This is the fourth question in a series estimating input parameters for Drake's equation, inspired by a recent paper, on the Fermi paradox.

The first question in the series, with more explanation, is here

The model in question uses probability distributions over the following parameters:

- log-uniform from 1 to 100.
- log-uniform from 0.1 to 1.
- log-uniform from 0.1 to 1.
- log-normal rate, (giving mean 0.5 and median - 0.63).
- log-uniform from 0.001 to 1.
- log-uniform from 0.01 to 1.
- log-uniform from 100 to 10,000,000,000.

In this case we will be addressing the fourth parameter in the Drake's Equation, . It is the fraction of suitable planets (see some discussion at the relevant question) on which life actually appears. Predictors should use the sliders to best approximate their estimate and uncertainties in this parameter.

Most estimates assume abiogenesis to be the mechanism by which life appears on a suitable planet, but panspermia and other means merit considering. Again the possibility of alternative biochemistries should be weighed in your answer.

The lower bound because there is no clear source of a lower limit on this number.

The resolution to this question will be the scientific consensus 100 years from now, regardless of any remaining uncertainty.