Starfish blotches.
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p.titchin
I'm getting puzzled by repeated images of very large blotches which are labelled 'starfish' blotches on HiRISE links. With these are usually lines of small venting along the developing ice fractures- developing linear venting. these are easy to accept with the current sublimation theories, but the pre-existing apparently random giant blotches are harder to explain. Any current thoughts from the experts??
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Kitharode
moderator
in response to p.titchin's comment.
Not being an expert I can't really help with this one. 'Starfish', I would guess, is a spider shape (?). Blotches because there's little wind at the time / in the area.
Yes, you need an expert - MEG, WASSOCK, WHERE ARE YOU? 😉
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wassock
moderator
Think thar they are just blotches, venting with no wind. Thi 'star fish' titles all seem to be from 2007 which I assume was before the term "spiders" had been coined
Still here but have a campsite ful of campers , inti 4th week of 18 hr days so a bit busy. Normal service will resume after the bank holiday
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Kitharode
moderator
in response to wassock's comment.
Thanks Wassock. I'd a feeling you might be busy this time of year - and with a nice summer for a change. Happy Camping.
Your '2007 pre-spider term' idea is interesting. Might be right there. Well spotted.
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Kitharode
moderator
Starfish feature unfrosted: http://planetfour.org/subjects/standard/5143480cea305267e9002fc1.jpg
HiRise image: http://hirise.lpl.arizona.edu/PSP_004941_0955
Strange territory indeed.
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Portyankina
scientist
Hi!
I think, "starfish" originally referred to the appearance of the multiple "fat" fans originating to different direction from same vents and hence resembling the shape of starfish... At least, this is my own explanation for the name of this region.
Anya
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p.titchin
in response to Portyankina's comment.
Thanks for the comments Anya and Kith, I think I've cracked it. I think the name was applied not to blotches, but to spider channels in the ice where there were 4 or more thin straight radial arms centred on a small 'hub'. The HiRISE from APF00017v6 is titled starfish feature, and the image at the start of the page (PSP_003982_0845) shows several of these in the ice which are tabbed as 'starfish' when you move the curser over them. They look like marine 'Brittle stars' 😃
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Kitharode
moderator
in response to p.titchin's comment.
I think you have it right. Strange little critters, not always easy to spot. The HiRise strip from your link above is most interesting. About a third of the way down the landscape goes 'polygonal'. The channels/cracks appear to be in the surface rather than on the surface and they are very reminiscent of 'linear venting features' in the icelayer.
It seems clear from the image that we're on the polar layered deposits, but I haven't checked that. http://hirise-pds.lpl.arizona.edu/PDS/EXTRAS/RDR/PSP/ORB_003300_003399/PSP_003345_0955/PSP_003345_0955_RGB.NOMAP.browse.jpg
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p.titchin
in response to Kitharode's comment.
Good polygons. See what you mean about cracks. It's interesting to see the way they evolve as you go down the strip. The strip is centred on lat 84.466. If you go to the bottom of the strip there are terraced layers, I guess these would fall into the 85_90 degrees lat the edges of the layers seem to be,if so
that would put the rest of the strip on the PLD's.
~PetePosted
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Kitharode
moderator
Angi60 has this in her 'recent' markings. Pretty much next door to the previous image. The HiRise page is titled 'Starfish-shaped blotches', suggesting that the blotches are shaped like starfish, which they are not. Some of the small 'starfish' channels are visible in the image and I think the title should probably read 'Starfish-shaped spider blotches'.
At 84 S and 242 E we are firmly on the SPLD's. I would suggest these are visible lower down in the HiRise image (running left to right) about one fifth up from the bottom. However, near the top of the image there is a strong 'top to bottom' alignment of blotches and fans. I've no idea if any of that is important or relevant, but there you go.
I've brought the image here because of the polygonal cracking that's going on. Definately one for students of Aquatic-Arachnids. * 😃 *
Angi's Polygons http://planetfour.org/subjects/standard/5143480cea305267e900269e.jpg
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p.titchin
in response to Kitharode's comment.
I also got an image for classifying yesterday , Hi RISE marked 'Starfish Blotches', I think,like me,some scientists have been confused by the nomenclature. 1, starfish shaped ice cracks, and 2. multi direction fans ( look nothing like starfish). I think some like me misunderstood the first description, because the blotches are obvious, the ice 'starfish' hard to see. Now the term seems to have been used,by those who didn't see the ice starfish, on blotches. Confusing. I can't see the reason to apply them to the blotches, maybe jellyfish, or amoeba blotches would be more understandable! The ice brittle stars win it for me!! By the by, on the subject of ' confusion', I'm trying to mark my own observations on the Mars map, so, East/West? As an old member of the Royal Institute of Navigation, what meridian is being taken for the start of measuring 'east'. Clockwise or anticlockwise doesnt matter, but I need a start. Thank goodness latitude is easy!
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Kitharode
moderator
Hahaha, yes latitude is easy. Here's what I think I know 😛
There is no universal agreement on which way the numbers run on the polar lat/long map. Many/most of the maps on here run 0-360 deg Clockwise (East). 90 deg is at '3 o'clock'. Anya's recent 'spider map', amongst many others, runs 0-360 deg Anti-clockwise (West). 90 deg is at '9 o'clock'. Both these systems can be, or are being used today. Hence, when meeting a new map the first thing I check is the 'numbers direction'.
So, directions East run clockwise and directions West run counter clockwise in both systems, even if the numbers do the opposite.
Anya's map is numbered 0-360 deg West (anti-clockwise), but we can refer to a location as say, 90deg East, at '3 o'clock' on that map.
I'll finish as I started: That's what I think I know. 😉
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Kitharode
moderator
PS: 'Equatorially' the prime meridian runs through crater Airey-0. http://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/MOLA_airy.jpg/275px-MOLA_airy.jpg
Beyond me, but seems relevant: http://pweb.jps.net/~gangale3/other/allison3_frm.htm
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p.titchin
in response to Kitharode's comment.
Thanks Kith, very helpful links, ! The prime meridian is the thing!, with that I can spot any different conventions when I see a map. Would seem to be long enough now for the same hymn sheet to have been issued!
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Kitharode
moderator
It'll definately have to be sorted by the time manned missions go to Mars for sure. Might start a new chat elsewhere on this, so we don't lose sight of the starfish. Whatever the situation, I'm having starfish as channels and blotches as ... blotches.
I think all this is helping out with some of the 'linear venting' images and what goes / doesn't go 'polygonal'. Great stuff.
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p.titchin
in response to Kitharode's comment.
I,m with you. shouldn't be hard to get the language right. I'm off tomorrow single handed on my yacht. Terrible mess if I cant navigate.I hope my soft ware problem is OK by the time I'm back 'on board' ( sorry, I couldn,t resist). I note the angular anomalies and disagreements result in a .002 variation. I'd love to go to Mars, but a launch from earth, and an automated arrival and decent given arc to time variables over the time scale would make me nervous at the moment,I have always been a back seat driver!
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