Posted: Jul 09, 2018 4:59 am
jamest wrote:felltoearth wrote:Why? Please explain your position. Cali just explained the mechanisms and why we are testing the possibility.
You're merely asking me to repeat myself then. Any physical life and attributes thereof that has evolved here is the culmination of Earth's dynamism and generally warm climate over a very long period of time. Why then should we be expecting life forms similar to those we might find here on another planet/moon that is nothing like the Earth?
Is the proposal that conditions don't need to be very dynamic or favourable for life? If so, then why haven't we found fuck all on Mars yet which we've been studying for decades? (Mars being much more favourable and dynamic than anywhere else we know)
Your question suffers from an imprecise (or rather, completely open) definition of 'similar'. To respond to your question about why we haven't found anything on Mars, yet, think about why we haven't found the wreck of MH370 on Earth, yet. The South Indian ocean is more accessible than Mars, when you really think about it.
Think about what the panspermia hypothesis implies as to how common microbes are in debris that must have traveled across interstellar distances. Think about how the surface of the earth was completely molten at several points in earth's early history, with temperatures that decompose organic material to simple inorganic molecules and methane. That fact alone suggests that panspermia must have occurred subsequently to the main process of planetary accretion, implying a lot of intricate timing. If panspermia is an interesting hypothesis, it is interesting only as a philosophical speculation that can be treated as marginally testable.
Abiogenesis is not a less-difficult hypothesis to test, but at least it doesn't depend on the long odds of finding microbes on other bodies in the solar system as well as on the longer odds alluded to above. Even if we don't eventually find microbes on Enceladus, we will find other interesting things to think about. Panspermia flatters the sensibilities of those who wish life to be common in the universe. The latter puts a crimp in religious notions of special creation, an idea that is more outlandish than panspermia only because it suffers fatally from not being testable. The best one can say about panspermia is that if it happens, it must be possible. Thereafter, it does nothing to assist anyone investigating abiogenesis.
Even if microbes, when found elsewhere in the solar system, turn out to have different biochemistry than terrestrial biota, it would not rule out multiple abiogenesis events in the cosmos. It would just lengthen the odds for believers in panspermia and give interesting insights into how different one can be.