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A Planet Four Update

Today we have a post by Candy Hansen, principal investigator (PI) of Planet Four and Planet Four: Terrains.  Candy also serves as the Deputy Principal Investigator for HiRISE (the camera providing the images of spiders, fans, and blotches seen on the original Planet Four project).  Additionally she is a  member of the science team for the Juno mission to Jupiter. She is responsible for the development and operation of  JunoCam, an outreach camera that involves the public in planning images of Jupiter.

Dear Planet Four Volunteers,

Years ago we enlisted your help to measure spring fans on the surface of Mars’ seasonal CO2 polar cap.  Our small science team had a vision of what we could learn from those fans about the weather on Mars, but we did not have the resources to make the needed measurements. 

With your investment of your time we now have an extensive catalog of fan measurements.  The catalog crosses space (the Mars south polar region) and time (8 years of Mars southern spring images).  The contents of the catalog and potential science use was documented in a paper by Michael Aye, published in Icarus in 2019.  We have a new paper by Anya Portyankina, in press at the Planetary Science Journal, that compares wind direction and speed (from your measurements of fans’ orientation and length) to one of the standard Mars weather models.  From this we can explore where the models do and do not do well to predict the weather.  This very important goal that we envisioned from the beginning has now been achieved thanks to your generous donation of your time to make these measurements. 

Over the years we have realized that seasonal activity is affected by Mars’ dust storms.  Using the catalog we can quantify the differences in the number and size of fans after a dust storm.  That work is now underway so we have posted more images and we hope you will help us again by making more measurements.  We know your time is valuable and we sincerely appreciate your willingness to help with this analysis of the weather on Mars.

One final note – we have explored doing this task via machine learning.  People still win!

Thank you,

Candice Hansen

New Planet Four: Ridges Search

Today we have a guest blog by JPL research scientist Laura Kerber,  our lead researcher on Planet Four: Ridges. Laura studies  physical volcanology, aeolian geomorphology, wind over complex surfaces, and the ancient Martian climate.

Greetings to you in these apocalyptic times! I hope that you and your families are doing well in isolation, or wherever you find yourselves to be.

 Over the last few years, Planet Four: Ridges has ranged far and wide across the Arabia Terra, from Nili Fossae near the future landing site of the Mars 2020 Perseverance rover, all the way to the plains of Meridiani Planum, near where little Opportunity lost its life in a 2018 global dust storm after 15 beautiful years of adventure. Along the way, you all have discovered many other treasures, including polygonal fracture networks, networks of dark lines, patches of desiccation polygons (mud-cracks) and many other fascinating features, each of which could seed a study of its own.

Your polygonal ridge discoveries are now being incorporated into a journal article, which has been undergoing many iterations as we prepare it for submission.

In the meantime, thanks to hard work by Meg Schwamb and Michael Aye, a new part of Meridiani has been opened up to us to search, just to the east of where we had been looking:

Figure 1. The broad region of study. The aquamarine dots are where you found Meridiani ridges in the last campaign. The turquoise squares are the footprints of the images that we’ll be looking through this time. The orange line is the fictional traverse of Mark Watney in the novel “The Martian” by Andy Weir. The yellow star is the location of the Opportunity rover. The background is from the Mars Orbiting Laser Altimeter, which gives us topography (blue is low and red is high).

On our last foray into ridge hunting, we learned that Meridiani has two distinct kind of polygonal ridges. There are regular polygonal ridges, which have straight connectors and enclose polygonal shapes (commonly found in northern Arabia Terra near Nili Fossae), and Meridiani ridges, which are often arcuate, enclosing circles or fractions of circles, and intersecting each other like tattered lace. While individual polygonal ridges are thin, Meridiani ridges can have wide, flat tops, or can appear splintered. There is a new tutorial to explain these two ridge types.

Your mission (should you choose to accept it) is to range around our new region of Meridiani, looking at images and classifying them into those that have regular polygonal ridges, those that have Meridiani ridges, and those which have neither (of which there are many!) I encourage you to use the “Done and Chat” button, hashtags, and collections to point out strange or mysterious things that you encounter on your way. There is a link on each image at the bottom (click the tiny “i” after clicking “Done and Talk”) that can take you to the source CTX image if you are curious about the area. Also don’t be afraid to zoom around on the Mars version of Google Earth (with the CTX global image layer on) and tell us what you find that way.

During this pandemic, many of us are cooped up in our homes with nowhere to go. Luckily, despite not being able to travel the Earth as we are used to, we are all free to fly over the vast empty deserts of planet Mars.

Whether you are a long-time Planet Four Ridge Hunter or you’re just joining us now, have fun exploring Mars and happy ridge-hunting!

Introducing the Planet Four Organization

The team has been blown away by the classifications that have pouring in over the past several weeks. We know it’s a difficult time around the world right now, and we wanted to thank you for taking time out of your day to help explore and study the Red Planet. The Planet Four science team has been working from home, and currently there are two papers drafts the team is focusing on: one paper examining the Planet Four derived wind directions compared to Martian climate simulations and the other paper exploring polygonal ridge distributions including Planet Four: Ridges classification data.

Today we’re pleased to announce the launch of the Planet Four organization. Organizations are a recently added feature for research teams with multiple projects on the Zooniverse platform. Now, there’s a place with links to all the Planet Four projects, plus links to the blog and our social media accounts, all in one place. You’ll be able to quickly see the status of each project and collective statistics about all three Planet Four projects.

Check out the new Planet Four organization webpage at

Launching Planet Four 2.0

Today we have a post by Candy Hansen, principal investigator (PI) of Planet Four and Planet Four: Terrains.  Candy also serves as the Deputy Principal Investigator for HiRISE (the camera providing the images of spiders, fans, and blotches seen on the original Planet Four project).  Additionally she is a  member of the science team for the Juno mission to Jupiter. She is responsible for the development and operation of  JunoCam, an outreach camera that involves the public in planning images of Jupiter.


We are delighted to be back in business with Planet Four on the Zooniverse’s Project Builder platform.  Thanks to all of your previous work the science team has been busy in the hiatus. 

As you know we published our first paper.  It describes the catalog of YOUR measurements that we have compiled, and the statistical analysis applied.  We are now able to query the catalog to get the measurements of fans, directions of fans, assessment of when seasonal activity begins and how it develops, for example.  This is allowing us to address the scientific questions that we laid out when we conceived this citizen science project. 

As a result, the second paper is well underway.  Like wind socks the fans tell us the direction of the wind at the time they emerge.  We are comparing the wind directions predicted by a regional scale atmospheric model with the actual measurements of fan directions.  Sometimes the predictions agree very well (typically in early spring), and sometimes they don’t.  When the predictions don’t agree we are analyzing why – for example, is there local topography affecting the wind direction?  Or is it because it is late in the spring and some areas of ground may be frost-free?  Or, and this is the most important, is the model lacking enough sophistication to reproduce the observed winds?  Your measurements are our guide to the actual on-the-ground environment, so if the results don’t agree, we know we need to improve the model.   

Our third paper is also almost finished.  Particles in the fans land on top of the layer of seasonal dry ice.  As time goes on the dark particles warm up and sink into the ice.  We can use your measurements of fan lengths to quantify this process.   Fan lengths slowly decrease with time as particles gradually sink.

We are looking forward to being back in business with your help, to tackle the next science question on our list:  how do Mars’ dust storms affect seasonal activity?  We will be posting the latest images from Manhattan, Ithaca, Inca City and Giza first because we have the longest time history for those locations.  Then we will add other locations to fill in some of the other longitudes. 

It’s great to be back working with you!  Please know that we value your generous contribution of your time, our most valuable commodity. Check out the new and improved Planet Four at

One Step Closer to Launching Planet Four 2.0

In May of last year, Planet Four project was paused. Since then we have been working on a new version of the project on the Zooniverse’s Project Builder Platform.  In October, we gave you a sneak peek of two potential versions of Planet Four 2.0.  Based on the feedback we received, we have made some tweaks and finalized the website design.

Before we officially launch the new website, we want your feedback.  Please go try our our latest version of Planet Four 2.0 and let us know what you think. You can take part here.

New data on Planet Four: Terrains

Planet Four: Terrains is back from hiatus. We’ve come up with a new set of images to search on the site. These CTX images will continue our trend of searching further northward and covering gaps in our coverage.


The figure above shows the newly uploaded CTX images on the geologic map of the Martian south polar region. The blue is the south polar layered deposits (SPLD). This is where most of the spiders are located, but we’ve already learned through Planet Four: Terrains that there are spiders also outside the SPLD, so that’s why the search region expands well beyond the SPD. The red rectangles show you the CTX images that we’ve currently uploaded to the site. The bright green rectangles are the second half of the dataset.

Our current plan is to write a summary science paper with a final catalog from the spider search over the past several years, after we get through both sets of CTX images. We’ll look at the soil thermal inertia and other properties and see if we find a links or correlations to where spiders are visible. We think this we’ll wrap up this phase of Planet Four: Terrains, but we already have some ideas where we might take the project next.

Thanks for your help! Dive in today at!

Help beta test the new Planet Four

In May, the original Planet Four project was paused. Since then the team has been working on a new version of the project utilizing the Zooniverse’s latest web tools. Great news! We’re nearly ready to launch the new and improved Planet Four on the Zooniverse’s Project Builder Platform.

Before we launch the site live, we need your help! We’re ready for you to take a sneak peek at the site and let us know what you think. We have developed two different styles for the classification interface, and the team is having trouble deciding between the two. We’d like you to try them out and let us know what you think. The team will be looking at performance of the two different classification interfaces and your feedback to figure out which design is the right one for the new Planet Four.

If you can spare a few minutes, please map fans and blotches in one or both of the workflow styles and let us know what you think. Try it out at

Not a Goodbye But A See You Soon

If you check out the Planet Four website now, you will now see that the site is on hiatus with the retirement of their older platform. A huge thank to you everyone who has contributed to Planet Four over these past six years and especially in the past few weeks. We completed the sets of HiRISE images we needed to complete before the site was shutdown. Mission accomplished. Thank you so much!

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This isn’t goodbye, it’s a see you soon. We’re learning so much from the Planet Four classifications/assessments that we’ll be back with more seasonal fans and blotches to map. We’re working on a new version of Planet Four with the Zooniverse’s new project builder platform, but it will take us time to build and test the new version of the project. In the meantime we have lots of classifications to analyze from the original site. The science team is currently working on four papers (!!!) based on your classifications, and this work will continue even if the website is paused. In addition,  Planet Four: Terrains and Planet Four: Ridges are on the Zooniverse’s newer platform and will continue to be active.


Final Push on Planet Four and Planet Four’s Future

We were formally informed this week by the Zooniverse, that the platform that Planet Four is hosted on will be retired and shutdown very soon. On April 30th, the platform will be shutdown. This means that the site will be on hiatus as the science team continues to work towards building a new version of the project on the Zooniverse’s project builder platform.  This is going to take several months to complete, but in the meantime we are also analyzing your classifications and the Season 2 and 3 fan and blotch catalog. The science team has papers in the works and have been exploring possibilities/synergies with machine learning as well.

Planet Four’s future is bright.  April 30th  won’t be the end of Planet Four. We’ll be back. For at least the time being Planet Four Talk will be accessible and you can login and continue to make posts. Some point in the future, Planet Four Talk will become read only. Rest assured, your comments, hastags, and collections are stored in the Planet Four Talk database, so that information is saved and accessible to the science team for further investigation.  We’ll keep you updated here on the blog.

Before we pause Planet Four, we need your help! We still have data on the site left to be classified. We believe we have found a connection between regional dust storms on Mars and the number of seasonal fans and blotches visible in a given spring season. To check whether or not these storms are playing a significant role, new images are live on the Planet Four website. We are hoping we can get as many images classified as possible before the site goes on hiatus.

Time is running out, and we need your help to get as many of these images classified before the old Zooniverse platform is retired on April 30th. If everyone classified 10 images, we’d be over the finish line. If you can spare a minute or two, please review images at 


A Sneak Peek at the Future of Planet Four

The science team is working on migrating Planet Four to the Zooniverse’s more modern project builder (or panoptes) platform. This is a slow process because things are different in how the newer Zooniverse platform displays images and also we want to take the lessons we’ve learned over the past 6 years and use it to make the web interface even better.  We thought we’d share some screen shots from our work-in-progress prototype.

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The next stage will be getting some images on the site and beta testing the changes we want to make and seeing how well these tweaks do compared to the current Planet Four website/classification interface. This might take a few months, but we’re working hard to have this ready before the end of the year.

In the meantime, we have new images on the original Planet Four website that we are hoping to get classified before the older Zooniverse platform that runs the current Planet Four site is officially retired. We’re trying to make the push in April to get these new images classified. If you can spare a few minutes to classify an image or two on the main Planet Four site, we’d appreciate it.