I am an advocate for the near-term human settlement of space. I am also an environmentalist. I was formerly a member of the Green Party of England and Wales, and stood as their parliamentary candidate for Leicester West in the 2015 election, scoring that parties highest ever vote there.

I accept the scientific consensus on anthropogenic climate change, and believe it is necessary for governments to take swift action. I am pro-nuclear – but that is not the reason I am no longer in the Green Party; quite a few people there are even though the leadership won’t admit it. I left as I thought the internal structures of the Party made it ineffective, and in any case its primary concern has now been adopted by every significant party in this country. This is an issue with many Green parties across the democratic world; the mainstreaming of the climate issue has left them without their main unique selling point, and they tend to default to being a protest party and/or just a woker version of their countries social democratic party. Regardless, I remain committed to supporting the decarbonisation of our economy and would not support or vote for a political party that does not.

I mention this, because in some corners, space settlement and protection of the terrestrial environment are portrayed as being in conflict. This is largely a one-way thing; no space advocate wants to see Earth’s biosphere damaged, but many environmentalists want to shut down (or at least restrict) human space settlement. There is tied up with this a fear that rich people will use a space colony as some kind of escape plan, shrugging off their social responsibilities and especially their environmental ones. The narrative as stated in this article is that, having fouled up this planet, billionaires will simply skip to the next one and leave the rest of us to clear up the mess.

One person who has taken this position is Carolyn Porco, a scientist who formerly worked on the Cassini mission for NASA. She has a recent TED talk on the issue which ends with a plea for Jeff Bezos and Elon Musk to abandon their efforts at putting humans into space and instead turn their wealth and efforts towards saving the Earth. Perhaps it is reasonable to direct such a charge at Bezos, but is she unaware of Musks other business interests?

I’m going to skip discussing Porco’s anti-capitalism for now; although this far from uncommon from people who take this position. There is plenty to discuss there – the worrying tendency in the last decade or so of the left to oppose spaceflight. I’ve covered this before, but here want to focus specifically on environmental matters.

The Carbon Cost

First I would like to address the direct environmental impact of SpaceX launches; at present the number of rockets they launch is not large enough to really make a difference on a global scale, but it still raises concerns in some quarters and if SpaceX massively increases their flight rate it is worth considering.

According to the SpaceX website, Each Starship/Superheavy vehicle contains 4600 tonnes of methalox propellant. I’ve created a spreadsheet, assuming perfect stoichiometric ratio of methane/oxygen, 50 passengers and 6 tankers per Starship to Mars and 500 per Starship to LEO, and then worked out the CO2 produced per flight. Taking per capita CO2 emissions from Our World In Data I have then worked out how long it would take to produce the same amount of CO2 just by day-to-day activity.

The CO2 emission data is averaged over very unequal populations, so is likely a substantial underestimate for the kinds of people who can afford to fly to space in the near future. Even so, it shows that removing wealthy westerners from the biosphere permanently is carbon negative if done at a reasonably young age. There may be still carbon emissions from launch cargo to Mars that they will use; but to get to a point where flights to Mars are regular enough for their CO2 emissions to be an issue then any settlements there will have to be fairly self sufficient. Very few people are rich enough to make a life for themselves on Mars using mostly imported goods.

There is the issue of water vapour produced by methane combustion; the contribution of this to the greenhouse effect is considered minimal at sea level, as it precipitates out, but at altitude the picture is more complex, and truthfully I don’t understand the latest research on this. However, even if water vapour had as much impact again as the CO2 emission then the conclusion would be similar.

The carbon emitted by a trip just to LEO is only a few months of normal emission in the West. At some future stage of space development, I expect both propellant for interplanetary transit and the cabins and supplies will be sourced from other celestial bodies, and thus a trip anywhere in the solar system will only have the impact of the Earth’s biosphere of a single passenger launch. If this could be done for trips to Mars, the carbon emissions of launch would be offset by your absence before you reached the planet.

This seems to get rockets off the hook for carbon emissions – and in any case, SpaceX intends to make them entirely carbon neutral by making methane through carbon capture – but it doesn’t mean that the environment can be saved, or seriously impacted in a positive way, by removing people from the planet. There are just far too many people. Musk is considered optimistic wanting a city of a million people on Mars, and removing a million people’s carbon emissions would do essentially nothing to arrest climate change. In the long run, the idea, touted by Jeff Bezos, of removing as much human activity from Earth as possible to preserve it is probably sound – be even he made it clear this is a multi-generational effort, for which he can only hope to lay the groundwork in his lifetime. Climate change is a problem right now, and as shown above it is orthogonal to rocketry.


The idea that rich people want to exit a dying planet is essentially expressing a problem of incentives. People like Carolyn Porco want to make sure that billionaires continue to be dependent on the same biosphere as the rest of us and so are sufficiently motivated to manage it correctly.

There are a few problems with this view. First is the idea that space settlement is for the rich only – if it is, it won’t work. The motivation for radically lowering the cost of space access, which SpaceX is doing right now and others such as Blue Origin hope to do in the future, is to open up access for a much larger portion of humanity than can presently go. They need to do this to create a market for space services large enough for their goals to be funded.

Secondly, the idea that rich people can fix climate change (or any other significant issue) is nonsense. The presumption that they can is based on the observation that they have a lot of money – but compared to governments, they really do not. Jeff Bezos is currently the richest man in the world. It varies with the price of Amazon shares, but his net worth is just shy of $200 billion. For comparison, the US Federal budget is over $4 trillion – per year. The Department of Defence alone has a $700bn/year budget, so a total liquidation of Mr Bezos would keep the lights on in the Pentagon for about 15 weeks, and then all his money would be gone, and you would have to then liquidate Elon Musk (net worth about $170 billion) to fund the following 13 weeks. The returns on this method of funding would fall off very quickly thereafter.

Also, governments can create money on this scale by diktat. The Biden Administration just signed a stimulus bill around ten times Jeff Bezos’ entire net worth. The description of currency such as the dollar as “fiat currency” is somewhat overused by people pushing fringe economic ideas, but there is truth to it – for situations like this a government simply says “let there be $2 trillion” and as if by magic it appears.

No Easy Answers

Billionaires aren’t going to save the planet because they can’t. If their wealth were enough to decarbonise the economy then governments would simply will that amount of money into existence and do it. So it doesn’t matter at all that some of them choose to spend their money on making humans a spacefaring species. Nor does it really matter than the US spends $20 billion or so each year when the US government can conjure up 100 times that much at the stroke of a pen. Neither public nor private spending on space is stopping the necessary environmental policies being implemented.

Whenever someone asks why society can’t do X, where X is saving the environment of sending humans to Mars or whatever a person cares dearly about, I think the more pertinent question is why society can’t seem to do anything. Aside from maintaining the status quo, western governments don’t seem to be capable of any sustained actions on anything – something painfully demonstrated by many of them during the current pandemic, which was seen off swiftly by different societies in the Far East. Both decarbonisation and space development are worthy goals, and I don’t think its helpful to play them off against each other.


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