Ptolemaeus
What Ptolemaeus is
Ptolemaeus is a crater — a circular depression, almost always an impact scar — on Mars, 165 km across, centred at 45.9° S, 157.6° W in the Phaethontis quadrangle. It is the 452nd largest named feature on Mars and the 40th largest of its class there.
Where the name comes from
Claudius; Greco-Egyptian astronomer (c. A.D. 90-160). The International Astronomical Union approved the name in 1973, under the theme it applies to every crater on Mars. Of the 1237 features of this class catalogued on Mars, the naming categories run United States (137), Russia (110), American (62), Great Britain (52).
What it would take to settle Ptolemaeus
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 45.9° S, 157.6° W.
What this spot has going for it is known ground — 2,284 km from Spirit (2004). What works against it is ground — mixed ground — a rim, a floor and slopes between them.
Computed from Ptolemaeus'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 crater features on Mars
All 1,237 craters on Mars — mapped together, with the naming theme and the size distribution.