Quote Originally Posted by Colin Robinson View Post
Bacteria and other microbes can certainly have a healthy eco-system without "the known healthy influence of higher trophic levels". Right here on Earth, for about 3 billion years the eco-system consisted of microbes only. The Cambrian explosion, which gave rise to those "higher trophic levels" was a mere half billion years ago — a very recent experiment, whose long-term viability remains uncertain.
So Mars is about the same age as Earth. If life in the form of bacteria developed on Mars in the past, then why would it just stop at bacterial levels?

Whilst the causes of the Earth's so-called 'Cambrian Explosion' have never been shown to be clear-cut, theories covering the emergence of species complexity turn out to be an inseparable mixture of ecological, environmental, developmental (evolutionary genetics) and complexity thresholding. I would have thought Mars would not be excluded from any of these so-called 'universal' phenomena? If not, then why would we prefer searches for bacteria? After all, I thought 'once life gets started', its evolution is inevitable as far as Astrobiology is concerned?

This' bacteria boundary' seems to be more like a mental block than any logical consequence of any current evidenced-based theories.

Why is Mars being treated as a pariah planet by our faithful and intrepid exo-life hunters?