Small Worlds

Three small worlds with their real shapes and heights: Pluto, mapped by NASA's New Horizons as it flew past in 2015, and the dwarf planet Ceres and the asteroid Vesta, mapped by NASA's Dawn, which orbited both. Ceres's flattened shape and Vesta's lumpy one, with the huge Rheasilvia basin near its south pole, are real.

New Horizons saw only one side of Pluto up close; the rest is filled in smoothly and shown blurred. Pluto's bright heart is Sputnik Planitia, a plain of frozen nitrogen. Occator crater on Ceres holds bright salts, and Ahuna Mons is a lone mountain of ice about 4 km high. They are drawn at true height; pick ×5 or more in the Splash tab to exaggerate them. A tap zooms in and names the spot from the IAU's list; tap again to go out.

3 worlds drawn from real maps (Pluto, Ceres, Vesta): every splat has its place's measured color and, where an elevation map exists, its measured height, and each named feature is where the planetary gazetteer puts it. The turning speed and the lighting are simplified, and labeled.

1. Correct

   The map and elevation is Pluto New Horizons LORRI MVIC Global Mosaic and DEM 300m.¹

   tools/sp2-maps.mjs reads the source file named in src/space/worlds.js and averages it into the splash's smaller maps (east longitudes from -180° to 180°).

2. Correct

   Pluto turns once every 153.29 hours, backward (its sidereal day), sped up by the chosen factor.²

   Each frame the drive adds the elapsed time times the speed-up, over the day's length, to the turn.

3. Correct

   A tap flies to Sputnik Planitia, a plain of nitrogen ice (the heart) at 19.51°, 178.69° east, and the map shows it there.³

   The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

4. Correct

   A tap flies to Wright Mons, perhaps an ice volcano at -21.36°, 173.24° east, and the map shows it there.⁴

   The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

5. Correct

   The map and elevation is Ceres Dawn FC global mosaic (DLR, 2015) and HAMO DTM (DLR, 2016).⁵

   tools/sp2-maps.mjs reads the source file named in src/space/worlds.js and averages it into the splash's smaller maps (east longitudes from -180° to 180°).

6. Correct

   Ceres turns once every 9.074 hours (its sidereal day), sped up by the chosen factor.⁶

   Each frame the drive adds the elapsed time times the speed-up, over the day's length, to the turn.

7. Correct

   A tap flies to Occator crater and its bright salt at 19.82°, -120.67° east, and the map shows it there.⁷

   The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

8. Correct

   A tap flies to Ahuna Mons, a lone mountain of ice at -10.48°, -43.8° east, and the map shows it there.⁸

   The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

9. Correct

   The map and elevation is Vesta Dawn FC HAMO Global Mosaic and DTM.⁹

   tools/sp2-maps.mjs reads the source file named in src/space/worlds.js and averages it into the splash's smaller maps (east longitudes from -180° to 180°).

10. Correct

    Vesta turns once every 5.342 hours (its sidereal day), sped up by the chosen factor.¹⁰

    Each frame the drive adds the elapsed time times the speed-up, over the day's length, to the turn.

11. Correct

    A tap flies to Rheasilvia, a basin almost as wide as Vesta at -71.95°, 86.3° east, and the map shows it there.¹¹

    The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

12. Correct

    A tap flies to Marcia crater at 8.98°, -20.45° east, and the map shows it there.¹²

    The drive turns the feature's direction to face the viewer and glides the camera to it; the test checks the turn and the map's heights round the listed center.

13. Not yet checked

    A tap names the place under it: the smallest named feature it lies in, what that lies on, and the plain or highland round it, from the IAU Gazetteer.¹³

    tools/sp3-places.mjs keeps each adopted feature center and size from the Gazetteer downloads; src/space/places.js finds the features a spot lies within (half their listed size from the center). tests/sp3.spec.mjs checks Tycho, Olympus Mons, Gale, Rachmaninoff, Maat Mons and Tranquility Base, and a tap on Tycho and on Olympus Mons in the browser.

14. Not yet checked

    Zoomed in, the ground comes from close-up tiles of the same maps, finer than the global map (the scales are in src/space/zoom.js); a feature named as a circle is an approximation of its real outline.¹

    tools/sp3-tiles.mjs averages each source into 10° tiles; tests/sp3.spec.mjs checks each world's tiles against its global map at a named feature.

1. 1Pluto New Horizons LORRI MVIC Global Mosaic and DEM 300m, NASA, Johns Hopkins APL, Southwest Research Institute, New Horizons mission; USGS Astrogeology Science Center
2. 2Pluto Fact Sheet, NASA Space Science Data Coordinated Archive
3. 3Gazetteer of Planetary Nomenclature, USGS, IAU
4. 4Gazetteer of Planetary Nomenclature, USGS, IAU
5. 5Ceres Dawn FC global mosaic (DLR, 2015) and HAMO DTM (DLR, 2016), NASA, JPL, MPS, DLR, IDA, Dawn mission; USGS Astrogeology Science Center
6. 6Ceres (dwarf planet), NASA Space Science Data Coordinated Archive
7. 7Gazetteer of Planetary Nomenclature, USGS, IAU
8. 8Gazetteer of Planetary Nomenclature, USGS, IAU
9. 9Vesta Dawn FC HAMO Global Mosaic and DTM, NASA, JPL, MPS, DLR, IDA, Dawn mission; USGS Astrogeology Science Center
10. 104 Vesta, NASA Space Science Data Coordinated Archive
11. 11Gazetteer of Planetary Nomenclature, USGS, IAU
12. 12Gazetteer of Planetary Nomenclature, USGS, IAU
13. 13Gazetteer of Planetary Nomenclature, IAU WGPSN and USGS Astrogeology Science Center

Simplified

The relief is exaggerated by default (ten or twenty times; Pluto, Ceres and Vesta are drawn at true height), as chosen and labeled in the Splash tab; close up during a fly it eases to at most twice its height. True height is one choice away.

Simplified

The world turns thousands of times faster than real (labeled in the Splash tab: an hour or a day each second).

Simplified

North is always up and the sun stays near the equator's plane: the axial tilt and the seasons are left out.

Simplified

The sun shades each slope by the cosine of its angle to the sun (Lambert's law) and leaves the night side dark, but nothing casts a shadow, and real surfaces scatter light in more complicated ways.

Simplified

The global map has about 1,000 by 500 heights and 2,000 by 1,000 colors; only the patches round the named features are sharper.

Simplified

New Horizons saw one side of Pluto up close; the rest of its map and heights are filled in smoothly from the edges.

Simplified

Ceres's heights are measured from a sphere of 470 km, so its real flattened shape shows.

Simplified

Vesta's heights are measured from a sphere of 255 km, so its real lumpy shape shows.