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Should we send astronauts to Mars?

Ian Crawford and Andy Fabian discuss

Dear Ian, 

Should public money be spent on a crewed Mars mission? The cost would probably exceed 100 billion dollars: I’ll ignore an estimate by a private company of less than 10 billion. But spending such large sums on this project means it would probably be labelled as a scientific enterprise and at least part of the money would come from budgets for genuine science (as happened in the US recently).

A successful mission would be a wonderful adventure, and an engineering and technical tour de force, but have little scientific impact. Humans may be smarter than robots, but for 100 billion a lot of smart robots could be sent to Mars and the spinoff from the development of such advanced robotics would likely be a far greater stimulus for science, engineering and technology.

The high cost is mostly due to the risks involved and the difficulty of landing humans on Mars. A crewed mission to Mars might be done by people with the ‘right stuff’ on the cheap if they're prepared for the high risk. I'm not sure that I or the public would be happy even then.

They might also rightly complain about littering our nearest Solar System neighbours with dead bodies and human germs.

Yours, Andy

Dear Andy, 

I agree that a human mission to Mars will be expensive, requiring careful justification for spending public funds. I think the potential public benefits of such a mission would outweigh its cost. In addition to advancing scientific knowledge, it would stimulate industrial and technological innovation, inspire young people to take an interest in science and engineering, and, in the context of an international programme, provide an uplifting and unifying project for humanity.

I think the science case is stronger than you imply. It’s not just that humans are more intelligent than robots, they are also much more mobile (for example, in three days the Apollo 17 astronauts covered the same 35 km that the Mars Opportunity rover covered in 8.5 years!). Crucially, because the astronauts have to return to Earth they can bring rock samples back, something that greatly enhanced the scientific benefits of Apollo. The same kind of scientific benefits will also apply on Mars.

However, I agree that it is premature to send people to Mars now. There is still a lot we need to learn about Mars (such as whether it supports indigenous life) before we can responsibly send people there. I agree that this preparatory work can only be done robotically.

Yours, Ian

Dear Ian, 

Can we discuss the risks involved a little? Space is a hostile environment with extremes of temperature and radiation, of all types. Had Apollo 17 landed on the Moon in August not December 1972, when a strong flare spewed highly energetic particles from the Sun, manned spaceflight might have evolved very differently. The astronauts could well have suffered severe radiation sickness requiring hospitalisation on their return. 

If this happened on the way to Mars, then hospitals are out of the question. We know that even larger flares do occur, and at present they are unpredictable.  Perhaps sometime in the future a way will be invented by which astronauts can, say, take  stem cells in a lead box in order to regenerate parts of themselves in the case of a massive flare. But for now the problem could be a showstopper.

Another problem is that of actually landing on Mars. Its atmosphere is only one per cent of Earth's and is gusty, making landing difficult and fraught. The latest Mars rover, Curiosity, did land safely using a sky-crane in August, but this required the correct firing of over 60 pyrotechnic devices. A sky crane might prove unworkable for humans. How would you safely land astronauts?

Yours, Andy

Dear Andy,

It is true that the risks to astronauts from radiation are potentially severe. Nevertheless, given a focussed research programme, both in predicting solar storms and in developing effective radiation shielding, these are unlikely to be show-stoppers.

For example, there is an innovative magnetic shield being studied at the Rutherford Appleton Lab which has the potential to ameliorate radiation hazards greatly for astronauts in deep space.

Similarly, I doubt that landing on Mars will present show-stopping challenges. A lot of experience has been accumulated on landing spacecraft on Mars. If and when a decision is taken to send people to Mars (for all the interrelated scientific, economic, and inspirational reasons I identified in my last email), then technical solutions are likely to be forthcoming.

However, it will take time to develop this competence. My view is that we should develop it first in returning people to the Moon (which would yield scientific and industrial benefits of its own), while continuing with the robotic exploration of Mars in parallel. There may then be a realistic chance that, sometime before mid-century, the former will have developed the human spaceflight expertise, and the latter the detailed knowledge of the Martian environment, to make human missions to Mars both scientifically worthwhile and technically feasible.

Yours, Ian

Dear Ian, 

I think that we are agreed that now is not the time to send people to Mars. There is much to be done to understand and if possible reduce the risk.

I truly hope that when it does happen it is driven by scientific curiosity and not one of the baser human traits, such as greed. The first person to step on Mars may well be alive now, although she/he is probably still very young and will be in their forties or older when they set forth!

As for the Moon, that does make more sense. The next people to set foot there could well be Chinese, given their growing space abilities and determination. In parallel, the use and development of advanced robotics to carry out much of the initial exploration and preparation does make enormous sense and promise many spin-off benefits.

Logic and science may not however be the main drivers for what does eventually happen. A lot of money will be needed. Big business may get involved, or ideas to exploit asteroids for minerals could be extended to Mars. I hope that whatever happens is closer to how Antarctica has been explored than what seems now to be happening to the Arctic.

Yours, Andy

Dear Andy, 

It looks like we have broadly reached agreement.

I accept that science is unlikely to be the main driver for sending people to Mars, just as it was not the main driver for Apollo, but I am convinced that science will be a beneficiary. In order to maximise these benefits it is important that, when the time comes, the human exploration of Mars proceeds in a responsible manner, with a robust, internationally agreed, legal framework in place to ensure that scientific interests are protected. Antarctica is indeed a good model.

I am somewhat more sanguine about the costs than you are. Even if a human Mars Mission cost $200-300 billion (spread over a decade or more), this is still far less than the cost of the bank bailouts (c, $2500 billion, although estimates vary), the Iraq war (c. $900 billion, with some estimates being much higher), or the world’s annual military spending ($1700 billion).

For a fraction of these latter sums we could afford to send people back to the Moon and to Mars, advancing scientific knowledge, driving technological innovation, and providing an inspirational, unifying project for humanity. Compared to some of the things governments spend money on, human space exploration looks positively affordable!

Yours, Ian

Ian Crawford
Ian Crawford is Professor of Planetary Science and Astrobiology at Birkbeck College London
Andy Fabian
Andy Fabian is Professor at the Institute of Astronomy, University of Cambridge
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