I think the astronomers were right. Venus is like Earth, and it probably did have a magnetic field. Likewise for Mars. And both could easily have developed life, and we might find evidence of that someday.Ann wrote:The way I read that Wikipedia article, astronomers believed that Venus had a magnetic field, and models showed that it ought to have a magnetic field, but observations showed that it did not have one.
Earth probably is typical in many ways of rocky planets. One thing that probably make it less typical is its stability, provided in part by the Moon, and perhaps by its complex biosystem, as well.
My expectation is that life is common on terrestrial planets in habitable zones (which I think are much wider than typically suggested). But in many cases, we may find that the period that life exists on a planet is only a few hundred million years, not the several billion as in Earth's case. Most life is probably equivalent to simple bacteria and plants, not complex animals.