Darwin proposed his theory of evolution on the premise of natural selection. According to him, organisms which possess favourable characteristics which enable them to survive in their environment are more likely to survive and reproduce, passing on these favourable characteristics to their offsprings.
According to Mendel, the unit of inheritance passed on from parents to offspring are genes. Hence Darwin's factors are Mendel's genes.
If Darwin knew of Mendel's work. It might have influenced his presentation of the idea of passing on favourable characteristics from parents to offspring in the light of genetics.
This would have made Darwin's work to have more empirical backing hence making it more widely accepted.
Asteroids vary greatly in size and are mostly made up of frozen water and gas. This one is true.
They are said to be "mostly formed of ice and gas" as they rarely can be found consisting of stone, nickel and iron. These are extremely dangerous in our Universe.
