One principal challenge in biology is defining a postulate by which the habitability of other planets can be assessed. Current assessments suffer from two potential weaknesses. With respect to other planets, either assumptions are made about the physical and chemical conditions of environments that err on the side of biological optimism without empirical constraint by spacecraft observations or novel physiologies of microorganisms are invented to fit extraterrestrial environmental conditions with no demonstrated microbiological counterparts on Earth. Attempts to assess the habitability of the early Earth suffer from similar problems. We discuss the following postulate: ‘the proposition that a planet is or was habitable requires that the physiological requirements of microorganisms on Earth known at the time of assessment match the empirically determined combined physical and chemical conditions in the extraterrestrial or early Earth environment being assessed’ as a means of evaluating ‘habitability’. We use as tests for our postulate the early Earth and the cloud deck of Venus (a habitat that has been a source of optimistic debate for forty years). We conclude that, although the early Earth was habitable, Venus is a dead world.

The special characteristics of Raman spectroscopy (relative insensitivity to water, non-destructive detection, sensitivity to bio- and geosignatures, molecular structural composition information, etc.) together with the development of miniaturized Raman spectrometers make the consideration of this technique for future robotic landers on planetary surfaces, particularly Mars, a very interesting option. The development of light and rugged Raman spectrometers limits the possible scope of the instrumentation which has particular importance in the recognition of biomolecular and mineral signatures. In this work, we evaluate the spectral resolution and scan time parameters and the effect that they have on the Raman spectra of extremophilic biomolecules, together with the wavenumber ranges which are critical for the detection of life signals. This is of vital relevance for the design of miniaturized Raman spectrometer systems. From our results, we conclude that for extraterrestrial biological signatures unambiguous Raman spectral identification provided with a minimum of 16 cm−1 spectral resolution is required for the most significant biosignature wavenumber range in the 1700–700 cm−1 region.

Science fiction (SF) is often perceived as a ‘fringe’ form of entertainment that excites the socially challenged. This misperception detracts from the critical, scientific and interpretive nature of the genre which can be directed into science teaching at school and university levels as an innovative way of exploring the cultural background, politics, leitmotif and themes of society, science and their operation. One example is the ‘alien’ theme in SF; it is perceptually one of the driving factors in the search for extraterrestrial intelligence (SETI). Such a topic can become an introduction to current technology, the motives and politics of science and the sociological implications inherent in a confrontation with the ideal of man's uniqueness in the cosmos. When applied to the SETI, SF engenders a constructive convergence in studies such as biological determinism, the evolution of life, communication, interstellar travel and methods of contact, thus enriching the consideration of possible life in the cosmos. Adopting elements of SF in lifelong learning therefore enables informed, imaginative reflection and debate that educates, trains and instructs, broadening the potential of students and their future roles by invoking an analysis of vital public, scientific and humanistic fields.

Imagination lies at the basis of all discovery

Octavio Paz