Mars in Opposition
There are always opponents to the concept of colonising Mars. Recently some of them seem to have coalesced around a few talking points. Let's address them.
I recently saw a video by Sabine Hossenfelder released a video criticising Elon Musk’s plans to set up a permanent human settlement on Mars. In it she cites people such as Lord Martin Rees and Neil DeGrasse Tyson whose arguments she largely aligns with:
It is safe to say these arguments are fairly popular in the public sphere then, and ought to be addressed, starting with the underlying facts of the argument.
Matters of Fact
There is a 3 minute segment of the video, prior to the main argument, labelled “background facts”. It is important to agree on facts prior to an argument, but unfortunately some of the facts here are wrong or misleading.
“The average temperature on Mars is -60°C”. Yes, but because Mars has an atmosphere with weather and an axial tilt coincidentally similar to our own, there is plenty of variation in the temperature. Its a minor nitpick but not mentioning the range it can reach - regularly above freezing point at the equator - is kind of putting a thumb on the scales when debating habitability. The average temperature of the Earth is 15°C, but if you live in Florida it will be pretty consistently warmer than that.
In the section on terraforming (which is a red herring for colonisation) “Mars doesn’t have a magnetic field. This is also why the radiation dose on the surface of Mars is rather unhealthy” - not true. The primary protection against cosmic rays on Earth is the atmosphere, with only minimal protection being given by the geomagnetic field. This is, for instance, astronauts on the ISS still get a substantial GCR dose despite having comparably as much protection as we do from the magnetosphere, why we can detect GCRs from aircraft and balloons without having to be outside the van Allen belts (I myself helped design a cosmic ray experiment for a balloon, although it did not fly), and why the regular sharp reductions in the Earth’s magnetic field do not cause mass deaths on Earth. The Martian atmosphere does provide shielding as well - its thin, but at shallow angles the radiation still has to pass through a good amount of matter to reach you - as modeled in this paper.
Not that terraforming is needed for colonisation, but the assertion that any generated atmosphere would be stripped by the solar wind in the absence of a magnetic field ignores the fact this would happen on a geological timescale. This paper modelling historical atmospheric loss from MAVEN data suggests a fall in surface pressure from 0.8 bar to the current near vaccuum over the course of several billion years.
On travel times “With current propulsion systems it would take 7 to 9 months to get there” - this may be news to Mariner 6, which made the trip in 5 months (February 25th to July 31st 1969). No exotic propulsion technology was used, only chemical rockets. Within each window its is possible to change trip time by applying more or less Δv (the trade off being typically represented in a porkchop plot) and based on the best publicly available figures Starship will indeed have the Δv for faster transfers if given enough propellant refills.
Not all of these are hugely wrong, but they are all erring in the side of supporting the opinion about to be expressed.
The Science
Hossenfelder argues that “for scientific purposes it makes more more sense to send robots” which is one of those things that is commonly presented as being so obvious it requires no proof, but when you look it doesn’t really hold up. Nobody working on robotics thinks that Mars rover are anywhere close to the capability of human astronauts in terms of movement or dexterity. For instance, the drilling done by Curiosity was slow and error prone in a way it would not have been with an on site human operator.
And in the end, all the robots we send are made and operated by humans - they can only operate better if humans are on hand to control them without several minutes of lag due to the immense distance, and to repair and upgrade them as they go. The future isn’t humans or robots, its humans AND robots.
The Money
The video quotes Lord Rees as saying
The idea of mass migration to avoid the Earth’s problems, which he and a few other space enthusiasts adopt, that I think is a dangerous illusion. I don’t think it’s realistic and we’ve got to solve those problems here on Earth.
The first thing to say about this is, what is this “we” business?
Those wanting to spend Mars aren’t a part of a “we” that have to collectively choose which one project to work on. Advanced technological civilisations can walk and chew gum at the same time, in large part to having many different members diverting their resources in different direction.
Later there is a clip of Neil DeGrasse Tyson making a somewhat related claim that governments will need to pay for a Mars colony:
The history of really expensive things ever happening in civilisation has in essentially every case been led geopolitically by nations. How would Elon get to send his rockets to Mars? From the playbook of history of geopolitics, What’ll happen? The United States decides we need to send astronauts to Mars one day
This may well happen. Maybe a threat from China spurs on the US government, but its not essential to happen. Its better to look at the economics of it than reason by analogy from history.
A Starship launch will probably have a long run marginal cost of around $10 million - I’ve seen multiple people make this estimate, and think it reasonably credible. Lets say the all up cost of sending a Starship to Mars including all the refuelling flights is then $100 million, how many can Musk afford to send before he needs to ask the government or anybody else for money? Well, his Tesla pay package is currently valued at over $100 billion, so assuming he ever receives it and then pays 37% federal income tax on it, that still leaves enough money from that windfall alone to buy 630 ships to the surface of Mars, delivering a total of 126,000 tonnes of humans and cargo. Its not enough for a city, but its a damn good start, and we haven’t considered the revenue SpaceX gets from Starlink being poured into flights, selling off of his Tesla stock or a future IPO of his other companies such as Neuralink. A combination of historically unprecendented wealth combined with a sharp drop in the cost of kilograms to Mars means he has an awful lot of runway before needing to ask for help.
Hossenfelder claims there are few interested in moving to Mars, and that Musk would have to offer them money, rather than charge them money, for doing so. Both of these seem bizarre claims on the face of it. There is literally an international society of people who want to go to Mars. Livestreams of Starship test launches attract millions of views. The Mars One project, despite being fairly obviously nonviable to me, still attracted 200,000 initial applications. Musk has 200 million followers on X, and if only 0.5% of them actually wanted to go to Mars, that would be enough people to populate the city he dreams of building there. What evidence there is points to ample demand to go, and no evidence is offered the other way.
She does believe existential risk is a good reason to move to Mars, but ultimately concludes it is too early and more research and development needs to be done first, and that presumably once that has happened, governments will fund it. The fact that she is mistaken about how severe the challenges and costs are I think undermines the conclusion. The greatest existential risk regarding Mars is that we end up never going, because there is always some way to argue for delay.
The Mars Plan
Part of the reason why these criticisms keep coming up is that so far, SpaceX has not gone into much detail about how to go to Mars and settle it. In contrast to one of Musk’s other ventures, Tesla, which is on its third iteration of a master plan to decarbonise the world. We have heard from SpaceX about how to ramp up the flight rate of Starship to enable large scale missions to Mars, which windows are going to be targeted for first landing, but little details on building the colony. Critics are free to speculate, and tend to speculate in such a way as to bolster their own arguments.
NASA has a “Moon to Mars” office, and although it might benefit from separating the Moon off as a separate concern, it is in principal in a position to make or contribute to such plans. Its current plans largely dismiss Starship as “conceptual” and instead focus on spending the next couple of decades developing a large nuclear/solar electric interplanetary ship, and then some time in the 2040s fuelling it with an ungodly amount of expensive and rare xenon in order to perform a 20 day surface stay (i.e. flag-and-footprints) mission.
This isn’t really a mission plan so much as a trade study (and one oddly biased towards a certain conclusion). Due to the need to present its in house technologies such as SLS and Orion as being on the critical path to Mars, NASA writes these things in a parallel universe where Starship is forever on the horizon, despite not planning their landings until the 2040s. The accelerating test program is going to make this politically useful fiction untenable soon. With a change of administration, now might be a good time for NASA and SpaceX to make the first iteration of their joint plans for sending humans to Mars and establishing a base there - and the the critics wouldn’t end up incorrectly filling in the gaps themselves.
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