Purpose and Conclusions of the Cross-disciplinary Perspective Groups (XPG)
There was some effort made to get people who might think outside the box and to avoid those with a large experience of space projects. Although names of individuals invited had been proposed by the advisory structure and by SPC delegations, only the chairs of the present ESA science advisory bodies were invited, as it was thought that the advisory structure's work in developing plans and targets for a programme would come later. The aim was not to set anything in stone but to check the boundary conditions of our present thought. The outline here is based on notes made at the two-day session. There was an enunciated ground rule that there should be no reference to any particular mission name but only to generic techniques; the rule was rarely broken.
It was asked that participants should not feel constrained by their discipline; long term scientific goals should be general and accessible to other scientists. People were encouraged to feel able to talk outside their particular area of expertise and were asked not to have prepared excessively for the exercise. In a similar spirit, no formal report was asked of the participants. At best they were asked for a set of bullets or guidelines for tackling some of the key issues of future scientific endeavour. Senior members of the ESA Science Directorate Executive were present but were asked to listen rather than lead.
Basics
The request to the attendees had been expressed as follows:
- Your primary task is to try to delimit the long-term scientific and societal goals that should be picked up by space science in the next two decades.
Why not science alone? Why should societal goals matter?
Space science is expensive and it seems fair to ask what it achieves for society as a whole as well as for scientists. Maybe the answer is nothing but at least someone should ask the question.
The philosophical level of the response was perhaps epitomised by the quotation of a Platonic dialogue from S. Vitale:
- Plato: Shall we set down astronomy among the subjects of study?
Glaucon: I think so, to know something about the seasons, the months and the years is of use for military purposes, as well as for agriculture and for navigation.
Plato: It amuses me to see how afraid you are, lest the people should accuse you of recommending useless studies.
Why do science at all in space? One should only do what cannot be done on the ground. Therefore reasons must include considerations like escaping terrestrial effects (escaping the veil of the atmosphere or escaping gravity), achieving baselines larger than the Earth, getting close-up to view celestial objects, or actually investigating celestial objects in situ.
Why continue to do space science in Europe? Science is basic in an advanced and wealthy society. Enhancing knowledge is the main social motivation for science at large.
Space itself represents not the environment for our whole planet but also its frontier. Doing space science is one aspect of our society looking outwards. As humans, we must have the capability to look out and explore and try to understand our universe. Moreover, in the long run, even the Earth itself has an uncertain future. Space may be essential for the survival of our civilisation and mankind.
Why should Europe be involved? Europe is rich and highly technically developed. Having a full space capability (applications and science) is a basic need whilst maintaining a space science programme is a basic part of contributing to the global society.
The intention of a European programme must be to rely on excellence of European scientists in specific fields but Europe is big enough that no field should be a priori excluded. Furthermore, although space science is a natural theatre for international cooperation having an autonomous capability is the best basis for making successful global cooperations. Wide international cooperation should be encouraged although evidently the USA would be a major partner.
Reasons for requiring autonomous space science capability go beyond being a good partner in international cooperation. Space science is a powerful driver (and even more important in a society with little military spending) in sustaining the infrastructure for space (launchers, launch facilities, upstream and downstream space industries). The US uses space as means to ensure and enhance worldwide predominance. [This point is made very clear in President Bush's recent speech announcing the new US Space Exploration Initiative.]
Well-funded space science helps, in a constructive manner, Europe to avoid declines in sectors such as the following: Mastering of scientific knowledge, nurturing a top-class scientific community, maintaining a solid technology base, maintaining and challenging a competitive space industry. Moreover, Europe can also exhibit leadership and impose its vision on the world through constructive international cooperation, as space science activities naturally gain public attention.
Perhaps most clearly the discussions on space science's role in society left it clear that technical spin-off should be a bonus not a motivation. That the ultimate criterion for choice should be based on scientific curiosity, pushing back the frontiers of knowledge and the inspiration that exploring our universe can bring to our society.
Technical discussions
The two major groupings for technical discussion were
- Physics and the physical processes in the universe
- Chemical and biological aspects of the evolution of the universe
Group 2 took life in the universe as its basic theme.
Group 1 faced a rather different and more difficult problem than was faced by group 2. The vast majority of the major results of the last 20-30 years of space exploration have concerned the physical universe. It was clear that astronomy and our physical knowledge of the universe was going to undergo a massive change once one could access radiation wavelengths that could not be observed from the ground. Common physical sense told us that X-rays and gamma-rays would allow us to look at extreme energetic phenomena whilst infra red light could tell us about star formation. Similarly going into space and measuring in situ brought immense numbers of discoveries. First missions are all discovery but then the rate of discovery slows with increasing knowledge. When and how does one decide to de-emphasise use of a particular technique because of diminishing returns? The group took the problem head-on and came up with its set of bullets as follows:
- Nature of physical laws including their immutability in time
- High energy physics beyond the accelerator
- Quantum world, edges of space, cosmic microwave background and black holes
- Complex systems, turbulence
- Universe: origin and evolution and changing nature of the universe
These summarised the target areas where they thought that the 'knowledge mine' was far from exhausted. They produced the list of basic reasons for doing science in space, given earlier, namely escaping terrestrial effects (escaping the veil of the atmosphere or escaping gravity), achieving baselines larger than the Earth, getting close-up to view celestial objects, or actually investigating celestial objects in situ. These reasons were given above but group 1 elaborated these in the light of the targets listed above.
Group 2 had a task much better ordered by the fact that there have been many recent new discoveries in its remit. In fact, in some areas their topics and aims overlap with the physical sciences.
Their first set of bullets was:
- What is life?
- What are the physical processes that make life appear on the Earth?
- How did it evolve? How will it evolve?
- Is life a consequence of the evolution of the Universe, of the increasing complexity of the Universe?
- Is there life elsewhere in the solar system?
- Is there life elsewhere in the Universe?
- Are there exo-planetary systems similar to our own?
- How planetary systems are formed?
- How common is the formation of planetary systems?
Some of the bullets were then expanded:
What is life?
- continuous or not continuous transition from not living to living ?
- if continuous: introduce a normative aspect
- which criteria ?
- a certain level of complexity
- assembly of building blocks.
What are we looking for currently?
- very simple molecules.
How stable are they?
- what would we really like to look for ?
- micro-organisms, biomarkers, prebiotic material, carbonaceous complex components
- how do organic molecules evolve ?
- some kind of organisation process in the interstellar clouds
What are the characteristics of exo-planetary systems ?
Are there other planetary systems similar to our own ?
What are the conditions for star formation ?
What are the conditions for formation of planets around stars ?
- formation and evolution of planetary systems
- stability of orbits
- planet migration
The group concluded its case by surveying solar system sites where one needed to look: Mars, Europa, Venus, Io, comets, meteorites, sample return from the interstellar medium. There should be means sought for systematic searches for exo-planets and their characterisation, with emphasis on terrestrial exo-planets, search for biosignatures, the characteristics of stars hosting the systems. In regard to Earth: which specificities produced the start of life? Furthermore, the work must not be confined to space. Simulations in terrestrial laboratories are needed.
Overall the discussions revealed an ever-opening vista of unknowns to explore as our capabilities expand. Perhaps most striking was that cross-disciplinarity worked in the sense that nobody disputed that focusing purely on astronomical observations (inevitably remotely sensed) was essential to many parts of the puzzle but by the same token so was exploration closer to home in the solar system, even in the lab. Even the controversial view that a human individual was an essential element for certain capabilities (in geological surveying, for example) was acknowledged in discussion.