Solar system moons: 450 natural satellites

README.md

@@ -3,7 +3,7 @@ license: cc-by-4.0
 pretty_name: "Solar System Moons"
 language:
   - en
-description: "All 440 known natural satellites of planets and dwarf planets in the Solar System with orbital elements, physical parameters, and discovery data. Sourced from NASA JPL Solar System Dynamics."
+description: "Every known natural satellite of planets and dwarf planets in the Solar System with orbital elements, physical parameters, and discovery data. Sourced from NASA JPL Solar System Dynamics.  This datase"
 task_categories:
   - tabular-classification
   - tabular-regression
@@ -18,6 +18,7 @@ tags:
   - orbital-mechanics
   - jpl
   - tabular-data
+  - parquet
 size_categories:
   - n<1K
 configs:
@@ -30,28 +31,64 @@ configs:
 
 # Solar System Moons
 
-*Part of the [Planetary Science Datasets](https://huggingface.co/collections/juliensimon/planetary-science-datasets-68214dab0f1e965e6741fcd2) collection on Hugging Face.*
 
-Every known natural satellite of planets and dwarf planets in the Solar System —
-currently **440** moons spanning discovery years **1610** to **2025**.
+<div align="center">
+  <img src="banner.jpg" alt="Jupiter's Great Red Spot and the Galilean satellites" width="400">
+  <p><em>Credit: NASA/JPL-Caltech</em></p>
+</div>
+
+
+*Part of a [dataset collection](https://huggingface.co/collections/juliensimon/planetary-science-datasets-68214dab0f1e965e6741fcd2) on Hugging Face.*
 
 ## Dataset description
 
-This dataset catalogs all recognized natural satellites orbiting the major planets
-(Earth through Neptune) and the dwarf planet Pluto, as maintained by NASA's Jet
-Propulsion Laboratory (JPL) Solar System Dynamics group. Each record combines
-discovery circumstances, mean orbital elements, and — where available — physical
-parameters (radius, density, gravitational parameter).
+Every known natural satellite of planets and dwarf planets in the Solar System with orbital elements, physical parameters, and discovery data. Sourced from NASA JPL Solar System Dynamics.
+
+This dataset catalogs all recognized natural satellites orbiting the major planets (Earth through Neptune) and the dwarf planet Pluto, as maintained by NASA's Jet Propulsion Laboratory (JPL) Solar System Dynamics group. Each record combines discovery circumstances, mean orbital elements, and — where available — physical parameters (radius, density, gravitational parameter).
 
 The dataset merges three authoritative JPL tables:
 - **Discovery circumstances** — name, parent body, year, discoverer
 - **Mean orbital elements** — semi-major axis, eccentricity, inclination, period
-- **Physical parameters** — mean radius, GM, density (for 46 major moons)
+- **Physical parameters** — mean radius, GM, density (for major moons)
+
+The natural satellites of the solar system span an extraordinary range of sizes, compositions, and dynamical histories. At one extreme, Jupiter's Ganymede (radius ~2,634 km) is larger than Mercury and possesses its own intrinsic magnetic field. At the other, many recently discovered irregular satellites are only a few kilometers across and occupy distant, highly inclined or retrograde orbits that betray their origin as captured objects from the primordial small-body population. The dynamical groupings recorded in this dataset — Galilean, Himalia, Ananke, Carme, Pasiphae for Jupiter; Inuit, Gallic, Norse for Saturn — reflect distinct capture and collisional fragmentation events that occurred during the chaotic early evolution of the giant planet systems.
+
+Several moons in this catalog are among the most scientifically compelling worlds in the solar system. Europa's subsurface ocean beneath its icy shell is a prime target for astrobiology, while Enceladus actively vents water vapor and organic molecules through its south polar tiger stripes. Titan maintains a dense nitrogen-methane atmosphere with a complete hydrological cycle of methane rain, rivers, and lakes. Io is the most volcanically active body known, driven by intense tidal heating from its orbital resonance with Europa and Ganymede. Triton, captured by Neptune from the Kuiper Belt, exhibits active nitrogen geysers and a retrograde orbit that is gradually decaying.
+
+The orbital elements in this dataset encode fundamental information about satellite dynamics: resonant relationships (such as the 1:2:4 Laplace resonance of Io, Europa, and Ganymede), tidal evolution timescales, and the stability boundaries that separate regular from irregular satellite populations. Combined with physical parameters like density and radius, these data enable studies of satellite formation, internal structure, and the delivery of volatiles to the outer solar system.
+
+
+## Schema
+
+| Column | Type | Description | Sample | Null % |
+|--------|------|-------------|--------|--------|
+| `name` | object | IAU name or provisional designation | Moon | 0.0% |
+| `parent_body` | object | Parent planet or dwarf planet | Earth | 0.0% |
+| `iau_number` | object | IAU Roman numeral designation | I | 0.0% |
+| `provisional_designation` | object | Survey designation (e.g. S/2003 J2) |  | 0.0% |
+| `discovery_year` | Int64 | Year of discovery | 1877 | 0.9% |
+| `discoverer` | object | Discoverer(s) or spacecraft mission |  | 0.0% |
+| `group` | object | Dynamical group/family (e.g. Galilean, Himalia, Norse) | Regular | 2.9% |
+| `semi_major_axis_km` | float64 | Mean orbital semi-major axis (km); ranges from ~128,000 km (Amalthea/Jupiter) to ~23.5 million km (Neso/Neptune) | 384400.0 | 2.4% |
+| `eccentricity` | float64 | Mean orbital eccentricity; regular (prograde) moons: <0.1; irregular (captured) moons: often 0.1–0.7 | 0.0554 | 2.4% |
+| `inclination_deg` | float64 | Mean orbital inclination to the planet's equatorial plane (degrees, 0–180); regular moons: <5°; irregular moons: can exceed 90° (retrograde); see also is_retrograde | 5.16 | 2.4% |
+| `orbital_period_days` | float64 | Sidereal orbital period (days); range ~0.29 days (Metis/Jupiter) to ~9,000 days (distant irregular moons); negative values indicate retrograde direction in some source conventions | 27.322 | 2.4% |
+| `arg_periapsis_deg` | float64 | Argument of periapsis of the moon's orbit (degrees, 0–360) at the reference epoch | 318.15 | 2.4% |
+| `mean_anomaly_deg` | float64 | Mean anomaly at the reference epoch (degrees, 0–360); used together with other elements to compute position | 135.27 | 2.4% |
+| `long_ascending_node_deg` | float64 | Longitude of the ascending node (degrees, 0–360) at the reference epoch | 125.08 | 2.4% |
+| `epoch` | object | Reference epoch for the orbital elements in Barycentric Dynamical Time (TDB) format | 2000-01-01.5 | 2.4% |
+| `mean_radius_km` | float64 | Mean radius (km); available for major/well-characterised moons only; range <1 km (small inner moons) to 2,634 km (Ganymede); null for most irregular moons | 1737.4 | 89.8% |
+| `diameter_km` | float64 | Mean diameter (km) = 2 × mean_radius_km; derived column; null when radius is null | 3474.8 | 89.8% |
+| `gm_km3s2` | float64 | Gravitational parameter GM = G × mass (km³/s²); null for moons without a reliable mass determination | 4902.8 | 89.8% |
+| `mean_density_gcm3` | float64 | Mean bulk density (g/cm³); icy moons: ~1.0–2.0 g/cm³; rocky moons: ~2.5–3.5 g/cm³; null when mass and radius are not both known | 3.344 | 90.4% |
+| `is_retrograde` | boolean | True if orbital inclination > 90° (retrograde orbit); most retrograde moons are captured irregular bodies | False | 2.4% |
+| `jpl_code` | object | JPL Horizons numeric satellite identifier used to query ephemerides | 301 | 2.4% |
 
 ## Quick stats
 
+- **450** total moons
 - **Saturn**: 285 moons
-- **Jupiter**: 101 moons
+- **Jupiter**: 111 moons
 - **Uranus**: 30 moons
 - **Neptune**: 16 moons
 - **Pluto**: 5 moons
@@ -62,36 +99,11 @@ The dataset merges three authoritative JPL tables:
 - **297** retrograde moons (inclination > 90°)
 - Largest moon: **Ganymede** (Jupiter, radius 2,631.2 km)
 
-## Schema
-
-| Column | Type | Description |
-|--------|------|-------------|
-| `name` | string | IAU name or provisional designation |
-| `parent_body` | string | Parent planet or dwarf planet |
-| `iau_number` | string | IAU Roman numeral designation |
-| `provisional_designation` | string | Survey designation (e.g. S/2003 J2) |
-| `discovery_year` | int64 | Year of discovery |
-| `discoverer` | string | Discoverer(s) or spacecraft mission |
-| `group` | string | Dynamical group/family (e.g. Galilean, Himalia, Norse) |
-| `semi_major_axis_km` | float64 | Mean semi-major axis (km) |
-| `eccentricity` | float64 | Mean orbital eccentricity |
-| `inclination_deg` | float64 | Mean orbital inclination (degrees) |
-| `orbital_period_days` | float64 | Sidereal orbital period (days) |
-| `arg_periapsis_deg` | float64 | Argument of periapsis (degrees) |
-| `mean_anomaly_deg` | float64 | Mean anomaly at epoch (degrees) |
-| `long_ascending_node_deg` | float64 | Longitude of ascending node (degrees) |
-| `epoch` | string | Epoch of orbital elements (TDB) |
-| `mean_radius_km` | float64 | Mean radius (km), major moons only |
-| `diameter_km` | float64 | Mean diameter (km), derived from radius |
-| `gm_km3s2` | float64 | Gravitational parameter GM (km³/s²) |
-| `mean_density_gcm3` | float64 | Mean bulk density (g/cm³) |
-| `is_retrograde` | bool | True if inclination > 90° |
-| `jpl_code` | string | JPL numeric satellite identifier |
-
 ## Usage
 
 ```python
 from datasets import load_dataset
+import matplotlib.pyplot as plt
 
 ds = load_dataset("juliensimon/solar-system-moons", split="train")
 df = ds.to_pandas()
@@ -108,36 +120,46 @@ retro = df[df["is_retrograde"] == True].sort_values("orbital_period_days")
 # Largest moons by radius
 biggest = df.dropna(subset=["mean_radius_km"]).nlargest(10, "mean_radius_km")
 
+# Plot moon sizes by planet
+fig, ax = plt.subplots(figsize=(10, 6))
+for planet in ["Jupiter", "Saturn", "Uranus", "Neptune"]:
+    subset = df[(df["parent_body"] == planet) & df["mean_radius_km"].notna()]
+    ax.scatter(subset["semi_major_axis_km"] / 1e6, subset["mean_radius_km"],
+               label=planet, alpha=0.7, s=40)
+ax.set_xlabel("Semi-major axis (million km)")
+ax.set_ylabel("Mean radius (km)")
+ax.set_title("Moon size vs. orbital distance")
+ax.set_xscale("log")
+ax.set_yscale("log")
+ax.legend()
+plt.tight_layout()
+plt.show()
+
 # Recent discoveries (2020+)
 recent = df[df["discovery_year"] >= 2020]
 ```
 
-## Data sources
+## Data source
 
-- [JPL SSD Satellite Discovery](https://ssd.jpl.nasa.gov/sats/discovery.html) — names, parents, discovery circumstances
-- [JPL SSD Orbital Elements](https://ssd.jpl.nasa.gov/sats/elem/) — mean orbital elements
-- [JPL SSD Physical Parameters](https://ssd.jpl.nasa.gov/sats/phys_par/) — radius, density, GM
+https://ssd.jpl.nasa.gov/sats/discovery.html
 
 ## Related datasets
 
-- [neo-close-approaches](https://huggingface.co/datasets/juliensimon/neo-close-approaches) — NEO close approaches from JPL CNEOS
-- [exoplanets](https://huggingface.co/datasets/juliensimon/exoplanets) — NASA Exoplanet Archive
-- [asteroid-orbits](https://huggingface.co/datasets/juliensimon/asteroid-orbits) — All asteroid orbital elements
+- [juliensimon/neo-close-approaches](https://huggingface.co/datasets/juliensimon/neo-close-approaches)
 
-## Pipeline
+- [juliensimon/nasa-exoplanets](https://huggingface.co/datasets/juliensimon/nasa-exoplanets)
 
-Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)
+- [juliensimon/jpl-small-body-database](https://huggingface.co/datasets/juliensimon/jpl-small-body-database)
 
 ## Citation
 
 ```bibtex
 @dataset{solar_system_moons,
-  author = {Simon, Julien},
   title = {Solar System Moons},
+  author = {juliensimon},
   year = {2026},
-  publisher = {Hugging Face},
   url = {https://huggingface.co/datasets/juliensimon/solar-system-moons},
-  note = {Based on NASA/JPL Solar System Dynamics satellite data}
+  publisher = {Hugging Face}
 }
 ```
 

data/solar_system_moons.parquet

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:74580fe99972dc1608081833fe2a3f236b6d53a61a944ad159b0cdbce72bd7dc
-size 36923
+oid sha256:d0d245478a98ef1c06ab2c33549682480eff9e18cd855130a98b95201a91e94f
+size 37074