The five reasons Mars may have never seen life has broader implications. The "snake oil" about life on Mars, or our solar system or even in our galaxy, is getting harder and harder to sell.
Even simple life forms, like bacteria or algae, are not likely to exist elsewhere than Earth. What is minimized, if not ignored, by SETI enthusiasts are the significant features of Earth and our solar system important to life which suggest that the probability of life elsewhere in our galaxy is extremely small, if not basically zero.
Besides the size of the Earth and a habitable distance from the Sun, these features include its elemental composition, a sufficiently large amount of liquid water, the composition and thickness of Earth's atmosphere, the rate of rotation on its axis, the strength of the magnetic field, the amount of radioactive elements, the movement of the tectonic plates, the thickness of Earth's crust, the size, density, orbital distance and tidal action of Earth's moon, the nearly circular orbit of the Earth around the sun, the tilt of Earth's axis, the ratio of land-to-ocean surface area, the arrangement of continents relative to the slight eccentricity of the Earth's orbit and axis, the orbital plane of Earth and the other planets around the sun, the size and relative position of the large gaseous planets, like Jupiter and Saturn relative to that of the Earth and the inner planets, the orbital locations of asteroid and planetoid groups, the lack of large planets inside the Earth's orbit, the elemental composition of our sun, the age and size of our sun, the heliosphere of the sun, the position of our solar system with respect to the galactic arms, the relative position of our solar system from any supernovas, the location of our solar system relative to the galactic center, and the size and shape of our galaxy. No doubt more could be listed.
For each one of these features, (sometimes even small) changes one way or the other would result in conditions where maintaining life (or intelligent life) on Earth would be impossible or unlikely.
All of those are not reasons at all — they merely state that, we are on Earth and know there is life here. It’s no more valid than saying, extraterrestrial intelligence couldn’t develop unless they have exactly five fingers on exactly two hands.
>>he “snake oil” about life on Mars, or our solar system or even in our galaxy, is getting harder and harder to sell.<<
When the Mother Ship returns, I will see to it you are one of the first ones against the wall...