Why not melt ice? (APOD 12 Jun 2008)
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Why not melt ice? (APOD 12 Jun 2008)
Actually, why not *try* and melt what *may be* ice? ;-)
I note with interest the shinny patch under the Mars polar lander. Today's (08/06/12) APOD says that the hole in that shiny bit is under the landing jet of the lander. I (obviously) have no idea what I'm talking about, but, it occurs to me: why not turn on that jet (gently!--not enough to flip the lander over!) and see if that deforms / melts the hole more? As another test of whether it's ice. (Needless to say, this assumes they can turn that jet back on in a controlled way and that there's fuel....)
Whadaya think?
I note with interest the shinny patch under the Mars polar lander. Today's (08/06/12) APOD says that the hole in that shiny bit is under the landing jet of the lander. I (obviously) have no idea what I'm talking about, but, it occurs to me: why not turn on that jet (gently!--not enough to flip the lander over!) and see if that deforms / melts the hole more? As another test of whether it's ice. (Needless to say, this assumes they can turn that jet back on in a controlled way and that there's fuel....)
Whadaya think?
- orin stepanek
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http://apod.nasa.gov/apod/ap080612.html
Right now they are looking for material in the ice that may be conductive to life. The material they scoop up does go into an oven and I believe that the contents are analyzed. So in a way they do melt the ice. 8)
Orin
Right now they are looking for material in the ice that may be conductive to life. The material they scoop up does go into an oven and I believe that the contents are analyzed. So in a way they do melt the ice. 8)
Orin
Orin
Smile today; tomorrow's another day!
Smile today; tomorrow's another day!
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Yes, but I'm impatient....
That's just so, of course! I guess I was just thinking of a way they could tell, visually, in a short time. Maybe after they've gotten their sample(s) they could blow this to see how't behaves....
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Why didn't ice melt in the first place?
Okay, my stupid question of the day...granted, I was raised in the pulp era of science fiction, but I don't think the melting temperature of water ice has changed much since my day -- if the lander was firing rockets all the way to touchdown, how can there be that much solid ice on the surface directly under it? (If they've invented cool fire, I want to know about that, too -- my cat's favorite perch is on top of my gas stove, and there's a disaster of some sort in the making...)
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Probably not...
...I'm assuming, though, that thruster rockets are somewhat hotter than propane torches and were firing for more than a second or two (else the lander would have gone splat-crunch, yes?) I'm fine with the idea that not all the ice would necessarily have melted -- it just seems odd to me that there would be such a large patch of unmelted ice right under a thruster. (Perhaps it has to do with the extremely cold (by terrestrial standards) temperatures? -- I know that glacier ice melts more slowly than "normal" ice, but I don't know how much of that has to do with temperature and how much with pressure.)
The jets fired only up to a point above the surface, and the legs attached to the lander were built to sustain a medium jolt from landing after the jets were cut-off just above the site. I'm thinking about a 3-4 foot drop maybe?
Saw a program last night showing the different testing phases, and it showed what the jets looked like (about 12 pulsating jets that weren't one continual blast) and how the legs stood up to test landing drops on surfaces much harder than what the martian soil looks like.
Get that oven going and give me my cookies dammit! =b
hold the martian blueberries.... =/
Saw a program last night showing the different testing phases, and it showed what the jets looked like (about 12 pulsating jets that weren't one continual blast) and how the legs stood up to test landing drops on surfaces much harder than what the martian soil looks like.
Get that oven going and give me my cookies dammit! =b
hold the martian blueberries.... =/
- iamlucky13
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Arramon, I think I watched the same program. Discovery channel?
Yes, the jets cut off about 1 meter above the ground. I don't think the jets they showed in the program up close were actually burning though. I think that was just an inert liquid being pumped through injectors to test the pulsed modulation system. Anyway, the caption is suggesting that the ice we think we see there isn't unmelted. Those two shallow holes are likely caused by the thrusters.
The don't want to fire the jets directly on the surface because the debris kicked up by the backblast could damage something, especially now that none of it is in it's protected landing positions. Also, there's probably not much fuel left, and there's no instrument designed to observe whatever might be kicked up. Basically all you would get out of it is a before and after photo. Not much return for the effort and risk when they can just wait a few more days and probably find the same thing with the shovel a few feet away.
Yes, the jets cut off about 1 meter above the ground. I don't think the jets they showed in the program up close were actually burning though. I think that was just an inert liquid being pumped through injectors to test the pulsed modulation system. Anyway, the caption is suggesting that the ice we think we see there isn't unmelted. Those two shallow holes are likely caused by the thrusters.
The don't want to fire the jets directly on the surface because the debris kicked up by the backblast could damage something, especially now that none of it is in it's protected landing positions. Also, there's probably not much fuel left, and there's no instrument designed to observe whatever might be kicked up. Basically all you would get out of it is a before and after photo. Not much return for the effort and risk when they can just wait a few more days and probably find the same thing with the shovel a few feet away.
"Any man whose errors take ten years to correct is quite a man." ~J. Robert Oppenheimer (speaking about Albert Einstein)
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June 12 Mars lander photo
June 12 Mars Lander photo .. http://antwrp.gsfc.nasa.gov/apod/ap080612.html
Those cones in the ice (or perhaps it's rock, but probably ice) are, if the photo is showing proper orientations, angled the wrong way to have been melted by the landing rockets' flames. I suspect they are vents .. and perhaps it's my imagination but is that a little hole at the base of one of the vents? The description says the cones are below the rockets, but that must be coincidence unless the picture was pieced together wrong.
Those cones in the ice (or perhaps it's rock, but probably ice) are, if the photo is showing proper orientations, angled the wrong way to have been melted by the landing rockets' flames. I suspect they are vents .. and perhaps it's my imagination but is that a little hole at the base of one of the vents? The description says the cones are below the rockets, but that must be coincidence unless the picture was pieced together wrong.
If man were made to fly he wouldn't need alcohol .. lots and lots and lots of alcohol to get through the furors while maintaining the fervors.
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06/12/08 Mars Lander Photo
Hello All,
Some thoughts........
1) Ice was melted by the thruster from a larger, shallower area at first and then, as the heat became more concentrated the closer it got, a deeper, more pin-pointed melting occurred which forced water out of the cone and onto the surrounding area to spread and refreeze.
2) The ice is very thin on top of a silica layer (the wavy edge is interesting).
3) PICK UP THAT SPRING AND PUT IT IN YOUR POCKET!!!!!! It would be an unprecedented gesture to not litter someone's/something's extraterrestrial home and set the tone for future visits. In which case, if we get domiciled there, maybe we'll take out more than we bring in. And the younger generations should watch us do it, too.
Some thoughts........
1) Ice was melted by the thruster from a larger, shallower area at first and then, as the heat became more concentrated the closer it got, a deeper, more pin-pointed melting occurred which forced water out of the cone and onto the surrounding area to spread and refreeze.
2) The ice is very thin on top of a silica layer (the wavy edge is interesting).
3) PICK UP THAT SPRING AND PUT IT IN YOUR POCKET!!!!!! It would be an unprecedented gesture to not litter someone's/something's extraterrestrial home and set the tone for future visits. In which case, if we get domiciled there, maybe we'll take out more than we bring in. And the younger generations should watch us do it, too.
"Everything matters.....So may the facts be with you"-astrolabe
Ummm... for water ice to melt at 0 degrees C doesn't the atmospheric pressure have to be 1 Atm? How would the very low pressure of the Martian atmosphere affect the melting point of water ice? And can this thin atmosphere conduct heat very well? Just wondering.
Evil and brief hath been my pilgrimage....
cgb wrote:Ummm... for water ice to melt at 0 degrees C doesn't the atmospheric pressure have to be 1 Atm? How would the very low pressure of the Martian atmosphere affect the melting point of water ice?
![Image](http://www.isa.org/Images/InTech/2003/April/20030408.gif)
Not much. Liquid water can only exist above the triple point temperature and above the triple point pressure (610 Pa). As you can see, ice does not have to be heated up to 0 C to be converted into water vapour: from red to blue in the image (recognizing colours is not my strongest asset). This process is called sublimation and is not shown in the image.
Conductivity of gasses becomes an issue at very low pressures, when a gas is so thin, it is called a Knudsen gas. Of the order of μPa. Heat transfer through the Martian atmosphere is mainly by convection.cgb wrote:And can this thin atmosphere conduct heat very well?
The pressure at Mars is about 10 mbar. For a spacecraft such an atmosphere is 'thick soup'. It would tumble out of orbit rather soon.
Regards,
Henk
21 cm: the universal wavelength of hydrogen
Henk
21 cm: the universal wavelength of hydrogen
Re: 06/12/08 Mars Lander Photo
You wouldn't get water. Ice on the martian surface goes directly to gas form, like dry ice (frozen CO2) does on Earth.astrolabe wrote:Hello All,
Some thoughts........
1) Ice was melted by the thruster from a larger, shallower area at first and then, as the heat became more concentrated the closer it got, a deeper, more pin-pointed melting occurred which forced water out of the cone and onto the surrounding area to spread and refreeze.
Minor correction: Looking at the phase diagram, find the letter "n" in the word "melting". The orange area covered by this label represents liquid water above the triple-point pressure but below the triple-point temperature.henk21cm wrote:Liquid water can only exist above the triple point temperature and above the triple point pressure.
Higher pressure means a lower freezing/melting point.
Phase diagram of water: melting line has a negative slope
Yes, you are correct. The slope of the solid-liquid equilibrium line is slightly negative: about -0.1 K/MPa, until about 210 MPa (i.e. 2100 bar). See http://www.lsbu.ac.uk/water/explan2.html#Pmelt and find out that the line is not straight, but slightly curved. For Martian conditions neglible. So i do not expect liquid water under natural conditions at the landing site of Phoenix. Pressures and temperatures are far beyond the possibilities as indicated in the phase diagram.apodman wrote: Minor correction: Looking at the phase diagram, find the letter "n" in the word "melting". The orange area covered by this label represents liquid water above the triple-point pressure but below the triple-point temperature.
Higher pressure means a lower freezing/melting point.
The first image of http://www.lsbu.ac.uk/water/phase.html shows a nice piece of linking. By clicking on one of the lines in the phase diagram you are transfered to the appropriate section.
Regards,
Henk
21 cm: the universal wavelength of hydrogen
Henk
21 cm: the universal wavelength of hydrogen