  Time is arguably the key limiting factor for interstellar exploration. At
high speeds, flyby missions to nearby stars by laser propelled wafersats taking
50-100 years would be feasible. Directed energy launch systems could accelerate
on the other side also crafts weighing several tons to cruising speeds of the
order of 1000\,km/s (c/300). At these speeds, superconducting magnetic sails
would be able to decelerate the craft by transferring kinetic energy to the
protons of the interstellar medium. A tantalizing perspective, which would
allow interstellar probes to stop whenever time is not a limiting factor. Prime
candidates are in this respect Genesis probes, that is missions aiming to offer
terrestrial life new evolutionary pathways on potentially habitable but
hitherto barren exoplanets.
  Genesis missions raise important ethical issues, in particular with regard to
planetary protection. Here we argue that exoplanetary and planetary protection
differ qualitatively as a result of the vastly different cruising times for
payload delivering probes, which are of the order of millennia for interstellar
probes, but only of years for solar system bodies. Furthermore we point out
that our galaxy may harbor a large number of habitable exoplanets, M-dwarf
planets, which could be sterile due to the presence of massive primordial
oxygen atmospheres. We believe that the prospect terrestrial life has in our
galaxy would shift on a fundamental level in case that the existence of this
type of habitable but sterile oxygen planets will be corroborated by future
research. It may also explain why our sun is not a M dwarf, the most common
star type, but a medium-sized G-class star.
