Planet Four: Terrain’s First Science Paper Accepted for Publication

I’m pleased to announce that our first scientific paper for Planet Four: Terrains  was accepted to the journal Icarus.  Below is a snapshot from the top of the paper manuscript, and the paper is publicly available via the free preprint we’ve put online here.

A big thank you to all the volunteers who contributed to the publication. We acknowledge everyone who contributed to the project on the results page of the Planet Four at: http://p4tauthors.planetfour.org

The paper presents the first spider and swiss cheese terrain catalog derived from your classifications. 90 CTX images comprising ~11% of the Martian South Polar region southward of -75 N latitude were searched by Planet Four: Terrains volunteers. This comprised approximately 20,000 subject images reviewed on the Planet Four: Terrains website with 20 independent reviews. The P4: Terrains search coverage is shown below:

Footprint of CTX image searched by Planet Four: Terrains for the first paper

Applying a weighting scheme, we combine classifications together to identify spiders and swiss cheese terrain. The weighting scheme isn’t testing anyone, but it helps us find more spiders by allowing us to pay slightly more attention to those that are better at identifying spiders and help increase the overall detection efficiency of the project. Details can be found in the paper.

Using the weighting scheme each Planet Four: Terrains subject has a spider score which is the sum of the  weights of the volunteers who identified spiders in the image divided by the sum of the weights of the volunteers who reviewed the subject image. Using classifications from Anya and I for a very small subset of the subject images, we found a spider scores above which we’re highly confident the identifications have few false positives.

To our surprise when we compared to the map of the secure spider locations to the geologic map of the South Polar region, we found araneiforms or spiders where we didn’t expect them to be. In previous surveys of the South Polar region, araneiforms were found to be located only on the South Polar Layered deposits (SPLD). The SPLD has been measured to have a height of ~4 km and covering a surface area of ~90,000 square kilometers mainly comprised of  varying dust and water ice layers as well as some buried carbon dioxide and water ice deposits. Previous works have theorized that something about the unconglomerated nature of the SPLD, might make it easier for spiders to form there than other areas of the South Polar region

CTX side view of the SPLD

Magenta points show the Planet Four: Terrains spider identifications on top of the geologic map. The dark blue represents the South Polar Layered Deposits (SPLD).

To confirm these identifications were real, we needed HiRISE imaging.  CTX has a resolution of 6-8 m/pixel. HiRISE can resolve up to a coffee table on Mars with a resolving power of 30 cm/pixel. With HiRISE we could see the wiggly dendritic nature of the channels and as well see seasonal fans to confirm that these form via the carbon dioxide jet process.  8 areas outside of the SPLD were targeted last Summer and Fall by HiRISE.

Below are just a few examples of the HiRISE subframes of these regions off the SPLD:

Image credit: NASA/JPL/University of Arizona

Image credit: NASA/JPL/University of Arizona – Schwamb et al. (in press)

Image credit: NASA/JPL/University of Arizona – Schwamb et al. (in press)

Image credit: NASA/JPL/University of Arizona – Schwamb et al. (in press)

Image credit: NASA/JPL/University of Arizona – Schwamb et al. (in press)

There be spiders! Araneiform channels can clearly be seen in the images above. The HiRiSE images confirm the spider/araneiform identification. We also see seasonal fan activity as well. For the first time we have found spiders/araneiforms outside of the SPLD!

This result is exciting. For some of these areas we have sequences with HiRISE taken over time which we hope we can put it into Planet Four to measure how the fans sizes and appearance are different from their counterparts on the SPLD. Now we get a chance to study how these locales off the SPLD are similar or differ from the SPLD and try to learn why these areas and not others have spider channels.

We’ve only searched a small fraction of the Martian South Polar region. We have more images on the site to expand the search area to see where else spiders/araneiforms may be. Help us today by classifying an image or two at http://terrains.planetfour.org