Boulders and a Planet Four Summer
Today we have the last post from Gauri Sharma who is spent her summer working on Planet Four as part of the ASIAA Summer Student Program. Gauri gave a talk at the end of August detailing her work with boulders and developing a pipeline to find the same position in one Planet Four image in others shown on the site. Below Gauri presents her talk slides and her project. Thanks Gauri for all your help this Summer!
I am gonna introduce you some of the features found on Mars’ South Pole and tools used to study these features. I will also tell quick logical science behind those features according my research in these last two months.
During the winter on South pole a, CO2 ice slab forms over the pole is nearly translucent and ~1m thick. When the ice slab forms, it comprises of frozen carbon dioxide and dust and dirt from the atmosphere. Below the ice sheet is layer of dust and dirt.
When the spring comes sunlight penetrates the CO2 ice slab, and the base of the ice cap gets heated. The temperature of the ice at the base increases causes CO2 sublimation. Sublimation of CO2 creates a trapped pressurized gas bubble beneath the ice layers, These beneath pressurized gas bubbles continuously pushes the upper layers of ice and at one point ice slabs get crack and pressurized gases vent out. A jet like eruption or geyser takes place. It is thought that material (dirt and dust) from below the ice sheet which has been taken by pressurized gas is brought up the surface of the ice sheet and is blown by the surface wind into a fan shape.
When there is enough wind on surface to blown the geysers material fans appears on surface and surface looks like fig1.
If wind is not much effective or not blown then geysers material deposits near the geyser source and a black spot appears on surface called blotches (shown in fig2).
Also during the spring and summer when the geysers are active, the trapped carbon dioxide gas before it breaks out from under the ice sheet is though to slowly remove material and carve channels in the dirt surface. In the mid summer when CO2 fully get vaporized channels are empty cracks. This is annual process of over time produces erosion on surface and channel network looks like spiders (or their official name araneiform).
In every spring and summer season, hundreds of thousands of fans wax and wanes on the Martian South Pole. These features have been captured by then HiRISE camera. HiRISE camera is onboard on Mars reconnaissance orbiter since 2005.
These are the sample images captured by HiRISE camera.
During analyzing of these images, scientists found difficulties, Automated computer routines have not been able to accurately identify and outline the individual feature. But scientists thought a human eye eventually can distinguish and outline these features and shape them. So, A group of scientists created Planet four website purposefully for research on Mars by public help.
This is how, Planet Four website looks like. Working with Planet Four is very easy, just sign up in Planet Four website and take in part of classify shapes on surface. Before getting started they provides a short intro to let you know “How to mark, and useful tools to classify features”. Volunteer classification are collected together and researchers combines these classifications (markings), and they found these markings produces an extremely reliable, fruitful results about features founds on Mars surface.
In slide 10, we seen Planet four images looks different from real images taken by HiRISE camera. Since HiRISE image is huge in size. So for proper analysis and accurate outlining Planet Four team made sub images of HiRISE images and kept them in Planet Four website, we call them tiles.
For my project Planet Four was one of the most important tool. I use Planet Four tiles to examine boulders. Boulders are one of the more interesting objects on Mars surface, and in the South Pole regions monitored by HiRISE only one area seems to have boulders. This region has been dubbed ‘Inca City.’ The boulders in Inca City are likely impact produced. Boulders are Interesting because we think they can help be a heat source of geysers formation. I am looking at how fans are associated with boulders more often than not and has been captured by HiRISE. I studied how surrounding of boulders changes time by time, are they really takes part as the source of geyser formation”.
I chooses some 35 tiles those contains BOULDERS and marked all BOULDERS (shown in fig2). After marking Planet Four provides a makings csv file. That contain your marked BOULDER x and y position and corresponding tile name.
To analysis surrounding of BOULDERS over a time, I need to search over the HiRISE 5year database with the help of markings csv received by Planet Four. Since HiRISE database contain more than 1 lacks tiles. Doing search manually and find useful data and then calculate information, collect belonging files and group them for looking yearly changes seems terrible.
So for this purpose I created a pipeline that can do all this in seconds. This is a very powerful pipeline that Planet Four team doesn’t have before me.
These are the results of my pipelines.
Images in blue box clearly shows, During a season as the month changes surrounding of boulders changes (fans wax and wanes) boulders gets covered with fans material and in next season again boulder start visible.,,,