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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Comparative planetary science | 5/5 | https://en.wikipedia.org/wiki/Comparative_planetary_science | reference | science, encyclopedia | 2026-05-05T14:33:48.769661+00:00 | kb-cron |
Earth is the only body known to contain life; this results in geologic and atmospheric life signatures apart from the organisms themselves. Methane observed on Mars has been postulated but cannot be definitively ascribed as a biosignature. Multiple processes of non-biological methane generation are seen on Earth as well. The detection of biomarkers or biosignatures on other worlds is an active area of research. Although oxygen and/or ozone are generally considered strong signs of life, these too have alternate, non-biological explanations. The Galileo mission, while performing a gravity assist flyby of Earth, treated the planet as an extraterrestrial one, in a test of life detection techniques. Conversely, the Deep Impact mission's High Resolution Imager, intended for examining comets starting from great distances, could be repurposed for exoplanet observations in its EPOXI extended mission. Conversely, detection of life entails identification of those processes favoring or preventing life. This occurs primarily via study of Earth life and Earth processes, though this is in effect a sample size of one. Care must be taken to avoid observation and selection biases. Astrobiologists consider alternative chemistries for life, and study on Earth extremophile organisms that expand the potential definitions of habitable worlds.
== See also == Europlanet List of Mars analogs Lunar Crater National Natural Landmark Terrestrial Analogue Sites
== Bibliography == Murray, B. Earthlike Planets (1981) W. H. Freeman and Company ISBN 0-7167-1148-6 Consolmagno, G.; Schaefer, M. (1994). Worlds Apart: A Textbook In Planetary Sciences. Prentice Hall. ISBN 978-0-13-964131-2. Cattermole, P. (1995). Earth And Other Planets. Oxford University Press. ISBN 978-0-19-521138-2. Petersen, C.; Beatty, K.; Chaikin, A. (1999). The New Solar System, 4th Edition. Cambridge University Press. ISBN 978-0-521-64587-4. K. Condie (2005). Earth as an Evolving Planetary System. Elsevier. ISBN 978-0-12-088392-9. C. Cockell (2007). Space on Earth. Macmillan. ISBN 978-0-230-00752-9. J. Bennett; et al. (2012). The Cosmic Perspective, 7th Edition. Addison-Wesley. ISBN 978-0-321-84106-3.
== References ==
== External links == NASA Astrobiology Astrobiology Magazine- Comparative Planetology Laboratory for Comparative Planetology, Vernadsky Institute