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NASA Images Suggest Water Still Flows on Mars
dvandorn
post Jan 6 2007, 08:36 AM
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I don't know that the impact rate is enough to cause huge problems for individually pressurized buildings and facilities. On Earth, there are several hundred lightning strikes per second, many of which occur close to buildings and people. And yet, while there is a certain amount of damage (mostly to trees) from lightning strikes every year, rather few people are injured or killed by lightning each year.

Now, compare the frequency of lightning strikes to the frequency of impacts on Mars, and factor in the percentage of those which are large enough (those that make craters of, say, 100m or more in size) to blast you even if they don't hit you directly, vs. those which create craters of only 10 or so meters or less in size (which could land 100 meters away and not damage your habitat), and I bet you're far less likely to get hit by a meteor, or have your domicile destroyed by a close impact, on Mars than it's likely you would get hit by lightning on Earth.

Also, look at the number of pieces of the space shuttle Columbia which fell onto a couple of towns in Texas. Out of all of those pieces, very few actually hit buildings, and *none* hit any human beings. Heck, I don't think there were any documented cases of any pieces hitting any animals, even. So, you can drop a good number of objects onto a fairly densely populated area without actually hitting anyone.

Now, I grant you, if you built big transparent pressure domes on Mars, you'd increase the probability of a meteor causing a depressurization event... but I'd bet you're not going to see anything beyond relatively small metal tubes in Martian colonial building styles for quite a while... smile.gif

-the other Doug


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Guest_AlexBlackwell_*
post Jan 9 2007, 04:39 PM
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Did anyone happen to listen to this Planetary Radio broadcast? I did and discovered a couple of things for first time during the Huntress interview:

1. MGS was the first spacecraft to use aerobraking, not Magellan.
2. THEMIS was an MGS payload and not, as I always suspected, on 2001 Mars Odyssey.
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djellison
post Jan 9 2007, 05:09 PM
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Yeah - I spotted that...I put it down to misscommunication between Wes and Matt.

Doug
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Guest_AlexBlackwell_*
post Jan 9 2007, 05:31 PM
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QUOTE (djellison @ Jan 9 2007, 07:09 AM) *
Yeah - I spotted that...I put it down to misscommunication between Wes and Matt.

Undoubtedly, and poor THEMIS. It and 2001 Mars Odyssey get no respect, except as a workhorse relay for MER. I remember when Christensen was a guest several weeks ago, when during the intro THEMIS was assigned to Mars Express (an error which was corrected in the next broadcast).

Aside from that, though, this latest broadcast and Huntress's whole discussion of water on Mars (and even the brief discussion of the new crater results) had a strange tilt to it, at least to me. I guess following Christensen and Edgett and their ultra-precise descriptions of the latest science results has its drawbacks.

This post has been edited by AlexBlackwell: Jan 9 2007, 05:32 PM
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Greg Hullender
post Jan 9 2007, 06:32 PM
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Meteor strikes on Earth aren't unheard of.

http://astro.wsu.edu/worthey/astro/html/im...or/strikes.html

Mrs. Hodges apparently never completely recovered from being hit by one.

--Greg
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climber
post Jan 9 2007, 07:59 PM
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QUOTE (AlexBlackwell @ Jan 9 2007, 05:39 PM) *
Did anyone happen to listen to this Planetary Radio broadcast? I did and discovered a couple of things for first time during the Huntress interview:
1. MGS was the first spacecraft to use aerobraking, not Magellan.
2. THEMIS was an MGS payload and not, as I always suspected, on 2001 Mars Odyssey.


I guess he considers Magellan aerobraking as a test, which, IIRC, it was at the origin since aerobraking was not used to get to primer orbit. May be not that accurate but far from the BBC's stuff.


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Guest_AlexBlackwell_*
post Feb 21 2007, 01:38 AM
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QUOTE (AlexBlackwell @ Dec 8 2006, 10:35 AM) *
Thanks, Tim. Is this figure from the paper "Evidence for aqueous deposition of hematite and sulfate-rich light-toned layered deposits in Aureum and Iani Chaos," which you and A. Deanne Rogers have submitted to JGR-Planets?

I just noticed that a preprint of this paper is now available (2.5 Mb PDF).
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Guest_AlexBlackwell_*
post May 30 2007, 06:16 PM
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QUOTE (AlexBlackwell @ Feb 20 2007, 03:38 PM) *
I just noticed that a preprint of this paper is now available (2.5 Mb PDF).

FYI, the final version of this paper should be published online tomorrow in JGR-Planets.
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marsbug
post Aug 30 2007, 01:36 PM
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Sorry to resurrect a long dormant thread but it seems like the best place to ask this question: In the planetary society blog Doug reported on a hypothesis that bacteria on mars could survive by using an intracellular fluid of water mixed with hydrogen peroxide. As an idea this makes some sense as at atmospheric pressure at least (I've not been able to locate a temperature-pressure curve for H2O2) a 60%-40% H2O2-H2O mix has a boiling point of 120 deg C and a freezing point of -50 degC. In other words its stable over nearly twice the temperature range of water. So (finally gets to the point) has it been considered anywhere that the liquid flowing down the gullies could be bleach? Google hasn't thrown up anything on the idea, although it has been convincingly argued that H2O2 could be produced in the martian atmosphere during storms and be coating the surface.


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djellison
post Aug 30 2007, 02:08 PM
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QUOTE (marsbug @ Aug 30 2007, 02:36 PM) *
a 60%-40% H2O2-H2O mix has a boiling point of 120 deg C and a freezing point of -50 degC.


And at 6 mbar? That's the crucial point. You can mix all sorts of things with water to change the boiling point and freezing point - H2O2 is one of the more unpleasent ways of doing it - particularly on the UV soaked surface of Mars.

Doug
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ugordan
post Aug 30 2007, 02:13 PM
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Not to mention the required quantities of H2O2 for the gullies. We'd be past talking about minute amounts but really significant quantities.


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marsbug
post Aug 30 2007, 02:48 PM
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Both good objections! I suppose if the peroxide is produced during storms, and has been doing so for a long time it could have reached quite high concentrations in some regions, mixed in with soil and ice. As to the question of how it behaves at 6mbar thats up in the air (pardon my bad pun), I can't find anything on it. Theres no reason to supppose hydrogen peroxide over any other possible candidate, other than the argument for its production on mars has already been put foward in detail. Personally I'd favour H2O2, or something like, as 'antifreeze' for the gully water over salts ,which are frequently suggested, because it lowers the freezing point by an extra 30 degC, which would make high latitude polar gullies easier for me to accept as water related. I've not done any legwork on the idea, it just caught my imagination. I'll do some more digging and see if I can come up with some numbers. smile.gif


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tty
post Aug 30 2007, 06:08 PM
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If - and it's a very big if - there are appreciable quantities of H2O2 on Mars it could have important consequences for future exploration if it could be extracted. H2O2 at high concentration decomposes catalytically into H2O and O2 at fairly high temperatures. Imagine having a steam turbine that also produces water and oxygen!
H202 is even a fairly good rocket monopropellant as the germans demonstrated with Me163B.
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paxdan
post Aug 30 2007, 06:41 PM
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QUOTE (djellison @ Aug 30 2007, 03:08 PM) *
And at 6 mbar? That's the crucial point.
Doug

Doug i appreciate that the 6 mbar point has been made, and made well with regard to liquid on the surface. However, i wonder how much depth of regolith/permafrost you need before the pressure of overlaying material allows H20, H202 etc to exist as a liquid? Is it 10s of meters or kilometers.

Do we have accurate modelling of the heat flow of hte martian crust to asses this?
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dvandorn
post Aug 31 2007, 03:07 AM
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QUOTE (tty @ Aug 30 2007, 01:08 PM) *
H202 is even a fairly good rocket monopropellant as the germans demonstrated with Me163B.

Also proven by the American Mercury capsule spacecraft. Its reaction control system fuel was H2O2.

-the other Doug


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