Today we have a guest post by Planet Four volunteer Peter Jalowiczor.
As a Planet Four contributor for a number of years this blog is a description of a presentation I recently gave at my local Astronomical society. It was based, of course, on my P4 work and included a preliminary discussion on Mars before starting on the focus of the talk – this project. About two months earlier I had given a talk based on material provided by Meg so everyone was already familiar with the project as well as everyone involved. Here is how the second talk was structured.
Introduction to P4
P4 is a citizen science project designed to help planetary scientists identify and measure features on the surface of Mars, the images on the site are around the Southern polar region, an area of Mars that we know little about and the majority of which have never before been seen by human eyes!
Mars throughout the Ages
Following the introduction came a brief discussion of the history of observation from the first observations of planetary motion by Kepler and the first telescopic observations of Mars by Galileo, to maps (of Mars) by Christiaan Huygens, Giovanni Cassini on to Beer & Madler, Richard Proctor, Schiaparelli, Camille Flammarion and of course Percival Lowell and his famous Martian Canals. But, how was this all relevant to P4? The answer was that the HiRISE experiment on the MRO spacecraft was mapping areas around the South Pole…
Mars in the Solar System
How does Mars compare as a planet within the terrestrial group? Following a comparative overview of the five terrestrial bodies (including the Moon) in the inner Solar System. In this group, Mars is intermediate in its properties. For example, compared to the largest body (the Earth) and the smallest (the Moon) it displays features on its surface, which are Earth-like: evidence of river valleys, lakes and the likelihood of an ancient Ocean in the Northern hemisphere. Whereas in the Southern hemisphere, the landscape is more primitive and cratered, more Moon-like. A discussion into why this was so and the importance of the surface area to volume ratio and its effect on planetary evolution across the terrestrial group. Mars’ properties in its own right was briefed.
The Planet Four Project
A detailed description of the project starting with the HiRISE experiment. From an altitude of 200 to 400 kilometers above Mars, surface images are acquired containing individual, basketball-size (30 to 60 centimeters) pixels, allowing features 1.2m to 2.4m across to be resolved. Large swaths of the surface are imaged: 20,000 x 126,000 pixels and the image is broken up into individual P4 tiles.
Citizen scientists mark dark fans and dark blotches that appear and disappear during Spring/ Summer around the South Pole of Mars. The dark fans and blotches appear in the Southern spring when the ice cap begins to thaw and sublimate back into the atmosphere. The fans and blotches then disappear at the end of the summer when there is no more ice left. How do these fans form, how they repeat from Spring to Spring? What does this tell us about the surface winds on the South Pole? How would these features enable scientists to build-up a global map of wind-directions on Mars.
30 images (tiles) were shown from categories such as: #spiders, #fans, #blotches, #yardangs, #dendritic features, #Mars-has-the-blues…
Results of work carried out by myself. Occasionally, during classification, the #measurement tag was used by myself to measure various features within the tile. This started out as no more than an intention to log the size of features. After a few years a few hundred measurements had accumulated.
I found that:
- This was biased towards the measuring of blotches.
- 31-40m was the modal, or most commonly occurring size of blotch within the tile.
- 10m-90m – fan sizes were grouped in this region.
- Where the blotch, spider or fan went outside the range, an attempt was made to estimate its size.
- The images of the tiles here ranged from ~150m x 200m to 366m x 475m.
However, the constraints of the tile parameters mean that the sizes may not be a true reflection of reality; and this was a simple experiment in science, The results could be improved with a larger sample size (more measurements) particularly if measurements taken outside the tiles.
This is based on questions/ discussions, which came up both during and after the lecture. Some I answered such as the linear venting (to the question below) as it was asked before the relevant slide came up! For some of the other questions I gave partial answers and we agreed that this should be forwarded on to Meg, and the Planet Four Science Team is going to answer these in a following blog post.
- What evidence is there for cracking (of the ice) in the Martian surface?
- Was there certainty that the channels were not ridges? (Yes, this is an optical illusion!)
- Where does the blue colour come from?
- Is the North Polar region of Mars going to be investigated in the same way as the South polar region?
- What height are the geysers?
- Is there an imaging dataset, perhaps an experiment on a satellite, which could enable these heights to be measured more accurately?
- How often do we return to each of the imaged areas? Surely there must be some follow-up to see how the features have developed.
The talk started with the good news of a certain Sagan Medal recipient and ended with the news that there was now an alternative to Mars bars with Martian cake, however this had to be refrigerated at Martian polar temperatures…
Now that we have frozen development of the clustering algorithms for both blotches and fans and reviewed the stage of combining the different types of clusters together, we are working on the next issue. This is dealing with markings from the overlap regions of Planet Four subject images. For most Planet Four subject images, there is 100 pixel overlap with a neighboring subject image. So in our current catalog we have duplicates possibly of seasonal fans and blotches that appeared in more than one Planet Four subject image.
We’ve started to look into what’s the best wave to deal with this. The main reason we have the overlapping regions between adjacent Planet Four subject images is to make sure we identify seasonal fans that would get cut off between the two subject images if there was no overlap. The overlap should ensure at least one of the subject images has full view of the source, so we don’t miss anything.
Here’s an example of four adjacent subject images combined and the clustered markings drawn on.
You can see that in the current catalog we get two overlapping blotches with slightly different orientations and centers generated from combining the volunteer classifications. If you look at what is in our catalog for each subject image that makes up the ensemble, you see that for one of the subject images the blotch is only partially on the image. The resulting blotch marker from the combined classifications is also partially on the image, it extends beyond. We might be able to use this fact that people extended the drawing markings to fit the shape if the source went over the edge, to identify those seasonal fans and sources that extend beyond the extend of the subject image and when that happens use the catalog entry from the overlapping subject images where the source was fully in the subject image. We’re testing this hypothesis by performing a manual review in the next week or so of the catalog output of a sample of overlap regions.
We’ve been reviewing the output coming from the full Planet Four data reduction pipeline now that we’ve frozen development on the fan and blotch clustering codes. Once we have the fan markings and blotch markings clustered individually, we then have a stage that combines the individual clusters to decide it a source marked by Planet Four volunteers is really a blotch or fan by find clusters where there centers on top of each other and then depending on how many fan markings went into the fan cluster and how many markings went into the blotch cluster we decide it’s a fan or a blotch for the final catalog. What we found in the catalog review that there are nice cases where there are sources that aren’t quite a fan only or not just a blotch. With a citizen science approach we’re able to capture that fuzziness which is fantastic. We highlight a few examples below selected by Michael Aye, who has been hard at work developing this pipeline over the past several years.
In all three figures: the top left is the Planet Four subject image, top middle is all the individual volunteer fan markings, top right is all the individual volunteer blotch markings, the bottom right is the blotch clusters after clustering, the middle bottom is the fan clusters after clustering, and the bottom left is the final sources after combining the fans and blotches (the dots in this panel show the center position of the final fan or blotch in our catalog).
As you can see from above, we’re making great progress on the Planet Four data reduction pipeline. Next steps including handing the fact that the edges of most of our Planet Four subject images overlap with neighboring subject images, and ensuring that we merge overlapping volunteer markings covering the same spot on two different subject images.
Happy Birthday Planet Four: Terrains! Last Thursday marked the second anniversary of the launch of Planet Four: Terrains. Thank you for all of your help over the past two years. We couldn’t do this without you. To celebrate here’s a recipe for a Martian South Polar Trifle for you to make for your own Mars party. It’s inspired by this recipe:
- 1 package (20 ounce) chocolate cream filled cookies like Oreos or Hydrox
- 16 ounces of cream cheese
- 1/4 cup of unsalted butter
- 2 cups of powdered sugar
- 2 small packages of instant vanilla pudding mix
- 3.5 cups milk (recommend dairy milk – skim to whole works fine)
- 1 tub (20 ounce) of whipped topping (not canned whipped topping but the kind you find in the freezer section). ( You can also make your own from scratch using whipping cream if you like. Just add a little bit of powdered sugar mixed in to taste)
Making the ground layer: Place chocolate cream filled cookie in a bowl or plastic bag, saving 4-6 cookies for the top later. Use a rolling pin, bottom of a glass, etc to crush the cookies. Place 3/4 of the crushed cookies on the bottom of a nine-inch glass pie plate or any glass container so you can see through the sides if possible.
Making the seasonal ice sheet mixed with seasonal ice and boulder: Soften the butter., then mix together cream cheese, butter, and powdered sugar until smooth (electric mixer or whisk is fine). With whisk combine the pudding mix with the milk until smooth and slightly thickened. Fold together cream cheese mixture, whip topping, and pudding mixture. Add 2-3 drops of red food coloring to get a light red color (the red food color and the power sugar represent the atmospheric dust trapped in the ice sheet). Then mix in the remaining 1/4 of the crushed cookies to represent boulders trapped in the ice sheet. Pour the mixture over the ground layer of cookies.
Topping of seasonal fans: Crush the remaining few cookies very finely, sprinkle on the top to create seasonal fan shapes
Refrigerate the trifle for 3 hours or more before serving.
I’ve been reviewing output from the blotch clustering with updated parameters, and the good news is the two problematic cases we were trying to have the clustering algorithm identify now are successful:
We’re looking a bunch of parameters, but the bottom left corner configuration is the parameters we think are best for the blotches and and fans.
Here we are showing just the clustering of the fan markings.
Here we are showing just the clustering of the blotch markings
Here we show the clustering of the blotch markings. Now the 2-scale blotch clustering identifies the volunteer draft markings for the large blotch below as well as smaller ones.
I think we’re at the point of locking development of the blotch pipeline. This will be a big step forward towards finishing the first paper and getting science results out of Planet Four. We’ll want to take a look at the next stage of the pipeline after two different types of markings are cluster and the algorithm picks the final shapes based on the number of classifiers who drew fans versus blotches for the same source. If that looks good as we expect it should from previous reviews of the pipeline output, then the next thing we need to do is look at the pipeline results near the edges of each of the cutouts where this is overlap between the different subject images.
Perusing Planet Four: Ridges Talk I came across the image below. I thought I’d say more about it in case you encounter similar types of images. What drew my eye was the large diffuse lighter streaker on the one side of the crater.
That’s called a wind streak. Wind streaks have been found not only on Mars but also on Venus and Earth. As their name implies, they are formed directly by the interactions of the surface wind with the soil. The wind is impacted by obstacles in its path on the surface like crater rims. As the wind moves around the crater rim either picks up dust particles pushing them together collecting them to create bright streaks visible from orbit or the wind excavates material exposing a darker material than the surrounding top surface layer. Wind streaks extend into into the direction the wind is moving towards, so they are also good indicators of past wind direction.
Today we have a guest post by Planet Four volunteer Peter Jalowiczor.
Why Ziggy Stardust and the Spiders from Mars? As we know Ziggy Stardust is David Bowie’s alter ego, a rock star who acts as a messenger for extraterrestrial beings. Unfortunately, no extraterrestrial beings have been found on Mars (at the time of writing, at least!). But spiders have definitely been discovered…
From this then, as a Planet Four contributor for a number of years now, I recently put together a talk about the P4 Project to be given at my local Astronomical Society: the MSAS (Mexborough and Swinton Astronomical Society). The society is based about 20km from Sheffield (pop. 570,000), England and was founded in 1978. Every Thursday evening is a social occasion centered around a talk. Members, such as myself are encouraged to give talks on different subjects. Usually once a month, an academic visits the society to lecture on an aspect of Astronomy. In March this year the MSAS held a ‘Back to Basics Workshop’ in conjunction with the BAA (British Astronomical Association).
Back to the talk: my initial presentation was to be a preliminary discussion about Mars in general, before focusing on the results (images) from the HiRISE (High Resolution Imaging Science Experiment).
After letting Meg know of my P4 talk, I was very kindly sent lecture materials over from Hawaii. and on June 1st did my best to interpret and present one of Meg’s lectures: ‘Exploring Mars with 150,000 Earthlings’. This was Meg’s lecture at the ‘Imiloa Astronomy Center of Hawaii from February. It was an introduction to the Planet Four Project and collaboration with over 150,000 citizen scientist volunteers worldwide. Describing how, by the power of the internet, volunteers map the fans and other surface features formed by carbon dioxide jets helping planetary scientists characterize surface features on Mars. There was also a discussion of the other Mars projects: Terrains and Ridges and how people can get involved in exploring Mars from the comfort of their own home.
Photos from just before start of the lecture are included here. On an evening where I was competing against the British weather – but this time it was a very beautiful, warm sunny evening (something to be cherished in the UK) so the turnout wasn’t that bad. The society was very interested in the research carried out by the team and is grateful to Meg for the material.
A quick update on the Planet Four: Terrains paper. For the past month or so the team has been working on making changes to the manuscript and creating new figures to address the concerns of the two independent referees who reviewed the paper. The referees are experts in the field who assess and critique the paper. Having an independent set of eyes give feedback is useful and makes the paper better. We’ve submitted the revised draft on May 16th with a list of each of the changes we made to address the points raised by the referees. We’re waiting to hear back from the journal. We hope that after this first round of review/edits that there will be only minor changes requested going forward. We’ll have to wait for the referees’ to read the revised manuscript and our report and send their assessment to the editor. Fingers crossed for a speedy review.
As a teaser, below is a new figure we made for the paper. The image is a subframe from a HiRISE observation of one of the regions targeted based on your classifications on Planet Four: Terrains. You can see that this area is like Inca City where we see fans emanating from a top the ice sheet where boulders are embedded/below the ice sheet. Not all the boulders exhibit seasonal fan/carbon dioxide jet activity when this image was taken
The science team is making great progress towards freezing developing of the Planet Four clustering algorithm. I reviewed some of the output from the pipeline Michael Aye has been writing. Basically the task was to check on the few issues we were working on addressing by having a two size regime clustering for blotches drawn by volunteeers and pick the parameters that seemed to work best for the data.The good news is we see an improvement.
I thought I’d share some of then plots so you so you can see how close we are to finalizing the pipeline. These plots are at the stage of clustering all the blotch markings alone and then clustering all the fan markings alone. We combine the fans and blotch markings into one later on in the process. For now we’ve just run the first part of the clustering pipeline and outputted the results to these figures. As you can see we’re doing pretty well at picking up all the fans and blotches marked by the majority of the classifiers who made a marking on the subject image.
We’ve got one or two more tweaks we brainstormed in the last science team call last week, and once we review those I think we’ll be freezing development on this part of the Planet Four analysis pipeline until after the first paper is submitted.