By Matthew Cobb
I have been spending quite some time recently helping scientists study the spiders of Mars. Not Ziggy Stardust’s band, nor, sadly, actual spiders, but strange geological formations in the Martian Antarctic.
And above all these:
Over at planetfour.org they have put millions of these images on line, obtained from the HiRISE (High Resolution Imageing Science Experiment) camera aboard the Mars Reconnaissance Orbiter, which has been mapping the surface of Mars with a 0.3 metre resolution. That means each of those pictures is about the size of two football pitches (of whatever kind – soccer, American or rubgy).
The planetfour folk are using the power of the crowd to scan those photos in a way that computers could not do, and to track the patterns of the blotches and fans you can see in the third image, plus anything else weird and wonderful, like you can see in the first two. As I write, nearly 50,000 people have been involved since the sit went live less than a week ago, and over 2 million images have been classified.
In the winter, the icy surface of the Martian Antarctic is covered with ‘spiders’, strange wiggly channels. As the Martian spring begins, the CO2 ice over the ‘spider’ melts, and the area becomes peppered with strange dark fans and blotches. This picture shows a timelapse sequence of a spider that was initially covered with a 1 metre of CO2 ice (top left) to ice-free (lower right):
Here’s an image of some fans in the northern polar region, with useful scale bar (taken from Portyankina et al, in press).
Sometimes there can be loads of fans in a given area (in fact, that’s what you can see in the first image at the top of the page – the “quilted”, brain-like appearance is an illusion, as your brain interprets a 2-D structure in 3-D).
The team think that the fans are produced by the sudden eruption of geysers of gas bursting through the melting CO2 ice, bringing with it all sorts of debris. That’s why the fans have a clear point of origin. The wind blows the debris, which explains why in many images the fans are pointing in the same direction. If there isn’t any wind, then you get a blotch.
Here’s a series of images from the website illustrating what they think is happening.
Here’s a dramatic artist’s impression of what happens when the geysers erupt (you wouldn’t want to be wandering about on Mars when this was happening):
An Artist’s conception of sediment-laden jets that shoot into the polar sky from the south polar ice cap as southern spring begins. CREDIT: Ron Miller/Arizona State University
Here’s an image from planetfour.org which some of the people on the site think is a geyser erupting:
[EDIT: It turns out the sun is coming from the bottom right, so this is a crater, not a dome. As one of the scientists has said in a blog discussion: "sun comes from the low-low right, therefore we believe this is a negative feature (crater-like). don't understand it yet,definit. weird"]
What the PlanetFour folk want us to do is to classify the features on these millions of images, using one of three tools (‘fan’, ‘blotch’ or ‘interesting’). Here’s a screenshot, showing a picture of massive fans on the icy surface that they just asked me to classify, along with the simple tool interface on the left.
The outcome of all this will be an accurate measure of the climate on this southern region on Mars, and an idea of how these weird formations occur during the year.
PlanetFour is just one example of the crowd-sourcing being carried out by Zooniverse – if you go to their website you can help in all sorts of project.
Finally, a lot of the impetus for the support for this came from the site’s appearance on the excellent BBC TV programme “Stargazing Live”, which went out on three successive nights on BBC2 last week from the Jodrell Bank raidio telescope at the University of Manchester, and fronted by comedian and Physics/Maths graduate Dara O Briain and by my colleague from the University of Manchester, Professor Brian Cox (I could be spotted in the audience on the first night…). Those of you in the UK can watch again on the BBC iPlayer by clicking on the link above. Episodes from previous years can be found on YouTube.
Anyway, you should all go over to planetfour.org, sign up, classify some images and DO SOME SCIENCE!
You can find out more about Martian spiders here.
Ganna Portyankinaa, Antoine Pommerola, Klaus-Michael Ayea, Candice J. Hansenb, Nicolas Thomasa (In Press) Observations of the northern seasonal polar cap on Mars II: HiRISE photometric analysis of evolution of northern polar dunes in spring. Icarus.