Crater Features

Since the launch of Planet Four: Craters a few weeks back, we have had several Talk posts regarding different features and markings that have been spotted in and around the craters themselves. This post will go through what some of these markings might be, and hopefully answer some of the questions you have had!

Recurring Slope Lineae (RSL)


Recurring slope lineae are narrow, dark markings found on steep slopes (like crater edges) that incrementally lengthen during warmer periods, then fade over cooler seasons and can recur over multiple Martian years. They can grow to be several hundred metres in length, and it has been suggested that they are caused by wet flow – originating from melted ice.

Active Gullies


Martian gullies are small networks of narrow channels, along with their associated down slope deposits, that occur on steep slopes, especially on crater walls. It has been suggested that they are formed by a flow of dry material, supported by a layer of dry ice just below the surface.

New Impacts

new impact

As the name suggests, these are craters that have been formed by impacts that have occurred in the near past. They are found all over the surface of Mars, and although they vary in size the smaller ones are much more frequent. They can be spotted by the darker coloured ejecta formed around them (due to the disturbed surface material that has yet to settle), or in some cases the presence of brighter patches – indicating where subterranean ice has been revealed.

If you have any other questions regarding some of the things you have spotted on Planet Four: Craters, please feel free to ask on Talk, and in the mean time please keep marking on!


Goodbye Inca City, Onward to Manhattan

Thanks to your help, the Inca City images we’ve been showing on the site for the past several months are complete, and we’re now back in the region known as Manhattan. We’ve been to Manhattan before, but that was during a different Martian year. HiRISE has been in orbit around Mars for almost 10 Earth years which equates to roughly 5 Martian years.  We’re showing new never-before-seen images on the Planet Four website right now. These observations are taken from HiRISE’s 4th Martian spring imaging the development of the windblown fans.

By examining the same region over and over again during different Spring seasons, we can study how this process of forming fans and geysers is evolving over time and how properties like topography, thermal inertia of the soil, presence of different types of spider channels, and changes in the Martian atmosphere impact the properties of the seasonal ice sheet and thus the formation and evolution of the seasonal fans (and by proxy the geysers that form them). In addition, the fan directions and lengths, as well as the presence of blotches, are an excellent probe of wind direction and strength throughout the Martian Spring. With your classification we will be able to see if the winds repeat the same each season or change direction.

For the rest of the South Pole we only have observations from Season 2 and Season 3 classified. With the completion of the previous set of Inca City images, we now have four seasons of fan formation mapping in Inca City. The extra two seasons doubles the temporal baseline we have on Inca City to look for changes and evolution in the fan formation process. The classifications you make now will help us have the same kind of dataset for Manhattan. Having fan and blotch maps for two regions with different topography and locations on the Martian South Pole will help us tease out which effects are due to local conditions and which ones are due to to the changes in the Martian climate (like more dust in the ice sheet).

Help classify the new images of Manhattan at

PS.  If you haven’t tried out Planet Four: Craters, do take a look and classify an image or two. Your classifications and feedback will help improve  the design of future Zooniverse projects.

Plane Four: Craters

Welcome to Planet Four: Craters!

Recently, a new version of the Planet Four project went live, and we are asking you to mark craters on the surface of Mars.

By counting the craters we will be able to figure out how old various geological surfaces are! This will be a big help for missions such as the 2016 NASA InSight experiment, which will use geophysical techniques such as seismology and heat flow to figure out how Mars has evolved. Knowing the age of the surface will help us to put a time-scale on that evolution.

Another aim of the project is to help improve the design of future Zooniverse sites.

When marking craters on Mars using this new version of Planet Four, you will be using one of three different classification interfaces. They each have different tools for you to use (on the left hand side of the page), and will ask you to complete tasks in differing orders for each image. Don’t worry! When you use one of these interfaces for the first time a tutorial will guide you through how to use it, in the same way the original Planet Four site did.

The reason for the different interfaces is that we want to know which one works the best, the one that you enjoy using the most and find the easiest to use, and gives the best crater marking results.

To find this out, we would really value your feedback. If you have a spare 15 minutes, there is a questionnaire on the Talk page (accessed through clicking the discuss button on the classify page) where you can answer questions and give your opinions about using the interfaces.

The information you give us will then be used to help design future versions of Planet Four, and other Zooniverse projects – so your opinions really count!

Get involved now at

Happy crater marking!


Clustering the PlanetFour results

Our beloved PlanetFour citizen scientists have created a wealth of data that we are currently digging through. Each PlanetFour image tile is currently being retired after 30 randomly selected citizens pressed the ‘Submit’ button on it. Now, we obviously have to create software to analyze the millions of responses we have collected from the citizen scientists, and sometimes objects in the image are close to each other, just like in the lower right corner of Figure 1.


Figure 1: Original HiRISE cutout tile that is being shown to 30 random PlanetFour citizen scientists.

And, naturally, everybody’s response to what can be seen in this HiRISE image is slightly different, but fret not: this is what we want! Because the “wisdom of the crowd effect” entails that the mean value of many answers are very very close to the real answer. See Figure 2 below for an example of the markings we have received.


Figure 2: Original markings of P4 Citizen scientists.

Note the amount of markings in the lower right, covering both individual fans that are visible in Figure 1. It is understandable that the software analyzing these markings needs to be able to distinguish what a marking was for, what visual object in the image was meant to be marked by the individual Citizen scientists. And I admit, looking at this kind of overwhelming data, I was a bit skeptical that it can be done. Which would still be fine, because one of our main goals is wind directions to be determined and as long as every subframe results in the indication of a wind direction, we have learned A LOT! But if we can disentangle these markings to show us individual fans, we could even learn more: We can count the amount of activity per image more precisely, to learn how ‘active’ this area is. And we even can learn about changes of wind direction happening, if at the same source of activity two different wind directions can be distinguished. For that, we need to be able to separate these markings as good as possible.

And we are very glad to tell you that that indeed seems possible, using modern data analysis techniques called “clustering” that looks at relationships between data points and how they can be combined into more meaningful statements. Specifically, we are using the so called “DBSCAN” clustering algorithm (LINK), which allows us to choose the number of markings required to be defined a cluster family and the maximum of distance allowed for a different marking before being ‘rejected’ from that cluster family. Once the cluster members have been determined, simple mean values of all marking parameters are taken to determine the resulting marking, and Figure 3 shows the results of that.


Figure 3: Clustered markings for P4 tile ZG7

Just look at how beautifully the clustering has merged all the markings into results have combined all the markings into data that very precisely resembles what can be seen in the original data! The two fans in the lower right have been identified with stunning precision!

For an even more impressive display of this, have a look at the animated GIF below that allows you to track the visible fans, how they are being marked and how these markings are combined in a very precise representation of the object on the ground. It’s marvelous and I’m simply blown away by the quality of the data that we have received and how well this works!


Figure 4: Animated GIF for the clustering of the markings of APF0000zg7

This is not meant to say though that all is peachy and we can sit back and push some buttons to get these nice results. Sometimes they don’t look as nice as these, and we need to carefully balance the amount of work we invest into fixing those because we need to get the publication out into the world, so that all the Citizen scientists can see the fruit of their labor! And sometimes it’s not even clear to us if what we see is a fan or a blotch, but that distinction is of course only a mental help for the fact if there was wind blowing at the time of a CO2 gas eruption or not. So we have some ideas how to deal with those situations and that is one of the final things we are working on before submitting the paper. We are very close so please stay tuned and keep submitting these kind of stunningly precise markings!

For your viewing pleasure I finish with another example of how nicely the clustering algorithm works to create final markings for a PlanetFour image:


Figure 5: Animation for the clustered markings process of P4 image ZMJ

2 Years On from BBC Stargazing Live

In the UK, tonight starts the latest installment of BBC Stargazing Live. Three nights of live astronomy television hosted by Professor Brian Cox and Dara Ó Briain.  Just over two years ago, we were preparing for the launch of the Planet Four live on television as part of Stargazing Live. Professor Chris Lintott from the BBC’s  Sky at Night and PI of the Zooniverse went out on the program broadcast live from Jodrell Bank and introduced to the world Planet Four,  asking for viewers help to map the seasonal fan and blotches visible in images of the Martian South Pole taken by the HiRISE camera.

For the past 9 years, the HiRISE camera aboard the Mars Reconnaissance Orbiter has been capturing stunning and dynamic images of the defrosting South Pole. During this time, carbon dioxide geysers loft dust and dirt through cracks in a thawing carbon dioxide ice sheet to the surface where it is believed that surface winds subsequently sculpt the material into dark fans observed from orbit. 30% of Mars’ atmosphere condenses out to form this ice sheet. Understanding the direction, frequency, and appearance of these fans (a proxy for the geysers) and how these properties are impacted by varying factors we can better understand the Martian climate and how it differs from Earth.

This is a project that we truly couldn’t do with out the help of citizen scientists and BBC Stargazing Live. Hundreds of thousands of fans are visible in HiRISE observations, but for years this rich dataset was not tapped to its full potential. Automated computer algorithms have not been able to accurately identify and outline individual fans in the HiRISE images,  but a human being intuitively can distinguish and outline these features. And thus Planet Four was born.

I can remember launch day like it was yesterday, waiting on the Talk Discussion tool for the flood of volunteers to start posting questions and sharing their thoughts and ideas about the images they were seeing. I and the rest of the Planet Four team anxiously waiting at our keyboards could tell immediately when the Planet Four segment aired. The response from Stargazing was incredible and overwhelming. Each night, the Zooniverse servers struggled to keep up serving images of Mars as the number of people on the site continued to rise. Thanks to the Stargazing Live viewers we were able to complete nearly all of the Season 2 and Season 3 HiIRSE monitoring campaign images.

So where are we now? Thanks to help of Planet Four volunteers including Stargazing Live viewers, we’ve made great progress since January 8, 2013. Over 4.6 million blotches and 3.8 million fans have been drawn to date (the great majority of these markings were made during BBC Stargazing Live). In the past two years, Planet Four has captured the equivalent of a full year of non-stop human attention (a single person working non-stop/no breaks for an entire year!). The science team has been working to create a software pipeline to combine the multiple classifications to identify fans and blotches. We have also been working to create an expert dataset classified by the science team for a very small subset of Planet Four images to compare to the volunteer classifications to  show that  Planet Four citizen scientists are very efficient and effective at detecting the seasonal fans and blotches in the HiRISE images.

I’m pleased to say the science team is very close to submitting the project’s first science paper to a journal before the end of the year (we’re aiming for end of Spring/Summer). We have more than half of the paper draft currently written. One of the last lines of the paper is:  ‘We thank all those involved in BBC Stargazing Live 2013.’ This is just the beginning. With this paper, we’ll be able to eventually  produce the largest areal coverage wind measurement of the Martian surface to date spanning two Martian years. These maps will reveal how the fan properties and numbers change from Martian year to year and location to location on the South Pole. We also have 3 more Martian seasons of HiRISE data that we’ve just barely scratched the surface of. The majority of these images have yet to be classified, including right before a Martian dust storm, so we can see how the dust storm has impacted the Martian climate and how long its effects last in the atmosphere and  the ice sheet by looking at the fans and geysers that are created in the seasons before and after the storm

This year the Zooniverse has something new up their sleeve that will be revealed during the broadcast, but while you’re waiting for the return of BBC Stargazing tonight, if you can spare a minute or two , we could use your continued help mapping the seasonal fans visible in the HiRISE images. There is so much of the South Pole (and 3 additional years of data to get through) that we have yet to study and explore! Classify a HiRISE tile or two at

Geometry of HiRISE observations is on Talk!

Good news: our wonderful development team has added new feature that many of our volunteers have asked for! Now you can see north azimuth, sub-solar azimuth, phase angle, and emission angle on the Talk pages directly. You can see an example here. These angles give you information about how HiRISE took the image and where the Sun was at that moment.

To understand what those angles are, here is an illustration for you:


You see how the MRO spacecraft flies over the surface while HiRISE makes an image. The Sun illuminates the surface .

Consider a point on the martian surface P.

Emission angle: HiRISE does not necessarily look at point P straight down, i.e. the line connecting point P and HiRISE has some  deviation from vertical line – it is noted as  angle e on the sketch. This is emission angle. It tells you much we tilted spacecraft to the side to make the image.

Phase angle: Because all the images you see in our project is from polar areas, the Sun is often low in the sky when HiRISE observes. To get an idea on how low, we use phase angle – it is the angle between the line from Sun to the point P and line from point P to the HiRISE. It is noted φ in the sketch. The larger phase angle is, the lower the Sun in the sky, the longer are the shadows on the surface.

Sub-solar azimuth: To understand what is the direction towards the Sun in the frame of HiRISE image, we use sub-solar azimuth. In any frame that you see on our project it is an angle between horizontal line from the center of the frame towards right and the Sun direction. It is counted clock-wise. The notation for it in the sketch is a.

North azimuth: The orbit of MRO spacecraft defines orientations of HiRISE images. North azimuth tells us direction to the Martian north pole. In the frame of an image it’s counted same as sub-solar azimuth, i.e. from the horizontal line connecting center of the frame and its right edge in the clock-wise direction.

I hope this helps you enjoy exploring Mars with HiRISE!



NASA funding for utilizing Planet Four markings

Champagne Explosion


It is really-really tough to get funding to do research. You have to have an idea to do something really new and important, something that will be interesting and useful. You need to gather a team that can do it. Then you have to write a proposal to explain your idea and to convince other scientists that this project is worth pursuing. And you’ll be competing with other projects for the limited budget pot. It was even tougher than usual this year for planetary research at NASA: only 14% of all submitted projects got funding.

But we did!

A little project that utilizes the data from Planet Four will be funded by NASA so that we can compare directions of winds mapped by our citizen scientists  (via fans, of course!) to the prediction of martian climate models!

This is so very exciting!

We have a great team here and I am convinced this project will be a great success! Thanks NASA and thanks all of our helpers on planet4!


Calling All Undergrads: Spend A Summer Working on Planet Four in Taiwan


I’m a postdoctoral fellow at the Institute of Astronomy & Astrophysics at Academia Sinica (ASIAA)  in a Taipei, Taiwan. As part of the 2015 ASIAA Summer Student Program, we’re looking for an undergraduate student to come to Taipei for the summer, from July 1st-August 28th, to work on Planet Four related research.

Last year, Chuhong Mai participated in the program and helped get the map project information we need to make the final catalogs for the first Planet Four paper. As a result of her efforts last summer, Chuhong is going to be co-author on the paper. You can learn more about her experience at ASIAA and as part of the summer program here.

ASIAA operates in English, and all research will be conducted in English.  The description of this year’s project can be found here. The aim will be help develop tools to look at wind directions based on the Planet Four fan markings for one of the HiRISE targeted regions  (likely Inca City or Manhattan) and see how fan directions change from year to year. Details about the Summer Student Program including rules and restrictions can be found here.

Applications are due before March 20th. If you have questions or if you would  like to know more, you can contact me via email at  mschwamb AT

Happy Chinese New Year

As many of you know, I’m currently a postdoctoral fellow at the Institute of Astronomy & Astrophysics at Academia Sinica in Taiwan. For the past year and half I’ve spent most of my time living and working in Taipei. Right now  in China and Taiwan, as well as  some other places around globe, people are celebrating the Chinese New Year (often referred to as the Spring Festival ), which is based on the lunar calendar. The celebration lasts in total 15 days, and it’s a time people gather and celebrate with family. Chinese New Year is in full swing, and as I’m writing this I can hear some fireworks being set off in the distance.

As part of the  festivities, ASIAA created a New Year’s greeting card. The director of ASIAA asked for images  and figures representing the range of research going on at the institute to use on the card. I send in images from Planet Four selected with some help from Planet Four Talk, and the images made the cut. Can you spot the two below?


Image credit: ASIAA

For those celebrating, we wish you a Happy Chinese New Year and a happy and healthy year of the ram.


A Different View of Mars


Image Credit: Chris Lintott, Becky Smethurst, Sandor Kruk, Ed Paget, CSO

Okay, so this is not your typical view of Mars. You’re used to the HiRiSE images  we show on the site, but the above figure is Mars too. We’ll it’s a spectrum of the upper atmosphere taken by some of the Galaxy Zoo lot , a little over a week ago. I’m collaborating wit them to look at a sample of blue elliptical galaxies  in the submillimeter using the aptly named Caltech Submillimeter Observatory (CSO) equipped with the Leighton telescope. It’s a 10.4-m single dish telescope located on the summit of Mauna Kea in Hawaii. I’ve observed with it remotely, but Chris Lintott, Becky  Smethurst, and Sandor Kruk from the University of Oxford, and Ed Paget from the Adler Planetarium went up the mountain for this run. Ed’s written an account of the trip that you might be interested in reading: Night 1, Night 2, Night 3, Night 4, Night 5, Night 6.

Leighton telescope at the Caltech Submillimeter Observatory with intrepid observers (left to right): Ed Paget, Sandor Kruk, Chris Lintott, and Becky Smethurst. Image Credit: Ed Paget

As a planetary astronomer I’ve pointed telescopes before, but I’ve observed in the optical and mid-infrared wavelengths using a big hunk of polished glass to collection the photons.  This observing project is the first time I’ve ever observed in the submillimeter and used a dish telescope. The aim of this project  is to look at the carbon monoxide (CO) in blue elliptical galaxies and see what it says about star formation. We’re actually looking at in particular  (2-1) rotational electron transition of the CO molecule. This transition occurs in the rest frame of the gas at 230 GHz, wavelengths where our eyes are not sensitive.

Turns out that the CSO uses Mars as a frequent calibrator and pointing target for the Leighton telescope. The first time I pointed the telescope back last July when we had observing time was the first time I’ve ever observed Mars, and it was just to check the pointing! There’s a lot of carbon dioxide (CO2), as you know.  30% of Mars’ atmosphere condenses out into the slab of  CO2 ice in the winter on the South pole that the geysers (and as a result the seasonal fans) will be spawned from. There’s also a lot of CO. CO in Mars’ atmosphere was detected and observed in the submillimeter.back in the 1960s ad 1970s. The result is  a strong absorption feature when you observe the disk of Mars and its atmosphere. You can use it to step the beam across as you tune the telescope and find the optimized pointing that gives you the strongest signal (and thus best pointing). So nightly the Galaxy Zoo gang were using Mars for calibration observations at the start of their nightly observations. It’s  a very different use for Mars’ atmosphere, but there is useful info in the spectrum you can extract about the state of the Martian atmosphere. The width of the line and depth tell you about the global amount of CO and the global average wind speeds. The guess from the Galaxy Zoo lot that night was that they were seeing something on the order of 10 km/s winds.

With Planet Four, we’ll also be getting estimates of the wind speeds on Mars, but from the bottom of the atmosphere at the boundary layer that meets the surface. So we’ll be probing a different regime that what the can be studied in the submillimeter. Assuming a particle size,  the length of the fans can tell us the strength of the wind.  The direction the fan is pointing in gives the direction that the wind is heading in. We’ll be able to compare those velocities and directions we extract from you markings to that produced by global climate models of the Martian atmosphere.


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