Why the prospect of life on Mars still fascinates us

“Hope” is now in orbit around another world! This is a technical triumph. Half the spacecraft sent to Mars in the past have failed in their mission: there is much to go wrong. And because a radio signal takes more than 10 minutes to traverse the immense distance, success depends on perfect pre-planning of the manoeuvres which must be carried out robotically, at the right time and in the right sequence. I watched the TV footage of the Hope control room, and can well imagine the elation when the engineers received the signals that confirmed the achievement of the intended orbit.

Hope is being joined this month by two other missions, one from the US and one from China. There should have been a fourth, from the European Space Agency, but sadly this vehicle encountered technical problems and will have to wait for the next launch opportunity. There are periodic launch windows when the Sun, Earth and Mars are optimally aligned; the next comes in about two years’ time.

Mars has held a special fascination for more than a century. Indeed, it was widely believed that it was inhabited by intelligent beings. We now know enough to rule out any "advanced" or conspicuous life on the Martian surface, though it's possible that some could have existed three or four billion years ago when there is evidence that there was more water on the planet than there is today.
We already have maps of Mars: indeed, we know more about Martian topography than about the bottom of Earth's deep oceans. And Hope will reveal far better images of the surface, and tell us more about the atmosphere and climate.

The question “is there life on Mars?” fascinates the public. But scientists regard it as crucial in a cosmic context – in answering the wider question: “Are we alone in a vast cosmos or do aliens exist, far away, on planets orbiting distant stars?” We don’t know how life began here on Earth – what caused the transition between complex chemicals and the first self-energised and reproducing systems that we’d deem to be “alive”. This could be a rare fluke – even perhaps unique to the Earth – or, at the other extreme, it could happen on any planet, around any star, where the conditions resembled those on the young Earth.

So, if life were found to have originated in a second location in our Solar System – twice around one star (our Sun) – then it can’t be a rare fluke. This would have the momentous implication that many of the billions of Sun-like stars in the Galaxy will harbour some form of life. Our entire Milky Way will be teeming. But until we find life elsewhere in our Solar System, it remains possible that Earth is a unique abode in the entire cosmos.

That’s why we’re keen to search for even the most vestigial evidence for life on Mars – and, thereafter, to extend the search to other locations in our Solar System. Within a decade or two, sophisticated robotic probes will venture to the moons of Jupiter or Saturn, with a focus on Europa or Enceladus, which both have ice-covered oceans in which some alien creatures could be swimming – as perhaps they did on Mars in the remote past.

Human spaceflight is more likely to involve national rivalry than the friendly cooperation associated with scientifically motivated ventures

The future of geologic investigation of other worlds lies with highly improved versions of present-day Mars rovers. These vehicles will deploy numerous tools, virtual-reality and artificial-intelligence capabilities to probe rocks and minerals, using a memory equal – and soon superior – to any human’s. They will traverse the Martian surface for decades, continuously learning about the topography, seismographic activity and distribution of geologic strata in bulk and in detail. Some will return samples to Earth for fuller analysis. Conceptually similar robots will eventually be able to repair space stations, or build complex structures in space.

Hope: the UAE's mission to Mars. Roy Cooper / The National

The robotic probes orbiting Mars, or trundling across its surface – and the flotilla of more advanced machines that will hopefully probe the outer Solar System – will represent the efforts of many spacefaring nations. We can hope that this noble enterprise of deepening our understanding of humanity's place in the wider cosmos will proceed in the cooperative spirit that characterises most of science.
Of course, a key question is whether and how quickly humans will follow these probes. The practical case is actually becoming weaker rather than stronger. Today, a trained geologist on the moon can perform better than a robotic explorer, but that won't be true a decade or two from now as miniaturisation and AI become more sophisticated.
There are, however, other reasons for enthusiasm about human space exploration. For many, the most compelling reason is simply "uplifting the human spirit". We applaud and are inspired by heroic accomplishments, and many of us would regard a human landing on Mars as a paramount achievement of our species. Do these emotions, though, justify the costs and dangers of such missions?

Unfortunately, human spaceflight is more likely to involve national rivalry than the friendly cooperation associated with scientifically motivated ventures. For instance, the former president Donald Trump exalted a future "when American astronauts will plant our beautiful Stars and Stripes on the surface of Mars", adding the pride of ownership to the thrill of human achievement.
There are other motivations for astronaut expeditions to our celestial neighbours. These include the belief that space offers an eventual refuge from a debilitated Earth and an eagerness to exploit raw materials.

Shortly before his death in 2018, my Cambridge colleague Stephen Hawking stated that “spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth.” More recently, Jeff Bezos of Amazon, who is deploying some of his vast wealth to fund the “Blue Origin” company to develop rockets (as is Elon Musk’s company SpaceX), has said that humans need space travel because “we are in the process of destroying this planet”. Among other outcomes, Bezos envisions in the far future that giant colonies would each allow millions of people to live in space.

For the enthusiasts, habitats on Mars offer not only sites to develop a better society but also places where humans could use advanced technology (bio and AI) to modify themselves – to adapt to the lower gravity and rarefied atmosphere on Mars or, in the Bezos scenario, produce an artificial gravitational force within the enormous rotating wheel of a million-person “posthuman environment”, where genetic engineering could attempt to reduce diseases and prolong human life.

Such plans appeal to those who see Earth’s future as deeply uncertain or even hopeless. A moment’s thought, however, reveals that the notion that we can learn from our errors on Earth in order to survive in space involves pie-in-the-sky optimism. And surely the billions of people to be left behind deserve greater consideration. If we can’t solve humanity’s problems on our home planet, we seem highly unlikely to be able to do so by establishing ourselves in space. Dealing with environmental issues like climate change on Earth, challenging though they are, are cheap and simple compared with “terraforming” Mars to render it habitable by ordinary humans.

I personally wouldn’t expect mass migration to Mars. We humans are far better adapted to our Earthly home. We should use space technology for fabricating large structures in space, for monitoring the environment, for communications, and perhaps for mining asteroids.

Nonetheless, I think it’s likely that some bold adventurers will walk on Mars by the end of the century. Maybe some privately funded risk-takers will go with a one-way ticket to occupy “bubbles” assembled in advance by robotic fabricators. I hope they go in the spirit of cooperation rather than hostile rivalry – coming from many nations, including the UAE.

Lord Rees is a member of the UK House of Lords and the British Astronomer Royal

Why the prospect of life on Mars still fascinates us

Until we find life elsewhere in our Solar System, it remains possible that Earth is a unique abode in the entire cosmos