Today we have a post by Dr. Candice (Candy) Hansen, principal investigator (PI) of Planet Four. Dr. Hansen also serves as the Deputy Principal Investigator for HiRISE (the camera providing the images of spiders, fans, and blotches seen on the site). She is also a Co-Investigator on the Ultraviolet Imaging Spectrograph on the Cassini spacecraft in orbit around Saturn. Additionally she is a member of the science team for the Juno mission to Jupiter. Dr. Hansen is responsible for the development and operation of JunoCam, an outreach camera that will involve the public in planning images of Jupiter.
Wow – I just checked Planet Four and found that we had passed 70,000 participants; 70,334 to be exact, as of today. Thank you all for your many hours of hard work (and fun!).
To keep our most dedicated folks going we’ve added the first year of Mars Reconnaissance Orbiter operation (Year 1) to the image collection, although we are not quite finished with Year 2 and Year 3. We started with Year 2 and Year 3 mainly because we were much better at picking good locations and configuring the camera properly. Year 1 is a little more challenging, but interestingly the spring was also rather different from that of the subsequent years. Just like on Earth in some years we have more severe winter storms than others.
In this case it appears that there was more frost and ice in Year 1 than Year 2 or 3, but it could also be that it just warmed up earlier in the latter years. So give it your best effort because I think the results will be fascinating.
In the meantime we are busy with our part of the task – digesting all of your measurements and figuring out what they are telling us about Mars. Sometimes I feel like we aren’t holding up our end of the bargain, but then again there are just four of us, and over 70,000 of you!
As you can see from Meg’s post, NASA HQ has taken notice of this effort. I reported on the Planet Four experience at our last HiRISE team meeting and a number of my colleagues were excited about other potential citizen science projects. Go Zooniverse!
Help us understand how Year 1’s weather and climate differs from Year 2 and Year 3 by mapping the fans and blotches on the new never-before-seen images on Planet Four today.
The Planetary Science Subcommittee NASA Advisory Council met at NASA Headquarters earlier this month and was given a status update on all of the research areas in planetary science related to NASA missions. The meeting and the role of the subcommittee is to gather input and report information from the scientific community and public relevant to current and future NASA missions and programs.
At the meeting Lisa May, Lead Program Executive for the Mars Exploration Program, presented on the status of the current and future Mars missions. In her presentation she talked about Planet Four and the work that you’ve all been doing marking the fans and blotches in the HiRES images or as she put it “tens of thousands citizens of planet Earth classify images of spring on Mars” Below is the slide from her talk.
You can read through the entire Mars Exploration Program presentation here.
With the HiRISE images we show on Planet Four, you’re peering down at the Martian surface from above, seeing the fans and blotches that we want you to you mark. What would something like the image below look like from the ground if you were standing on the thawing carbon dioxide ice sheet during the Southern spring?
Well, if the geysers were actively lofting carbon dioxide gas and dust and dirt from below the ice cap up onto the surface and into the Martian air, you’d probably see something like the artist’s conception below.
How high are the plumes? Current estimates suggest that the geysers and material it lofts stay relatively close to the ground going probably no higher than about 50-100m into the air according to previous estimates based on fan length and simple deposition models. Though more likely, the geysers achieve smaller heights than that most of the time. To try and directly measure the geyser plume heights, stereo imaging where Mars Reconnaissance Orbiter pointed at the same spot twice at different look angles has been used. The two resulting HiRISE images are then combined to give height information in much the same way our brains combine the images obtained from our eyes, each viewing at a slightly different angle and position than the other, to get depth perception. HiRISE would have been able to see the geyser plumes above the ground in the combined stereo pairs, if the majority achieved heights of 50-100 m, but no image to date yet has caught a detection of a plume. So that suggests that the geysers may not reach these maximum heights but instead only go up to maybe 5-10m off the ground.
Your clicks may be able to help constrain better the height of the geyser plumes. With your classifications, we will have the largest sample of fan lengths and directions and blotch radii ever measured on the Martian South Pole. With the fan lengths from your markings, a measure of the terrain’s slope, and an assumption for the particle size of the Martian dirt/dust being entrained by the escaping carbon dioxide gas, you can estimate the maximum height needed to loft the material for it to fall at a given distance from the geyser for a range of wind speeds.
Dear citizen scientists!
Back then I promised to get HiRISE to image this scene again when the ice is gone. The image is now here, very fresh from the production pipeline:
I framed this image exactly the same as the original “topic-starter”. This way everybody can see that we are talking about the same feature, as 2 months ago. The ice cover is not completely gone yet: one can still see small persistent leftovers in some shadowed places, mostly in small channels. But ice has cleared the feature in question. It happened to be a crater with an unusual inner surface. As often it is hard to see if it is a cone or a depression, but we know that the sunlight comes from bottom right-ish and this tells us it is a crater. To see it better, here is the best zoom HiRISE has to offer (appr. 30 cm/pix resolution):
Without the ice the crater floor looks smooth and its sides show very pronounced polygons. The ice in the trenches between these polygons created the illusion of a bright branching “crown” in our original image. And smooth blanketing on one side of the crater had smooth ice cover that tricked people into seeing Dalek or octagonal-based chimney. So sorry that neither of those are real!
When I saw the polygons inside the crater, I decided to ask my more knowledgeable colleague about them. Mike Mellon (from Southwest Research Institute in Boulder, CO) did a lot of research about polygons on Mars and Earth. He had a look at both, old and new, HiRISE images for us:
“I can see that there are loads of eroded polygons in the region. There are large ones with clear evidence of subdivision into smaller forms. Smaller polygons cover nearly all the surface (roughly 3 meters in diameter). In some areas they are clear and in others they are so small and flat they are a little hard to see. They are completely invisible at the old image because of its poor resolution. The polygons inside the crater are on the order of 5 meters with more deeply incised troughs, so they are easier to see. The crater floor looks featureless. I see these same larger polygons in the neighboring pits, the pits that appear arrayed N-S. The larger polygon size in the crater may be caused by sun light on the crater slopes.
The presence of polygons and their sizes are consistent with ice cemented soils about 2-5 meters deep. But it is not easy to interpret the details and especially hard to eliminate the seasonal effects from this discussion, as this location is very close to the polar cap and spider-related processes happens here and there.”
With this we came back to where we have started from: fans and spiders. The image made it to this project because it had them all. Now plus polygons, minus the chimney.