Reull Vallis
What Reull Vallis is
Reull Vallis is a vallis — a valley — on Mars, 1,052 km across, centred at 42.1° S, 105.0° E in the Hellas quadrangle. It is the 73rd largest named feature on Mars and the 7th largest of its class there.
Where the name comes from
Word for "planet" in Gaelic. The International Astronomical Union approved the name in 1979, under the theme it applies to every vallis on Mars. Of the 157 features of this class catalogued on Mars, the naming categories run Italy (14), France (12), Greek (10), United States (9).
What it would take to settle Reull Vallis
Mars scores 26.6 as a world. That number is the same for every square metre of it — but sunlight, water, radiation and the ground under your feet are not. This is the same question asked at 42.1° S, 105.0° E.
What this spot has going for it is temperature — about -65 °C mean at this latitude. What works against it is water — outside the ice-bearing latitudes.
Computed from Reull Vallis's catalogued latitude, longitude and feature class — 74% of the model's weight had a basis here, and 2 axes were dropped as not applicable to Mars (radiation geometry, earth link). Gravity, pressure, delta-v and distance from the Sun are the same everywhere on Mars and are already counted in the world's own index, not again here.
What this cannot see: elevation. Slope, local shadowing and the polar “peaks of eternal light” — ridge tops near the poles of a barely tilted world that catch sun almost continuously while a crater floor kilometres away never does — need a terrain model this does not have. Where a real mission targets a pole, that is usually why.
What is next to it
The largest vallis features on Mars
All 157 valles on Mars — mapped together, with the naming theme and the size distribution.