L10 review Group G part 1 of 2: caption verification (G3, G4, G5)

Three of the six Group G items resolved using local source-paper PDFs and direct image inspection. The remaining three (G1 Widemann, G2 Bibring, G6 Zahnle citation) are deferred — see commit footer.

G3 Wordsworth+2016 schematic (fig:wordsworth-schematic): VERIFIED genuine. The hand-drawn cartoon IS Figure 5 of the Wordsworth+2016 AREPS review (page 23 of the PDF; verified against ~/git/references/exoplanets/Wordsworth+2016_AREPS.pdf). Wordsworth drew it himself in that informal style for the review. The memo's concern that it might be a third-party cartoon is unfounded. Caption tightened to make the (Fig. 5) provenance explicit.

G4 Wicht+2017 offset-dipole (fig:wicht-offset): caption claimed "red equatorial flux concentrated in the northern hemisphere"; the image clearly shows yellow/orange (positive flux) concentrated in the LOWER hemisphere of all three Mollweide panels, with blue (opposite-sign flux) in the upper hemisphere. This is the correct physical signature of Mercury's northward-offset dipole: the magnetic dipole sits ~480 km north of the planetary centre, so the southern surface lies closer to the dipole's pole-end and samples a stronger field. Caption rewritten to flip "northern" -> "southern" and to include the ~480 km offset that explains the asymmetry.

G5 Margot+2007 libdata (fig:margot-libdata): the figure annotation explicitly reads "C/MR^2 = 0.380" while the lecture body text on lines 67 and 79 quotes the modern best value 0.346. Verified by direct inspection: the histograms ARE of C_m/C (mantle moment fraction, x-axis label), and 0.380 is parenthesised in the panel as the assumed total moment used at the time of Margot+2007. The 0.346 in body text comes from later refinements (radio science + improved libration with MESSENGER). Caption updated to acknowledge the 2007 vs modern values, removing the apparent contradiction without rewriting the figure or body text.

DEFERRED items (Group G part 2):

- G1 Widemann+2023 three-missions render (fig:venus-render): caption claims background is "Akatsuki UV imaging"; cannot verify without source paper. Tim has access via institutional library if confirmation is needed.
- G2 Bibring+2006 phyllosilicate map (fig:venus-terrains or similar): cannot verify crop and panel identity without source paper. As above.
- G6 L9 line 929 NC/CC noble-gas dichotomy citation: per Tim's pre-stated preference (decision 3 in sec.6.1), this citation-attribution call is flagged for Tim to adjudicate manually rather than Claude opening source PDFs and choosing.

Tracked in planning/course_development.md sec.6.2 Group G.

Author: timlichtenberg

book/10_mercury_mars/mercury_mars.md

@@ -56,7 +56,7 @@ Radar speckle correlation functions from {cite:t}`Margot2007` demonstrating the
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-Histograms of best-fit values for the diagnostic moment-of-inertia ratio $C_m/C$ (the fraction of the total moment carried by the silicate mantle alone), drawn from Monte Carlo realisations of {cite:t}`Margot2007`'s data with two different sets of constraints. The distributions are inconsistent with a fully solid Mercury and require a decoupled, at least partly liquid core.
+Histograms of best-fit values for the diagnostic moment-of-inertia ratio $C_m/C$ (the fraction of the total moment carried by the silicate mantle alone), drawn from Monte Carlo realisations of {cite:t}`Margot2007`'s data with two different sets of constraints (panels A and B). The annotation $C/MR^2 = 0.380$ in the original figure reflects the total moment-of-inertia value adopted in 2007; subsequent refinements (radio-science and improved libration measurements with *MESSENGER*) have lowered this to $C/MR^2 \approx 0.346$, the value used in the body text and in the interior structure inversion below. The distributions are nevertheless inconsistent with a fully solid Mercury and require a decoupled, at least partly liquid core.
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 A second consequence is that the rotation rate itself is a sensitive probe of Mercury's interior. {cite:t}`Margot2007` used Earth-based radar to track surface speckle features across multiple Mercurian rotations and measured the **forced libration in longitude**, the small back-and-forth wobble of the planet over its $88$-day year. The amplitude of that wobble depends on whether the entire planet (mantle plus core) responds rigidly to the time-varying solar torque, or whether a fluid core decouples from a thinner librating mantle. The measured value of $35.8 \pm 2$ arcseconds is roughly twice what a fully solid Mercury would show. This was the first direct observational evidence that Mercury's outer core is liquid today, in contradiction to the picture (held since *Mariner 10*) that such a small body would have cooled and frozen completely.
@@ -117,7 +117,7 @@ Mercury's magnetic field is unique among solar system bodies in two ways. First,
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-Maps of the radial magnetic field at the surface of Mercury (top) compared with two of {cite:t}`Wicht2017`'s numerical dynamo models (CW3, middle, and CW4, bottom) that incorporate a thermally stratified outer core layer. The hemispheric asymmetry of the radial field, with red equatorial flux concentrated in the northern hemisphere, is the surface signature of the offset dipole. Models with a stably stratified upper core can reproduce both the weakness and the asymmetry of the observed field.
+Mollweide maps of the radial magnetic field at the surface of Mercury (top) compared with two of {cite:t}`Wicht2017`'s numerical dynamo models (CW3, middle, and CW4, bottom) that incorporate a thermally stratified outer core layer. The hemispheric asymmetry of the radial field, with positive equatorial flux (yellow/orange) concentrated in the southern hemisphere and weaker, opposite-sign flux in the north (blue), is the surface signature of the dipole that is offset $\sim 480$ km northward of the planetary centre: the southern surface lies closer to the magnetic-pole end of the dipole and therefore samples a stronger field. Models with a stably stratified upper core can reproduce both the weakness and the asymmetry of the observed field.
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 Both features are difficult to explain with the standard convection-driven, $\alpha$-$\Omega$ dynamo picture used to model Earth's field. Two mechanisms are usually invoked. The first is a **thermally stratified outer layer** at the top of Mercury's liquid core, in which heat is carried by conduction rather than convection. Such a layer can act as a low-pass filter on the dynamo, suppressing high-degree harmonics and damping rapid time variations. The second is a **stable, conductive inner core boundary** that introduces a north-south asymmetry into the convecting region, perhaps because of latitude-dependent freezing of the solid inner core under Mercury's distinctive thermal regime. Numerical dynamo simulations that combine these ingredients can reproduce both the weakness and the offset of Mercury's field, but the parameter space is large and several competing models exist {cite:p}`Wicht2017`.
@@ -435,7 +435,7 @@ The textbook candidate is a thicker $\mathrm{CO_2}$ atmosphere. Increasing atmos
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-Cartoon of the major climate processes operating on Mars in the Noachian and early Hesperian as conceived by {cite:t}`Wordsworth2016`. The "icy highlands" picture: snow accumulates in the elevated southern highlands, where adiabatic cooling makes them effective cold traps; episodic warming from impacts and volcanism delivers transient meltwater that flows downhill into the northern lowlands as standing bodies of water. $\mathrm{CO_2}$ clouds at high altitude can scatter or absorb infrared radiation but in net cool more than they warm.
+Schematic of the major climate processes on early Mars in the Noachian and early Hesperian periods, reproduced from Figure 5 of the {cite:t}`Wordsworth2016` AREPS review (Wordsworth's own hand-drawn cartoon). The "icy highlands" picture: snow accumulates in the elevated southern highlands, where adiabatic cooling under a thicker atmosphere makes them effective cold traps; episodic warming from impacts and volcanism delivers transient meltwater that flows downhill into the northern lowlands as standing bodies of water. $\mathrm{CO_2}$ clouds at high altitude can scatter or absorb infrared radiation but in net cool more than they warm.
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 Several escape routes from this contradiction have been proposed. One important class of solutions invokes additional reducing greenhouse gases such as $\mathrm{H_2}$ or $\mathrm{CH_4}$, supplied by volcanic outgassing or by serpentinisation of ultramafic rocks. {cite:t}`Wordsworth2017` showed that **collisionally induced absorption (CIA)** between $\mathrm{H_2}$ and $\mathrm{CO_2}$, in particular, has a much larger effect than previously appreciated and can significantly raise surface temperatures with modest concentrations of $\mathrm{H_2}$ ($\sim 1\%$ to $10\%$ by volume). This allows a warm or warm-and-episodic early Mars without unphysical $\mathrm{CO_2}$ pressures.