Mars lander Perseverance reaches Mars

[pbrower2a]

NASA announces (and demonstrates) the successful landing of Perseverance upon Mars.

[Captain Genet]

If Perseverance doesn't find any signs of life, will NASA decide the search is over? At what point can science establish as a fact that life never existed on Mars?

I would love if we found out that the Earth is the only planet in the Cosmos to harbour life. It would make us cherish the life that we have like never before. It would also be a strong argument for the existence of God.

[David Horn]

(02-27-2021, 05:53 AM)Captain Genet Wrote: If Perseverance doesn't find any signs of life, will NASA decide the search is over? At what point can science establish as a fact that life never existed on Mars?

I would love if we found out that the Earth is the only planet in the Cosmos to harbour life. It would make us cherish the life that we have like never before. It would also be a strong argument for the existence of God.

On your first point: proving a negative is impossible, so that will never happen. On your second point: the likelihood of earth being a unique bio-environment is incredibly small.

[pbrower2a]

(02-27-2021, 08:02 AM)David Horn Wrote:

(02-27-2021, 05:53 AM)Captain Genet Wrote: If Perseverance doesn't find any signs of life, will NASA decide the search is over? At what point can science establish as a fact that life never existed on Mars?

I would love if we found out that the Earth is the only planet in the Cosmos to harbour life. It would make us cherish the life that we have like never before. It would also be a strong argument for the existence of God.

On your first point: proving a negative is impossible, so that will never happen. On your second point: the likelihood of earth being a unique bio-environment is incredibly small.

Life on Mars is likely to be micro-organisms living in favored environments. The big hazard to life of any kind on Mars is the lack of shielding against radiation. There could be underground locations analogous to the "black smokers" at undersea volcanoes that release gases suitable for a rich biota. Those "black smokers" are rich ecosystems that few suspected to exist before their discovery. The deep sea was long considered a biological desert.

Maybe life is possible on Mars, relics of a time when Mars is assumed to have had liquid water under adequate pressure. Mars has a thin atmosphere due to its inadequate gravitation. Venus has enough gravitation to hold its two main gases nitrogen and carbon dioxide, but it is marginal for methane, ammonia, and water vapor. Mars is chilly enough to hold carbon dioxide but has too little gravitation to have a firm grip on methane, ammonia, and water vapor. Basically almost all life on Earth is derivatives of methane, ammonia, and water even if the Earth's atmosphere holds practically no methane or ammonia because those gases are not in equilibrium with oxygen that plant life release. Biochemistry suggests that terrestrial life formed when the Earth's atmosphere was still rich in ammonia and methane... and living things have a chemistry that allows the creation of derivatives of methane and ammonia (and either carbon monoxide or carbon dioxide). 

Under the current conditions, if Earth were to be sterilized of all life, then life would not form anew. Plants have a way of sequestering carbon dioxide and water, and without that the Earth would quickly become a wet greenhouse much as Venus became. Some calculations of the habitable zone for life put Earth outside the habitable zone on the hot side... and that it is plant life that keeps Earth alive by sequestering the two most important greenhouse gases (carbon dioxide within the atmosphere and water vapor before it can evaporate). Mars may surprisingly be closer to the center of the habitable zone than Earth; it simply lacks the atmosphere.