‘Is there life on Mars?,’ asked David Bowie, and would not stay for an answer. The astrobiologist Steven Benner has an answer – which is that Mars not only has had life but still does. The first part of that answer is broadly accepted; the second remains highly contentious. His book is a scattershot plea for increased attention to be paid to searching for evidence – or, as he sees it, more evidence. The stakes are high. As he says in his introduction, if life exists only on Earth, that’s a coincidence; if it exists on Earth and a close neighbour, that’s the start of a pattern.

Mars has always excited the imagination. No one has ever speculated hubristically about the chances of anything coming from Mercury. C.S. Lewis apart, the literature of Venus is as thin as its atmosphere is dense. It is Mars where Elon Musk dreams of dying – ‘but not on impact’. As Benner notes, the film of Andy Weir’s book The Martian made $630 million worldwide; throwing in Interstellar and Arrival brings the total pretty close to the budget of an actual Mars mission.

Benner’s advocacy is needed, because for half a century the consensus among what he terms ‘the community’ has been that the planet shows no signs of life. Benner describes how the Viking mission in 1976 intended, among other priorities, to detect life. The three main experiments, on their own terms, showed positive results, albeit not without complications. Another less sensitive experiment, GC-MS, appeared to show the reverse – again not without complications. Initial reports were soon drowned out by a community view that the Viking results proved the precise opposite of what they actually suggested. Gerald Soffen, the mission’s chief scientist, declared: ‘That’s the ballgame, no organics on Mars, no life.’

Benner then maps the reputational and financial risks of departing from this consensus: the political processes that allocate scarce taxpayer dollars to a handful of approved space science projects. Gil Levin, a sewage engineer who designed detection systems for bacteria, one of which flew on Viking, and who was an early sceptic of GC-MS, presented his arguments at the National Academy of Sciences to a hostile reaction. ‘Attendees shouted invectives at me. They were ready to throw shrimp at me from the shrimp bowl. One former adviser said: “You’ve disgraced yourself, and you’ve disgraced science.’” Anyone who has voiced an unpopular truth in a large organisation will recognise the tone.

Essentially, Benner argues, all the institutional incentives impel towards over-caution. It’s much safer to insist that there is no life on Mars than to suggest that there is and be proved wrong.

But this is not, in principle, how the scientific method works. Theories are meant to be the best possible explanation, given current evidence – always subject to later revision as new data and new interpretations emerge. Of course, as Thomas Kuhn declared in The Structure of Scientific Revolutions, changing a dominant paradigm is uphill work because, unsurprisingly, scientists are no happier to be proved wrong than any other eminences. In Max Planck’s aphorism: ‘Science advances one funeral at a time.’

Benner is horrified at how this is evidenced in his particular field:

Science cannot work if scientific reputations can be ‘damaged’ by a good-faith interpretation of data that later turns out to be wrong. After all, the same describes most interpretations of most experiments in most of the biggest science. Even the reputations of Newton, Einstein and Darwin are ‘damaged’ by this standard. Yet that was the culture.

It is Mars where Elon Musk dreams of dying – ‘but not on impact’

The culture prevailed to the extent that for decades the committees that governed science funding ignored, or failed to understand, or failed to take seriously, subsequent work that questioned Soffen’s calling of the ballgame.

Now the competition is heating up. Nasa aims to establish human settlement on the Moon in the 2030s; either the Chinese or SpaceX or both may beat it there. Uncrewed probes are going there first. So Benner sets out four propositions: that life arose on Mars; that it is still extant there; that it can be identified when found; and that the places where it can be found can be accessed. He ends with a call for the astrobiologists of the world to unite to design the experiments needed and to lobby for them.

A Martian might wonder who this book is for. The most interesting of its narratives, to a lay reader, is about the institutional failures of academic science. There is also an increasingly detailed set of arguments about extraterrestrial organic chemistry, which will soon tax the abilities of anyone without a degree in the subject. Tonally it ranges from the out of touch (science fiction references from the 1960s; constant allusions to humans as ‘ape descendants’) to the patronising: ‘Now it is time for you to play Sherlock Holmes. You are a clever person. You are (we hope) not infected by the biases of the culture.’ The text is studded with the kind of relentlessly unfunny cartoons that a professor might deploy to amuse his dopier students. This manifesto would have lifted off faster with a tighter, lighter payload.