Talk:Planetary habitability/Archive 1

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Has anyone else noticed that someone has replaced the word "the" with "Squirrel"? This is also means that words like "there" become "squirrelre".
Good article though, despite the prank.
This was vandalism- it already has been reverted. --Adam (talk) 17:09, 23 January 2006 (UTC)
replies: text: Pypex's point has been incorporated. Marskell 23:13, 22 September 2005 (UTC)
thread_title: Untitled

message: You're right, it never actually states "gas giants do not have life and can not host life on satellites." Who knows, satellites of gas giants maybe where it's at; or the atmospheres of giants may be full of life, unknown to us. Perhaps below section 2 headline there could be a general paragraph about this. Marskell 00:00, 2 September 2005 (UTC)
thread_title:  Gas giants 

message: I've started a very incomplete and probably incorrect in places section on the chemistry required for life as we know it. It needs a lot more research and time but it's two in the morning now and I need to sleep. Please tear it to pieces if you feel it is warranted. 
Good night.
Serendipitous 01:08, 2 September 2005 (UTC)
replies: text: Reads fine to me and I now honestly think every major issue is covered in some form. The length and detail is in keeping with the rest of the article; I just tweaked it slightly. Marskell 11:14, 2 September 2005 (UTC)
thread_title: astro-biochemistry

message: The Milankovitch cycles of axial tilt and climate fluctuation suggest to me that, in fact, a planet with a radically titled axis of rotation is as likely to be habitable. I feel it is likely that the circulation would be altered in such a way as to moderate the seasonal effects at high latitudes resulting from radically tilted axes. Milankovitch cycles show that increasing global warmth results during periods of higher axial tilt, and this would eliminate ultra-severe winters whilst allowing more activity at high latitudes and permitting homeostasis.
Whilst I see that a very low axial tilt might make life impossible to achieve, radical tilt I feel is less likely to do this.
:Perhaps "radically unstable" is better than "radically tilted" though the next point covers that. At some point the tilt (75 degrees? 85?) has to impact negatively on habitability wouldn't you say? If the tilt were parallel to the ecliptic could you imagine homeostasis being achieved? I suppose if it's observed below that sufficient heat transfer to the night side of a tidally locked planet is conceivable perhaps even in this case adequate circulation could be achieved. Anon, if you have an outside source detailing this that would be helpful. Marskell 11:45, 7 September 2005 (UTC)
replies: text: It does help, thank-you. I updated the page accordingly. The one thing I would like is a very reliable source on the number of red dwarfs. Wiki itself is I think in contradiction on the point and in reading you here anywhere from 70 to 90+. Marskell 16:45, 13 September 2005 (UTC)
thread_title:  "If it is radically tilted..." 

message: I have just created a proper reference section. I personally don't like the main body link simply directing you to the bottom of the page. Thus, everything is double-linked: the links as they were remain and everything gets noted again at the bottom as primary or secondary. The primary sources are described as they would be in a normal bibliography while the secondary sources are just given a short description (and arranged alphabetically based on that description rather than their occurence in the article).
In general, we need a few more references. If this gets up to two dozen odd references, including six or eight primary I think I'll ship it off to peer review and eventually make a Featured Article request. Marskell 17:14, 23 September 2005 (UTC)
thread_title:  References 

message: My apologies. I made an error in my "Red Dwarf habitability" section. I claimed that a habitable planet orbiting Proxima Centauri would have an orbital period of slightly over a day, but that guesstimate assumed (rather stupidly) that the star in question was our Sun. I had my suspicions, and checked on a science forum. As it turns out, Prox's substantially smaller mass dramatically decreases a planet's orbital speed, so its orbital period is actually about 6.3 days. 
Again, sorry. Serendipodous 17:24, 8 October 2005 (UTC)
thread_title: Orbital period blunder

message: ...that my definition of planet article is good enough for peer review? I've added a number of references, and finally managed to excise some of the article's blatant POV. What do you think?Serendipodous 16:39, 16 October 2005 (UTC)
thread_title: Marskell, do you think...

message: It would seem that the habitable zones around red dwarf stars are within zones of captured rotation. If the planet in question has a thin atmosphere, then temperature differences between day sides and night sides would be extreme (example: Mercury or the moon). But if the planetary atmosphere is relatively thick, then differences of temperature would be less severe (Venus) -- but only with strong winds and severe storms that themselves would make sessile life difficult even if temperatures were moderate. --66.231.41.57 03:53, 17 December 2005 (UTC)
thread_title:  Red dwarfs and extreme day-night cycles 

message: I keeping thinking "everything stated" and then something else occurs. We should probably mention:
* Gravity and habitability (presumably under mass matters). I can't find a single source though, beyond generic, sci-fish references ("high-grav planets will have stocky aliens" etc.).
* Importance of magnetic field in protecting planet (this could probably get a single sentence in mass matters as well).
Thinking it through, this probably needs a dozen more references. There's much stated as if obvious (Mars probably geologically dead) and even some unsourced stats (red dwarfs may have light dimmed by 40%). 
Finally, anything that reads too much like an editorial aside is being moved to the new Notes section. Marskell 15:59, 23 October 2005 (UTC)
thread_title: More stuff

message: I tracked this down: . I, uh, understand it perfectly ;). Red Dwarf section could be re-jigged slightly to accomodate the source given that we over-rely there on article. Marskell 11:41, 24 October 2005 (UTC)
replies: text: Not at all! I wasn't suggesting removing him or anything only that two sources is better than one for a longish section. Marskell 14:55, 5 November 2005 (UTC)
thread_title:  Primary source 

message: To all of those who have worked on this article, I thank you. It is very well structured and very informative. Keep up the good work. Zhatt 23:01, 27 October 2005 (UTC)
thread_title:  Thank you 

message: I added the statement that brown dwarfs are not considered stars, because the first paragraph under red stars could be confusing, stating that over 70% of stars are red dwarfs, then stating that brown dwarfs are like more numerous -Satori (talk) 00:05, 12 November 2005 (UTC)
replies: text: True. Thx. Marskell 10:03, 12 November 2005 (UTC)
thread_title:  Brown dwarfs 

message:  — Yaohua2000 17:34, 14 December 2005 (UTC)
replies: text: Fixed. Marskell 09:41, 15 January 2006 (UTC)
thread_title:  Two references/note tags with number 12 

message: What do they mean about "Dangerous spiral arms" in this article?  I don't think the spiral arms of a galaxy swing around like a circular saw blade, destroying life.  Seems invalid.  --Shanedidona 04:13, 23 January 2006 (UTC)
thread_title: Dangerous Spiral Arms

message: It seems like the article is describing the covalent bonding between hydrogen & carbon atoms incorrectly as a "hydrogen bond", which is something altoghether different, being a medium strength attraction between partially-charged atoms typically in solution.  In fact, the whole sentence is questionable - carbohydrate metabolism isn't life's (only) fuel even on earth.  The article seems to imply that it will be a universal characteristic of life.
Good points. I'll change them. Serendipodous 13:31, 23 January 2006 (UTC)
thread_title: Mistakes regarding carbohydrates and hydrogen bonding

message: This article not only was very intuitive, but gives the reader an extreme sense of appreciation of our home planet. As we all know there is an over whelming number of star systems Universe wide. Earth is so very rare. 
I always viewed volcanic and tectonically active planets as a "hostile" environment. But to discover these attributes are a requirement for life... Amazing, how Earth has successfully balanced a ‘safe enough' environment from a hostile one, adds to her rareness.
--206.223.21.130 18:04, 23 January 2006 (UTC)
replies: text: Read Rare Earth if you haven't! It is a beautiful thing to consider. Marskell 18:24, 23 January 2006 (UTC)
thread_title:  Appreciation for Earth 

message: So after yesterday we have two new small sections, "Gaia" and the "Privileged planet." The latter appears to be a strawman (Guillermo Gonzalez has apparently deployed Rare Earth to argue for a creator BTW) and I'm not sure if it belongs. However, one option is to make a final level two section "The Earth in context", or maybe "The pale blue dot" which could be a place-holder for the two sections, i.e., having evaluated Planet hab we make one final comment on Earth's rarity. It needs to be short though--we're over 40k now. Thoughts? Marskell 07:25, 24 January 2006 (UTC)
replies: text: Hi. Sorry if I shouldn't have added that on "PP" - I see it was edited away, and when I did my edit, I hadn't realised how much of a process underlaid the article. However, regardless of whether you accept Gonzalez/Richards' conclusions, the hypothesis (that there is a link between habitability and the ability for intelligent life to make observations) is an interesting one, and one that as yet hasn't been refuted. I would have thought that if this article is to be up-to-the-minute, this is an interesting perspective.--Exiled from GROGGS 12:18, 27 January 2006 (UTC)
thread_title:  New sections 

message: The article states that "smaller planets have smaller diameters and thus higher surface-to-volume ratios than their larger cousins. Such bodies tend to lose the energy left over from their formation quickly and end up geologically dead".
This is incorrect. The earth is kept warm by radioactive materials releasing energy. The earth would have cooled to be solid within a few million years otherwise. It is the presence of heavy radioactive materials that allows the earth (or other planets) to be gealogicaly active.
I also am not certain that, in general, a moon would have any positive affect on reducing precession - indeed the moon is the main cause of procession! Mars, for example, rotates almost inline with the sun and has very little precession, so far as I am aware. Pogsquog 10:48, 24 January 2006 (UTC)
replies: text: "All of the geological activity on the earth today is driven from this initial source of heat at the earth's formation, aided and abetted by continued radioactive decay of elements in the earth's interior" (James Madison University) . Incomplete rather than incorrect. I will edit accordingly and should have done so already; I recall reading that up to 80% is now radioactive decay though I now can't find it. However, the analysis of surface-to-volume ratios remains sound I think. Marskell 12:04, 24 January 2006 (UTC)

text: Re second point: "Mars, for example, rotates almost inline with the sun." I'm not sure what you mean. Mars' axial tilt is currently 25 degrees and precession is dramatic, ranging from 15 to 35 (though over 90 000 yrs). Marskell 12:15, 24 January 2006 (UTC)

text: Thanks Pog. That section may indeed have some problems with due emphasis. You'll note that we definitely mention obliquity (axial tilt) in the second bullet point and again in reference to the moon but only in the mean sense and not in terms of variation. Also in re-reading it I notice "must have..." has been deployed thrice which is too didactic for this topic. I'll try to shake it up a bit soon (or feel free yourself). Marskell 17:03, 24 January 2006 (UTC)
thread_title: Axis and procession

message: I think that the "Other Considerations" section would be better split between other sections. "Red dwarf systems" could be combined with "binary systems" to create a section on alternative stellar systems; "Galactic neighborhood" could be considered a stellar attribute. One of the principal attributes of a star, after all, is where it is. "Good Jupiters" could (loosely) be considered a planetary attribute, since the existence of a "good Jupiter" directly affects the evolution of a planet. Serendipodous 11:47, 24 January 2006 (UTC)
replies: text: I could live with Alternative stellar systems. Above or below Planetary characteristics? I don't like the idea of going through most of the article without discussing planets directly but the Red dwarf business probably flows more naturally after the first section (or even as a part of it, but that would make for a massive section). I think Good Jupiters and and Galactic Neighborhood should be left where they are. Finally, while Gaia deserves mention given that the topic has some popular awareness, I think Privileged Planet may be Intelligent Design by the backdoor. I'd like to remove it but it was a good faith addition by an anon who I think subsequently got an account so I was hoping for other thoughts on what to do with it. Marskell 17:13, 24 January 2006 (UTC)
replies: text: What do you think? I honestly think it works, but then I'm a bit anal when it comes to sections :). As for the "privileged planet" argument, creationist or not, the addition isn't very well thought out or explained, and I really think it should be ditched.Serendipodous 23:22, 25 January 2006 (UTC)
replies: text: I think it's fine now, though the refs are going to have to be re-numbered. I think a section "Life and habitability" would work under other considerations. That is the degree to which the first emergence of life has a subsequent affect on habitability. This could incorporate Gaia and also theory from David Grinspoon. Marskell 09:59, 26 January 2006 (UTC)
thread_title: I'm thinking of doing a reordering of the page

message: Perhaps a consideration for planetary habitability ought to be the pre-biotic conditions (reactions conditions - pressure, temperature, reactants etc.) conducive to initiating life aswell as the considerations taken - in this article -toward sustaining it. This would probably involve looking at self-replicator cells and the reaction mechanisms of DNA molecules.
I am not sure whether these points are suitable for inclusion in the article, as they involve more about the origin of life than a planet's suitability to sustain life, but still there could be room to look at some factors as regards a planet's suitability for initiating life (if it is at all possible that life can originate in such a way without recourse to God?). 62.249.242.232 20:18, 24 January 2006 (UTC)
replies: text: For the time being, some one might might disambig an existing phrase in the text with origin of life. Marskell 17:33, 25 January 2006 (UTC)
thread_title:  First self-replicator