Talk:Geology of Mars/Archive 1

Martian spiders / spherules?
I think it might be appropriate to include a mention of the southern hemispheric Martian spiders and other cryptic region features. These are a geological feature of some notable debate currently. Seems worthy of inclusion in an article of Geological features of Mars? Also, wouldn't hurt to update and expand that article, either.

While we're at it, we might also note the Martian spherules in slightly more detail, with a link to the main article. These also seem to be a geological feature of some notable debate curently. May also note similarity to Moqui Marbles, and Stone spheres of Costa Rica on Earth. There may or may not be common causation between all the similar features. If nothing else, almost perfectly spherical natural objects seem to be slightly rare/mysterious. Just a thought.

Both of these notes could be, if nothing else, short snippets mentioning them and very basic info about what and whree, wit ha link to the "main articles" as they exist currently... Mgmirkin 17:41, 4 November 2006 (UTC)


 * The following discussion is an archived debate of the . Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section. 

PAGE MOVED per request. -GTBacchus(talk) 08:15, 11 January 2007 (UTC) "perfectly spherical natural objects" are not remotely rare in geology. Oolitic limestone is built from them... Ezkerraldean (talk) 14:34, 6 June 2010 (UTC)

Proposed move of Areology to Geology of Mars
FOR As someone who studies the geology of the Moon and Mars, I have to say that "selenology" is a dying term, and Areology is almost never used. Even popular articles use expressions like "geomorpology of mars", "the martian geotherm", and others. These "selono-" and "Are-" terms were introduced as soon as one realized that one could study the geology of the Moon and Mars. However, it was later realized that the same geologic processes operate on these bodies, and it thus made no sense to use separate terms for each planet that describe the same phenomenon. Now that we can study the geology of tens of bodies, the proliferation of new words would become absurd if this practice was carried out to its logical extremum. For instance, what do you call the geology of Io, Ganymede, Titan, Tritan, Pluto, etc.??? And what is geometry when you are on Mars? Finally, many find these terms to be pretentious. Lunokhod 17:02, 9 January 2007 (UTC)


 * Also, please consult with planetary geology. Lunokhod 17:12, 9 January 2007 (UTC)

Support: As mentionen at Areography and Areology pages there is no literature using this term. --Stone 19:37, 9 January 2007 (UTC)

Support: Wikipedia article titles ought to use the most prevalent term for the subject matter. Areo- terms are not commonly used in general discussion (do a Google search) and in modern professional settings are almost never used (from personal experience and Google searches). However, a sentence within the articles about the areo- terms is quite appropriate. Jespley 21:53, 10 January 2007 (UTC)
 * The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

More formally known as Areology?
A recent edit has changed to introductory sentence from "sometimes known as Areology" to "formally known as Areology". As is clear from the above discussion, this page was moved from "Areology of Mars" to "Geology of Mars" because this is, in fact, not true. If the author of this change does not add a reference attesting to the verifiability of this statement, I will revert back to "sometimes known as." Lunokhod 13:16, 17 January 2007 (UTC)

Information about the Core
The core may be completely fluid. See recent article, Science (vol 316, p 1323), for new work on Fe-S solidus. Additionally, same phrases about the core in two places, removed one of them -changes were reverted, redid them. Seorwz 20:09, 7 June 2007 (UTC)Seorwz
 * I also stumbled across this after reading the 2007 Science article (and an earlier one in 2003 ) and found that the text in this article was in disagreement with both studies. I have changed it to match the two Science articles and placed tags on the other stuff I can't find references for. Smocking (talk) 02:36, 24 February 2010 (UTC)

Central dynamo collapse
The reference which has been provided to support the phrase "polarity reversal of its dipole field occurred when the central dynamo collapsed, leaving only residual permanent crustal dipoles" does not mention dynamo collapse as far as I can see sbandrews (t) 15:10, 19 August 2007 (UTC)
 * You're right. I gave the wrong cite.  I'll have to chase it down again.  Mea culpa. LeadSongDog 13:51, 24 August 2007 (UTC)

The ionosphere is everywhere and crustal fields aren't necessarily dipoles
I don't have the inclination or time to look up detailed references for every little correction I make but I'll point you to review articles by Connerney and Nagy in Space Science Reviews from about 2004. If anyone really wants these citations then you should be able to find them with google or ads. Jespley 15:59, 18 October 2007 (UTC)

Here, I found them. These two references should cover most anything basic about plasma (including the ionosphere) and crustal fields at Mars. Unfortunately, they require subscriptions but any major research library will have one. http://adsabs.harvard.edu/abs/2004SSRv..111...33N http://adsabs.harvard.edu/abs/2004SSRv..111....1C Jespley 16:27, 18 October 2007 (UTC)


 * Thank you for the refs. I didn't think you really intended implying that Mars is host to the only Magnetic monopoles ever found. On the other hand if you want to say something to the effect that the crustal magnetic field is composed of a complex superposition of many static and induced dipoles, go ahead and make it explicit.  While the Nagy articles are not in open journals, there are references to them, such as this.


 * They help to elucidate that to correctly interpret the satellite based magnetic data one has to be sensitive to the time-of-sol and use the diurnal variations to distinguish induced from permanent features. I think we can presume that competent researchers would have considered this.  More subtly, it raises the question of whether the locked-in stripes in the crustal field could have been originally caused simply by temporal variations in the iononspheric field over the time period the crust cooled rather than changes in a central magnetic core.  If there's analysis on that line of thinking it would certainly be worthy of mention.LeadSongDog 16:56, 18 October 2007 (UTC)


 * Yeah, it'd be pretty cool if they were monopoles but sadly I have no evidence for that. :) My edit regarding the dipoles was, as you surmised, related more to the fact that the fields aren't necessarily best represented as a bunch of little dipoles.  Some have to tried to model them as such (cf. papers by Purucker et al.) but these models have not been well accepted (cf. Connerney, SSR, 2004 and Brain, JGR, 2006).  Other models have been created using spherical harmonics (cf. papers by Arkani-Hamed or Cain).  In reality, of course the actual magnetic fields are surely a tremendously complicated mess of superimposed fields created from the individual magnetic mineral grains.


 * As to the magnetic stripes, it's highly unlikely that they were created by variations in the ionosphere. I'm not aware of any research pursuing this idea. The amplitude of the fields in the ionosphere is too small (40 nT) and the time scale for their variations (~sec, min, days) is too short.


 * And yes, removing the external (i.e. ionospheric/solar wind) contributions from the measured fields so that one is left with only the intrinsic (e.g. crustal) fields is an important but tricky business (cf. http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2019.pdf).
 * Jespley 18:15, 18 October 2007 (UTC)

catenae & a shifting crust
Years ago, Science News reported on an article, that claimed that catenae on Mars suggested, that the crust as a whole has shifted over time. Sorry, can't find it in the SN archives; it might be too old (say from Viking). The only explanation they could come up with for these four very long crater chains was the breaking up and impact of small moons, and the older the chains, the higher the angle they were from the equator. They speculated that the mass of Olympus and Tharsis as they formed may have destabilized the rotation of the planet, and the crust shifted to compensate, presumably after the cessation of any tectonic activity. Has this been followed up, and is it still thought reasonable? kwami (talk) 21:52, 20 November 2007 (UTC)

Noachian Era
I've always read that the Noachian era was between 4.6 bya and 3.5 bya. However, on Wikipedia it says 3.8 bya to 3.5 bya. I have some references such as http://phoenix.lpl.arizona.edu/mars174.php as well as a textbook which agrees. However, I have no idea how to cite my change or even do the footer, so if anyone would like to help, thanks! 68.228.85.87 (talk) 14:58, 19 March 2008 (UTC)Kevin 3/19/2008

Edit: I have the textbook reference now. Croswell, Ken. Magnificent Mars, 188. New York, New York: Free Press, 2003. —Preceding unsigned comment added by 68.228.85.87 (talk) 15:05, 19 March 2008 (UTC)

Picture of the magnetic field?
What happened to the picture of the magnetic fields? I'm not enough of a wiki guru to track it down and figure out why it disappeared. If necessary, I can produce a duplicate version of that figure using my own code and the original data. I'm not sure how all the copyright stuff for pictures works. Jespley (talk) 20:11, 1 October 2008 (UTC)

Comments requested
There are two WP articles dealing with specific geological features on Mars: Dark dune spots and Martian Spiders which I have proposed for a merge with each other; I invite the editors interested in geologial features of Mars to please review the resarch papers presented and express their opinion on the merge proposal taking place at Talk:Dark dune spots Cheers, BatteryIncluded (talk) 00:53, 3 September 2009 (UTC)

The tectonics section needs serious attention
There are lots of tectonic features on Mars but the only two things which are discussed are (a) plate tectonics [which are dubious] and (b) the crustal dichotomy, which has been tectonic modified but impossible to gain any understanding of the crustal dichotomy from the text of this article alone.

Someone interested in working on this could start with the excellent albeit old discussion of tectonics in Exploring the planets: http://explanet.info/Chapter06.htm

--just saying —Preceding unsigned comment added by 128.148.116.88 (talk) 22:32, 11 November 2009 (UTC)

I agree absolutely. I will address this deficiency as I get to it (after volcanism). Schaffman (talk) 13:10, 28 November 2010 (UTC)

Geological epochs
Is there a definitive source for the martian geological epochs? I checked the following source:

and it lists: These values differ significantly from the numbers in this article.&mdash;RJH (talk) 15:08, 9 April 2010 (UTC)
 * Noachian: to 3.7 Gya
 * Hesperian: 3.7 to 3 Gya
 * Amazonian: 3 Gya to present

The dates aren't fixed at all - we don't have a single absolute date on any known surface locale so to put precise dates on the periods would be pretty dodgy. Different timescales will have different dates but all are estimations. Ezkerraldean (talk) 14:31, 6 June 2010 (UTC)

I agree, we have no firm absolute ages, but the numbers currently shown on the time bar are grossly different than what our current best estimates are. I vote for Noachian 4.5 to 3.7; Hesperian 3.7 to 3; and Amazonian 3 to present, while noting the tremendous uncertainty of the numbers, particularly the age of the Hesperian/Amazonian boundary. These are the numbers in Michael Carr's "The Surface of Mars," (2006) which I believe were taken from Hartmann (2005) or Hartmann and Neukum (2001). Schaffman (talk) 19:03, 10 September 2010 (UTC)

Speleology of Mars? Premature, but ....
I moved discussion of likely cave entrances from Caves of Mars Project to the vulcanology section, on the reasonable assumption that these pits are lava tube skylights. However, until that's certain, maybe another categorization might be better? Yakushima (talk) 08:29, 1 July 2010 (UTC)

Areology
As noted in previous posts, the term areology as a synonym for Mars geology is not used in the professional literature. Using this term in the introduction of an article on the Geology of Mars tips off the knowledgeable reader that the writer is not intimate with the subject matter. I have edited the opening paragraph to correct this problem.Schaffman (talk) 14:38, 9 September 2010 (UTC)

I asked Michael Carr at USGS Menlo Park about this. He says that my statement "the term areology is rarely, if ever, used by professional geologists and planetary scientists" is correct. If anyone should know, it's him. I have added personal communication to references.Schaffman (talk) 22:21, 13 September 2010 (UTC)

Elemental Composition
While factually correct, the first paragraph lacks context. It seems geared to readers who are unaware that the planets all have pretty much the same elements. Is that the appropriate level for the article? I am rewriting it. Any comments? Schaffman (talk) 18:38, 9 September 2010 (UTC)

Timeline
I'm not sure if this is a Wikipedia or pedagogical thing, but the term "timeline" is not used often in geology as far as I know. A heading like Geologic History or Geologic Timescale seems more appropriate. Schaffman (talk) 18:49, 10 September 2010 (UTC)

Use of Term Epoch
Use of the term Epoch in the Timeline section is improper. The term should be system or period. "Epoch" is the geologic time equivanent of a "series, which is a subdivision of a time-stratigraphic "system." The amount of cratering defines three time-stratigraphic "systems," Noachian, Hesperian, and Amazonian. In units of geologic time, "systems" correspond to "periods." For example, one would say: "Basalts in Hesperia Planum are part of the Hesperian System...The basalts formed from lava flows that were deposited during the Hesperian Period." The distinction is subtle but important. Based on crater density, Tanaka (1986) defined 8 time-stratigraphic series on Mars: Lower Noachian, Middle Noachian, Upper Noachian; Lower Hesperian, Upper Hesperian; Lower Amazonian, Middle Amazonian, and Upper Amazonian. The corresponding epochs in geologic time are Early Noachian, Mid Noachian, Late Noachian...etc. I know this is confusing, but refer to wikipedia article: system (stratigraphy). Schaffman (talk) 20:27, 11 September 2010 (UTC)

Global Dichotomy
The article mentions the crustal dichotomy only in passing. The dichotomy is a fundamental geologic feature of the planet and needs to be called out early. Likewise, Tharsis/Elysium and the Hellas, Isidis, Argyre basins. I'm working on an Overview section to briefly describe these and other large-scale features. Schaffman (talk) 14:17, 13 September 2010 (UTC)

Global Physiography
I have added a section on the global physiography of Mars that acts as an overview to the large-scale geologic features of the planet. I intend to modify and rewrite as needed rest of article. Any comments/criticisms? I don't want to step on anyone's toes. I know the article is long right now. Hopefully, I can cut and shorten as I figure out how best to organize material. I'm hoping these changes add to the quality of the article. Schaffman (talk) 18:08, 16 September 2010 (UTC)

Surface Properties
I have put in the first section of a discussion of Mars' surface characteristics Schaffman (talk) 17:03, 18 September 2010 (UTC)

Section now completed except for continuing edits. Schaffman (talk) 15:22, 20 September 2010 (UTC)

Mineralogy
I'm about ready to start revising section on mineralogy. Schaffman (talk) 15:21, 20 September 2010 (UTC)

Still trying to edit mineralogy and petrology section. Schaffman (talk) 14:33, 30 September 2010 (UTC)

Editing for length
I'm trying to edit this article for length before I add any more material after the mineralogy section. Any comments would be appreciated. Schaffman (talk) 14:08, 25 September 2010 (UTC)

Arg. I need to expand the Rocks and Minerals section slightly, otherwise it's incomplete. I'm still trying to shorten the overall article, but the organization needs to be worked out first. Bear with me, please. Schaffman (talk) 21:38, 2 October 2010 (UTC)

Impact Craters
I think several of the photos in the gallery should be removed because they add little to the section. Yuty is fine to keep. So is the nice photo of the pedestal crater in Amazonis. I'm thinking of adding examples of a simple and complex crater. Also, a close-up of a crater rampart would be nice. Comments? Schaffman (talk) 22:35, 2 October 2010 (UTC)

I am currently reworking the impact crater section. Comments welcome. Schaffman (talk) 11:56, 7 October 2010 (UTC)

Volcanoes
I think this section should be renamed Volcanism, since volcanic features such as ridged plains are not associated with volcanic constructs but are clearly volcanic in origin. Schaffman (talk) 13:23, 21 October 2010 (UTC)

Over half of the surface of Mars is covered by volcanic materials.
True, but saying "over half" implies a quantification I'm not sure exists. Much of the highlands probably contain Noachian-aged lava flows and pyroclastics that have been so altered by impact and weathering that their original volcanic nature is obscured. Anyway, does over half mean 51% or 95%? Big difference. I'd simply say: Much of the martian surface is covered by volcanic material. Schaffman (talk) 10:22, 31 October 2010 (UTC)

I've changed volcanic materials to volcanic stuctures and landforms. Almost all of Mars is covered by materials with some volcanic components, if you count the dust. Schaffman (talk) 20:18, 24 November 2010 (UTC)

Still working on the volcanism section.Schaffman (talk) 09:00, 17 November 2010 (UTC)

Adding material on general differences between Martian volcanoes and those on Earth. Expanded first paragraph of Volcanism section into two paragraphs. Schaffman (talk) 14:36, 22 November 2010 (UTC)

"These volcanoes may have been caused by the great impact that produced the Hellas impact crater"
This is somewhat misleading. The impact may have created deep-seated fractures that were later exploited by rising magma to reach the surface.Schaffman (talk) 14:41, 24 November 2010 (UTC)

The "Circum-Hellas volcanic province"
To me the salient features of these volcanoes are their extreme ages and different morphology from younger martian volcanoes. The idea that Alba Patera may have resulted from seismic disruption antipodal to the Hellas impact is interesting but irrelevant to this subsection. I'd delete or place it elsewhere. Also, reference 115 has broken link.Schaffman (talk) 15:06, 24 November 2010 (UTC)

This is just my opinion, but I object to statements such as: "This discovery may be of great importance for future colonization of Mars because these types of faults and breccias dikes on earth are associated with key mineral resources. Perhaps, when people live on Mars, these areas will be mined just as they are on earth." I think these speculative statements are appropriate for an article on the colonization of Mars, but not one on the geology (or science in general) of Mars. I would delete this. Schaffman (talk) 15:18, 24 November 2010 (UTC)

I recommend removing discussion of breccia dikes in Syrtis Major section. while interesting, they seem too narrow a topic for broad scope of this article. Schaffman (talk) 11:08, 25 November 2010 (UTC)

Alba Patera
Alba is such an interesting and unusual feature, that it probably deserves its own brief subsection. Schaffman (talk) 16:06, 24 November 2010 (UTC)

Volcanic Plains
Article does not cover ridged plains and flow plains. I need to add a subsection on these features. Schaffman (talk) 20:23, 22 November 2010 (UTC)

Effect of Volcanoes on Climate
I recommend moving paragraph on volcanoes and early Mars climate to the Climate of Mars article. If there are no objections, I'll do this now.Schaffman (talk) 12:32, 26 November 2010 (UTC)

Lava Flow Photos
The photo with the crater ejecta overlying the lava flow is a beautiful illustration of Steno's law of superpositioning. I'm moving it to the Geologic History section. Schaffman (talk) 15:20, 27 November 2010 (UTC)

Still Working on Volcanism Section
I am actively working on the volcanism section. The rest of the article at and below Volcano Interactions with Ice are not my work. this is an ongoing project for me. I plan to address later features of the article as time permits. Once again, I welcome any comments on this rewrite effort.Schaffman (talk) 16:33, 27 November 2010 (UTC)

I'm now nearing completion of the volcanism section. Doing general cleanup, editing, and adding links and references where needed. May do some reorganizing. Section of equatorial frozen seas will be deleted and incorporated into discussion of lava flow plains. I don't think the interpretation of the flow plains in Cerberus as pack ice is now a majority opinion. But I could be wrong. I need to look some more.Schaffman (talk) 13:40, 30 November 2010 (UTC)

After completing this section, I'm thinking about moving it to the Volcanism on Mars article, which needs to be expanded.Schaffman (talk) 15:56, 30 November 2010 (UTC)

Still reorganizing volcanism section and adding references. I'm thinks of moving possible caves on Mars section to a new section at end of article called Interesting Geological Features. Schaffman (talk) 11:18, 1 December 2010 (UTC)

I'm currently rebuiding Volcanism on Mars article based on material here. Afterward, I will write a short summary to include in this article (thereby shortening it). This will take some time. Schaffman (talk) 14:08, 2 December 2010 (UTC)

I have put under construction tags on volcanism sections and subsequent sections. I'm taking a brief hiatus while I complete Volcanism on Mars article. Schaffman (talk) 18:18, 3 December 2010 (UTC)

Inverted Relief
I don't think this topic warrants its own section on par with, say volcanism or tectonics. Inverted relief can form by a variety of geologic processes (e.g., eskars). I'm moving it to the interesting geological features section for now. Schaffman (talk) 19:11, 1 December 2010 (UTC)

Dates?
Um... If there's no life on Mars, how does one determine or even approximate the dates given? On Earth, dates are always given by tree rings, contemporary records, or otherwise radiocarbon dates from previously organic tissue. Since there has never been found any kind of organic tissue on Mars, let alone trees or civilization, then are all these date wild guesses by so-called authorities? If so, then I would think such dates have no place on Wikipedia. And if they are not guesses, then how on Mars did we come up with that? I would appreciate an answer sooner rather than later. LutherVinci (talk) 00:02, 25 February 2011 (UTC)


 * The ages are based on the crater density of surfaces, just like on the moon. This is all explained in the Geologic History section of the article. Please read. Schaffman (talk) 09:42, 18 April 2011 (UTC)