Re: Lunar Mare Brecchia: Massive Bombardment or Formational Impact
George
"z7-x332a" <kevin...@gmail.com> wrote in message
news:1156278291....@h48g2000cwc.googlegroups.com...
> Due to the impossibilityl of a massive bombardment period creating the
> lunar maria all at the same time, I will propose the theory that the
> brecchia used to date these impacts instead show the time of actual
> lunar formation.
>
> The maria are therefore exposed crustal surface, rather than infilled
> impact remnants.
Umm, the problem with that theory is that:
1) The Breccia overlays much of the maria basalt, particularly on the
fringes of the basins;
2) The Breccia would have to be significantly older than the maria basalt,
and I've seen no evidence that this is the case.
3) Your theory poses no reason why massive bombardment cannot occur at or
nealry at the same time.
George
z7-x332a
George wrote:
> "z7-x332a" <kevin...@gmail.com> wrote in message
> news:1156278291....@h48g2000cwc.googlegroups.com...
> > Due to the impossibilityl of a massive bombardment period creating the
> > lunar maria all at the same time, I will propose the theory that the
> > lunar formation.
> >
> > The maria are therefore exposed crustal surface, rather than infilled
> > impact remnants.
>
> Umm, the problem with that theory is that:
>
> 1) The Breccia overlays much of the maria basalt, particularly on the
> fringes of the basins;
There is still the implication that the cause of the basins is also the
source of this breccia.
> 2) The Breccia would have to be significantly older than the maria basalt,
> and I've seen no evidence that this is the case.
Is there evidence that the mare basalt is from a time after the
breccia-causing impact.
> 3) Your theory poses no reason why massive bombardment cannot occur at or
> nealry at the same time.
It just seems statistically impossible. Add to this the science which
proves the impossibility of an infilling event on the scale currently
proposed for the maria basalt, and any new theory has more grounds than
the present one.
George
>
> George wrote:
>> "z7-x332a" <kevin...@gmail.com> wrote in message
>> news:1156278291....@h48g2000cwc.googlegroups.com...
>> > Due to the impossibilityl of a massive bombardment period creating the
>> > lunar maria all at the same time, I will propose the theory that the
>> > breccia used to date these impacts instead show the time of actual
>> > lunar formation.
>> >
>> > The maria are therefore exposed crustal surface, rather than infilled
>> > impact remnants.
>>
>> Umm, the problem with that theory is that:
>>
>> 1) The Breccia overlays much of the maria basalt, particularly on the
>> fringes of the basins;
>
> There is still the implication that the cause of the basins is also the
> source of this breccia.
The maria 'basins' were likely created during the formation of the moon,
while the maria basalts filled those basins soon thereafter. There is
plenty of evidence that the breccia was created during the late bombardment
3.8 billion years ago. The breccia cannot overlay the maria basalt if the
basalt was formed as a result of events which also created the breccia.
Think about this, then get back to me.
>> 2) The Breccia would have to be significantly older than the maria
>> basalt,
>> and I've seen no evidence that this is the case.
>
> Is there evidence that the mare basalt is from a time after the
> breccia-causing impact.
No, the mare basalt formed prior to the breccia-forming events.
>> 3) Your theory poses no reason why massive bombardment cannot occur at
>> or
>> nealry at the same time.
>
> It just seems statistically impossible. Add to this the science which
> proves the impossibility of an infilling event on the scale currently
> proposed for the maria basalt, and any new theory has more grounds than
> the present one.
Umm, what science would that be?
http://www.psrd.hawaii.edu/June00/lunarMaria.html
The lunar maria, the dark, smooth areas on the Moon, formed when lava
flowed across the surface billions of years ago. Samples returned from the
Moon by astronauts and by automated spacecraft suggested that the maria
consist mostly of basalts with either low (less than about 5 wt%) or high
(more than about 9 wt%) contents of titanium dioxide (TiO2). Scientists
wondered why there were so few lava flows with intermediate titanium
concentrations, and they invented some elaborate, interesting explanations.
However, the samples came from only a few places on the Moon. Recently, Tom
Giguere and his colleagues at the University of Hawai'i used data from the
Galileo and Clementine missions to evaluate the compositions of the maria
over the entire lunar globe. Their results show that there are plenty of
lava flows with intermediate amounts of TiO2; in fact, there is a
continuous spectrum of titanium contents from low (most abundant) to high
(least abundant). This gives a different view of the nature of the lunar
interior, and is consistent with the idea that the Moon melted soon after
it formed [forming the maria].
George
z7-x332a
maria? I'd been given that impression in a different group.
I will also post the article about infilling.
My opinion is that, prior to solar ignition the moon was as ice-covered
as Ceres or some of the outer moons and protoplanets. The maria could
thus be explained as shields denoting former polar positions. This
theory would also solve the mystery of the antipodal
magnetosphere/swirls.
z7-x332a
> > proves the impossibility of an infilling event on the scale currently
> > proposed for the maria basalt, and any new theory has more grounds than
> > the present one.
>
> Umm, what science would that be?
Here's a link to an article by Ivanov & Melosh:
In terms of the titanium and so forth, why couldn't those flows have
occurred under a mantle of ice -- during a more malleable period?
If there actually are lunar paleopoles, then their locations may prove
important to future exploration. Heavier metals might be more
predictable if the lunar clock can be turned back to the earliest
distribution patterns.
George
> So the breccia isn't used to date the impacts which formed the circular
> maria? I'd been given that impression in a different group.
>
> I will also post the article about infilling.
>
> My opinion is that, prior to solar ignition the moon was as ice-covered
> as Ceres or some of the outer moons and protoplanets. The maria could
> thus be explained as shields denoting former polar positions. This
> theory would also solve the mystery of the antipodal
> magnetosphere/swirls.
I've never heard anyone suggest that the moon was formed before the sun had
already begun burning hydrogen. If the earth impact theory is correct,
then the moon had to have formed after the proto-earth and was impacted by
another planetary body. Perhaps you have a link that could set this matter
straight. My understanding of the planetary geology of the moon is that
after the impact which created the earth-moon system, the geological
development of both bodies began after the solidification of global
magmatic oceans - granitic on the earth, and anorthositic on the moon.
Further evolution of the bodies occurred in two stages. The 1st stages
were typical melts generated in depleted mantles. However, 2.2-2.0 billion
years ago on earth, and 3.0-3.8 billion years ago on the moon, other types
of magmas appeared; Fe-Ti enriched picrites and basalts on the earth, which
are characteristic of plume-related scenarios, and basaltic mare magmatism
with high-Ti varieties on the moon.
This suggests that evolution of earth's magmatism was related to ascending
mantle plumes of two types:
1) generated in the mantle, depleted during solidification of magmatic
ocean and archean magmatic activity; and
2) generated at the core-mantle boundary.
The moon may have generated its crust by similar processes (i.e., magma
plumes generated in the depleted mantle - magnesian suite in the
highlands, and later generated at the moon's core-mantle boundary - mare
basalts and picrites with high-Ti varieties).
As for the moon being ice-covered, the problem with that is that there is
no evidence that hydrogen has ever been present in significant quantities
there. Analyses of rocks brought back by the Apollo astronauts, and by the
Russian space probes show a conspicuous lack of hydrogen. None of the mare
basalts contain any hydrogen or hydrated minerals at all. In contrast,
most terrestrial basalts contain hornblende (a hydrated silicate), and
other hydrated minerals - positive evidence (ignoring the fact that 70% of
the earth's surface is composed of liquid water) of water on the earth.
Subsequent analysis by probes have verified this in all but one location -
the south pole of the moon within one crater only. And if there is
water-ice there, it may have originated from cometary impacts, and may
still exist there only because it is residing in a crater that is deep
enough to always be shaded from the sun.
George
P.S. as an aside, I understand that recent analysis of the material
collected from the tail of comet Wild-2 by the Stardust space probe
indicated the presence of abundant olivine (as well as high-refractory
minerals). This is significant, since olivine has also been detected in
particles collected from the sun by the same stardust spacecraft. And
olivine is a major component of terrestrial basalts, Moon maria basalts,
Martian basalts, and melts from analyses of other asteroids and comets as
well. What this indicates is that the nebular hypothesis is likely
correct, and that all of these bodies originated from the same primordial
nebula, and nebula that was enriched in Iron. Having said this, they have
yet to verify that the material blasted out of the comet actually
originated in our solar system. They are currently conducting isotopic
analysis to determine if the ratios indicate an origin within the solar
system (and hence the solar nebula) or if they indicate an extra-solar
origin. All indications, though, so far, are that they originated from
within the solar system.
George
> George wrote:
>
>
>> > proves the impossibility of an infilling event on the scale currently
>> > proposed for the maria basalt, and any new theory has more grounds
>> > than
>> > the present one.
>>
>> Umm, what science would that be?
>
> Here's a link to an article by Ivanov & Melosh:
>
> http://64.233.179.104/u/lpl?q=cache:g6RKrf4iEjkJ:www.lpl.arizona.edu/~jmelosh/ImpactVolcanism.pdf+ivanov&hl=en&ie=UTF-8
>
Ok, let's reset here so we are both clear on what we are talking about.
That article is arguing that the maria basalts didn't form due to impacts,
and I agree. The marias formed from deep-seated mantle plumes that erupted
to the surface likely after impacts had fractured the crust. In other
words, the fractures formed by the impacts were likely conduits through
which these mantle plume magmas flowed, but the magma itself wasn't
generated from the impacts. Remember, the early moon was hot, and it's
core molten. So there was tectonic activity at the time. Once the core
cooled (likely because there weren't enough radioactive isotopes present in
the core to keep dynamo going), tectonic activity stopped, and the moon has
been dead ever since.
> In terms of the titanium and so forth, why couldn't those flows have
> occurred under a mantle of ice -- during a more malleable period?
Several reasons why that is not possible:
1) The presence of titanium in the mare basalts indicates a deep-seated
origin for these rocks.
2) Neither the maria basalts, nor any of the other rocks and soil collected
from the moon during the Apollo space program (and the Russian Luna
program) contain evidence of hydrogen or hydrated minerals.
3) How do does ice co-exist with 4,000 F flood basaltic magma flows?
> If there actually are lunar paleopoles, then their locations may prove
> important to future exploration. Heavier metals might be more
> predictable if the lunar clock can be turned back to the earliest
> distribution patterns.
The evidence I've seen indicates that the moon's current pole has been in
the same place nearly since the moon's formation. In other words, the moon
has had the same side facing the earth nearly since the moon first formed.
It is locked in a rotation that is resonant with its orbit about the earth.
Secondly, I fail to see a link between the position of the lunar pole to
the presence of heavy metals. I just don't see it, nor do I know of any
mechanism that would cause such an occurance. Or else, I misunderstood what
you are saying here.
George
z7-x332a
planetary bodies. Do circular shields result from early planetary
development under icecaps? Does protoplanetary magma become hydrated
under CO2 and other ices?
Can one consider those massifs of Argyre, Caloris and the circular
maria as normal crater rims -- comparable to those of Aristarchus and
Hellas?
How much of Earth/Moon prehistory took place in the absence of solar
wind?
Can the position of heavier metals be tracked, over time, in a molten
body experiencing true polar wander?
:)
kk
George
>I suggest that this will require further investigation of ice-covered
> planetary bodies. Do circular shields result from early planetary
> development under icecaps?
Umm, I have no idea what you are talking about.
> Does protoplanetary magma become hydrated
> under CO2 and other ices?
Since no one has observed protoplanetary magma, I doubt that anyone knows
for certain.
> Can one consider those massifs of Argyre, Caloris and the circular
> maria as normal crater rims -- comparable to those of Aristarchus and
> Hellas?
Aristarchus is much younger than the maria rims, and likely younger than
Argyre and Caloris as well. Define normal.
> How much of Earth/Moon prehistory took place in the absence of solar
> wind?
Very little, I suspect.
> Can the position of heavier metals be tracked, over time, in a molten
> body experiencing true polar wander?
>
> :)
>
> kk
I'll assume that this wasn't a real question begging for an answer.
George
z7-x332a
> "z7-x332a" <kevin...@gmail.com> wrote in message
> news:1157755850....@e3g2000cwe.googlegroups.com...
> >I suggest that this will require further investigation of ice-covered
> > planetary bodies. Do circular shields result from early planetary
> > development under icecaps?
>
> Umm, I have no idea what you are talking about.
As an adjunct to my theory, I'm positing that the surface of an
ice-covered body like Ceres may also show carbon dioxide paleopoles
similar to Argyre, Caloris and the circular maria.
> > Does protoplanetary magma become hydrated
> > under CO2 and other ices?
>
> Since no one has observed protoplanetary magma, I doubt that anyone knows
> for certain.
Since the south pole of Mars is mostly carbon dioxide, and -- according
to my theory -- left a trace named the Argyre Planitia, then similar
paleopoles on the Moon or Mercury are not likely to be hydrated.
Rather, they might show the influence of dry ice.
> > Can one consider those massifs of Argyre, Caloris and the circular
> > maria as normal crater rims -- comparable to those of Aristarchus and
> > Hellas?
>
> Aristarchus is much younger than the maria rims, and likely younger than
> Argyre and Caloris as well. Define normal.
In this instance, a normal crater is one which does not have a smoothly
rounded surface, apparently flush with the planetary crust. For
example, the large Hellas crater on Mars does not appear to be filling
in anytime soon.
> > How much of Earth/Moon prehistory took place in the absence of solar
> > wind?
>
> Very little, I suspect.
In an earlier solar dust-disc period, far more volatiles were likely to
accrete than after solar ignition. The solar wind seems to have swept
much of this material away. If the planets had already become iceballs
by that time, then many surface features were already being created
beneath those ices.
Kevin
George
> George wrote:
>> "z7-x332a" <kevin...@gmail.com> wrote in message
>> news:1157755850....@e3g2000cwe.googlegroups.com...
>> >I suggest that this will require further investigation of ice-covered
>> > planetary bodies. Do circular shields result from early planetary
>> > development under icecaps?
>>
>> Umm, I have no idea what you are talking about.
>
> As an adjunct to my theory, I'm positing that the surface of an
> ice-covered body like Ceres may also show carbon dioxide paleopoles
> similar to Argyre, Caloris and the circular maria.
>
Umm, what evidence do you have that CO2 was/is present on the lunar marias?
>> > Does protoplanetary magma become hydrated
>> > under CO2 and other ices?
>>
>> Since no one has observed protoplanetary magma, I doubt that anyone
>> knows
>> for certain.
>
> Since the south pole of Mars is mostly carbon dioxide, and -- according
> to my theory -- left a trace named the Argyre Planitia, then similar
> paleopoles on the Moon or Mercury are not likely to be hydrated.
> Rather, they might show the influence of dry ice.
As for Argyre Planitia:
http://en.wikipedia.org/wiki/Argyre_Planitia
As for your paleopoles on the moon or Mercury showing the influence of dry
ice, I've not seen one shred of evidence suggesting that this is the case,
or that either of these two bodies ever had substantial quantities of CO2
in whatever tenuous atmosphere they may have had at one time in their past.
>> > Can one consider those massifs of Argyre, Caloris and the circular
>> > maria as normal crater rims -- comparable to those of Aristarchus and
>> > Hellas?
>>
>> Aristarchus is much younger than the maria rims, and likely younger than
>> Argyre and Caloris as well. Define normal.
>
>
> In this instance, a normal crater is one which does not have a smoothly
> rounded surface, apparently flush with the planetary crust. For
> example, the large Hellas crater on Mars does not appear to be filling
> in anytime soon.
This doesn't provide an adequate explanation for the usage of the term
"normal". Many "normal" craters certainly do have smoothly rounded
surfaces (although the term "smoothly no doubt is a relative term)
"apparently flush with the planetary crust. Erosion tends to do that to
craters.
>> > How much of Earth/Moon prehistory took place in the absence of solar
>> > wind?
>>
>> Very little, I suspect.
>
> In an earlier solar dust-disc period, far more volatiles were likely to
> accrete than after solar ignition.
Assumming that the sun was at least as large and as intense as it is today.
I don't think the evidence shows that at all. In fact, my understanding is
that the solar wind, and indeed the sun itself was much smaller and the
solar wind much less intense when if first lit up than it is today.
> The solar wind seems to have swept
> much of this material away. If the planets had already become iceballs
> by that time, then many surface features were already being created
> beneath those ices.
Except that obviously neither the moon nor Mercury ever had significant
quantities of ice. And whatever surface the earth may have had at that time
has long since been destroyed by erosion, impacts, and tectonic forces.
George
z7-x332a
> >
>
> Umm, what evidence do you have that CO2 was/is present on the lunar marias?
none yet -- but would such ice leave traces on the underlying material?
> >
> > Since the south pole of Mars is mostly carbon dioxide, and -- according
> > to my theory -- left a trace named the Argyre Planitia, then similar
> > paleopoles on the Moon or Mercury are not likely to be hydrated.
> > Rather, they might show the influence of dry ice.
>
> As for Argyre Planitia:
>
> http://en.wikipedia.org/wiki/Argyre_Planitia
>
> As for your paleopoles on the moon or Mercury showing the influence of dry
> ice, I've not seen one shred of evidence suggesting that this is the case,
> or that either of these two bodies ever had substantial quantities of CO2
> in whatever tenuous atmosphere they may have had at one time in their past.
>
> >> > Can one consider those massifs of Argyre, Caloris and the circular
> >> > maria as normal crater rims -- comparable to those of Aristarchus and
> >> > Hellas?
> >>
> >> Aristarchus is much younger than the maria rims, and likely younger than
> >> Argyre and Caloris as well. Define normal.
> >
> >
> > In this instance, a normal crater is one which does not have a smoothly
> > rounded surface, apparently flush with the planetary crust. For
> > example, the large Hellas crater on Mars does not appear to be filling
> > in anytime soon.
>
> This doesn't provide an adequate explanation for the usage of the term
> "normal". Many "normal" craters certainly do have smoothly rounded
> surfaces (although the term "smoothly no doubt is a relative term)
> "apparently flush with the planetary crust. Erosion tends to do that to
> craters.
The surfaces of Argyre, Caloris and Maria may show erosion but they are
far too large to have originated from shallow craters which were
smoothed over.
>
> >> > How much of Earth/Moon prehistory took place in the absence of solar
> >> > wind?
> >>
> >> Very little, I suspect.
> >
> > In an earlier solar dust-disc period, far more volatiles were likely to
> > accrete than after solar ignition.
>
> Assumming that the sun was at least as large and as intense as it is today.
> I don't think the evidence shows that at all. In fact, my understanding is
> that the solar wind, and indeed the sun itself was much smaller and the
> solar wind much less intense when if first lit up than it is today.
>
> > The solar wind seems to have swept
> > much of this material away. If the planets had already become iceballs
> > by that time, then many surface features were already being created
> > beneath those ices.
>
> Except that obviously neither the moon nor Mercury ever had significant
> quantities of ice. And whatever surface the earth may have had at that time
> has long since been destroyed by erosion, impacts, and tectonic forces.
>
> George
Since there still is no exact timeline to compare planetary accretion
with the presence of solar wind, it isn't possible to claim that all
planetary development took place after solar ignition. If there were
any minor ice caps on Mercury and the lunar surface when the sun lit
up, no trace would be left (besides the possible shields left beneath
former ice cap locations) -- just as we see today. The only argument I
have to fall back on, besides the swirl/magnetospheres on the moon, is
evidence that the physical shape of the northern Martian ice cap seems
to match up with geological surface features of Utopia Basin. If the
newly-arrived Mars probe uncovers more magnetospheres at the polar
opposites Utopia and Argyre, then this should raise the question of
whether Argyre is a paleopole created by the mostly carbon dioxide
southern ice cap.
Kevin
George
> George wrote:
>
>> >
>>
>> Umm, what evidence do you have that CO2 was/is present on the lunar
>> marias?
>
> none yet -- but would such ice leave traces on the underlying material?
I don't see why it wouldn't, assuming it was ever there in the first place.
Certainly it could leave a mineralogic signature.
>> >> Aristarchus is much younger than the maria rims, and likely younger
>> >> than
>> >> Argyre and Caloris as well. Define normal.
>> >
>> >
>> > In this instance, a normal crater is one which does not have a
>> > smoothly
>> > rounded surface, apparently flush with the planetary crust. For
>> > example, the large Hellas crater on Mars does not appear to be filling
>> > in anytime soon.
>>
>> This doesn't provide an adequate explanation for the usage of the term
>> "normal". Many "normal" craters certainly do have smoothly rounded
>> surfaces (although the term "smoothly no doubt is a relative term)
>> "apparently flush with the planetary crust. Erosion tends to do that to
>> craters.
>
> The surfaces of Argyre, Caloris and Maria may show erosion but they are
> far too large to have originated from shallow craters which were
> smoothed over.
What are you suggesting here? What is so smooth about Argyre?
http://ltpwww.gsfc.nasa.gov/tharsis/argyre.insight.highres.jpg
http://www.lpi.usra.edu/publications/slidesets/stones/slide_9.html
http://adsabs.harvard.edu/abs/2002P&SS...50..939H
It certainly appears to be quite rugged to me. There appears to be some
erosion there, but it is, nonetheless, quite rugged topography. And it
certainly does have all the features I would expect to see in a large,
ancient impact basin.
>> Except that obviously neither the moon nor Mercury ever had significant
>> quantities of ice. And whatever surface the earth may have had at that
>> time
>> has long since been destroyed by erosion, impacts, and tectonic forces.
>>
>> George
>
>
> Since there still is no exact timeline to compare planetary accretion
> with the presence of solar wind, it isn't possible to claim that all
> planetary development took place after solar ignition. If there were
> any minor ice caps on Mercury and the lunar surface when the sun lit
> up, no trace would be left
Not so. If there had been minor ice caps on Mercury and the lunar surface
when the sun lit up, there would be trace evidence in the form of hydrated
minerals. I can't speak for what evidence or lack thereof there is with
regard to Mecury, but the moon certainly has virtually no mineralogical
evidence at all that significant amounts of water (whether in ice form,
vapor, or water) ever existed there. If there had been, it would show up
in the minerals. Olivine, the most abundant mineral on the moon, is very
reactive with water, as are the pyroxenes. They readily react with water
to form other hydrated silicates. None of these hydrated minerals have
been detected on the moon. In fact, as far as I know no significant
hydrogen has ever been detected on the moon, and certainly no hydrated
minerals. Here is a link to the results of the Lunar Prostector impact:
http://www.sciencedaily.com/releases/1999/10/991014080522.htm
The controlled crash of NASA's Lunar Prospector spacecraft into a crater
near the south pole of the Moon on July 31 produced no observable signature
of water, according to scientists digging through data from Earth-based
observatories and spacecraft such as the Hubble Space Telescope.
> (besides the possible shields left beneath
> former ice cap locations) -- just as we see today. The only argument I
> have to fall back on, besides the swirl/magnetospheres on the moon, is
> evidence that the physical shape of the northern Martian ice cap seems
> to match up with geological surface features of Utopia Basin. If the
> newly-arrived Mars probe uncovers more magnetospheres at the polar
> opposites Utopia and Argyre, then this should raise the question of
> whether Argyre is a paleopole created by the mostly carbon dioxide
> southern ice cap.
>
>
> Kevin
http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_45478.htm
Henry Spencer
George <geo...@yourservice.com> wrote:
>Not so. If there had been minor ice caps on Mercury and the lunar surface
>when the sun lit up, there would be trace evidence in the form of hydrated
Not necessarily. That happens only if the water is liquid for a
significant period, giving it a chance to react with the minerals. If
it began as ice and then sublimated into vacuum as the temperature rose,
there would never have been an opportunity for hydration to occur.
>I can't speak for what evidence or lack thereof there is with
>regard to Mecury, but the moon certainly has virtually no mineralogical
>evidence at all that significant amounts of water (whether in ice form,
>vapor, or water) ever existed there...
Moreover, in the case of the Moon there is clear evidence that the whole
body was thoroughly baked early in its history. Not just water, but all
other volatiles are essentially completely missing. Even semi-volatile
metals like lead and zinc are badly depleted, and various details indicate
that they were lost very early, not partway through the Moon's history.
(For example, there is a long-lived radioactive isotope of rubidium --
which is semi-volatile -- that decays into an isotope of strontium --
which is not. Had there been significant rubidium on the Moon for a
while, lunar strontium should be detectably enriched in that isotope, and
it's not.)
>...In fact, as far as I know no significant
>hydrogen has ever been detected on the moon...
Uh, you're a bit out of date -- Lunar Prospector's neutron spectrometer
unambiguously found sizable deposits of slightly-buried hydrogen near the
lunar poles. (It is only a guess, although a fairly plausible one, that
this is in the form of ice.)
>The controlled crash of NASA's Lunar Prospector spacecraft into a crater
>near the south pole of the Moon on July 31 produced no observable signature
>of water, according to scientists digging through data from Earth-based
>observatories and spacecraft such as the Hubble Space Telescope.
There are several possible reasons for this, starting with the fact that
the exact impact location was not controllable and in fact is not known.
The LCROSS secondary payload of LRO will do the same experiment but with
much better control (and direct observation from nearby).
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | he...@spsystems.net
George
"Henry Spencer" <he...@spsystems.net> wrote in message
news:J6E3t...@spsystems.net...
> In article <yYidnfjCLMIeaYbY...@insightbb.com>,
> George <geo...@yourservice.com> wrote:
>>Not so. If there had been minor ice caps on Mercury and the lunar
>>surface
>>when the sun lit up, there would be trace evidence in the form of
>>hydrated
>>minerals...
>
> Not necessarily. That happens only if the water is liquid for a
> significant period, giving it a chance to react with the minerals. If
> it began as ice and then sublimated into vacuum as the temperature rose,
> there would never have been an opportunity for hydration to occur.
That's true. But if the ice is in contact with the underlying rock
surface, it is not exposed to the vacuum of space. There should be at
least a film of water between the ice pack and the underlying rock (the
pressures there should prevent sublimation). And most planetary bodies as
large as Mercury or the moon that have or are known to have had ice packs,
also have atmospheres (i.e., Mars,Europa, etc.). In addition, even if
there was no liquid water, a significant ice pack would leave telltale
traces etched in the rock, especially if the pack was the size of a polar
ice pack. Ice packs are notorious for ripping up the rock beneath them and
leaving copious amounts of debris behind as well as scars on the bedrock.
One would think that some of those could be seen from space probe images.
Certainly, we could see it if it had occurred on the moon.
>>I can't speak for what evidence or lack thereof there is with
>>regard to Mecury, but the moon certainly has virtually no mineralogical
>>evidence at all that significant amounts of water (whether in ice form,
>>vapor, or water) ever existed there...
>
> Moreover, in the case of the Moon there is clear evidence that the whole
> body was thoroughly baked early in its history. Not just water, but all
> other volatiles are essentially completely missing. Even semi-volatile
> metals like lead and zinc are badly depleted, and various details
> indicate
> that they were lost very early, not partway through the Moon's history.
> (For example, there is a long-lived radioactive isotope of rubidium --
> which is semi-volatile -- that decays into an isotope of strontium --
> which is not. Had there been significant rubidium on the Moon for a
> while, lunar strontium should be detectably enriched in that isotope, and
> it's not.)
>
>>...In fact, as far as I know no significant
>>hydrogen has ever been detected on the moon...
>
> Uh, you're a bit out of date -- Lunar Prospector's neutron spectrometer
> unambiguously found sizable deposits of slightly-buried hydrogen near the
> lunar poles. (It is only a guess, although a fairly plausible one, that
> this is in the form of ice.)
I know about the lunar prospector results. They have yet to be duplicated.
Having said that, I am aware of the fact that there may be diminutive
quantities within at least one crater located at the south pole of the
moon. The question is, if it is real, where did it come from? Is it
native to the moon, or did it arrive there on a comet or some other body.
I think the verdict is still out on that one.
>>The controlled crash of NASA's Lunar Prospector spacecraft into a crater
>>near the south pole of the Moon on July 31 produced no observable
>>signature
>>of water, according to scientists digging through data from Earth-based
>>observatories and spacecraft such as the Hubble Space Telescope.
>
> There are several possible reasons for this, starting with the fact that
> the exact impact location was not controllable and in fact is not known.
> The LCROSS secondary payload of LRO will do the same experiment but with
> much better control (and direct observation from nearby).
> --
> spsystems.net is temporarily off the air; | Henry Spencer
> mail to henry at zoo.utoronto.ca instead. |
> he...@spsystems.net
It will be interesting to see those results.
George