Archive by Author | Meg

The Invisible Winds that Shape the Fans

Today we have a guest post by Tim Michaels. Tim is a research scientist at the SETI Institute who studies how the weather and climate of other worlds affects their surface features.

The Planet Four science team has recently been using the catalog of your fan markings to compare to the wind speed and direction estimated by computer calculations of how Mars’ atmosphere moves around.  These wind estimates are calculated by a complex computer program known as a mesoscale atmospheric model, very similar to those that forecast the daily weather on Earth.  There are no actual wind measurements in the southern polar regions of Mars, so we use these modeled wind estimates to better interpret what your fan markings tell us about the planet’s weather and climate.

The figure below shows an example of the modeled wind estimates near the Manhattan Classic fan site (86.4S, 99.0E) in the early evening at Ls 190.  The area shown is about 135 km by 135 km, south is toward the upper right side, and every arrow is about 1.5 km apart (every model gridpoint; the numbers on the sides count these).  This area is at the head (top) of the great south polar valley Chasma Australe, and the white topographic contours (in meters) show the upper reaches of that valley running downhill from center right toward the lower left.  The arrows show wind direction and speed (arrow length, see the 10 m/s scale in the upper right corner).  Wind speed is also indicated by the color of the arrows — cooler colors (like blue and purple) for the slower winds, warmer colors (like red and orange) for the faster winds.  The fastest wind speeds in this scene are about 11 m/s.

You can see how the wind directions and speeds vary a lot across this area — those patterns change quite a bit with the time of day, as well.  Our preliminary results show that the strong winds from the east near the center of this figure may be related to the formation of the fans in this area.  Much more work still needs to be done to better understand what all of your markings of fans and blotches tell us about the winds on Mars, but we wanted to give you a glimpse of what the (invisible) winds that sculpt the fans may look like.

An Update on Planet Four: Ridges

It’s been a busy summer for the Planet Four: Ridges science team. The project’s first research paper was submitted to the journal Icarus. A big thank you to all the volunteers and our active volunteers on Talk who have contributed lots of great polygonal ridge locations that went into the paper’s analysis. Below you’ll find a map showing the CTX images that were searched by Planet Four: Ridges volunteers using the main classification interface as part of the study.

Map of the locations of the CTX images searched on the Planet Four: Ridges website that was used in the analysis of the project’s first paper.

The first step in this process is getting the referee reports back. The referees are researchers studying Mars who give independent feedback on the paper. Normally the identities of the referees are anonymous, and the author does not know who they are. The referees read the paper and give the editor their opinion on whether the paper is of sufficient quality to be published in the journal and give feedback on how the manuscript/work could be improved. The job of the referee is to point out areas that should be clarified in the paper and where more analysis needs to be done if needed before the paper can be accepted for publication in the journal.

We’ve recently received the feedback from the two anonymous referees. The referees see that there is merit in the Planet Four: Ridges catalog. Thye also gave a lot of great feedback on where we can improve the analysis and manuscript. We’re working on addressing the referee’s comments and taking on board their feedback. We’ll keep you posted as we move through the paper revision process. We’ll do some further analysis, reworking of the paper draft, and add some additional text. Once we’ve done that, we’ll write a response to the referee’s report outlining what was changed/added to the paper to address the points raised by the referees. Then we’ll resubmit the paper and send the response to the referees to the journal. The referees will read everything and send back further questions, concerns, and points that need clarification. We will post more details about the key results of the paper once the paper is accepted and published by the journal.

A Peek at the Planet Four Catalog

The Planet Four science team is collaborating with machine learning researchers in Australia. We’re working on a joint paper that looks at using the current Planet Four seasonal fan and blotch catalog that was generated from the HiRISE season 2 and season 3 images from the original Planet Four website. Michael Aye made some great images for the paper showing examples of what gets generated from your classifications. I thought I would share some of the figures.

In the figures below you’ll see the Planet Four subject image or tile on the left that we have asked volunteers to classify and the right the image is overlaid with the resulting fans (shown in green) and blotches (show in magenta) identified. Each Planet Four subject image has about 30 people review it and map fans and blotches they see in image. We then take all the individual marks and combine them together to identify which sources are fans or blotches. This blog post gives some more information on how we developed the clustering code that combines your classifications together.

With Planet Four 2.0, the current version of the project, we’ll be using the same method and software to combine the markings you are making now to identify the fan and blotches in the subject images. So think of the images below as a sneak peek of what your clicks will be turned into.

Planet Four on Planet Three

The Planet Four team has participated in a couple of outreach events over the past few months. We wanted to share the links with you.

Michael, Candy, and myself from the core Planet Four team with Zooniverse Co-PI Laura Trouille were featured on a Live Chat/webinar with the Science Friday team today (Monday April 27) . It was great combo of tea discussion, answering questions from the viewers, and demos. You can find the recorded video on Facebook live;

A few weeks later, I was interviewed on the BBC Sky at Night’s May episode talking about Planet Four and the other projects that make up the Planet Four organization. If you’re living in then UK, the episode is available online for stream in BBC iplayer. It also happened to be the 800th episode of the Sky at Night, and it was also the first episode where all the presenters, Sky at Night crew, and interviewees were all working from home.

In these challenging times, I wanted to take a moment and thank everyone for their contributions to all three Planet Four projects. We appreciate the time, effort, and energy you are contributing.

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!

Planet Four Team + Science Friday Live Chat – Today (Monday April 27) at 4pm EDT/9 pm BST/1 pm PDT

The Planet Four will be participating in Live Chat/webinar with the Science Friday team today (Monday April 27) at 4pm EDT/9 pm BST/1 pm PDT . The webinar is open to the public and you can ask some of the team questions, see demos of the projects, and more. We’ll be highlighting all the Planet Four projects. You can find connection details and more here.

If you can’t make our live chat, there were will be a several others this week from other projects from around the Zooniverse as well. Also we’ll post a link to the recorded video when it’s available. And as always, the team is available on Talk, so feel free to jump in on any of the Planet Four projects Talk and ask the science team questions there too.

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

Ideas on the Formation of Resistive Polygonal Ridges on Planet Mars

Today we have a guest post from Planet Four: Ridges volunteer, Bill Hood (geocanuck). Bill Hood is a semi-retired Canadian geologist who has spent 40+ years in the mineral exploration business as a contractor, consultant and prospector. When not wandering around in the mosquito-infested swamps of northern Ontario or the grizzly-prone mountains of the Yukon, he can be found residing in a small town near the city of Winnipeg. A self-confessed Star Trek fan, Bill occasionally argues that it is mineral exploration that will drive human exploration of space, and is rumoured to have already started Mars Palladium Corp. Bill spotted the NASA P4R news release in early 2017, and has been addicted to Mars images/geology ever since.

It appears customary on Planet Four, that after one does a talk or presentation involving Planet Four: Ridges material, a blog is in order. On January 8, 2020, I did a talk titled “Ideas on the Formation of Resistive Polygonal Ridges on Planet Mars” at a meeting of the Manitoba Mineral Society here in Canada. The Society meets monthly in the city of Winnipeg in the local planetarium building, so there’s a slight crossover with the astronomy crowd.

My presentation comprised three main parts: 1) fun facts about Mars, 2) Planet Four: Ridges and the science arising from it, and 3) my ideas on the formation of polygonal ridges. After a brief run-through of the basic geography of Mars, locations of all the landers, and some fun images of faces, structures and items that look like they could only have been constructed by beings with opposing digits or sharp teeth, I outlined how the Zooniverse Planet Four websites functioned to generate Mars data. Next, I outlined some of the science interpretations coming from this data, including the abstract for the talk by Aditya Khuller, Laura Kerber et al, at the 2018 American Geophysical Union convention, as well as a proposed paper titled “Polygonal Ridge Networks in Arabia Terra, Nili Fossae and Nilosyrtis: Evidence for Groundwater Influence”, presently in preparation by the same authors. I then summarized the basic hypothesis of this work to date, which suggests that “Nili” type polygonal ridges on Mars have resulted from burial, compaction and faulting of shallow-basin, clastic sediments, with subsequent groundwater flow and mineral deposition along these polygonal-oriented fault/fracture systems. Subsequent erosion exposed these hard, resistive ridges on Mars. Terrestrial models from the North Sea basin and resistive ridges exposed across the Middle East seemed to be an entirely plausible analogy.

But being a person of contrary character and residing in the frozen environs of rural Canada, I explained to the members of the society that I had difficulty being convinced by the proposed ridges formation argument. When I looked at Mars images, I saw glaciers and pingos and permafrost patterned ground that looked like something out of Arctic Canada, while my on-line Zooniverse friends, most residents of warmer climates, saw a world of palm trees and torrid deserts. As I told my friends in the local Mineral Society on that cold January night, it was clear that I had not just a responsibility, but a Canadian national duty, to advocate a “permafrost hypothesis” for polygonal ridges on Mars.

From my observation, it appears that the “Nili” type polygonal ridges, named for a future type locality in the Nili Fossae region of northeast Arabia Terra on Mars, comprise a range of polygonal oriented resistive ridges, as well as irregular or semi-circular ridges which enclose the margins of ridge areas. It appears that these polygonal ridges are forming in the subsurface, within the basal clastic sediments in local craters, valleys and basins, just above the unconformity at the top of the older Noachian cratered basement rocks on Mars. The similarities to ice fracture patterns and permafrost patterned ground were fairly obvious. So I presented a couple dozen slides, both from Mars and Earth, pointing out fracture pattern similarities, with the caution that there were scale differences and the obvious sub-sediment vs. sub-aerial disparities.

I concluded my talk showing a series of hypothetical cross-sections illustrating a possible process for forming these unusual polygonal ridges in the sub-surface on Mars. The basic idea I am presenting is that a sub-surface permafrost cap may have formed a confined groundwater aquifer. Evidence of sub-surface artesian flow is rather obvious in many Mars images, but the question of what triggered this flow is important. I’m suggesting that the accumulation of aeolian sediment may have formed a thermal blanket which allowed remnant geothermal heat to erode the permafrost cap, triggering artesian flow from the aquifer into basal clastic sediments above the unconformity and into overlying ice-wedge fractures in the permafrost. Having a long residence time, these groundwaters would be at maximum total dissolved solids, so mineral deposition would be significant on evaporation/sublimation. 

So that’s my Planet Four blog. I’ll conclude with one takeaway, which is that if this ridge process consumed all the subsurface ice, the Nili ridge areas may not be the best places to send future Mars colonists. I can also advise that the members of the Mineral Society asked that Mars be added to the summer field trip schedule. 

Early Warm Wet Mars
Cooling Mars. Permafrost.
Confined Aquifer. Aeolian Deposition.
Thinning Permafrost. Artesian Flow.
Open Aquifer. Evaporation/Sublimation.
Induration/Lithification of Basal Sediments/Fractures.
Erosion. Variable Exposure. 

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.