![]() On Earth, the instructions for building and operating an organism is encoded in genes, carried on a molecule like DNA, whose information is copied and inherited from one generation to the next. The 'capable' in NASA's definition is key because it means astrobiologists don't need to watch and wait for extraterrestrial life to evolve, just study its chemistry. In the early 1990s, an advisory panel to NASA's astrobiology program, which included biochemist Gerald Joyce, came up with a working definition: Life is a self-sustaining chemical system capable of Darwinian evolution. Adaptability is shared by all life on Earth, which explains why NASA used it as the basis for a definition that might work in helping to identify life on other planets. An alternative approach is to use the theory considered to be a defining feature of life: Charles Darwin's theory of evolution by natural selection, the process that gives life the ability to adapt to its environment. Are entities such as viruses really life-forms, or merely life-like? Using a list definition, that largely depends on the criteria you choose to include, which is mostly arbitrary.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |