Wikipedia:Peer review/Rhea (moon)/archive1

Rhea (moon)

I've listed this article for peer review because I've spent some time improving and expanding it lately, with the aim of nominating it for GA in the fairly distant future. I'd like to know how I've done so far, and what, if any, the major problems with the article are.

Thanks, Cremastra (talk) 21:31, 14 June 2024 (UTC)

Comments from ArkHyena

First, props to you for helping improve an article of one of Saturn's major moons! Their expansions and rewrites are certainly far overdue, and many articles of Saturn's moons still undersell how cool they are.

Comments and suggestions after a skim:

Lede

• Ref for the "hydrostatic equilibrium" claim in lede is not needed, as it is adequately sourced later in text.  Done
• Rhea's discovery is relegated to a single-sentence paragraph in the lede. This should be expanded upon: where did Cassini discover it, and were there any further astronomical developments before the beginning of the Space Age? Additionally, a quick synopsis of Rhea's exploration could do well here.  Partly done

Discovery

• Rhea is considered a member of the historical Sidera Lodoicea, perhaps this could be mentioned?  Done

Orbit

• More info could be added; I dug up an open-access article[1] that seems to note how some of Saturn's moons, including Rhea, may have been influenced by evection resonances or near-resonances (resonant perturbations from the Sun) throughout their histories and that, due to dynamical similarities with Dione and Tethys, Rhea may once have had trojan moons of its own that are now lost/destroyed due to crossing an evection resonance.

Physical characteristics

• Rhea's radius is listed quite late; should be moved up as it's a basic yet important figure.  Done
• Mentioning or crediting specific astronomical figures throughout, esp. in the paragraph discussing internal structure, should be done.
• "Rhea has a rather typical heavily cratered surface" > "Rhea's surface is dominated by heavily cratered terrain", perhaps?
• Merge the final paragraph with another; consider integrating it with "The extensive dark areas are thought to be deposited tholins ... and hydrogen."  Partly done, might need a bit of polish.

Formation

• "However, a proposed model..." by whom?  Done

Atmosphere

• "The surface density of the exosphere is from 10⁵ to 10⁶ molecules in a cubic centimeter..." A comparison with the density of Earth's atmosphere at sea level may be helpful, as 10⁶ molecules/cm² can seem like a lot to a layperson when it (relatively) isn't.

Exploration

• This section is unusually brief overall, and the very short portion dedicated to Voyagers 1 and 2 is uncited. In particular, what discoveries did the Voyagers make, and could scientists deduce any properties from Voyager obs? Perhaps Cassini even upended old assumptions based on Voyager data.

Kusma

Comments to follow soon. —Kusma (talk) 07:37, 18 June 2024 (UTC)

• Is there a difference between having a synchronous orbit and tidal locking? (Is there a difference between what happens with Rhea and with the Earth's Moon)?
• "Like Dione" who is Dione?  Done
• "The surface temperature is hundreds of degrees Celsius below freezing" that is a weird way to express that it is below -200 C (the only "hundreds" you can be below of) and not the same as the infobox's max temperature of 99K. Better to say something like "between -220 and -170 C" or to use Kelvin  Done
• Discovery: Who was Cassini, and where did he live? Who paid for his telescope?
• Gloss the Sidera Lodoicea (what are they?) and explain what the name means. (I see this happens in the next section; instead of duplicating, perhaps just remove the "Sidera Lodoicea" from this section, or join Discovery and Naming and talk more about Cassini's studies of Saturn in general for context).
• Mention that Titan had already been discovered by Huygens and was not actually called "Titan" until later?
• Physical characteristics: What is Ice II, and why do people believe it exists inside Rhea?  Done
• "a surface area of about 7,325,342 square kilometres" seven significant digits and "about" do not work well for me.

@Kusma: Sorry, it is a bit unclear what you want here. Something in between the two? Removal of the vague 'about'? Cheers, Cremastra (talk) 21:49, 18 June 2024 (UTC)

Remove the fake precision. "7.33 million square kilometres" would be a lot better. —Kusma (talk) 07:12, 19 June 2024 (UTC)

Also, this appears to be the surface area of the ball with the same volume, which is not the same as the surface area of Rhea. Even discounting the craters, Rhea does not seem to be perfectly spherical but "well described by [a] triaxial ellipsoid" [2]. —Kusma (talk) 09:35, 19 June 2024 (UTC)

• Are the moments of inertia measured or theoretical? (how does one measure these?)
• Link Moment of inertia factor. That article gives 0.3911 ± 0.0045, almost as homogeneous as the Moon.
• " dissimilar leading and trailing hemispheres, suggesting similar composition and histories" What is similar and what is dissimilar? Is the leading hemisphere of Rhea similar to the leading hemisphere of Dione, or is Rhea's leading hemisphere different from the trailing one and also different from Dione's leading hemisphere?  Done
• "wispy terrain" shouldn't this be something like "previously described as "wispy terrain""?  Done
• "trailing hemisphere (the side facing away from the direction of motion along Rhea's orbit)" this explanation should be at the first mention of the trailing hemisphere, or if you repeat it, at the first mention in this section.
• "anti-Cronian hemisphere" if you do not reuse this word, there is little point in introducing it here? Or is this something everybody talking about moons of Saturn needs to know?  Done
• "roughly comparable to the basin Odysseus on Tethys" in what way? size? shape?  Fixed
• "may be one of the youngest craters on the inner moons of Saturn" can you be more precise? Better to attribute such hypotheses  Done
• "model proposed by Erik Asphaug and Andreas Reufer for the formation of Titan" this is cited to a 2012 pop-sci article; it would be good to dig out the most current scientific literature about this (citations of the article by Asphaug and Reufer would be a place to start)
• Generally a lot of the sources is over a decade old. Is all of the research still up to date? This is especially a question for the "ring system" issue.
• Exploration: what kind of images did we get from these flybys? Say more about the Voyager missions; how close to Rhea did they come? What was the mission of Cassini?  Partly done
• Notes a/b/c are repetitive and a bit odd, really. Are they just supposed to say "didn't find this in the sources, so I did a routine computation to present these values"? I would expect that there are sources, and if not, to say exactly how things were computed (and from which sourced values), or to just not present values not in the literature.

An interesting article about a moon I had not read about. To get this up to scratch, I suggest some expansion along the lines of the above plus a thorough literature search to make sure the article is up to date on the current scientific consensus. Happy editing, —Kusma (talk) 12:51, 18 June 2024 (UTC)

Femke

• It is the smallest body in the Solar System for which precise measurements have confirmed a shape consistent with hydrostatic equilibrium. --> Do we need to start with such a difficult concept? Or can we say in simpler terms? If not, I would omit from the lead per WP:EXPLAINLEAD
• A layer of Ice II (a high-pressure and extra-low temperature form of ice) is believed, based on the moon's temperature profile, to start around 350 to 450 kilometres (220 to 280 mi) beneath the surface --> I find it slightly akward to read. Maybe an n-dash rather than commas would improve flow? The reason it reads awkward to me is that we have two "interruptions": the hyphens and the subclause.
• In a paper published in 2007 it was claimed --> argued? Claimed may imply they were wrong. Overall, this seems to be an old debate, and one before at least a couple more flybys. Do we need it here, or can we just discuss the current thinking? I always prefer to keep these old debates of of articles to keep them accessible and in symmary style.
• Rhea has a rather typical heavily cratered surface, with the exceptions of a few large Dione-type chasmata or fractures (formerly known as wispy terrain) on the trailing hemisphere (the side facing away from the direction of motion along Rhea's orbit) and a very faint "line" of material at Rhea's equator that may have been deposited by material deorbiting from its rings. --> Another one of these sentences with too much interruption. Maybe a split in 2 or 3 might help? —Femke 🐦 (talk) 19:18, 4 July 2024 (UTC)
• The formation section seems to be based on an old press release, which may result in undue attention to this one paper. Is there a recent paper discussing this? I would avoid mentioning the authors inline. —Femke 🐦 (talk) 19:53, 4 July 2024 (UTC)