diff --git a/src/app/shared/astro/horizons-page.spec.ts b/src/app/shared/astro/horizons-page.spec.ts
index 44938ef..ad1e141 100644
--- a/src/app/shared/astro/horizons-page.spec.ts
+++ b/src/app/shared/astro/horizons-page.spec.ts
@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 
-import { extractGmKm3PerS2, extractRadiusKm, extractRotationPeriodHours, isTidallyLocked } from './horizons-page';
+import { extractGmKm3PerS2, extractObliquityDeg, extractRadiusKm, extractRotationPeriodHours, isTidallyLocked } from './horizons-page';
 
 // Lines as the Horizons pages print them.
 const JUPITER = `  Vol. Mean Radius (km) = 69911+-6          Flattening            = 0.06487
@@ -57,3 +57,10 @@ describe('Horizons page GM', () => {
     expect(extractGmKm3PerS2(HYPERION)).toBeUndefined();
   });
 });
+
+describe('Horizons page obliquity', () => {
+  it('reads the arcminutes Mercury gives its tilt in, and the degrees every other page uses', () => {
+    expect(extractObliquityDeg("  Obliquity to orbit[1] =  2.11' +/- 0.1' Hill's sphere rad. Rp = 94.4 ")).toBeCloseTo(2.11 / 60, 9);
+    expect(extractObliquityDeg('  Obliquity to orbit    =   25.19 deg     Max. angular diam.    =  17.9"')).toBe(25.19);
+  });
+});
diff --git a/src/app/shared/astro/horizons-page.ts b/src/app/shared/astro/horizons-page.ts
index 16cb634..0cf02d9 100644
--- a/src/app/shared/astro/horizons-page.ts
+++ b/src/app/shared/astro/horizons-page.ts
@@ -38,7 +38,8 @@ const ROTATION_PERIOD_PATTERNS = [
   /Rotation(?:al)?\s*period[^=]*=\s*(-?[\d.]+)\s*(h|hr|hrs|d|day|days)\b/i
 ];
 const SYNCHRONOUS_PATTERN = /Rotation(?:al)?\s*period\s*=?\s*:?\s*Synchronous/i;
-const OBLIQUITY_PATTERN = /Obliquity\s*to\s*orbit[^=]*=\s*(-?[\d.]+)/i;
+/** `25.19 deg` on most pages, `2.11' +/- 0.1'` in arcminutes on Mercury's. */
+const OBLIQUITY_PATTERN = /Obliquity\s*to\s*orbit[^=]*=\s*(-?[\d.]+)\s*(')?/i;
 /** `GM (km^3/s^2) = 106.10` on a moon's page, `GM (planet) km^3/s^2 = 869.326` on Pluto's. */
 const GM_PATTERN = /GM\s*(?:\(planet\)\s*)?,?\s*\(?km\^3\/s\^2\)?\s*=\s*([\d.]+)/i;
 
@@ -74,9 +75,13 @@ export function extractRotationPeriodHours(text: string): number | undefined {
   return undefined;
 }
 
+/**
+ * Tilt of the rotation axis from the orbit, in degrees. Mercury's page gives its tilt in
+ * arcminutes, which read as degrees made it 2.11 where the IAU's pole puts it at 0.034.
+ */
 export function extractObliquityDeg(text: string): number | undefined {
   const match = text.match(OBLIQUITY_PATTERN);
-  return match ? Number(match[1]) : undefined;
+  return match ? Number(match[1]) / (match[2] ? 60 : 1) : undefined;
 }
 
 /**
diff --git a/src/assets/data/bodies.json b/src/assets/data/bodies.json
index db4912e..e929fd3 100644
--- a/src/assets/data/bodies.json
+++ b/src/assets/data/bodies.json
@@ -24,7 +24,7 @@
     },
     "orbitSource": "JPL approximate mean elements (Standish), fit for 3000 BC to AD 3000",
     "rotationPeriodHours": 1407.512239412851,
-    "obliquityDeg": 2.11
+    "obliquityDeg": 0.035166666666666666
   },
   {
     "id": "venus",