Why should we send people to the moon rather than getting robots to do the job?

Why should we send man back to the moon when we can simply send a spacecraft to do the experiments and then return to Earth? - Question posed by A. Nonymous

Before I respond to this question I want to make it clear that this post will be mostly based on my personal opinion, and that everyone's opinion will be slightly different. So, whether you agree or disagree with what I say, please feel free to get in on the debate by commenting below!

I'll comment from a viewpoint that assumes everyone thinks going back to the moon in some form is generally a good idea otherwise this response may become needlessly complicated; the arguments for and against further exploration of the moon (and other bodies) is food for another post. With regards to this question, I'll look at the arguments either way:

Why should we send robots to do the work?

The biggest reason is one of safety. Space is a dangerous place for humans as we are not naturally adapted to survive in it, so there need to be several levels of safety mechanisms and procedures in place to ensure that any person sent into space survives the experience. Also, the very act of getting into space necessitates the use of highly explosive chemicals in close proximity to any travellers. So far 22 people have died either in space or trying to get there, which represents around 5% of the total number of space travellers. Fatalities are much higher when you also consider ground crew and civilians who have been killed as a direct result of training, testing and launch. Robots and spacecraft can be specially designed to work successfully in vastly differing environments and are, to a certain extent, expendable so negate the need for quite so stringent safety considerations.

Cost is another important factor: sending humans into space costs a lot of money in comparison with sending machines in our place, largely due to the safety issues mentioned above.

Finally, longevity is a driving factor in decisions to send robots and probes to do our work. Human missions beyond a week or so become prohibitively expensive and difficult due to a number of factors, not least transporting enough food and oxygen to keep the participants alive for the duration. There are also the physical implications of extended periods in a low gravity environment and the psychological effects of being stuck with the same people in cramped conditions for too long. Robotic craft would not suffer from the latter problem, and the former is solved more easily by using long-lasting energy sources.

The longest amount of time spent in space (consecutively) by a human is 437 days, by Mir cosmonaut Valeriy Polyakov from 1994 to 1995. Compare this to the Opportunity rover which has been in operation on Mars for almost seven years, blasting its original design specification of 3 months to dust. Even this pales next to Voyager 2, who has been operating continuously for 33 years and is expected to continue sending us data until at least 2025, more than forty years after its launch.

Why send humans, then?

There are some things that robots just can't do, and possibly will never be able to. A human geologist on the moon could make inferences from a rock in front of them that a robot could never think of. Humans are far more adaptable than robots- any problems with machines on other bodies have to be solved by humans back on Earth and, with signal lag caused by the distances involved, it may be too late. Humans can make decisions on the spot, come up with imaginative solutions to problems and notice and recognise things of interest outside  their mission specifications. Humans can be trained for a wide variety of applications, but robots are generally built to perform only a limited number of tasks.

There's a human interest element, too: sending living, breathing humans into space captures the public imagination much more than unmanned spacecraft and robots do, and this is a very important part of acquiring funding and support for space missions.

Research and development for many aspects of human space flight, including advances in medicine and food preservation for example, have direct applications down here on Earth: scratch-resistant lenses, cordless power tools, foil-packed crisps and water filtering jugs are just some of today's normal household items that have come about as a direct result of research for manned space missions. Many of these have paid for their own development costs many times over.

So should we send robots or humans?

Well, that's up to you. What do you think? Feel free to comment with your ideas!