# Io scene C ("Krafla plume field" → `io.pele`): credits and data provenance

Helios is non-commercial. Every source below is used under its stated licence. **Real data** means measured elevation or scanned geometry/texture; **procedural** means generated by our scripts. The map is a real Earth landscape (Krafla caldera, NE Iceland) re-dressed as Io; nothing in it is Io topography.

## Elevation (real data)
| What | Source and citation | Licence | How we changed it |
| --- | --- | --- | --- |
| Base terrain, whole 7.168 km map (EPSG:3057 x 597716–604884, y 578316–585484) | Porter, C., Howat, I., Noh, M.-J., et al., 2023, *ArcticDEM – Mosaics, Version 4.1*, Polar Geospatial Center, Harvard Dataverse, https://doi.org/10.7910/DVN/3VDC4W ; 2 m mosaic tiles 17_53_1_2 and 17_53_2_2 from https://pgc-opendata-dems.s3.us-west-2.amazonaws.com/arcticdem/mosaics/v4.1/2m/17_53/ (DEMs provided by the Polar Geospatial Center under NSF-OPP awards 1043681, 1559691 and 2129685) | CC BY 4.0 | Reprojected from EPSG:3413 to ISN93 (bilinear, 2 m); WGS84 ellipsoidal heights kept; infrastructure inpainted (below); Víti lake surface levelled (frozen floor); bicubic resample to 1 m; heights shifted by −600 m for the world frame; kit-bash additions below. |
| Context apron outside the map (28 km) | Same ArcticDEM mosaic, averaged to 16 m, resampled to 32 m | CC BY 4.0 | Outside the two tiles (9 % of the apron) it is smooth inverse-distance fill, not data. |
| Collapse pit with the lava lake (round 2) | **Puʻu ʻŌʻō crater, Kīlauea East Rift Zone, after the 2018 collapse.** U.S. Geological Survey (2018), *Kīlauea Volcano, HI July 2018 Acquisition* airborne lidar survey (flown 2018-07-08..12), distributed by OpenTopography, https://doi.org/10.5069/G9M32SV1 ; file `[path removed]`, 0.5 m bare-earth DTM, EPSG:6635 (research clip `[path removed]`). OpenTopography lists no explicit licence for this dataset; it is a USGS acquisition (U.S. Government work); used here with full citation for a non-commercial project. | No licence stated (USGS / OpenTopography; cite as given) | No-data filled (IDW ≤ 100 m), block-averaged 0.5 → 1 m, **native scale** (no horizontal or vertical scaling), rotated 15°, expressed relative to a plane fitted to the surrounding cone flank (r 450–520 m) and added to the Krafla base; the pit (everything > 20 m below that plane inside 330 m) is added whole, the cone flank outside is kept at 55 % and feathered out between 330 and 520 m. Lake surface levelled 105 m above the pit floor minimum. |
| Collapse pit (round 1, replaced) | Plosky Tolbachik summit pit, ArcticDEM v4.1 2 m (tiles 75_24_2_2 + 75_24_1_2) | CC BY 4.0 | Round 1 only: scaled 0.32 / 0.28 and steepened; no longer in the map. |
| Flow-field surface texture (relief only) | INGV Pisa, *2004–05 Mt. Etna compound lava flow field: orthophotos and topography*, lidar 29 Sep 2005, 1 m, https://www.pi.ingv.it/banche-dati/2005-04-etna-lava-flow-data/ ; Favalli, Fornaciai & Pareschi (2009) Geomorphology 111, 123–135 | CC BY 4.0 | Cropped (x 690–2770, y 0–1800 m of the sample), detrended (σ 35 m); ~130 tiles of 700 m cut at random places, rotated to the local flow direction, half of them mirrored across the flow axis, blended with overlapping raised-cosine windows (stitched mosaic), × 0.4, added inside the simulated flow outline with a 14 m feather. |
| Distal pressure ridges (relief only) | U.S. Geological Survey 3DEP 1 m DEM (Big Obsidian Flow, Newberry Volcano, Oregon) | Public domain | Detrended (σ 25 m); ~100 stitched 800 m tiles as above, × 0.14 (basalt-size ridges), only on patchy zones of the lobes > 900 m from the vent. |
| Spatter-cone row | U.S. Geological Survey 3DEP 1 m DEM (Great Rift, Big Craters and Spatter Cones, Craters of the Moon, Idaho) | Public domain | A 1.1 km strip along the cone chain, detrended (σ 90 m), rotated onto the north vent-fissure segment (x 380→560, z −1870→−2900), relief × 1.3, side/end feathers 70/140 m. |

## Human-artifact removal
OpenStreetMap contributors, Overpass API extract (2026-10-12) of roads, tracks, paths, geothermal pipelines, buildings, the Kröflustöð power plant, the IDDP drill site, parking areas and ponds (© OpenStreetMap contributors, ODbL 1.0). Used only to build the mask of what to inpaint; no OSM geometry ships with the scene. Place names (Víti, Leirhnjúkur, Krafla) for orientation also come from OSM.

## Textures (real scans and CC0 photo-textures)
| Layer | Source | Licence |
| --- | --- | --- |
| Sulfur yellow, iron red, salt white, mixed ochre, green crust, terrace pools (plume deposits, fumarole crusts, frost) | Io asset kit `dallol-*` texture sets, cut from: Grunwald, O.; Delage, E.; van Wyk de Vries, B. *Topographic 3D model: Dallol domes – Dataset*. OPGC / LMV, Université Clermont Auvergne. https://doi.org/10.25519/TXZC-1724 | CC BY-NC 4.0 |
| Fresh pahoehoe | Io kit `basalt-pahoehoe-fresh`: "Lava field from Mauna Ulu – Kilauea, Hawaii" by Tom (trbaker), Sketchfab | CC BY 4.0 |
| 'a'a clinker | Io kit `basalt-aa-clinker` (ambientCG Rock031) | CC0 |
| Hot crust / crack pattern | Io kit `lava-crust-hot` (ambientCG Lava001) | CC0 |
| Cliff basalt | Io kit `basalt-cliff` (Poly Haven Dark Rock 02, Amal Kumar) | CC0 |
| Old basalt ground | Io kit `basalt-old-weathered` (Poly Haven Dark Rock, Amal Kumar); Poly Haven `rock_ground` | CC0 |
| Dark pyroclastic fan | Io kit `basalt-cinder-ground` (Poly Haven Terrain Red 01, Rob Tuytel) | CC0 |
| Scoria wall beds (tint source) | Poly Haven `terrain_red_01` (Rob Tuytel) | CC0 |

## Scatter meshes (real scans)
From the Io asset kit (`[path removed]`, decimated by the kit agent; our LOD1/LOD2 are further quadric decimations):
- `rock-aa-clinker-daal`, `rock-scoria-bomb-daal`: "Igneous rock: Basalt (A'a Lava Rock)" and "Scoria", Digital Atlas of Ancient Life (Emily Hauf), Sketchfab, CC0.
- `rock-pahoehoe-block-kantanat`: "Pahoehoe basalt" by Kantanat, Sketchfab, CC BY 4.0.
- `rock-scoria-boulder`: "Scoria Rock Scan" by fevenkitsune, Sketchfab, CC BY 4.0.
- `rock-vesicular-block-bustos`: "Lava rock scan" by Elan Bustos, Sketchfab, CC BY 4.0 (albedo projected from ambientCG Rock031, CC0).
- `rock-basalt-block-ph07`, `rock-basalt-slab-ph09`: Poly Haven Rock 07 / Rock 09, CC0.
- `rock-sulfur-cianciana`: "SULFUR" by MSU SEES, Sketchfab, CC BY 4.0 (hand sample from Cianciana, Sicily).
- `rock-pahoehoe-slab-maunaulu`: from "Lava field from Mauna Ulu – Kilauea, Hawaii" by trbaker, CC BY 4.0.
- `rock-ropy-lobe-mangere`: "Lava flow" by b_nealie, Sketchfab, CC BY 4.0 (Mangere Mountain shore, Auckland).
- `dallol-crust-mound`, `dallol-twin-mounds`, `dallol-salt-pillars`: pieces of the OPGC Dallol domes model (doi:10.25519/TXZC-1724), CC BY-NC 4.0.
Exact credit lines per item are in `[path removed]` (copied from the kit manifest).

## Sky
Jupiter: NASA Scientific Visualization Studio, *Hubble Maps Jupiter in 4k Ultra HD* (OPAL 2015), https://svs.gsfc.nasa.gov/12021, NASA/ESA/A. Simon (GSFC), public domain (`jupiter_2k.jpg`, as in map A).

## Colour references (not shipped)
Galileo SSI I32 Pele night image and Io mosaic crops in `[path removed]`[path removed]`io-pele-plume-deposits-gameplay.png`.

## Procedural (not data)
- Lava-flow outlines and thickness: cellular-automaton spread (residual-thickness model, slope-dependent critical thickness, downslope bias), 24 overlapping flow units from the south vent fissure on the real Krafla topography; the pit is an obstacle for the flows.
- Sulfur deposits: offline Io-ballistic particle simulation of one Pele-type plume (g = 1.796 m/s², no atmosphere, terrain collision, 3 eruption episodes with azimuthal mass and range lobes, ~6 M particles), a dark pyroclastic fan from the coarse proximal clasts, incidence/lee weighting from the real slopes, fumarole crusts along hand-placed polylines on the real Krafla fissures, Víti rim, the Leirhnjúkur solfatara and the pit rim, SO₂ frost from horizon-shadowed insolation and lows. Parameters in `[path removed]`.
- Lava emission (crack networks, fissure segments, cone throats), the lava-lake crust (procedural rafted plates of 2–40 m, torn seams, incandescent margin; round 2), lake spatter fountains, lava irradiance, plume volume and particles, heat shimmer, stars.
- Scatter placement (talus, flow blocks, bombs, sulfur blocks, mounds).
- The plume vent, lava lake, vent fissure and cone row are our design choices placed on the real map; they are not real Krafla vents. The fumarole lines follow real Krafla fissures and the real Leirhnjúkur hot ground.