Could life on Earth have come from Mars?

Post of the Month: September 2013

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Subject:    | Nyikos may be right about panspermia
Date:       | 08 Sep 2013
Message-ID: | 9244dc57-01b5-4ad2-9083-653e11753a17@googlegroups.com

Lets assume that the nonsentient weak panspermia (NWP) hypothesis is correct. Life arose on some other world. A meteor blasted some nonsentient organism into space, the resulting meteor orbited around the sun for an indeterminate amount of time, the meteor landed on earth, organisms in the meteor found something to eat, and their descendents evolved into us.

Nonsentient here means no space ships or intelligent aliens. Weak means that the organism really did evolve on Mars. Hoyle believed in panspermia. However, he also believed in a Steady State universe. Hence, he didn't have to concern himself with the ultimate origin of life. Life always was and always will be, according to Hoyle. Since most scientists agree with some version of the Big Bang Theory, Hoyles' version of the Steady State Theory is out. A biogenesis occurred the first time on some planet.

Let us assume that the first living thing formed on Mars. I don't believe that myself. However, this hypothesis doesn't ring my Insanity Detector.

Let us discuss two forms of radiation: solar UV and interstellar cosmic rays.

Some multicellular organisms are able to survive in direct UV exposure. However, multicellular organisms probably couldn't survive the shock and heat of being blasted out into space. Furthermore, multicellular organisms eventually age. There is no dormant phase of any extant multicellular organism that could survive more than a few thousand years. A red wood tree could resist UV and live a thousand years, but it probably would be destroyed by the shock of being propelled into space.

Hypothetically, the organism propelled into outer space was unicellular. Some unicellular organisms have a dormant phase that can survive in a dry environment for very long time periods. These include bacterial endospores, bacterial halophiles, and dinoflagellate cysts. Vacuum is very dry. However, I agree that organisms similar to these may be able to live millions of years in a vacuum. Therefore;

Let us assume that the organism in the meteor had a dormant phase somewhat like either a bacterial endospore, a dormant halophile, or a dinoflagellate cyst. Let us not make any hypothesis about the active phase of the microorganism. For instance, no autotrophic bacterium forms an endospore. However, I find it plausible that an extinct form of bacterium may have formed endospores and used photosynthesis. If you don't like that, recall that dinoflagellates have some stages in their life cycle where they practice photosynthesis. The meteor may have contained something analogous to a dinoflagellate cyst.

So the life span of organisms does not invalidate NWP. Time by itself does not invalidate NWP. Vacuum by itself does not invalidate NWP. Yes, there are organisms that could "hold their breath" for 100 million years. However, they would be dormant. An organism could not remain both bone dry and active. Hence, they couldn't multiply while in the meteor. Any spore killed by a cosmic ray would not be replaced while the meteor was in orbit.

The organisms still has to survive radiation over a very long time span. The trip would most probably last millions of years. These organisms would have to be in the shade to survive UV radiation even a few minutes. So one has to figure out how the hypothetical spores get shielded from UV. Cosmic rays would kill the spores more slowly because cosmic rays have a lower flux.

UV rays are highly absorbed or reflected by almost all solid materials. So it is easy to imagine some form of UV shield forming "accidentally". Never the less, UV radiation is even more lethal to a unicellular organism than cosmic rays. Therefore, the nature of this shielding has to be addressed even before cosmic rays.

There is no natural shielding that would protect the spore from cosmic rays. Organisms are protected on earth from cosmic rays by the atmosphere. However, our atmosphere is very thick. The spore would have to be so deep in the meteor that the meteor material provides the same level of protection. If the meteor were solid rock, then no organism would be able to get that deep into the rock. If the meteor were porous, then the shielding would probably not remain intact during during ejection from Mars.

The only thing that I can think of is that maybe the trip did not take millions of years. Maybe by "accident" the meteor was launched on a direct route that took months. I don't think this is probable. However, I haven't done any calculations. Maybe the probability of such an event over the time span of a billion years is large. Maybe the frequency of asteroid hits on Mars was much larger 4 billion years ago than the frequency of asteroid hits today.

Just for the record, I think NWP is implausible. However, I haven't rejected on a priori grounds. A little data or calculation could spin me either way. Vague references to improbability and complexity won't convince me either way.