Mars: a historical Viking mosaic, real close approach, and no invented terrain

Measured facts

Classification

Terrestrial planet

Mean radius

3,390 kmPublished mean radius stored as renderer geometry.

Mean diameter

6,779 km

Mean radius in Earth radii

0.532

Appearance

Tiled observational surface

Observation epoch

Historical multi-observation mosaic; not live

What you are looking at

The delivered resolution is not the source resolution. The Viking source is sampled at 232 m per pixel, but NASA’s finest delivered matrix at the equator is about 326 m per pixel, and that is the number COSMOS reports.

The 400 km approach floor was chosen from measured pixel footprints. An earlier 110 km trial over-magnified the map, so it was replaced; the floor is a scientific limit, not an arbitrary camera guard rail.

Rotation follows IAU_MARS pole, prime-meridian and all 26 retained phase terms from pck00011, evaluated in TDB and validated against independent CSPICE fixtures at six epochs before it was wired in.

Distance, scale and light time

Distances here are computed from the shipped JPL Horizons state archive, sampled once per day across its declared coverage (2020-01-01 00:00 TDB through 2040-01-01 00:00 TDB). Because both bodies move on different orbits, the separation changes constantly; the figures below include the dates at which the extremes occur.

Distance from Earth

1.866 AU · 279,189,487 kmAt the recorded snapshot epoch 2026-08-29 00:00 TDB, one-way light time 15.52 minutes.

Distance from the Sun

1.516 AU · 226,795,803 kmComputed in the same epochs and frame (Earth-centred ecliptic J2000.0 / ICRF).

Closest Earth approach in the archive

0.380420 AU on 2035-09-12One-way light time then: 3.16 minutes.

Farthest separation in the archive

2.675112 AU on 2034-08-20One-way light time then: 22.25 minutes.

Mean separation across the archive

1.675823 AUSampled once per day across 2020-01-01 00:00 TDB through 2040-01-01 00:00 TDB (7,306 samples).

Delivery and camera limits

COSMOS stops the camera at 3,790 km from the body centre (400 km above the mean-radius surface) for Mars. Surface providers are protected because every imagery product has a native ground sampling distance, and magnifying past it would imply resolution the dataset does not contain.

Appearance status

Tiled observational surface

Renderer provider id

mars-visual-v1

Declared resolution

232 m/pixel source; 326 m/pixel finest delivered tiles at equator

Closest permitted approach

3,790 km from the body centre (400 km above the mean-radius surface)400 km minimum safe altitude keeps delivered imagery pixels near the rendered pixel footprint. The renderer clamps the camera's centre distance, so the two figures differ by one mean radius.

Rotation model

IAU_MARS — pck00011 (2022-12-27), IAU 2015 Mars modelSource: https://naif.jpl.nasa.gov/pub/naif/generic_kernels/pck/pck00011.tpc

Geometry

mean-radius-sphereMean-radius sphere; no ellipsoid or terrain displacement yet

Provenance

Appearance provenance is carried by the provider at runtime, not added by the page: an active appearance layer is registered.

Category

observational-composite

Provider

NASA/JPL Mars Trek · USGS Astrogeology · NASA Ames

Project / mission

Viking Orbiter VIS

Dataset

Viking MDIM 2.1 colorized global mosaic

Version

MDIM 2.1; NASA Trek matrix checked 2026-09-05

Licence

USGS public-domain product; no use constraints

Attribution

USGS Astrogeology / NASA Ames / NASA/JPL Mars Trek; Viking imaging teams

Source checked

2026-09-05

Limitations COSMOS discloses

• No terrain displacement
• Static mosaic does not change with ephemeris date
• Detail stops at the delivered imagery ceiling
• No MOLA terrain, no CTX or HiRISE regional imagery and no shape model: the globe stays a mean-radius sphere.
• The mosaic is a historical composite that does not change with the selected date; the selected date changes position, not imagery.
• Source shading is baked in, and COSMOS does not claim a surface landing or a ground-level view.
• Position is interpolated inside 2020-01-01 00:00 TDB through 2040-01-01 00:00 TDB; requesting an epoch outside that window is rejected instead of extrapolated.