Available energy, and microgravity, radiation, pressure and temperature are physical factors that affect astroecology. The ways by which life can reach space environments, including natural panspermia and directed panspermia are also considered.[4][5][6][7][8] Further, for human expansion in space and directed panspermia, motivation by life-centered biotic ethics, panbiotic ethics and planetary bioethics are also relevant.[7][8][9]