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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:

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



New Images on Planet Four: Ridges

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

New Images on Planet Four: Ridges

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.


Generated using JMARS ( The magenta region shows the footprints of the CTX images previously searched The cyan area shows the new CTX data that has been uploaded to the Planet Four: Ridges site.


zoomed in view- Generated using JMARS ( The magenta region shows the footprints of the CTX images previously searched The cyan area shows the new CTX data that has been uploaded to the Planet Four: Ridges site.

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

Spiders are now in Planetary Database

Hi everyone!

Citizen scientists are helping us to find new targets for HiRISE on Planet Four: Terrains. They are looking at CTX images.

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.

HiRISE Targets

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!


One of the new targets of interest found by Planet Four: Terrains that will monitored by HiRISE during the spring and summer on the south pole of Mars starting in the coming months. This subject was classified as part of the second set of CTX images classified on Planet Four: Terrains  Discovery details

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

Footprints of the HiRISE observations

I’ve been learning to use JMARS  (Java Mission-planning and Analysis for Remote Sensing) to plot the coverage of the CTX images for Planet Four: Terrains. JMARS is a really nice tool for overlaying observation footprints and different maps and datasets on top of each other for Mars and other planets.

I decided to take a look at what the HiRISE Season 2 and Season 3 observations, that the science team is currently working on writing up, look like on a map of the South Pole when you plot their physical coverage on the pole . You can really see the overlap and what a small area that HiRISE covers compared to CTX.

Here’s the footprint  HiRISE observations for Seasons 2 and 3 outlined in red on the elevation and topography map of the Martian south pole (latitude and longitude lines are in 10 degree intervals).


Here’s a zoom in on one of our favorite regions, Inca City. You can really see the repeat coverage outlined in white in this case.


Screen Shot 2016-03-15 at 10.16.25 AM

Here’s another zoom in of a different area, where you can see multiple seasonal targets outlined in red:



For comparison here’s the footprints of the first set CTX images  (latitude and longitude lines are in 10 degree intervals). The colors represent geologic units, but for this comparison we’re focusing on spatial distribution and coverage.

south_pole_mola_geology_with_pointings copy


Countdown to Picking New Proposed HiRISE Targets

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


New Images on Planet Four: Terrains


Thanks to your help we’ve added in new images to Planet Four: Terrains. Like the image above, these are additional locations on the South Pole that we hope might contain activity from the seasonal carbon dioxide geysers. These images have never been looked at by humans in such detail before. Who knows what interesting things you might find.

Help classify an image or two today at

Some More Example Terrains

Over the past couple of days, I’ve started looking at the Planet Four: Terrains classifications data. I’ll be looking at how best to combine the assessments to identify the different terrains, but for now I’m taking a preliminary look at the raw data. I tallied up the votes for each of the images we’ve shown on the site that have been completed (have had at least 20 independent reviews).  Perusing the results I have found some nice examples that I thought I’d share below.

Swiss Cheese Terrain
 Image Credit:NASA/JPL-Caltech/Malin Space Science System

Image Credit:NASA/JPL-Caltech/Malin Space Science System

 Image Credit:NASA/JPL-Caltech/Malin Space Science System

Image Credit:NASA/JPL-Caltech/Malin Space Science System

 Image Credit:NASA/JPL-Caltech/Malin Space Science System

Image Credit:NASA/JPL-Caltech/Malin Space Science System


Image Credit:NASA/JPL-Caltech/Malin Space Science System


Image Credit:NASA/JPL-Caltech/Malin Space Science System

 Image Credit:NASA/JPL-Caltech/Malin Space Science System

Image Credit:NASA/JPL-Caltech/Malin Space Science System

Channel Network
 Image Credit:NASA/JPL-Caltech/Malin Space Science System

Image Credit:NASA/JPL-Caltech/Malin Space Science System

 Image Credit:NASA/JPL-Caltech/Malin Space Science System

Image Credit:NASA/JPL-Caltech/Malin Space Science System

 Image Credit:NASA/JPL-Caltech/Malin Space Science System

Image Credit:NASA/JPL-Caltech/Malin Space Science System

You can also find more examples on our Site Guide.

Why we need Planet Four: Terrains?

Hi there!

I want to talk why we created the new project Planet Four: Terrains if we have Planet Four already.

The very high resolution images of HiRISE camera are really impressive and one might think that there is no reason to use a camera with lower resolution anymore. Wrong!

First, high resolution of HiRISE image means large data volume. To store on-board and to download large data from MRO spacecraft to Earth is slow (and expensive) and this means we are always limited in the number of images HiRISE can take. We will never cover the whole surface of Mars with the best HiRISE images. Sadly. so we use different cameras for it. Some – with very rough resolution and some – intermediate, like context camera (CTX). We can use CTX, for example, to gain statistics on how often one or the other terrain type appears in the polar areas. This is one point why Planet Four: Terrains is important.

Second, because HiRISE is used for targeted observations, we need to know where to point it! And we better find interesting locations to study. We can not say “let’s just image every location in the polar regions!” not only for the reason 1 above, but also because we work in a team of scientists and each of them has own interests and surely would like his/her targets to be imaged as well. We should be able to prove to our colleagues that the locations we choose are truly interesting. To show a low-resolution image and point to an unresolved interesting terrain is one of the best ways to do that. And then, when we get to see more details we will see if it is an active area and if we need to monitor it during different seasons.

Help us classify terrains visible in CTX images with Planet Four: Terrains at