More on Merdiani-type Polygonal Ridges

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.

Merdiani-type Polygonal Ridges

 

Merdiani-type Polygonal Ridges

Hello Ridge Hunters!

We are nearing the end of the year on Earth, but we’re only in Martian month 4 on Mars (Solar Longitude = 99.2; Sol number = 214). But what a year on Earth it has been for Planet Four: Ridges. Since our launch on January 17th, thanks to 7,453 registered volunteers, we have retired 11,999 images! We have mapped ridges the length and breadth of the dichotomy boundary near Protonilus Mensae, Nilosyrtis Mensae, and Nili Fossae.

We are now moving into the strange and wondrous land of Sinus Meridiani, not too far from where the Opportunity Rover has been roving along at what might be the shore of a vast, ancient inland sea. The ridges in this new area are different—they are flat on top and splintered, and they can be dark or light compared to the background terrain. Instead of true polygons, they make broken circles. Take a look at the update tutorial to see examples of this new and strange type of ridge. By mapping ridges in Sinus Meridiani, we can compare and contrast them with their more northerly brothers, and determine why their morphologies are so different and what this meant for their environment and process of formation.

Happy Ridge Hunting, and if you find anything strange, let us know in the comments!

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Planet Four: Ridges is Back

We’re thrilled to announce that Planet Four: Ridges is back. We’ve completed the Arabia Terra search for now, and today we’ve launched a new workflow to search for a different type of polygonal ridge that we’ve searched for previously. This new type of polygonal ridge is found in Sinus Meridiani,  a darker area of Mars located in the northern midlatitudes of  just south of the equator. You can see it’s located below Arabia Terra, the previous region we’ve been searching.

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Hubble Space Telescope Image of Mars. Arabia Terra is the large triangular shaped region in the center. Sinus Meridiani can be seen as the darker region below Arabia Terra. Image Credit: NASA, ESA, and L. Frattare (STScI)

Meridiani-type polygonal ridges often look like broken spider webs or tattered lace. These ridges do not usually form neat boxy shapes, but they can be interconnected, looping, or branching. We need your help to identify these features, so that we can see if the Meridiani-type polygonal ridges follow the same trends we’re in seeing in the Arabia Terra polygonal ridges.

Meridiani-type Ridges in CTX subframes

We are continuing to work on analyzing and reducing the classifications from the Arabia Terra search. You can learn more about that in this previous blog post from Laura.

Dive back into Planet Four: Ridges today at http://ridges.planetfour.org

Planet Four at the Division for Planetary Sciences Meeting

The American Astronomical Society’s Division for Planetary Sciences meeting was held last week in Provo, Utah. We presented results from Planet Four: Terrains, but it wasn’t the only Planet Four project represented. There was an update on Planet Four. Chase Hatcher attended the meeting ready to talk about Planet Four. Chase is, a student at the University of North Carolina at Chapel Hill and he spent this past summer working in Colorado with Anya and Michael on Planet Four analysis.

Chase presented a poster on his work at DPS as well as some of the other progress on the Planet Four data analysis we’ve made. Thanks Chase for all the hard work and for representing Planet Four. You can find Chase’s poster below.

 

 

Planet Four: Terrains at the Division for Planetary Sciences Conferences

 

Image credit: DPS/AAS/ https://dps.aas.org/

Greetings from Provo, Utah. I’m here to present science results on Planet Four: Terrains among other things.  The DPS is now trying out a new set of poster presentations using large touch screens, which they are calling iPosters. My abstract was selected for an iPoster. This means you can currently explore view and my iPoster online here. Enjoy!

Sagan Medal Public Talk at the Division for Planetary Sciences Meeting

This week I’m receiving the American Astronomical Society’s Division for Planetary Society’s Carl Sagan Medal for Excellence in Public Communication in Planetary Science in part for my activities with Planet Four. You can read the citation here.

I want to thank the Planet Four team and the Zooniverse team for all that they do. The Planet Four projects really are a team effort. I also want to take a moment to recognize the nearly 200,000 volunteers who have contributed their time and energy to the Planet Four projects.  A little slice of this medal belongs to each and every one of you. I’ve been truly amazed what your combined effort has achieved, and I can’t wait to see what comes next. Thank you for time and your contributions. We couldn’t do this without you.

It’s traditional for the Sagan Medal recipients to give a public talk one evening of the meeting. I just got back a little while ago from giving the public talk on Brigham Young University’s campus. This year there are two Sagan Medal recipients: myself and Henry Throop, so we each gave a half hour public talk. I decided to talk about Planet Four and Planet Four: Terrains.

Last night, I recorded my practice run through of the talk so that I could share the talk with all of you. This very close to the version I gave tonight in Provo, Utah.

An Update on Planet Four: Ridges

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!

Thanks to you, we have mapped ridges all over Nili Fossae and Nilosyrtis Mensae!!

As you might remember, our ultimate goal was to determine the distribution of ridges so that we could see if they were correlated with any other types of interesting features, like valley networks, clay or chlorite detections, or even just with the dichotomy boundary itself, which could have aligned with the edge of an ancient ocean. Since I have found polygonal ridge networks in other places near the dichotomy boundary, I was thinking that there might be a relationship between the hypothetical ancient ocean and the ridge networks. Indeed, there are many polygonal networks in shallow marine environments on the Earth, thought to be due to shrinking that happens when water is forced out of clay layers as they are pressed. Thanks to your efforts, we discovered that the Nili ridges are very localized along the dichotomy boundary, crowded into Nilosyrtis Mensae, Nili Fossae, and Antoniadi crater, but missing in Protonilus Mensae and further west along the dichotomy boundary. These means that something special must have been going on close to Nili Fossae. It could be that the ridges were only forming in this region, or perhaps we see a deeper exposure of the subsurface here, which allows the ridges to be exposed. One intriguing possibility is that the presence of the ridges is related to the availability of carbonate, which is a common ridge-forming substance in some terrestrial deserts (in the form of the mineral calcite). The Nili Fossae region is one of the only regions on Mars where lots of evidence for carbonate minerals has been found. Perhaps ground water circulation through fractures was happening all across Mars, but only in the area where there was CaCO3 in the water could the mineralization of these fractures take place. WE DON’T KNOW!

The next step for us to take is to study all of the great examples that you have found and to tie them to their geological context, both in terms of where they are with respect to the dichotomy boundary, but also how they relate to #darklines, glaciers, and other interesting things in the area. (I think I’ve seen enough of the area by now to say that they don’t seem to be related to glaciers).

I have been working with Meg over the last couple of weeks to get all of the data that you have collected into a usable format so that we can start to write the paper. The actual writing process will take a number of months.

Meanwhile, we decided to expand our search to a slightly different part of the Arabia region—Meridiani Planum.

 

Here is a map showing roughly where we have been looking (jagged gray area with a black background) in the context of the broader Arabia area. Arabia is an interesting place because it is very dusty (making it hard to see what minerals are there) and it has an unusual chemical signature (it has elevated hydrogen compared to other nearby places). The white area is where I have previously found ridges in Meridiani Planum (and the center of where we will be looking next).

If you think you spy a crater whose name sounds familiar, it could be because we’re getting closer to the territory that Mark Watney traversed in Andy Weir’s The Martian.

[Spoiler Alert]: In the book, Mark Watney has to traverse from the northern plains through Mawrth Valles (another popular landing site candidate!) to get to Schiaparelli Crater. You can chart his course here on this cool fan-made website: http://www.cannonade.net/mars.php#map

In 2004, the Opportunity Rover landed in Meridiani Planum. Its landing site was a wide, flat plain. In the 13 years since its landing, Opportunity has made some amazing discoveries, including the discovery of sedimentary rocks emplaced and modified by water, evidence that Opportunity’s landing site was close to the shoreline of an ancient, salty, shallow body of water. To the north of Opportunity’s landing site, Meridiani Planum becomes much less “plain-like”. Instead, it devolves into a tangle of arcuate, intersecting ridges.  While it would be a nightmare for a small rover (or Mark Watney) to traverse, this kind of bizarre geomorphology is fascinating from a geological point of view. In particular, these ridge patterns are similar in shape and morphology to some of those shallow marine polygonal networks that I was looking for along the dichotomy boundary. On Earth, one such polygonal network can be seen an ancient shallow marine environment now exposed in Egypt’s white desert. The desert is white because of the expose chalk formations, and the entire area is criss-crossed with veins full of calcite and hematite.

 

The Meridiani ridges are similar to the ridges that we have been finding so far in that they are intersecting, but those of you who have been with the project for a while will see immediately how different they look.

While the Nili ridges were rather narrow, discrete, angular, and polygonal, the Merdiani ridges are feathered, arcuate, varying in width, and flat-topped. They also seem to merge together in multiple areas, like in this image, where there seems to discrete ridges but also amalgamations of ridges that form a kind of mesa.

 

The other strange thing about the Meridiani ridges is that they are not always the same color. For the most part, the ridge-forming unit is white and the background plain is dark, but sometimes it looks like the opposite, as in the above image.

We will keep you updated as work progresses on the first paper. Meanwhile, we will work on getting you some images of Meridiani Planum to map!

If you are bored while you are waiting, try looking along the dichotomy boundary the other direction… around the Isidis Basin and into Nepenthes Mensae. Maybe the ridges appear on either side of the Isidis Basin, and represent circulation of groundwater caused by the remnant heat of the Isidis impact……

 

Finalizing the Planet Four Seasons 2 and 3 Fan and Blotch Catalog

Michael produced these great plots below showing the fan and blotches identified in each subject image showing 6 overlaping subjects. We have overlap to ensure that we don’t miss marking features at the edges of subject images.  We had to cut up the HiRISE images into smaller chunks in order to get the resolution needed  and make the Planet Four website as easy to use as possible.

Each color in the plot below represents a Planet Four subject image. The dashed blue lines are to show the overlap region boundaries and the solid blue lines are the boundaries between the subject images.

 

 

These are all from Ithaca where the fans tend to be very wide. It’s a very flat region on the Martian South Polar region, which might have something to do with it. So it’s one of our best cases to look at what we should do about combining the sources from different subjects in the overlap region.

Looking at these plots, we see fan directions aren’t impacted. That although in some cases we have to fans or two blotches on top of each other with different widths and extents, the direction of the source is well represented. By using shapely we’ll be able to deal with this. For the project’s first paper, we’re focused on wind directions so we’re calling the catalog done for now and will do the Shapely stage next for fan and blotch areas and counts.

We can now confidently turn your clicks into wind directions. This is a big milestone for the project. It means we get on to writing the second half of the Planet Four paper, talking about the catalog and what we see for wind directions.  Onwards and upwards!

Planet Four and Shapely

I thought I’d share a figure from last week’s science team call that the science team discussed.  Michael was looking at combining clustered features with Shapely, a Python package for manipulation and analysis of planar geometric objects. Partly this is to investigate whether this could be used to deal with differing clusters in the overlap regions between neighboring subject images and also test out if we can use the software package to easily calculate the total area covered by the seasonal fans and blotches.  Shapely does a good job of merging the blotches together as you can see from the figure below. This definitely looks like a way forward for calculating the total surface area per time of year covered in dark fan material.

 

Image credit: K-M aye

New Data Coming to Planet Four: Ridges Soon

Thanks to your help, we’ve finished search area two for Planet Four: Ridges. We’re working on analyzing the results and hopefully starting work on a paper based on those results. Laura has come up with a new region and slightly different type of polygonal ridge to search for. We’re working on getting that dataset processed and uploaded to the site. We hope to have this completed by the end of September with updated tutorials. We’ll keep you posted. In the meantime, Planet Four and Planet Four: Terrains could use some help if you can spare the time to classify an image or two.

 

Dealing With Overlap

We’re now working on dealing with the last major component of the Planet Four data processing pipeline, the overlap regions of neighboring subject images. We divide each HiRISE images into many smaller 840×648 pixel subimages or subjects that we show on Planet Four. To make sure we capture fans and blotches that are the edges of our subject images, we have a 100 pixel overlap between the neighboring left and bottom subject images. This means that we have duplicate markings that cover the same source which we need to identify as being the same source to allow for counting the number of seasonal sources and to also accurately measure the shape of very large fans or blotches.

We spent part of the last science call looking at some examples of overlap regions and the outputting fan and blotch shapes after clustering to decide what to do.

 

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Image credit: K-M. Aye

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If you focus on the center sources in the two plots above, you see there are lots of markings identifying the same shape from the different subject images that contained varying parts of the central  blotch or fan. Based on what we see, we think we if in the overlap region we only keep the largest source and anything that extends beyond that we will accurate identify the fan or blotch being marked. We’re going to test that this week and review the output from the catalog for a small portion of the overlap regions to confirm.

Once we sort what to do in the overlap regions, the focus should be writing all of the steps in the processing pipeline into the paper draft.