Abstract

The routine detection of exoplanets has started to yield a candidate list of new worlds potentially capable of harboring or sustaining life. To date 3775 exoplanets have been confirmed contained within 625 planetary systems. Of the 3775 planets, 55 are deemed suitable to support life of which 1 is subterran (0.1-0.5ME or 0.4-0.8RE; ME=Earth mass, and RE=Earth radius), 22 are terran (0.5-5ME or 0.8-1.5RE) and 32 are superterran (5- 10ME or 1.5-2.5RE) [1,2]. Facilitated in part to date by the Gaia [3,4] and Kepler space telescopes [5,6], the launch of the Transiting Exoplanet Survey Satellite (TESS) on April 18th, 2018 [7,8] which will monitor more than 200,000 stars for temporary drops in brightness caused by planetary transits further increases what is surely a highly likely outcome; identification of a set of candidates for further exploration. In 2018, the principle driver for identification of an ’Earth 2.0’, a planet very close to Earth characteristics is scientific curiosity and to determine whether life exists in, or beyond our Solar system. However, there is now growing evidence that the activities of humans as of 12,000yrs ago and to the present day have increased extinction rates of many species and that we are experiencing the 6th extinction level event (ELE) or the Holocene extinction [9,10]. The consequences of this latest ELE may add urgency to considering other planets for where mankind can migrate and settle, in part as a potential staging post for further exploration and in part as a failsafe should Earth become inhospitable to supporting life as we know it today. For both near (solar system) and deep (beyond solar system) space travel, the ergonomic challenges facing manned spaceflight for both human physiological and psychological adaptation to microgravity are well understood and countermeasures for and mitigation of the effects of microgravity are being developed [11], which include generation of artificial or simulated gravity in space [12-14]. The longevity of human lifespan is an as yet unsurmountable obstacle for reaching even the nearest stars with propulsion technologies available today and strategies are being considered which may prolong functional lifespan [15]. An alternative route to exploring deep space is to deploy unmanned space probes which combine the evolving fields of artificial intelligence, design and deployment of nano spacecraft and the futuristic concept of sending humans as avatars on small lightweight spacecraft as an e-crew. Taken together, it is possible to construct two parallel lines of thinking and simple decision matrices which utilize manned or unmanned space craft and in the first review we will consider their application to both near and far distance space travel missions.