The success of the Apollo moon landings led the renowned rocket scientist, Werner von Braun, to advocate a human expedition to Mars. His was the first serious detailed study into a human mission, produced decades earlier in 1947/8. Notably, this featured winged landing craft because at the time it was not known how thin the atmosphere of Mars was! He was trying to sell the old nineteenth-century romantic vision of Mars influenced by Sciaparelli’s maps and early ideas of intelligent life on Mars as popularised by the science fiction works of H.G. Wells and E.R. Burroughs. Unfortunately, the disappointment of the desolate rocky Mariner 4 images in 1965 dampened the public's enthusiasm for a Mars mission and this was not to be fully rekindled until the 1997 Pathfinder/Sojourner mission found the presence of rounded pebbles on the surface. The pebbles suggested that Mars had a warmer, wetter past with the potential for life. Notwithstanding this dip in support, detailed studies into Mars missions have continued unabated since von Braun's original and this book lists a staggering 65 proposals up to its 2016 publication date.

In "Next Stop Mars - The Why, How and When of Human Missions", Giancarlo Genta brings together and discusses in detail the myriad of issues and factors associated with the extremely complex and expensive endeavour of successfully landing people on Mars and bringing them back safely. He expertly identifies all of the challenges before describing the current approaches and solutions being investigated. The sheer magnitude of the task may mean that a successful mission will need to be an international affair, perhaps following the successful ISS model, or be a mix of both public and private, building on a combination of differing interests and ideas. After all, any mission to Mars needs to be properly worthwhile, providing decent scientific returns and perhaps making steps towards the establishment of an outpost. A simple “flag and footprint” approach like the Apollo moon landings would be inappropriate for a destination so far away and a stay simply examining the planet from Phobos/Deimos may be easier and more affordable to achieve but would be unlikely to satisfy the public or scientific community. This book, then, emphasizes long-stay missions with crews staying on Mars for hundreds of days to take advantage of optimal launch windows.

Mission design comprises a kit of options for each phase so there is a lot for Genta to talk about and it is good to have all the different parameters brought together into a single publication, be they technical, economic or human. (In fact, I can think of no aspects omitted apart from one - rather sensibly, Genta does not delve into the politics of international Mars missions!). As the assessment of each topic is particularly thorough and detailed this makes for an authoritative, fully referenced textbook that is "not quite a cover-to-cover read" for the layman. A ton of data is presented, both tabulated and illustrated by black-and-white graphs, which are accompanied by relevant scientific equations. If, like me, your mind is not geared up for engineering texts, you might find the sections on the interplanetary journey to Mars to be dry and tough going especially when it delves into spacecraft trajectories and the characteristics of various thrust options (something covered in even greater detail in the appendices). You will also have to prepare yourself for the staggering amount of acronyms littering the text (thankfully listed at the front of the book), which serve to deliver concepts quickly once you have learned to recognise them.

Nevertheless, with so much covered here you will find some topics utterly fascinating and there are plenty of coloured pictures, diagrams and photographs to help put information across. There is a chapter giving a refresher on the physical features and surface conditions of Mars before the text addresses all manner of interesting topics such as landing site selection, the most likely locations for evidence of life, habitat & spacesuit design and even a possible approach for terraforming the planet!

How feasible is a trip to Mars? How does that change/improve with time? It might seem that the aim of putting humans on Mars will be just too complicated to achieve, however, the book ends with a positive tone and presents a series of convincing real-world example missions based on different propulsion systems and the research of Salotti et al (published 2014). These are all aimed at utilizing the 2035 (for cargo) and 2037 (for crew) launch windows and make the goal of a Mars mission seem more attainable. In addition, there are also a couple of more futuristic missions with technologies more advanced than those considered possible for the 2030s launch windows. Notionally, the challenge of a successful Mars mission becomes increasingly plausible as time passes and new technologies develop. There can be benefits provided by technological developments that occur entirely independently of any decisions about space travel (such as nuclear energy production). Also, if a base can be established on the Moon then it will become an excellent testing bed for many of those new technologies necessary for a Mars mission. Who knows, perhaps a mission similar to one that Genta outlines in this book will be realised after all.