Starship Asterisk*

Okay, so I've come to believe water[ice currently] is much more prevalent on Mars than ever thought. Not only do we land atop it, but the [url=http://antwrp.gsfc.nasa.gov/apod/ap080723.html][color=blue][u]July 8 APOD[/u][/color][/url] looks to me to have a floor of water vs the lava speculated. There is [url=http://asterisk.apod.com/viewtopic.php?t=14334][color=blue][u]APOD discussion[/u][/color][/url] (you'll have to skim over all the posts concerning optical coloration); but I can't, having been a commercial crab fisherman in the Aleutians, escape the similarity those cracks in the smooth valley floor have in common with Arctic ice leads which open in the Spring and Summer only to refreeze in the Fall.

I wish we could do some experiments with water and see how fast it sublimates in shade versus full sun at the poles and equator. And additionally how much of the reflective, insulating soil is necessary to eliminate the sublimation.

Mars has become a much more interesting planet than originally envisioned.

you're right..they will likely not risk the camera going under the lander but since the image of the lander leg was taken by that same camera, they could take another image from the same location of the same location and see if the debris is still there

Wow...I didn't hear this before. Is the splashing confirmed by NASA anywhere?

The is a camera on the robotic arm. It is not a microscope, but it can focuse pretty close. However, it can not operate underneath the lander, or at least the operators will not risk moving it around under the lander.

Okay, it seems that the strut was splashed with some of the water melted from "Ice Queen"
when landing. It appears to have frozen as it splattered onto the strut and frozen as shown in

[img]http://antwrp.gsfc.nasa.gov/apod/image/0806/whitepatch_phoenix.jpg[/img]

I wonder, after the recent ice sublimation in the scoop hole, if this strut ice had also sublimated.

And isn't sublimation better than distillation in concentrating solutes?

What kind of instruments are available on this lander? Any microscopes?

[quote="iampete"]Actually, I was thinking more along the lines of clumps of dust/dirt, rather than pebbles. [/quote]

Pete, that can not be excluded. Note that the objects on the strut are lighter than the surrounding soil, in the shade. (125,90) has a pixel value of 122, the soil just below has values of 50 to 60. If any dirt, it must be white dirt.

[quote="iampete"]is it credible to think that in the final few deciseconds prior to thruster shutdown, there exists a swirl of dust/soil particles and melted water droplets under the lander? [/quote]

The melted water droplets must have a Martian origin, since hydrazine produces no [url=http://www.jpl.nasa.gov/news/press_kits/phoenix-landing.pdf]water vapour[/url]. On Phoenix there is no oxygen on board to oxydize the hydrazine. It is not necessary.

[quote="iampete"]This re-freezing would not be extremely quick, since even after thruster shutdown, the radiative heat from the thrusters themselves would take some time to dissipate.[/quote]

When water freezes on a surface, there are two forms of apparition:
[list]Slow freezing produces transparent ice.
Quick freezing, as when sprinkling water droplets on a tube, just being dipped in liquid nitrogen (77 K), produces white ice.[/list]
The latter form is more likely, when looking at the brightness information in the [url=http://www.jpl.nasa.gov/images/phoenix/collection_16/under-full.jpg]image[/url].

[quote="Bad Buoys"]And there seems to have been slight horizontal movement of the craft at touchdown. In the far blast exposure there seems to be a very small amount of soil disturbed by the pad and rolling down ending atop all else. So the engines must have been shut down just prior to touchdown.

And while two thrusters appear flared, the nearest seems to be in some degree of focus.[/quote]

Indeed, the Phoenix team has stated that there was a slight horizontal motion at the time of touchdown and the lander "slid" a few inches, and the engines shut down a few feet above the ground to reduce the amount of debris kicked up to where it could land on the deck. The legs were designed to absorb the shock of hitting the ground at a few feet/second.

I'm undecided if the 3rd thruster didn't flare as much, the soil consistency was slightly different (perhaps it was aligned over the edge of a polygonal trough), or the arm is too far underneath the craft to see a similar bare area. Perhaps "Snow Queen" is the third bare patch? I haven't taken a thorough look over the images for a couple days to get a sense of the position of these features.

If the white stuff is rock the depressions will without question be 'potholes' common on earth - carved by water current using a small, hard stone or stones to grind the depression. If the white stuff is rock that means Phoenix landed on an extinct riverbed or lakeshore. Has the white stuff's composition been determined yet?

I see now that this coding is put in automatically if I use the "Reply With Quote" button adjoining the author's submission. I never looked.

Eureka!

This was not indicated in the mouseover examples on my system.

Thank you all.

[quote="apodman"]like this?[/quote]

[quote="apodman"]how do I put...[/quote]

Okay, I got that far on my own.

My question is, how do I put the author's name where the word "Quote" is?

[quote]This is only a test. Thanks B.B. Sorry everyone for using this actual forum for training.[/quote]

[quote="henk21cm"] . . . But why does this dust stick to the tubes? A rounded pebble lying on a round tube is in a very unstable position. To put this to the test, tilt a broomstick to the wall an drop randomly some pebbles on the broomstick. Do they stick on the broomstick? You may try a meter of rain drain pipe as well.

Moreover there are some protruding objects at the side of the tube. Those should have been falling down. . . [/quote]

Actually, I was thinking more along the lines of clumps of dust/dirt, rather than pebbles.

Your analysis of the potential for melting of ice leads me to consider another mechanism: is it credible to think that in the final few deciseconds prior to thruster shutdown, there exists a swirl of dust/soil particles and melted water droplets under the lander? When the thrusters shut down and things start to settle, some of the water droplets mixed with the dust settle on the leg surfaces as well. In the absence of heat from the thruster plumes, the water (mixed with the dust) would re-freeze and "stick" on the structure. This re-freezing would not be extremely quick, since even after thruster shutdown, the radiative heat from the thrusters themselves would take some time to dissipate.

[quote="iampete"]

The decomposition of hydrazine is highly exothermic (per Wikipedia, combustion chamber temperatures hit ~800 C) and produces large volumes of hot gas. Would it not be reasonable to expect that exposure to the plumes even of a second or less (assuming the plumes are at least a meter or two in length just prior to touchdown) would have created some visible deformation/sculpting/whatever to the patches if they were in fact ice? [/quote]

Pete, that is quite possible. You write the exhaust gasses are hot (1000K in the combustion chamber) and they have a large volume. I have to estimate the volume and its pressure. Well, estimate, it is rather a wild guess. Suppose 1 m³ of hot gas at 100 kPa pressure comes free during the last few seconds. Since the temperature is high, the mass of the exhaust is smaller than at 273K. Roughly four times smaller: 0.25 kg.

Specific heat of ice at 200 K is 1.5kJ/kg/K
Specific heat of nitrogen gas at 500 K is 1 kJ/kg/K.
Melting heat of ice: 240 kJ/kg

So solve the equation:

Cooling the hot gas - heating up and melting ice = 0, or:

0.25 * 1 * (1000-273) + x * ( 1.5 * (150-273) - 240) = 0. This leads to:

x = 0.25 * 737 / (240 + 185) = 0.45 kg

(mass * specific heat * temperature difference = heat)

Half a liter of water! Feasible, when one looks at the size of the holes in the soil.

[img]http://www.jpl.nasa.gov/images/phoenix/collection_16/phx20080601b.jpg[/img]

It is better to flip the image upside down, it looks a bit more logical. My impression of the size of the holes: roughly 0.1m wide and 0.1m deep. However, there is no reference other than some pebbles near the hole.

Concluding: the amount of ice to melt is of an order of magnitude comparable to the potential size of the holes. It is neither 1000 larger nor 1000 times smaller. So melting can not be excluded, however it is not proven that the melting hypothesis is true. We need more accurate volumes and pressures of the exhaust gasses. Thats an item to be dealt with by NASA's rocket scientists.

About the 'barnacles':
[quote="iampete"]My gut feel is that that is unlikely. Thruster shutdown likely takes on the order of tens, possibly a few hundred, of milliseconds and the amount of non-decomposed hydrazine is probably miniscule as the thruster temperature still remains high.

It is more likely to be soil that was displaced by either the plumes and/or the shock of actual landing that, in falling back down, happened to stick to the structure. [/quote]

You are right about the trusters. Shut those down immediatedly, if you want an undisturbed site! But why does this dust stick to the tubes? A rounded pebble lying on a round tube is in a very unstable position. To put this to the test, tilt a broomstick to the wall an drop randomly some pebbles on the broomstick. Do they stick on the broomstick? You may try a meter of rain drain pipe as well.

Moreover there are some protruding objects at the side of the tube. Those should have been falling down. These object can not be seen on the other legs, most likely due to the limited resolution of the jpg and its lossy compression. I hope to stumble over a lossless image, like TIFF or png. Maybe something for an APOD in the near future?

Note: I had to edit this message due to a silly error. Where i had [i]heat capacity[/i] written, it should have been [i]specific heat[/i]. That has been corrected now.

I had not seen the photos of what looks like thruster-dug pigs before posting .. but if they were thruster dug wouldn't the caption have included that information? In any case .. hey .. does anyone want to form a partnership for Martian ice mining .. how about $100,000 per ice cube to cool a Billionaire's vodka?

Another factor in all this which has been mentioned in the forum is that ice will melt at different temperatures according to composition. A World War Two effort involved building transport ships out of ice using water mixed with sawdust. I think the sawdust ice melted 10 times slower.

The chances of the craft landing atop ice would be, I estimate, 100% .. because it is close the North Pole and the pole's icecover .. and according to what I consider the best educated guesses based on spectral analysis etc. there are continent-large areas of ice not far beneath the topmost, thin layer of soil even at the equator. I think it more than likely that Mars had continents and oceans, and the oceans evaporated into space only to an extent, before freezing. Then the big volcano blew dust all the over the planet, thinly covering the ice. However, yes, I would have expected ice to have been more deformed by the thrusters, except perhaps considering the sandy soil would be a tremendous insulator, and only the lander's operators know how long the thrusters operated at intimate distances. Does anyone know anyone to ask to determine how long the thrusters would operate between the point the first hot gas touched the surface, and touch down and shut off? perhaps the thrusters shut off even before touchdown, and that would disturb the environmentas little as possible before experiments began. I have to admit I'm so clever to think of these things .. I sure wish I was educated.

Apodman: I also notice you'll see the exact coding which must be typed for my last by clicking on "Quote". That and the mouse-over examples should give you the programming.

Apodman: there are examples to follow as you mouse-over each command [and they only appear when posting]

But there are a couple more interesting items about the [url=http://antwrp.gsfc.nasa.gov/apod/ap080602.html][color=blue][u]APOD image[/u][/color][/url]. Firstly it seems to be too jpg degraded [note the worms frothing the soil in shadow] for too detailed an analysis.

But someone mentioned the scales on the nearest pad strut. And that does appear interesting as I don't see anything similar on other horizontal surfaces.

And there seems to have been slight horizontal movement of the craft at touchdown. In the far blast exposure there seems to be a very small amount of soil disturbed by the pad and rolling down ending atop all else. So the engines must have been shut down just prior to touchdown.

And while two thrusters appear flared, the nearest seems to be in some degree of focus.

JPL has [url=http://www.jpl.nasa.gov/news/phoenix/images.php][color=blue][u]other images[/u][/color][/url] most of which are dealing with the before and afters of Pheonix's first scoop whose contents are also shown.

But there is another ice(?) structure under Pheonix which they've named "Snow Queen". This time I'll try to link the image to the JPL page. See if it works and click on the Snow Queen picture below.
[url=http://www.jpl.nasa.gov/news/phoenix/images.php?fileID=8062][img]http://www.jpl.nasa.gov/images/phoenix/collection_16/phx20080601b-br.jpg[/img][/url]

[quote="ta152h0"]does ice turn to vapor without liquefying first on MARS ? unlike beer here on Earth ?
Pass the beer :D :D :D[/quote]
For the most part, yes. Liquid water can exist on the surface of Mars in a very narrow temperature range, but sublimation would certainly be much more common.

maybe they can jump the beast by firing the thrusters and move to another location, a la Surveyor ?

Hello iamlucky13,

I'm inclined to agree with you on this one; it appears to me that the landing pads are sitting on small berms. Another thing is the area around the far pad looks relatively free of stones that are seen farther out. The rocks may in fact be there but were covered by sand blown aside by the thrusters.

And another apology. Animation wrote "would just be ice under the craft" and I read and repied to "would be ice under the craft", leaving out the meaning added by the critical word "just". Again, sorry. I'm going to stay away from the keyboard until a degree of competence returns.

P.S. If somebody can tell me how to insert a quote or image without hacking it up like I just did, I'd appreciate it. I apparently don't understand the proper use of the formatting tools in the text editor.

[quote="henk21cm"] . . . My conclusion -and hypothesis- is that the white patches are rock, exposed to the sunlight in a dusty environment. Yes, i know, this conclusion may be completely wrong. . .[/quote]

Something to consider that might lend support to your hypothesis:

The decomposition of hydrazine is highly exothermic (per Wikipedia, combustion chamber temperatures hit ~800 C) and produces large volumes of hot gas. Would it not be reasonable to expect that exposure to the plumes even of a second or less (assuming the plumes are at least a meter or two in length just prior to touchdown) would have created some visible deformation/sculpting/whatever to the patches if they were in fact ice? (EDIT: the picture in Bad Buoy's post on the following page exhibits some of the deformation/sculpting/whatever I would expect from an ice chunk exposed to a thruster plume for a short period.)

[quote="henk21cm"] . . .What tickles the imagination are the barnacle shaped protruding objects on the leftmost struct (124, 90). What are those? Lumps of frozen propellant?[/quote]

My gut feel is that that is unlikely. Thruster shutdown likely takes on the order of tens, possibly a few hundred, of milliseconds and the amount of non-decomposed hydrazine is probably miniscule as the thruster temperature still remains high.

It is more likely to be soil that was displaced by either the plumes and/or the shock of actual landing that, in falling back down, happened to stick to the structure. As to why more stuck on that leg than the others, I don't know, but it may have something to do with the fact that it is in the shade and doesn't experience the same thermal influences as the others, which had their collection fall off.