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List of illustrations
The legacy of comets
1 Cometary orbits
17 other sections not shown
astronomical atmosphere atoms attack rates bacteria bacteria and viruses bacterium biology carbon chemical civilisations clouds Comet Encke Comet Halley cosmic dust degree detected disease dust particles Earth energy enzymes epidemic event evidence evolution exist experiments explosive extraterrestrial intelligence fossil record freezing nuclei frequency galactic galaxy genes genetic Giotto heat highly human hydrogen infection influenza infrared radiation inorganic interstellar interstellar cloud known laboratory life-forms liquid water lunar magnetic field Mars Martian material meteorites metres microbial micrometres microorganisms microwave million years ago non-biological nuclear nutrient observed occur orbit organic molecules origin period planet planetary system population possible present produce properties protons radio recently region satellites seen shepherd satellites signals similar solar system space species spectrum spiral spiral galaxy star formation structures sunlight surface survival telescope temperature terrestrial theory thought tion Universe Vale of Glamorgan viral virus wavelength