Seasonal Processes and Wind Direction on Mars South Pole
Today we have a post from Gauri Sharma who is working on Planet Four this summer as part of the ASIAA Summer Student Program. Today Gauri gives an all overview of her project and the seasonal processes on Mars’ south pole.
My project is on “seasonal processes and wind direction on Mars south pole”, I read about how seasons and winds really taking part on the surface and inside atmosphere of Mars. So, 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.
Currently the rotational period and seasonal cycle on Mars are similar to the Earth, as is the tilt causes the seasons, But scientists do not measures year for Mars in days or month as we measures on Earth. Its calculated by Solar longitude (Ls), when Ls = 180 there is first day of spring on south pole, It’s known as “Martian vernal” equinox too. The seasons on Mars differ from those on Earth, as the atmosphere is much thinner and compromised primarily of carbon dioxide. When winter season comes, one of the poles is fully in darkness and temperatures get low enough that-out 25-30% of atmosphere snows out as carbon dioxide (CO2) ice slabs forming polar ice caps.
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. The temperature on Mars south pole in spring is -78 °C (351K) but dry CO2 triple point is on 7 pascal and -53°C (220 K), So According to thermodynamics when temperature and pressure of any substance is above the triple point sublimation takes place). 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 captured by pressurized gas is brought up the surface of the ice sheet and is blown by the surface wind into a fan shape. When the wind is not strong enough or not blowing, the material is thought to deposit around the geyser source like spot or blotch on the surface At the end of the summer, the ice is gone the fan’s material disappears and blends back in with surface remaining.
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. 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. On this website scientists provides HiRISE images in the form of subimages or what we call tiles. A HiRISE image is ~20,000 × 126,000 pixels and each pixel covers ~0.3m surface of Mars. The image is big so that HiRISE images are diced into tiles that are shown on the Planet Four website. 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.
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 will talk about the rest of my analysis in next blog post. Till then bye…