Re: Why do people call a small outpost a colony ?
There is a very good precedent. Greenland was colonized by Norway in around 980 AD. The colony was self-sufficient in food and the basics of life, but it needed resupply on a regular basis for wood (there are no useful trees in Greenland) and manufactured goods (e.g. iron). It did fine for about 400 years, with regular resupply. But when the resupply stopped, the colony failed and the colonists disappeared, probably intermarrying with and being absorbed by the Inuit. It is hypothesized (but not proven) that much the same happened to the Roanoke colony in the 16th century - resupply failed, and the colony had to integrate with the native population to survive. At its peak, the population of Viking Greenland was probably around 1000. The exact date at which the last Norse settlement collapsed is unknown, but I have read excellent accounts of the archaeology of a Norse farmstead, where it is clear that the slow wearing out of essential equipment put an end to the lifestyle of the Norwegians. Of course, the Inuit were adapted to a different way of life that didn't depend on stock-rearing and farming. The Norwegian resupply voyages were probably on the same order of time, cost and difficulty as a routiine supply by spacecraft today.
Here on Earth, we have plenty of examples of the various balances that can be struck between resupply and self-sufficiency. Given the obvious difference in the survivability of the environment, it is clear that a self-sufficient Martian colony would require a large population to sustain the necessary industrial base; manufacturing (for example) electronics (which would be essential for many purposes) would be impossible without a population comparable to a city on Earth. But with resupply, it entirely depends on the level of resupply. If the colony only produces the basics (air, water, food, power), then substantial inputs of raw materials and manufactured goods are required. If the colony can source and produce raw materials, then less resupply is needed, but a larger population to sustain the manufacturing base on Mars.
I note that Viking Greenland only survived at all because there was a viable trade in walrus ivory, furs and falcons. This trade was severely limited by the development of the Hanseatic League in Europe, which restricted such trade and resulted in the slowdown and almost cessation of the resupply voyages.. SO -perhaps we need to think about what a Martian colony could trade in to ensure the resupply was cost-effective?