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The Kitchen Junk Drawer, Exchanges that need to be put somewhere
Paolo
post Jan 4 2013, 03:35 PM
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disappointed I mean... a false friend between French and English
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TheAnt
post Jan 17 2013, 11:02 AM
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Junk Drawer? I guess this one fits right in here:
New Solar System Discovered Four Feet From Earth
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ElkGroveDan
post Jan 17 2013, 02:37 PM
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QUOTE
astronomers at the Palo Alto Observatory on Monday identified a new, previously unknown solar system approximately four feet from the Earth's surface. The system, located directly over nearby Van Nuys,


This is how I know the story is fake. Van Nuys is 350 miles from Palo Alto.


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dburt
post Feb 7 2013, 07:49 AM
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QUOTE (JRehling @ Feb 6 2013, 11:15 AM) *
...Opportunity: In situ detection of minerals and geomorphology that indicates standing (acidic) water.
...

Despite what has popularly been stated, there may (or may not: an old discussion) have been standing water at Meridiani, and there probably was acid water (or at least volcanic or impact-generated steam), but it's highly unlikely that there ever was standing, acidic water for any significant time period anywhere on Mars, because it would have been neutralized by the broken fresh basaltic rock that litters the surface and constitutes the fractured crust. This is elementary high school chemistry. Even hematite dissolves in acid.

As Roger Burns noted long ago in proposing jarosite formation on Mars, acid salts such as jarosite are a form of crystalline or fossil acid. They indicate that ephemeral acidic waters (or steam) have quickly evaporated or been frozen before they could react with the rocks around them. This is an old observation for UMSF, already discussed extensively, that I repeat here only for newcomers. No further discussion is needed.
- dburt
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serpens
post Feb 10 2013, 09:43 AM
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The Oxford dictionary defines water as a colourless, transparent, odourless, liquid which forms the seas, lakes, rivers, and rain ..... By definition the other H2O phases, ice and vapour, are not water. Ice and water vapour have been identified, but to the best of my knowledge water has not been detected on mars other than maybe perhaps on the Phoenix strut which was not a native Martian event and really should not count. But the evidence of water in the past, of varying pH, is pretty convincing.
The elementary high school chemistry argument is something of a red herring. Early on Martian water may well he had a reasonably high pH. In the later, volcanic period then it is true that acidic water weathers basalt and basalt buffers acidic water. But in a system where acid is being constantly replenished by volcanic influences then regardless of the presence of basalt we can end up with acidic water near the surface and deeper alkaline water. The plethora of potential mixing relationships can result in products such as hematite concretions and Calcium sulphate deposition.

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dburt
post Feb 10 2013, 06:44 PM
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QUOTE (ElkGroveDan @ Feb 10 2013, 10:01 AM) *
...which evidence you may feel is or is not conclusive proof of water on mars at the time it was acquired. It was a request for a list of "evidence." ... all of us would be fascinated by that "list" and how it has evolved over the years.

Umm. If we're going to get historical, let us certainly not forget the directly-observed-and-mapped-by-famous-astronomers canals of Mars, or the still observed annual color changes, which everyone once "knew" were caused by seasonal changes in water-fed vegetation (as on Earth). When it comes to putative evidence for water on Mars, past OR present, I think a whole lot of humilty is called for, even among those who pontificate anonymously on this forum. (And, before anyone gets upset, I could be thinking of the evidence allegedly provided by young gullies here, on which I personally published several probably-mistaken papers about 10 years ago, instead of that allegedly provided by Meridiani cross-beds or spherules. In the case of gullies I basically went along with the conventional wisdom, and appear to have been wrong.)
- dburt

[MOD]: And this post is a contribution to a list from credible sources as defined by EGD how?
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dburt
post Feb 11 2013, 06:11 AM
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[MOD]: And this post is a contribution to a list from credible sources as defined by EGD how?
If anyone wants "a list from credible sources," just look at the above-mentioned Wikpedia article "Water on Mars" (most recently modified by someone today, 2/10, incidentally) and be done with it. And you can add to the Wikipedia article yourself, if you see that it's incomplete. Instant credibility?

The purpose of my "need for humility" post was simply to note that today's "credible sources" regarding evidence for water on Mars can easily become tomorrow's "known to be spurious" sources (with considerable overlap in timing possible, depending on who is doing the writing). The canals or alleged annual vegetation changes are the best-known examples, safely in the distant past, so that all the scientists involved are dead. The "young gullies" feature (see posts 1 and 5 above), discovered from orbital images in 2000, could well turn out to be another dud (and I was directly involved in that discussion, probably on the wrong - wet - side). In regard to gullies, for example, Richard Kerr's AGU "Snapshots from the Meeting" summary in the 12/21/12 issue of Science discusses "New evidence that changes in the appearance of martian gullies from year to year are the result of carbon dioxide frost (aka dry ice)".

So no list of evidence for past or present liquid water on Mars, no matter how elementary, would be complete without noting that the evidence, in many if not most cases, is equivocal and subject to changes in interpretation. That is, valleys, gullies, and conical debris aprons can be formed by various types of flows, rocks can be rounded by any type of friction or certain types of weathering, hydrous minerals and salts can form in hot steam as well as in lakes and seas, cross-bedding forms in many distinct types of flow environments, spherules are formed by a huge variety of geologic processes, the temperature stability of liquid water with regard to freezing or evaporating/boiling can be modified by a variety of solutes, and so on. That is real nitty-gritty science, not press releases or greatly simplified Wikipedia articles.

For Mars, the direct observations (e.g., young gullies and debris aprons) remain valid as interesting scientific discoveries, but the human interpretations (e.g., evidence of recent water flows) are invariably subject to our prior experience and expectations. Possible observer bias and the influence of expectations on scientific outcomes (e.g., involuntarily making what becomes a self-fulfilling prophecy; we expect or hope to see evidence of X, and therefore we do) is a subject much studied by psychologists such as Robert Rosenthal, and regarding which there are many articles in Wikipedia and elsewhere. I hope you agree that this general topic (basically, urging caution in interpreting the evidence) is relevant, especially given its well-documented prior history in martian water studies.
- dburt
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Floyd
post Feb 11 2013, 01:12 PM
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Thanks dburt. Doing good science is a difficult process--interpritations are tricky--ultimately science is self correcting, but it can take years. I even appreciated the humor in your understated post #16 rolleyes.gif


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serpens
post Feb 12 2013, 02:39 AM
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QUOTE (dburt @ Feb 11 2013, 06:11 AM) *
I hope you agree that this general topic (basically, urging caution in interpreting the evidence) is relevant, especially given its well-documented prior history in martian water studies.


Couldn't agree more. There are an awful lot of conflicting hypotheses on this subject from credible sources (in terms of credentials, experience and position) and this is quite right and proper. All possible explanations for observed phenomena must be considered as the evidence is sifted. But proof is a different matter. There is certainly proof of ice and proof of water vapour on Mars and with Phoenix we actually saw the transition in phase on the mirror. But there is no proof of existing water. With apologies to EGD, in colloquial use ice and water are different things and since the initial request was directed to a talk to schools and general public the semantics are somewhat significant.
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ElkGroveDan
post Feb 12 2013, 05:05 AM
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QUOTE (serpens @ Feb 11 2013, 06:39 PM) *
With apologies to EGD, in colloquial use ice and water are different things and since the initial request was directed to a talk to schools and general public the semantics are somewhat significant.

And I didn't say the phases weren't relevant, I said THIS TOPIC isn't the place to compare, contrast and debate them. If someone wrote a paper, or if some agency held a press conference, they almost certainly would have made that distinction -- liquid, ice, vapor, gas or whatever -- with regard to their "discovery".

All we were looking for in this discussion was a LIST of "discoveries" not a discussion of them.


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centsworth_II
post Feb 12 2013, 05:19 AM
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QUOTE (serpens @ Feb 11 2013, 09:39 PM) *
...in colloquial use ice and water are different things and since the initial request was directed to a talk to schools and general public the semantics are somewhat significant...
I would be more concerned with making clear that not all ice on Mars is water ice, that much of it is CO2.
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brellis
post Feb 12 2013, 05:38 AM
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2 fine cents there, centsworth II smile.gif
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centsworth_II
post Dec 24 2013, 02:38 PM
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QUOTE (kenny @ Dec 24 2013, 04:45 AM) *
....Cernan did not take a proper "selfie". That picture was taken by Jack Schmitt.
The reflection seems to show an extended arm holding a camera. Schmitt can be seen looking on (circled) but not obviously taking a picture.
Attached Image
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Ian R
post Dec 24 2013, 03:03 PM
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This is ridiculously off-topic, but the Hasselblads were chest-mounted, so it's only to be expected that the visor reflection doesn't appear to show Jack taking this picture (the TV footage proves he was indeed the photographer).


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Ian R
post Dec 24 2013, 03:19 PM
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Actually, on this occasion the Hasselblad wasn't on the chest-mount; Jack was holding it in his right hand, kneeling down to get Gene, the flag, and Earth in the frame.

Attached Image


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