FAQ - Check here first
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by
wassock
moderator
Hi we are going to try to gather together all the commonly asked questions and stick them here at the top of this board. This thread will be locked so that the information doesn't get buried as the number of posts grows.
If your question isn't answered here then please open a new thread on the main help board and we'll do our best to find the answer for you.
Work in progress at the moment so please bear with us while we get it sorted.
Frequently Asked Questions from the FAQ
What are all these black blobs?
These are the point of this exercise, which is to measure them and try to gauge wind speed and direction from the measurements. In most of the images you will see, the surface is covered in a layer of carbon dioxide ice and in some places CO2 gas escapes from beneath this ice layer and carries dust with it. Where there is a wind the dust is blown by it and forms a characteristic fan shape on the surface, if there's no wind the dust settles around the point is comes out from to form a round(ish) blob of blotch.
There are more details about this process here http://planetfour.org/#/about and there’s lots more background information in the Blog http://blog.planetfour.org/What is the Scale of the images?
There is some variation but for the most part the images you are looking at are around 200 metres across, occasionally you'll see a picture which is twice that and there are some odd ones at different scales. The smallest object that is resolved in the images is between 1 and 2 meters, often referred to as ‘dining table’ size.
This object APF00009ju can be seen in this larger image from HiRise http://hirise-pds.lpl.arizona.edu/PDS/EXTRAS/RDR/ESP/ORB_011300_011399/ESP_011348_0950/ESP_011348_0950_RED.abrowse.jpg
Which does include a scale at the top – the width of this strip is about 5.2 km and the feature can be found about 2/5 of the way down as a bright dot in the middle.Where do the images come from?
The images are from near the South Pole of Mars in areas where an ice (carbon dioxide) layer forms during the winter months and then slowly thaws during the Martian spring.
Is this feature a hill or a valley?
The images are all presented ‘upside down’ so that North is at the bottom and the sunshine usually comes from the bottom right of the picture. This makes most people view the images such that they see hills as depressions and vice versa. The features you will see, known as ‘spiders’ and looking like a network of waterways or a root system, are channels in the surface of Mars. It is thought that these have been made by the movement of gas and dust beneath the ice layer. More detail on this can be found in the Blog
What are those wiggly ridges/channels/veins? Are they rivers/river deltas?
Those wiggly line structure are actually troughs in the Martin surface. Several of these troughs that converge to one central point are called spiders (or araneiforms). But sometimes they randomly cover area (lace terrain) or form something like polygonal terrain. The troughs are carved by carbon dioxide gas, not liquid water, as one could first think from their appearance. It is too cold in this areas for liquid water, about -123C. More details on the process of troughs formation is here http://planetfour.org/#/about and also here http://blog.planetfour.org/
There is a lot of water on Mars but most of it remains frozen at the poles. The ice layer which forms each year is made of Carbon Dioxide, but because the pressure on Mars is so low, this can’t exist as a liquid and when the ice thaws it sublimes directly from solid to gas. Liquid water is thought to have not existed on the surface for 2 to 3 billion years and whilst features formed by liquid water are still visible it is thought that the spiders are caused by the action of subliming gas beneath the annual ice layer.
What are these bright red/blue/green patches/dots/lines? Why is this image totally GREEN?
The color images are combinations of 3 color filters, and their appearance is nowhere close to the realistic color. Usually they are stretched to highlight the interesting features best. This leads to some images being greener, others - redder. If you see just a green stripe or bright red dot or strikingly blue smudge - that likely means that there is data missing in the other filters. For example, sometimes you'll see half of the image being plain green - this means data from the red filter is missing. When whole image appears dark red - blue filter is missing. These are tiny technical glitches.
What are the bright/white/blue fans?
These blue fans are fresh CO2 crystals that are either 1) got exposed while dark dust sinks through CO2 ice layer or 2) recently condensed on top of dust. We still do not know which one is the right answer. you can see more on this in our blog here: http://blog.planetfour.org
I Keep seeing images with parallel lines in them, what causes this?
These are thought to be systems of ridges, called yardangs, caused by the action of wind, there's more information about these in the Blog
Deja Vu - I'm sure I've seen this before
The images come from several different dates and so you may see the same area more than once, but from a different time in the year or even from a different year. Some features also get repeated to ensure that things which fall on the edge of one image are visible in another.
What are these bright circular features at the sources of fans? Are they craters?
These a boulders. They stick out of the ice layer and get warm faster than the ice around them. Only the ice that directly touches them starts to sublime, this is how the fans tend to develop starting at those boulders.
Why are 'The Objects' on all three Boards?
It's a method for sorting discussions. When marking the fans and blotches on the Classify page, you will meet objects you want to discuss. After marking, press 'Finish'. You can go to 'Next' image or you can 'Discuss' the image you have marked. Before posting your discussion you will need to choose whether it goes onto Help, Chat, or Science. Whichever one you choose is the place you will find it on the Boards. You can't get it wrong, just take your best guess and it'll be fine.
If I 'Compose Message' do I have a Mailbox?
Yes. The left hand column of your 'Profile' page is your mailbox. When you compose and post a message it will appear at the bottom of your list. When you receive a reply the message jumps to the top of your list with a black dot beside it.
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