of Auqakuh Vallis is dominated by etched terrain, and we can even see that part of the valley has been inverted by erosion (what was once the valley floor is now standing higher than everything around it). We can also see that the western branch of Auqakuh Vallis has cut this positive feature, meaning that it was active long after the eastern branch stopped flowing. There were a lot of ridges identified both surrounding the river deposits that make up the top of the inverted Auqakuh Vallis channel and around it. This may suggest that ridges are preferentially forming in old river sediments:
But why aren’t there ridges further north along Auqakuh Vallis?
Actually… there are! Here is an image further north along the Vallis. We can see that northern Auqakuh Vallis cuts through a ridge-containing unit, but in most of the surrounding area, the ridge-containing unit is capped by a unit with glacial morphology that hides the ridge unit from view:
Our current hypothesis: The ridge unit formed before or at the same time as the valleys were being cut. Afterwards, glaciers and ice sheets covered the area and deepened and widened the valleys. The glaciers covered the northern Auqakuh Vallis region and most of the terrain north of it, including the western part of the study region.
The next group of CTX images extends our search area to the east. This is the area where this type of polygonal ridges were first mapped, before we had CTX images covering the entire area like we do now. The first mapping project (in 2006) identified ridge lattices inside mostly inside craters, leading to the hypothesis that they were impact-related breccia dikes. The second project (in 2013) mapped ridges along the Nili Fossae trough system, leading those scientists to hypothesize that the original fractures may be related to the trough system. Our study of the ridges to the west has been offering an expanded context for these hypotheses. The other special thing about this region is that we will be covering two of the three remaining potential landing sites for the next NASA Mars rover, called “Mars 2020”. Mars 2020 is carrying a suite of instruments that it will use to search for habitable places on Mars as well as organic material. The new rover will also carry a drill that it will use to take samples of many different rocks and cache them in tubes for a future mission to bring back to Earth. Wouldn’t it be great if they could bring a bit of ridge back for us?
We’ve got some good news for your weekend. We’ve got brand new images on Planet Four: Ridges, expanding further south and east of our original area. More area covered, gives more opportunities to find unknown polygonal ridges. The more ridges we find, the better statistics we will have when we compare to other orbiter data sets to see if ground water is the main source for how these ridges form. You can see where the search area is in comparison to our first data set below. The cyan show the footprints of the new CTX images on the site, the magenta are the footprints of the CTX images we had uploaded at launch. We thought the magenta area would take a year to search, so we’re thrilled that we can expand the search radius. Thanks for your time and your contributions. We really appreciated.
We’ll have some more blog posts in the coming days and weeks to talk more about this new search region.
Dive in and search for polygonal ridges today at http://ridges.planetfour.org