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 want to share a quick update on the depth and details we are investigating to close out the last issues for our analysis pipeline for identifying the fans and blotches from the classifications from the original Planet Four.
We recently realized that it might be a good idea to allow different limits for clustering depending on the general marking size. Intuitively this seems to make sense as one automatically takes a bit more care the smaller an object is to mark.
However, more clustering versatility also means more parameters to set which need to be tested for their efficacy.
Below you can see two plots, one for “fan” markings, the other for “blotch” markings, that show different parameter settings for a clustering run and their effects on the final result.
This planet four image tile with the ID ’17a’ is one of the more problematic ones due to its very large but diffusively defined blotch and the markings are, understandably, all over the place.
Each plot title has the values EPS and EPS_LARGE called out. These are the above mentioned distance limits for clustering to happen. Here I leave the EPS value, the one for smaller markings constant over several tests, while I step the one for larger markings, EPS_LARGE, between 50 and 90 in steps of 20.
As one can see the large blotch is “surviving” in all cases (which it wasn’t before we introduced the split-by-size clustering approach), while in the fan case it only survives when the “MS” parameter, the number of minimum markings that a surviving cluster needs to have, is at 5. When requesting 7, it’s just not enough markings to have it survive. But that’s okay, because I’m pretty sure that we will have this survive as a blotch rather than a fan, due to the higher number of markings that voted for that.
We’re now 60% through the third set of CTX images on Planet Four: Terrains. We’ve started to think about where we want to search next. We want to continue to fill in the area searched from -70 N latitude to the Martian South Pole. I’ve been coming up with the CTX image selection since the launch of Planet Four: Terrains. I wrote a code that goes through the list of publicly available CTX images and tries to pull out a well balanced distribution of ice-free CTX observations across specific latitude and longitude bins. I thought I’d share my proposed set of new CTX images to search. I’ve sent this list of images to the rest of the science team, and I’m awaiting their feedback. The new set if accepted by the team, will fill in gaps in our coverage and especially between -70 and -75 N latitude. When we have a final list of CTX image to search after dataset 3, we’ll update you here on the blog.
Color Code for figures below.
Red= first dataset at launched and used in our first paper
Green= second dataset
Magenta = third dataset that expanded out to -70 – currently being reviewed on the site
Gray = 4th proposed set of CTX observations to search
The CTX image outlines are overlaid on an elevation interpolated map. Latitude and longitude lines are in 10 degree intervals for above and below. The colors below represent geologic units, but for this comparison we’re focusing on spatial distribution and coverage. More details can be found here
It is my great pleasure to announce that we have written up the first science results for Planet Four: Terrains in a science paper. After months of writing an analysis we have a final draft ready, and last night I submitted it to the journal Icarus to be considered for their Mars Polar Science special issue.
Right now the manuscript is in the hands of the editor. After some checks, the paper should be sent on to two anonymous reviewers. In what we call the peer review process, these reviewers are independent researchers in the field who read the paper, critique it, and provide feedback which the I will have a chance to respond to and make some or all the recommended revisions to the paper. This process can have a few rounds of iterations with the referee. Ultimately, the referees will recommend to editor of whether the paper merits being published, and the editor makes the final decision.
So now we wait. The manuscript is in the hands of the editor at Icarus who is likely selecting and contacting possible referees. In a month or so we should get back the first round of reviews. I’ll keep you posted here on the blog. So stay tuned! This paper focuses on the distribution of spiders and swiss cheese terrain from the data on the site at launch. We’ve also included analysis of some of the HiRISE observations taken of some of these new spider locations. I’ plan to write a fully summary of the paper results once the paper is hopefully accepted in a few months.
Thank you to all of you who have participated in Planet Four: Terrains. We could not have done this without you. We appreciate the time and effort you put into this project. Thank you for collaborating with us.
We also want to thank the Zooniverse team for giving the research team early access to their Project Builder platform to build and design Planet Four: Terrains.
Planet Four: Terrains is not finished. This is just the beginning. We’ve expanded out search more areas way from the South Pole. Many of those images are in need of review. So jump in and help explore Mars today at http://terrains.planetfour.org
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.
I once did a very similar search with Mars Orbital Camera (MOC) images. The camera worked on Mars Global Surveyor from 1997 to 2006. It had 2 sub-systems: a wide-angle camera and a narrow angle camera. The narrow angle camera obtained grayscale images with resolution from 1.5 to 12 m per pixel. It was just good enough to resolve larger spiders and fans.
In 2004 I looked through all MOC images that existed at the time and were located south of latitude -75º. I was hunting for spiders. The result is a list of MOC images that feature spiders and it is now being added to Integrated Database of Planetary Features. It will be available as a layer in JMARS system in a couple of months.
You can see Spiders map on Database of Planetary Features.
When we have a catalog of CTX images with spiders created by you, we will also integrate it into this database! Then everyone can easily navigate around different locations of spider terrains.
We started Planet Four: Terrains with the main goal of finding new regions to study during the upcoming seasonal processes HiRISE campaign. The idea was to have people scour low resolution Context Camera (CTX) images for terrains indicative of sculpting during the seasonal processes produced by never-ending cycle of carbon dioxide ice being deposited on the surface in the winter and that ice sublimating in the spring and summer. We would then select a portion of those areas for further study with high-resolution imaging with HIRISE. With the varied textures of the Martian surface it would be difficult for a machine to do this task, but the human brain is well suited to this task.
We launched Planet Four: Terrains at the end of June as part of the launch of the Zooniverse’s new citizen science platform and project builder portal. Planet Four: Terrains had little less than a year to review 90 full frame CTX images divided into 20,122 subimages or subjects as their known on the website. With your help, the project was able to get through all 20,122 subjects in time, and even put in more images. Thanks to your classifications and Talk discussions, the science team was able to come up with a list of images and locations for further study. We aim to have the HiRSE camera point at these locations and snap images. Some of these locations will be monitored throughout the Southern spring and summer. Right now these locations have been entered in the HiRISE target database. This means that Planet Four: Terrains has successfully achieved one of its prime goals!
Now, Candy Hansen, PI of the project and head of the seasonal processes campaign with HiRISE, will prioritize our targets with the rest of the regions that the HiRISE team wants to study. The first of these should with any luck get images in the next few months. We’ll keep you updated here on the blog.The final list of targets from Planet Four: Terrains is a mix of locations found on Talk and through the classification interface. We’ll have more details as we get closer to the start of Southern spring (July 5th), but we wanted to share one of the new locales,spotted thanks to the volunteer contributions on Planet Four: Terrains, that will be imaged by HiRISE. This specific region shown above was highlighted on Talk. It was noticed by the science team, and we agree it is an interesting area to look at how spiders develop. We’re interested to see how the seasonal fans and blotches over the coming Martian Southern spring and summer. We’re currently planning a sequence of images at this location. CTX has a resolution of 6-8 meters per pixel. HiRISE has a resolution of 30 centimeters per pixel, so we’ll get to see a lot more detail particularly in the structure of the spider channels than what’s current visible in the CTX image above.
This isn’t the end of the project, we’re really just getting stared. Because of your classifications, we’ve found spiders in interesting and potentially unexpected regions so we’ve decided to keep the project going with new locations to review. Help today at http://terrains.planetfour.org
WeMartians is a brand new podcast aimed to engage the public in the exploration of Mars. The latest episode is about citizen science on Mars with Michael talking about Planet Four and Planet Four: Terrains. Listen to Michael (and cameos of other familiar Zooniverse voices) below or on the WeMartians website.
One of the key goals of Planet Four: Terrains is to identify new areas of interest to observe with HiRISE during the seasonal processes campaign so that we better learn about the carbon dioxide geyser process and about how and were spiders and related channels form. You can read more about the particular goals of Planet Four: Terrains here. Over the months we’ve read the discussions and comments on Talk and been making a list of regions to consider from your observations. We’re really intrigued by many of the things you’ve all spotted. Which is fantastic news! Talk has been a huge asset for this work, but we’re also using the classifications from the classification interface as well. I’ve spent the past three weeks putting together a software pipeline to take the multiple classifications per CTX subframe (typically 20 people review each subject image) to identify spiders, baby spiders, channel networks, craters, and the Swiss Cheese Terrain.
Now that the machinery is all together combined with the interesting gems on Talk we’re ready to make our list of proposed new HiRISE monitoring targets. By April 20th I aim t provide the rest of the Planet Four: Terrains science team a compiled list of locations for them to review. Then Anya will input these into the HiRISE planning system where they will be considered with the HiRSE team’s science goals and eventually Candy who wears many hats including Deputy Director of the HiRISE camera and lead of the seasonal processes campaign will prioritize these new areas with the already existing targets in the seasonal processes observing program. We aim to be ready for HiRISE’s first attempt to image the South Pole which is coming up in about 60 days or so.
This is where you come in. We have new images of different areas on the site now. There have already been some interesting images from this set I’ve forwarded to the rest of the team after seeing discussions on Talk. Let’s make a push to classify as much of the new data set as possible before the 18th of April. The more subjects reviewed the greater chance to include those areas at the start of the monitoring campaign. Not to worry though, we’ll also have a few chances to include additional targets later in the Spring Season to the HiRISE monitoring campaign if need be or to the next one.
If you have a free moment, classify an image or two at http://terrains.planetfour.org
I thought for this week’s blog post, I would talk a bit more about what happened in last week’s science team call and what we’ve been up to over the past month or so. Last month was the Division of Planetary Sciences meeting where for the first time, Michael, Candy, Anya, and I have been in a room together. So we had dinner and went through the paper draft and what’s left to do in terms of getting the paper out. Michael’s poster at the meeting showed the first results of the full pipeline run identifying fans from blotches. So the results of that was also discussed during our meeting.
Most of the time we rely on email and team calls to work together. Right now every two weeks we have an hour call between Michael, Anya, Candy and myself. I think they’ve been really important in helping us work together over such long distances as I’m based in Taipei, Candy is based in Utah, and Michael and Anya live in Colorado. It’s our chance to update each other, talk over issues and stumbling blocks, and talk about the data.
Michael’s been hard at work this year getting all the pieces in place to make the final catalog for Season 1 and Season 2. Overall the software pipeline Michael has built works incredibly well, but we still need to check all the edge cases where we might need to tweak the process. I took the task of going through and checking a subset of subjects with the identified fans and blotches plotted compared to the individual volunteer markings to look for any anomalies or issues with the clustering pipeline. The algorithm Michael’s developed takes your classifications and combines them together to identify where there are fans and blotches and based on how many people used which tool (fan or blotch) we determine if the dark region is a fan or a blotch. I did this review shortly after DPS meeting, and Michael and I filled in the Candy and Anya during the call.
Michael’s now working on implementing some changes to his pipeline, and we’ll take a look at those result soon. Now that we’ve got this first pass from the full pipeline, we can start building the codes to make the plots we want for the first paper and look at the distributions of fans and blotches over time and across the different target regions in Seasons 2 and 3. We spent a good chunk of this month’s call talking about what plots would be the most diagnostic. We also talked about the strategy we wanted to use to compare images with different binning/image resolutions. Anya and Michael are going to work on that over the coming weeks. I’ve got some tasks assigned for the next call as well, including using Michael’s catalog to compare to the gold standard dataset the science team generated.
We also talked about the new text Michael wrote in the paper draft, and set a deadline for the rest of us to read it and give back comments. The next full team call will be in early/mid January. We’re getting closer and closer to having a complete Planet Four science paper ready to submit to a journal.It’s nice to see the progress and watch everything coming together. Thanks for your continued clicks. The hardest part is getting the pipeline complete. Once we have this huge step completed, it means we can rapidly produce catalogs for the entire Planet Four classification database and start working on comparing the mapped observations from 4 Mars years of Manhattan and Inca City that you’ve marked. I’m really looking forward to seeing what we learn from that.