Semi-autonomous colony

A semi autonomous colony on Mars lives basically on its own production of energy, food and air, provided by imported technology from Earth. All vital systems are lo-tech and can be maintained from local resources. Additional goods are regularly imported from Earth:

Complicated medical equipment
Drugs for medical treatment
Luxury foods
Non-vital hi-tech equipment (e.g. computers)

As part of a colonization strategy it may be an advanced step in the colonization program.

Limitations of shipping

Shipping to Mars with current launcher technology is expensive. Cheaper commercial launchers must be developed if continued shipping is to be a reality. Although landing large payloads on the surface is difficult, this could be done with technology designed for the original construction of the colony. The limitations on shipping, however, mean that any large settlement will be fairly close to an autonomous colony.

What if support from Earth stops?

However, if the shipments were to stop, the colony might be able to sustain itself for the long run, based upon the lo-tech equipment. Some people may then choose to return to Earth if space access is possible.

As an alternative to a low tech society, a reasonable precaution would be for the settlement to stock a strategic amount of supplies of essential elements or equipment. The stockpile should be sufficient for the settlement to have the time required to develop local sources for the supplies. For example, digging for cobalt on Mars might be uneconomical compared to shipping from Earth. But if shipping from Earth stops, the settlement would develop local mines, whatever the cost, as they would become essential. This way a higher technology settlement could be maintained.

Minimum viable population

What is the minimum population on Mars that can maintain a high enough technology to live indefinitely with only local resources? This is highly dependent on the available technology, however some studies have been made in the similar case of generation ships for Interstellar travel and others have proposed values.

Genetically, studies have shown that starting with sufficient diversity, the minimum viable genetic population is about one hundred individuals https://arxiv.org/abs/1806.03856
Statistical analysis Cameron Smith, an anthropologist at Portland State University in Oregon, proposed a minimum of 14 000 people, with a safer value of 40 000 in 2014 https://ui.adsabs.harvard.edu/abs/2014AcAau..97...16S/abstract. He brought this down to 4 000 in a 2020 paper (references).
Aurora, Kim Stankey Robinson Robinson, for his novel, Robinson showed a population of about 10 000 failing at maintaining a viable technological society and having to return to Earth.
Elon Musk has proposed a target of one million people for a self sustaining civilisation.
xxx has proposed several million people. (The minimum number might be 50 million people? 500 million people?) If a Martian colony was cut off from Earth, and had to survive indefinitely with a low population, it would likely not survive.^[1]^[2]^[3]