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The following is an archived discussion of a featured article nomination. Please do not modify it. Subsequent comments should be made on the article's talk page or in Wikipedia talk:Featured article candidates. No further edits should be made to this page.

The article was promoted by Karanacs 18:32, 12 May 2009 [1].

243 Ida

[edit]
Nominator(s): Wronkiew (talk), Reyk YO!
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I am nominating this for featured article because Reyk and I have significantly improved it and would like an independent assessment. This was previously assessed as a good article by OhanaUnited and later received a thorough peer review by Chzz and several other editors. 243 Ida is one of the few asteroids imaged by a space probe. Wronkiew (talk) 01:35, 16 April 2009 (UTC)[reply]

  • Wronkiew and I have extensively rewritten this article and improved it a lot. The suggestions and concerns raised at the Good Article review and the Peer Review have, I think, been addressed and have further improved the article. I think it is now good enough that it meets, or at least is very close to meeting, all of the featured article criteria. Reyk YO! 01:44, 16 April 2009 (UTC)[reply]
  • Tech. Review
  • There are no disambiguation nor dead external links found with dab finder tool and the links checker tool, respectively.
  • The following ref is used more than once, and appears more than once in the ref section, use the ref name already used before.
Collapsed resolved issues. Wronkiew (talk) 04:19, 25 April 2009 (UTC)[reply]
    • "but its mass constitutes an insignificant fraction of the belt's total" This seems a tad unnecessary. Isn't the main belt comprised of enough asteroids that no one asteroid would ever constitute a significant fraction of the total?
      • Well, 1 Ceres and 4 Vesta account for a third and a tenth of the mass of the asteroid belt respectively, so the really big ones can constitute a significant fraction. Ida isn't one of them. Wronkiew wanted this sentence left in because it gives some perspective on Ida's size compared to other asteroids. I agree, but it could be made clearer- I'll have a think on how to do that. Reyk YO! 00:39, 17 April 2009 (UTC)[reply]
      By my calculations, Ida makes up 0.001% of the belt's mass, but since you're the second to recommend against the comparison, I removed it. Wronkiew (talk) 01:07, 17 April 2009 (UTC)[reply]
    • "Ida was named by Moritz von Kuffner" This is the only mention of Kuffner. Who was he and why was he the one who got to name the asteroid instead of Palisa?
      I'm working on this one, but it's going to take some time to come up with additional sources. Wronkiew (talk) 01:25, 17 April 2009 (UTC)[reply]
      Added more detail on von Kuffner. Palisa's reasons for letting von Kuffner name his asteroids is probably lost to history. Wronkiew (talk) 06:10, 17 April 2009 (UTC)[reply]
    • "Ida's reflection spectra was measured on 16 September 1980 by astronomers David J. Tholen and Edward F. Tedesco as part of the eight-color asteroid survey (ECAS). This led to the classification of Ida and other members of the Koronis family as S-type asteroids"
    • "Many observations of Ida were made in early 1993 by the US Naval Observatory in Flagstaff and the Oak Ridge Observatory, prior to the Galileo flyby" Yikes, not very good use of the comma there. "prior to the Galileo flyby" needs to be worked into the sentence better or dropped completely. Also, what Galileo flyby? The sentence is written as though the reader should already know what it is. I don't.
      I removed the "prior to" clause, as it was repetitive. The flyby was introduced in the lead. Wronkiew (talk) 04:18, 18 April 2009 (UTC)[reply]
    • "These improved the measurement of Ida's orbit around the Sun and reduced the uncertainty of its position during the flyby to within 60 km (37 mi)" Alright, what was the uncertainty before these observations?
    • "The decision to attempt an Ida flyby was delayed until the consequences of the loss of 34 kg (75 lb) of propellant, the amount needed to change Galileo's trajectory, could be evaluated" Not clear what's going on here. Who lost the propellant?
    • "it flew by Ida on 28 August 1993 at a relative speed of 12,400 m/s (28,000 mph)" Relative to Ida, correct? Then what was its absolute speed?
    • "Because Ida has a short rotation period, the probe imaged about 95% of the its surface during the flyby" It isn't entirely clear how the rotation period affects the surface imaging. Perhaps you should include how long the entire flyby lasted.
    • "Ida's relatively large surface exhibits a diverse range of geological features." Should be past tense, yes? We can't be entirely certain that the surface hasn't changed since Galileo.
    • What is stony-iron?
    • "and that the asteroid contained mostly core material" What is "core material"?
      Reworded. Wronkiew (talk) 06:42, 17 April 2009 (UTC)[reply]
      Still confusing. What do you mean by "from the core"? Did it start at the center and work its way out? Or did it come from the core material of some other object? --Cryptic C62 · Talk 18:27, 17 April 2009 (UTC)[reply]
      The two sentences comparing stony-irons to OC meteorites aren't vital to understanding the discoveries made by Galileo, so I removed them. Wronkiew (talk) 06:45, 18 April 2009 (UTC)[reply]
    • "Calculating Dactyl's orbit around Ida enabled a rough measurement of Ida's density"
    • "This low density ruled out the presence of significant quantities of metal, and indicates a non-stony-iron composition" Switches from past to present tense.
    • "The Galileo images also led to the discovery of a space weathering process active on Ida" Reads awkwardly. Suggestion: "The Galileo images also led to the discovery of an active space weathering process taking place on Ida"
      Done, though I edited your version a bit. Wronkiew (talk) 17:56, 17 April 2009 (UTC)[reply]
      Looks good, but now I've noticed something else: "The Galileo images also led to the discovery of an active space weathering process on Ida, which causes older regions to become more red in color" This sentence reads as though the "which" refers to the discovery, not the process. Here's an idea: "The Galileo images also led to the discovery that space weathering was taking place on Ida, a process which causes older regions to become more red in color over time." or something like that. --Cryptic C62 · Talk 04:56, 19 April 2009 (UTC)[reply]
    • "Space weathering changes the appearance of Ida's surface over time, with older regions becoming more red in color" I thought this was going to be a brief generic explanation of space weathering, but then it mentioned Ida. It should either serve as a standalone explanation or the relevant details (more red over time) should be merged into the previous sentence.
      Done, good idea. Wronkiew (talk) 06:54, 18 April 2009 (UTC)[reply]
    • "The same process affected both Ida and its moon, although Dactyl showed a lesser change. " So what does this mean? Is Dactyl younger than Ida? This just seems like an important but somewhat dead-end statement.
      Sorry, not enough information in the sources to say for sure what causes it. Wronkiew (talk) 06:54, 18 April 2009 (UTC)[reply]
      Alright, fair enough. I was just curious to see if the sources made any conclusions, but if not, then that's fine. --Cryptic C62 · Talk 04:56, 19 April 2009 (UTC)[reply]
    • "The color change revealed another detail about Ida's composition" This may be confusing for some readers since the previous sentence also dealt with Dactyl's color change.
      Reworded for flow. Wronkiew (talk) 06:54, 18 April 2009 (UTC)[reply]
    • "S-types are the most numerous kind in the inner part of the asteroid belt. OC meteorites are, likewise, the most common type found on the Earth's surface" Both of these statements should make it explicitly clear what "kind" and "type" refer to.
    • "Ida's mass is between 3.65 and 4.99 x 1016 kg, a measurement derived from the poorly constrained orbit of its satellite"
    • "This field is so weak that an astronaut standing on its surface could leap from one end of Ida to the other.[39] An object moving in excess of 20 m/s (70 ft/s) could escape the asteroid entirely" Consider merging these two sentences together, as they are making essentially the same point.
      Done. Wronkiew (talk) 07:00, 18 April 2009 (UTC)[reply]
    • "Ida's weak gravity coupled with its short rotational period produces some counterintuitive effects" This is true, but somewhat confusing. It might help to include the phrase "trajectories of projectiles" as it appears in the source.
      I don't have a better way to explain it, and it isn't vital information, so I removed the two sentences about projectile trajectories. Wronkiew (talk) 08:09, 18 April 2009 (UTC)[reply]
    • "Ida is a distinctly elongated asteroid, with an irregular surface,[41]" Ref 41, Bottke et al, doesn't really seem to be an appropriate reference for this statement. The ref seems to be a very broad overview of several satellites, not a presentation of new information: "We briefly review their characteristics below" Surely a claim as simple as this one can be attributed to a primary source.
    • "Whilst steep slopes tilting up to about 50° are present on Ida, the slope rarely exceeds 35°" These two claims seem to contradict each other. Suggest rewording the second clause to "the slope is generally less than 35°." or some such.
    • "Besides craters, other features are evident, such as grooves, ridges, and protrusions." A sentence like this should ideally come right after the bit about craters, not at the end of the paragraph. Assuming you keep the paragraph at all, that is.
      We're keeping the paragraph. Like you said, it explains terms which are used later in the section. Wronkiew (talk) 04:54, 22 April 2009 (UTC)[reply]
      Erm, perhaps I wasn't clear. "the bit about craters" refers to "Ida's surface appears heavily cratered and uniformly gray, although minor color variations mark newly formed or uncovered areas. Cratering has reached the saturation point, meaning that on average new impacts erase evidence of previous ones, leaving the total crater count unchanged." I wasn't suggesting to remove it from the paragraph altogether, I was suggesting to just move it up a few sentences. --Cryptic C62 · Talk 17:47, 22 April 2009 (UTC)[reply]
      I see now. Done. Wronkiew (talk) 01:26, 24 April 2009 (UTC)[reply]
    • "The surface is covered in a blanket" The surface of what? :)
    • Caption: "Galileo mosaic recorded 3.5 minutes before its closest approach" Uh... what? Might be less confusing if you nix the technical details and just say something like "Image of Ida's surface taken by Galileo."
      I reworded it to make it clear that this is a mosaic of images. Wronkiew (talk) 04:54, 22 April 2009 (UTC)[reply]
    • "The material for this layer originates from the many impact craters" This sentence is written as though the craters intentionally donated material for the regolith project. Perhaps "The material in this layer originated from the many impact craters" or some such.
      Reworded. Wronkiew (talk) 05:50, 22 April 2009 (UTC)[reply]
    • "Regolith can be moved over the surface of the asteroid by geological processes. One observed by Galileo was the downslope movement of debris." Yikes, needs some serious reordering. How about "Geological processes and Ida's own gravity can cause the regolith to move across the surface of the asteroid." or something?
      Reworded. Wronkiew (talk) 05:50, 22 April 2009 (UTC)[reply]
      I think you've cut too much out, because now the reader is given no clue as to why/how the regolith moves. --Cryptic C62 · Talk 17:47, 22 April 2009 (UTC)[reply]
      I restored the detail that it moves downslope. Wronkiew (talk) 04:09, 23 April 2009 (UTC)[reply]
    • "The appearance of this substance changes over time through a process called space weathering" Which substance? Silicate? Or olivine? Or pyroxene?
    • "The older regolith appears more red in color compared to freshly exposed regolith" It isn't entirely clear that this is connected to space weathering. Consider merging with the previous sentence.
      Clarified. Wronkiew (talk) 05:50, 22 April 2009 (UTC)[reply]
    • "Impact event" is used several times. It should be linked or explained at some point, as its meaning might not be clear to non-nerds. --Cryptic C62 · Talk
      Wikilinked, good idea. I don't think an explanation is necessary, as the term is not used in an introductory section. Wronkiew (talk) 01:22, 24 April 2009 (UTC)[reply]
    • The introductory paragraph of "Surface features" does not have any references. I see that the information is repeated later on in the subsections. Is this paragraph even necessary then? It may be confusing for some readers that terms like "regolith" and "ejecta block" are linked and well-defined here but not later on.
      Yes, it's just a summary of and introduction to the material in the section. If there's anything controversial there, I can add a reference to it. We didn't reference anything in the lead, either. Wronkiew (talk) 04:54, 22 April 2009 (UTC)[reply]
      Well, if we're going to treat this paragraph as a lead, then we'll follow WP:LEAD, which specifically states that information introduced here must also be present in the main body. "Saturation point" appears here but not in the crater section. Ida's color ("uniformly gray") is mentioned here but not later. "ejecta blocks" are explained in detail here, but not later. Either cite the new information in this paragraph, or make sure to include/cite everything in the main body. --Cryptic C62 · Talk 17:47, 22 April 2009 (UTC)[reply]
      I waffled on the "uniformly gray" sentence and added an inline citation for it. Inline citations are not required for every piece of new information. In the two other cases that you brought up, these definitions could be considered "subject-specific common knowledge", and are well covered by the sources in the references section. If you think either of these definitions are controversial or contain original research, I can add more inline citations. Wronkiew (talk) 16:39, 23 April 2009 (UTC)[reply]
      Alright, I'll buy the "subject-specific common knowledge", I had forgotten about that exception. However, "saturation point" should still be mentioned in the Crater section. --Cryptic C62 · Talk 00:01, 25 April 2009 (UTC)[reply]
      Moved it to the crater section and added a ref. Wronkiew (talk) 21:37, 25 April 2009 (UTC)[reply]
    • "Most of them are located within the craters Lascaux and Mammoth, but were not produced there." I skimmed through the source you've cited for this statement and found this statement: "The blocks that lie within or near the rims of craters Lascaux and Mammoth were likely mobilized in the low-velocity tail portion of the excavation flow that formed those craters." The inclusion of the word "likely" in this statement makes me think that "but were not produced there." is a bit too strong. You're more familiar with the material than I am, but my instinct tells me that "but were not necessarily produced there" would be a better choice.
      You're right. Done. Wronkiew (talk) 21:03, 25 April 2009 (UTC)[reply]
    • "This area attracts debris due to Ida's odd gravitational field." Perhaps "irregular" instead of "odd"?
      Done. Wronkiew (talk) 21:03, 25 April 2009 (UTC)[reply]
    • "Some blocks may have been ejected from the young crater Azzura on its opposite side" Eh? Whose opposite side?
      Clarified. Wronkiew (talk) 21:06, 25 April 2009 (UTC)[reply]
    • "The asteroid appears to be split into two halves, each featuring slightly different geology, connected by a "waist"... If [the waist] formed from impact craters, then the two halves may share the same geology" These two statements seem to contradict one another.
      Not really contradictory, more an indication that several interpretations exist about Ida's geology. I removed this and some other speculative material in the section. Wronkiew (talk) 21:26, 25 April 2009 (UTC)[reply]
      Well, I didn't think the material had to be deleted, it just needed to be clarified that the two ideas are both speculative. --Cryptic C62 · Talk 22:18, 25 April 2009 (UTC)[reply]
    • The two sections of the asteroid that are separated by the waist are Regions 1 and 2, yes? This isn't made explicitly clear in the Structures section. Also, it might be useful to have some sort of simple comparison between the two, such as noting which of the two is larger.
      The main difference between them seems to be the crater size distribution. I noted that the "regions" refer to the two halves of Ida. Wronkiew (talk) 05:40, 27 April 2009 (UTC)[reply]
    • "One is a prominent 40 km (25 mi) ridge named Townsend Dorsum that stretches 150 degrees around Ida's surface.[26][52]" Ref 52 adequately covers this material, but Ref 26 (Chapman p. 707) does not. I read through that page, but didn't find any mention of Townsend Dorsum. It only vaguely alludes to "the prominent ridge". Was this just a superfluous reference, or did you mean to cite a difference page?
      Only one prominent ridge on the asteroid, but the extra ref was superfluous. Wronkiew (talk) 05:40, 27 April 2009 (UTC)[reply]
    • "Ida's Region 2 features several sets of grooves, usually about 100 m (330 ft) deep and up to 4 km (2.5 mi) long" The use of "usually" implies that these grooves are not permanent. Also, what defines a "set" of grooves?
      Replaced "usually". The relevant dictionary definitions of "set" are sufficient to describe the arrangement of grooves, and I don't think we need to repeat that definition here. Wronkiew (talk) 06:29, 27 April 2009 (UTC)[reply]
      Alright, I was just wondering if there was a more specific definition that the reader should be aware of. --Cryptic C62 · Talk 14:27, 27 April 2009 (UTC)[reply]
    • "for example a set opposite the large indentation Vienna Regio" I don't think "the large indentation" is necessary, as you introduced Vienna Regio just a few sentences earlier.
      Removed the duplicate information. Wronkiew (talk) 05:40, 27 April 2009 (UTC)[reply]
    • Caption: "Asymmetric 1.5 km (0.93 mi) crater Fingal at 13.2°S, 39.9°E" What measurement does 1.5 km refer do? Diameter? Depth?
      Clarified. Wronkiew (talk) 05:40, 27 April 2009 (UTC)[reply]
    • "leaving the total crater count unchanged" Not necessarily true. Consider replacing "unchanged" with "approximately the same".
      Done. Wronkiew (talk) 06:29, 27 April 2009 (UTC)[reply]
    • "It is covered with craters of all sizes and stages of degradation" Is there something to which we could wikilink "stages of degradation"?
      Stage of degradation is a descriptive rather than a technical term. A possible link is to Erosion, but that doesn't describe the erosion of asteroid craters better than this article does. Wronkiew (talk) 06:29, 27 April 2009 (UTC)[reply]
    • "The major craters are named after caves and lava tubes on Earth" Is this true for all craters? Or just craters on Ida?
      Clarified. Wronkiew (talk) 06:29, 27 April 2009 (UTC)[reply]
    • Infobox: "Alternate name[note 1] A910 CD; 1988 DB1[2]" Note 1 doesn't seem to work. Ref 2 says it's just A910 CD; 1988 DB1, no subscript.
      The subscript is standard notation for provisional designations. However, a provisional designation from 1988 doesn't make any sense for this object. Without any other source to corroborate the alternate designation or any explanation in the JPL database, I think we may have misinterpreted the data. I've removed it until another source can be found. That also takes care of the strange note, which was a standard part of the infobox. Wronkiew (talk) 05:41, 28 April 2009 (UTC)[reply]
    • "The craters are simple in structure, bowl-shaped with no flat bottoms and no central peaks" That comma should be replaced with either a colon or "and".
    • "The composition of Ida's interior has not been directly analyzed, but is assumed to be similar to OC material based on observed surface color changes and its measured density" Whose measured density? Ida's? Or the interior's?
      In this case, it doesn't matter. As explained in this section, Ida's density is even throughout its extent. Wronkiew (talk) 16:55, 28 April 2009 (UTC)[reply]
      Well, I'd say it does matter. To someone who assumes that "it" refers to the interior, the notion that the interior's density has been measured conflicts with the notion that the interior has not been directly analyzed. --Cryptic C62 · Talk 03:22, 29 April 2009 (UTC)[reply]
      Fixed. Wronkiew (talk) 04:23, 30 April 2009 (UTC)[reply]
    • "and the asteroid's spin indicates an even density" Perhaps "consistent" rather than "even" ? "Even" implies that the density is a multiple of 2.
      Done. Wronkiew (talk) 04:23, 30 April 2009 (UTC)[reply]
    • "The range of stable orbits for Dactyl correspond to a bulk density between 2.27 and 3.10 g/cm3 for Ida" Does Dactyl's generally stable orbit vary within a certain range? Or is its exact orbit not known?
      Removed the information about Dactyl's orbit. This is already covered in more detail elsewhere. Wronkiew (talk) 04:23, 30 April 2009 (UTC)[reply]
    • "The grain density of Ida's chondritic material would range from 3.48 to 3.64 g/cm3" The use of "would" implies that these values are derived from the previous sentence, but the next sentence discusses the discrepancy between the two sets of values.
      Rewritten. Wronkiew (talk) 04:23, 30 April 2009 (UTC)[reply]
    • "The mineral content appears to be homogeneous throughout its extent. Galileo found minimal variations on the surface, and the asteroid's spin indicates a consistent density" minimal variations of what?
      Minimal variations in mineral content. I don't think it needs to be re-stated. Wronkiew (talk) 04:44, 1 May 2009 (UTC)[reply]
    • "Prior to the flyby" Erm, what flyby? The lead previously mentioned that the asteroid was visited. Do "visit" and "flyby" refer to the same thing?
    • "Ida's irregular shape is responsible for the asteroid's highly uneven gravitational field. The surface gravity is lowest at the extremities due to the fast rotation, and near the minimum radius due to less mass being present interior to that location" Why is this in a separate paragraph? It doesn't really make sense to discuss the gravitational field in two different paragraphs, though I see that this information should follow the paragraph about Ida's shape. Consider merging this paragraph into the astronaut rock chucking paragraph, then moving that paragraph to after the shape paragraph. Also, this little paragraph makes total sense up until the final clause about the interior location radius birthday present. I had to read that at least 3 times, and I'm still not entirely sure what it means.
      • Merged the paragraphs as you suggested. Reyk YO! 22:02, 17 April 2009 (UTC)[reply]
        • Good, but the part about the interior mass gravity thingo is still confusing. --Cryptic C62 · Talk 22:50, 20 April 2009 (UTC)[reply]
          Rewritten. Wronkiew (talk) 04:44, 22 April 2009 (UTC)[reply]
          I understand what you're trying to communicate with this statement, and I've been wracking my brain trying to come up with a clear, concise way to explain it, and it looks like you guys have been too. I think splitting it off from the extremities sentence definitely helps. I think the best thing to do would be to fully explain the characteristics of the "waist" when you first introduce it earlier in this paragraph. That will allow you to explain the differences in the gravitational field like this: "The gravitational field is also weaker at the "waist" because it encompasses less mass than the main body of the asteroid." That's not exactly a perfect sentence either, but eh. I definitely think giving more info about the waist earlier on will help. --Cryptic C62 · Talk 17:47, 22 April 2009 (UTC)[reply]
    • "Some grooves are related to major impact events" Perhaps this sentence should include "though" or "however" as it contrasts the sentence before it.
      It does not contrast. The only seismic waves on an asteroid are caused by impact events, and I think that's knowledge we can expect readers to start with. Wronkiew (talk) 05:40, 27 April 2009 (UTC)[reply]
      Clearly not! I, too, am a reader, and I had no idea that that was the case! --Cryptic C62 · Talk 14:27, 27 April 2009 (UTC)[reply]
      I attempted to explain the association between impact events and seismic waves, but the resulting prose had so many "might be"s and "appear to"s that I decided to drop it entirely. Wronkiew (talk) 16:46, 28 April 2009 (UTC)[reply]
      Cool. Also, what does it mean to be "related to" impact events? "Caused by" seems more logical. --Cryptic C62 · Talk 03:22, 29 April 2009 (UTC)[reply]
    • "and range in age from fresh to very old" Yikes. This sentence is totally useless without some hard numbers. Even rough estimates would be better than "fresh" and "very old".
      The next sentence defines "very old" as comparable in age to Ida itself. Wronkiew (talk) 06:29, 27 April 2009 (UTC)[reply]
      ...Which isn't discussed until section 7. If, by chance, the reader reads through the article backwards and gets a sense of the age of Ida by the time s/he gets to this section, "How old is very old?" will have been answered, but "How fresh is fresh?" will remain. --Cryptic C62 · Talk 14:27, 27 April 2009 (UTC)[reply]
      Clarified. Reyk YO! 00:26, 29 April 2009 (UTC)[reply]
      I think the "range" has lost its meaning entirely at this point. Why not just shorten it to "and some are as old as Ida itself."? --Cryptic C62 · Talk 03:22, 29 April 2009 (UTC)[reply]
    • "Region 2 contains nearly all of the craters larger than 6 km (3.7 mi) in diameter, but Region 1 has no large craters at all. Some craters are arranged in chains" Cool stuff. Any conclusions that can be drawn from these statements?
      I believe we have hit the best parts of the available literature. Wronkiew (talk) 06:29, 27 April 2009 (UTC)[reply]
      Well, I had a look for myself, and found this sentence: "Crater chains may result from low-velocity impact of ejecta from a primary crater (although no crater chain can yet be linked to a larger primary) or from a string of original impactors". Also, this source was published in March 1994 and is based on images taken in August 1993. The author makes reference to new images that would be made available during that spring, as well as the increased accuracy in identifying features that such images would provide. Has any attempt been made to find an analysis of these images? --Cryptic C62 · Talk 14:27, 27 April 2009 (UTC)[reply]
      Chapman 1996 and Sullivan et al. 1996 seem to be the most detailed analyses of the full set of images. I have not seen a better analysis of the crater chains, and the one in Greeley et al. 1994 is not specific to Ida. Wronkiew (talk) 00:52, 29 April 2009 (UTC)[reply]
    • "Another significant crater is Afon, which marks the prime meridian" You've linked to prime meridian, but that is an article that is devoted almost entirely to discussion of the prime meridian on Earth. Did you mean to link to a subsection? --Cryptic C62 · Talk 14:27, 27 April 2009 (UTC)[reply]
      Prime meridian does emphasize the prime meridian on Earth, but the lead section contains a useful definition of the term which applies to all bodies. Wronkiew (talk) 00:40, 28 April 2009 (UTC)[reply]
      Are we reading the same article? Nothing in the lead of prime meridian gives any indication of its use on other bodies. Perhaps linking to the woefully inadequate subsection on other planetary bodies would help. --Cryptic C62 · Talk 03:22, 29 April 2009 (UTC)[reply]
      We are. The lead section contains the important information that the prime meridian is arbitrary and that it corresponds to the International Date Line on the Earth. The other planetary bodies section contains no useful information whatsoever in the context of Ida's prime meridian. Wronkiew (talk) 00:39, 30 April 2009 (UTC)[reply]
      Bah. Why don't you just say something like "marks Ida's prime meridian" rather than "marks the prime meridian" ? --Cryptic C62 · Talk 21:47, 30 April 2009 (UTC)[reply]
      Done. Wronkiew (talk) 16:49, 12 May 2009 (UTC)[reply]
    • "Olivine and pyroxene were detected by Galileo" This sentence should include "Ida" in it somewhere.
      Done. Wronkiew (talk) 05:41, 28 April 2009 (UTC)[reply]
      Argh, now the sentence reads quite awkwardly: "Olivine and pyroxene were detected on Ida by Galileo." How about something like this: "During its flyby, Galileo detected the presence of both olivine and pyroxene on Ida's surface." --Cryptic C62 · Talk 21:47, 30 April 2009 (UTC)[reply]
    • "interior voids have been predicted by simulations and observed on other Solar System objects" Shouldn't this be in other objects? Also, "simulations" is a tad vague.
      Removed. Wronkiew (talk) 04:23, 30 April 2009 (UTC)[reply]
    • "the asteroid's spin indicates an even density." This sentence seems to conflict with the final paragraph in this section. How can an object with interior voids and a layer of megaregolith have a consistent density?
      "Interior voids" removed, as it was general to all asteroids and not Ida in particular. I don't see a conflict beteen the roughly consistent density and the fractured rock throughout. Wronkiew (talk) 04:23, 30 April 2009 (UTC)[reply]
      Alright, perhaps I'm envisioning "fractured rock" differently than I should. However, the conflict still remains with the interior voids, though it seems you've swept that under the rug, something I'm not really a fan of. You said there were simulations which predicted voids. I said your description of said simulation was vague. Vagueness and the fact that the content "was general to all asteroids" is not an excuse to eliminate relevant conflicting content. --Cryptic C62 · Talk 21:47, 30 April 2009 (UTC)[reply]
      Not really "swept under the rug". I can explain the discrepancy, but it's just not worth going into that much detail about scientists' theories about what Ida's structure might be. If you think this information is vital to the article, I can add it back with a better explanation, otherwise I'd rather stick to more solid facts if possible. Wronkiew (talk) 04:44, 1 May 2009 (UTC)[reply]
      Why don't you just explain it to me here so we can discuss it in greater detail? --Cryptic C62 · Talk 19:34, 3 May 2009 (UTC)[reply]
      Sure. What we really know about Ida's internal density variations is that it is roughly consistent in terms of angular momentum. This would imply a homogeneous interior only if Ida were shaped like a perfect, tasty doughnut. Since it is a three-dimensional, irregularly shaped object, it could have extreme variations in density and coincidentally look like it had a consistent density. For example, Ida could be made of styrofoam in the northern hemisphere and lead in the southern hemisphere, and it would move the same way that Galileo observed. However, this is considered unlikely based on our understanding of how asteroids are formed. The nature of this measurement also leaves open the possiblity of large internal voids inside Ida, because if they are distributed evenly throughout it, they would be undetectable. What this all really means is that the two halves of Ida do not differ in bulk density to a measurable degree. Wronkiew (talk) 04:52, 7 May 2009 (UTC)[reply]
    • "The calculated maximum moment of inertia of a uniformly dense object the same shape as Ida coincides with the spin axis of the asteroid." Um, what? "Coincides" implies that these two values are comparable, which is mathematically unsound. This is like saying "The maximum number of employees at Big City Construction coincides with Eric Bobrow, the foreman." Yes, the two are related, but in no way do they "coincide". My guess is that you meant to say something like this: "For an object with the same shape as Ida, the maximum possible moment of inertia is achieved when the object is uniformly dense and has a certain axis of rotation (INSERT DESCRIPTION OF AXIS HERE). Ida's axis of rotation (SUMMARIZE DESCRIPTION OF AXIS HERE), implying that it is uniformly dense." That isn't perfectly logical either, but at least it provides all of the steps required for the comparison to make sense to the reader.
    • "Ida's axis of rotation precesses with a period of 77,000 years" Another mention of the axis of rotation, but still no description of such an axis!
      Not sure what you're looking for here. The direction of Ida's axis is defined in the infobox. We don't have any additional information on where Ida's spin axis is located, except at +90 and -90 degrees latitude. Wronkiew (talk) 05:11, 1 May 2009 (UTC)[reply]
      The whole time I've been reading this article, I've had no idea how the latitude-longitude coordinate system works. It totally makes sense on the lovely spherical Earth on which we live, but I don't understand how it applies to asteroids. Perhaps this is something that those in the field of astronomy would consider "common knowledge", but not all of our readers are astronomers. What I'm trying to get at here is that some sort of of physical landmark would be incredibly useful in helping users to visualize this. Does the spin axis go through the waist?
      Ida and Earth both rotate around a single axis, marked by the poles. The midpoint between the north and south poles, in spherical coordinates, is the equator, or zero degrees latitude. The equator does not coincide with the waist, and no one has planted a flag on its north pole yet. You might want to watch the Galileo approach animation for a better sense of Ida's rotation. Wronkiew (talk) 04:52, 7 May 2009 (UTC)[reply]
      *headdesk* Perhaps I'm not making it clear what I'm asking for. The animation is helpful, but not precise. My question is this: Where (physically where, don't tell me 90° north latitude) is Ida's spin axis? The article repeatedly abuses the coordinate system without ever making it clear how it is defined on this asteroid. Something like this would help: "The spin axis runs perpendicular to the asteroid's longest dimension and passes through the asteroid approximately 20 meters from the waist." Do you see what I'm getting at? Physical landmarks. Not flags. Not mumbo jumbo. --Cryptic C62 · Talk 05:15, 7 May 2009 (UTC)[reply]
    • There is a section labeled "Orbit and rotation". It contains no information about the orbit. It does, however, contain totally irrelevant historical information that should probably be moved to "Origin".
      Discovery information moved to "Discovery and observations", added more detail about Ida's orbit. Wronkiew (talk) 05:11, 1 May 2009 (UTC)[reply]
      Much better, though I think this paragraph would benefit from some more numbers. What is Ida's orbital speed relative to the sun? You say it orbits at an average distance of 2.862 AU. Any mention of what the variation is? --Cryptic C62 · Talk 19:34, 3 May 2009 (UTC)[reply]
      More detail about Ida's orbit can be found in the infobox, where it belongs. Wronkiew (talk) 04:52, 7 May 2009 (UTC)[reply]
      Unfortunately for the entire non-astronomy-obsessed English-speaking Wikipedia-browsing population of the Earth, the infobox uses terms that go way over our heads. This section gives you an opportunity to explain some of the more interesting orbital characteristics in full sentences. --Cryptic C62 · Talk 05:15, 7 May 2009 (UTC)[reply]
    • "However, this is inconsistent with the estimated age of the Ida–Dactyl system of less than 100 million years; it is unlikely that Dactyl, due to its small size, could have escaped being destroyed in a major collision for longer" Yikes, very awkwardly arranged. How about: "However, it is unlikely that Dactyl, due to its small size, could have avoided being destroyed in a collision for more than 100 million years."
      I think the first version is clearer, if a little verbose. Wronkiew (talk) 06:45, 9 May 2009 (UTC)[reply]
    • "The difference in age estimates may be explained by an increased rate of cratering from the debris of the Koronis parent body's destruction" Not entirely certain what this sentence means. My understanding is thus: At some point, the Koronis parent body was destroyed entirely, and the resulting debris created craters on Ida's surface much faster than before. This discrepancy in the rate of cratering affected the accuracy of the age estimate, yes?
    • "A small satellite named Dactyl" Is there something to which we could link "satellite"? Some of the less nerdy readers might not be aware that "satellites" are not necessarily man-made.
      Done. Wronkiew (talk) 04:52, 7 May 2009 (UTC)[reply]
    • "Dactyl was initially designated 1993 (243) 1" Was this meant to be a placeholder name like ununoctium?
      This is explained in the wikilinked article. Wronkiew (talk) 04:52, 7 May 2009 (UTC)[reply]
    • "Dactyl is an "egg-shaped", but "remarkably spherical" object measuring 1.6 × 1.4 × 1.2 km (0.99 × 0.87 × 0.75 mi). It was oriented with its longest axis pointing towards Ida" Why the random switch from present to past tense?
      It's safe to say that it did not change shape in the past 15 years, but we've no idea if it is still oriented the same way. Wronkiew (talk) 04:52, 7 May 2009 (UTC)[reply]
    • "These features, and Dactyl's spheroidal shape, imply that the moon is gravitationally controlled despite its small size" This strikes me as being a bit odd. Why would the size of an object be relevant to whether or not it is gravitationally controlled?
    • "roughly 10–20 times smaller than Ida" I've never understood how something can be "10 times smaller" than something else. Does this mean Dactyl is 1/10th to 1/20th the size of Ida? Or that Ida is 10 to 20 times larger than Dactyl? Both of these mean the same thing and are clearer than the phrasing currently employed.
      Removed. Wronkiew (talk) 06:45, 9 May 2009 (UTC)[reply]
    • "the Hubble Space Telescope observed Ida for eight hours and was unable to spot Dactyl" Bolded for emphasis. Not particularly scientific.
    • We now seem to have the opposite problem here: Dactyl's rotation and orbit section has no information about its rotation!
      Renamed the section. Wronkiew (talk) 16:47, 12 May 2009 (UTC)[reply]
    • "It is extremely unlikely that it was captured by Ida" Because...
    • I recommend that instead of giving Dactyl four subsections (which are confusingly similar to those about Ida), you split Dactyl off into a separate article.
      This has come up before. In my opinion, we do not know enough about Dactyl to make a decent standalone article. Wronkiew (talk) 16:47, 12 May 2009 (UTC)[reply]
    • Backtracking: "Ida's rotation period is 4.63 hours, making it one of the fastest rotating known asteroids. It is in the top 10% of measured asteroids by spin." Yuck. How about: "Ida's rotation period is 4.63 hours, making it one of the fastest rotating asteroids yet discovered." the second sentence is useless trivia.
      Done. Wronkiew (talk) 16:47, 12 May 2009 (UTC)[reply]
  • This concludes my read-through. Good work so far. --Cryptic C62 · Talk 17:02, 7 May 2009 (UTC)[reply]
  • Tentative support—It's good overall, with only a couple of nits to pick:
    • "...Ida is one of the larger asteroids in the main belt." Unfortunately this doesn't really say anything. A JPL Small-Body Database query finds 1,735 known MBAs with a diameter of 15 km or larger. So you could potentially say something more definitive, such as it is among the 2,000 largest known MBAs.
      I couldn't find a reliable source that has a size distribution of main belt asteroids, so I removed the comparison. Also, the diameter is 31.4 km, according to the source cited in the infobox, so I fixed that as well. Wronkiew (talk) 04:38, 21 April 2009 (UTC)[reply]
    • "Estimates of Ida's density are constrained to less than 3.2 g/cm3 ... This low density rules out the presence of significant quantities of metal..." Please clarify whether you mean iron here. Note that the the density of aluminum is 2.7 g/cm3 and the density of silicon is 2.33 g/cm3, which are both lower than this value and the latter implies there is a non-trivial proportion of denser elements. Also, wouldn't a maximum porosity of 42% indicate a much higher density for the solid parts?
      I reworked the sentence with information from a new source. Wronkiew (talk) 06:47, 21 April 2009 (UTC)[reply]
    Thank you.—RJH (talk) 19:29, 20 April 2009 (UTC)[reply]

Image review as follows:

  • File:Ejecta block on 243 Ida.svg: how did you obtain the image from http://pds-imaging.jpl.nasa.gov/cgi-bin/Nav/GLL_search.pl? Why is it an SVG?
    SVG is the native format for this diagram. It could be converted to JPEG, but it would lose some information. The ID 202562313 is the time stamp for the image, which you can search for in the database with the start and end time fields. Wronkiew (talk) 15:19, 28 April 2009 (UTC)[reply]
    See below for comments regarding the format. I am still rather confused on how to obtain the image. The PDS brings up a field of checkboxes, tabs, and fields. I keyed the ID in the OBSERVATION_ID and clicked on SUBMIT, but the next screen stated the image cannot be found. Jappalang (talk) 01:16, 29 April 2009 (UTC)[reply]
    You need to enter the ID in both the Min and Max fields of SPACECRAFT_CLOCK_START_COUNT. The database does not allow direct links to the images. Wronkiew (talk) 05:52, 29 April 2009 (UTC)[reply]
  • File:Fingal on 243 Ida.svg: why is this an SVG?
    Same as above. Neither of these images have a particularly large file size. Wronkiew (talk) 15:19, 28 April 2009 (UTC)[reply]
    That does not quite answer the question. Inproper format comes into play here. SVGs are containers of vectors; they are scripts of lines (text), not data. The two images are not rendered in terms of vectors; rather, their bitmaps are pasted in the scripts as arrays of raw data, which would not benefit from the scaling that vectors give and may result in larger file sizes than JPGs. No benefit is derived from them as SVGs. I have constructed File:Fingal on 243 Ida.jpg from the large image. Is this acceptable (as inserted in the article)? Jappalang (talk) 01:16, 29 April 2009 (UTC)[reply]
    I would prefer that the SVG version be placed in the article. The Fingal image in particular contains a rather high-resolution overview which is lost in the JPEG version. The SVG version is also not much larger than the file sizes of its included images. The overview image by itself, in JPEG format, takes up 238 KB. The SVG is 245 KB. A rasterization of this diagram at full resolution in JPEG format would take many times that amount. In my view, this is an entirely appropriate use of the SVG format, and, on top of that, it's in an editable format, so labels and other elements can be added later with no loss in quality. As for WP:IUP, it says diagrams should be in SVG format, while photos should be in JPEG format. We obviously disagree over whether these images are diagrams or photos, but, in any case, these recommendations are subject to common sense. There is no reason to degrade the quality of these images as displayed in the article just to follow the policy. Wronkiew (talk) 05:52, 29 April 2009 (UTC)[reply]
    I still fail to see the purpose of it stuffed in SVGs. The "rather high-resolution overview" is of no use; no one would get to see its full resolution unless they open it in an SVG editor and zoomed in. The overview is simply a reduced size File:243_Ida_large.jpg with an orange box to denote the zoomed in area. There is no degradation of image quality as far as I am concerned. It also does not answer why the above image (Ejecta) is in SVG; it has no high resolution texture stuffed in it. Diagrams, as definitions go, are plans, sketches, drawings, or outlines. While I do not disagree that this definition could be narrow in the sense that marked photos serve pretty well as illustrated guides, there could be reasons why such wording is used. SVGs are advocated for diagrams, mainly (in my opinion) because text and fine lines will not be lost when rescaled; I doubt it is to stuff high resolution textures into small size images. Jappalang (talk) 12:36, 29 April 2009 (UTC)[reply]
    I posted a comparison of the two images at 800x800 on the talk page. 320x320 is just the preview resolution for the SVG. Wronkiew (talk) 16:01, 29 April 2009 (UTC)[reply]

WP:IUP would ask for the two above images to be JPGs. All other images are verifiably in public domain or appropriately licensed. Jappalang (talk) 07:05, 28 April 2009 (UTC)[reply]

  • Support — I'm not at all familiar with asteroids or space objects, but this article was written well enough and included enough information for me to understand the subject and grasp its significance. Nice work by everyone who contributed. I've got just one criticism — commas aren't being used correctly in spots throughout the article. In the last sentence of the first paragraph: "It was the second asteroid to be visited by a spacecraft, and the first found to possess a satellite.", you shouldn't use the comma before "and". This is because the second clause — "the first found to possess a satellite" — can't stand alone as a sentence. If you'd said "It was the second asteroid to be visited by a spacecraft, and it was the first found to possess a satellite.", the comma would be needed. But since the subject isn't restated, you shouldn't use a comma before the conjunction. I found a handful of examples of this throughout the article. But as I said, this is a minor thing and doesn't affect the ability of a reader to understand the article. Nice work. JKBrooks85 (talk) 08:16, 10 May 2009 (UTC)[reply]
The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.
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