According to current understanding, key requirement/s for life is/are: 

What do we conclude if a planet has few impact craters of any size? 

Which of the below are properties that life does not possess? 

Fossil evidence suggests that life on Earth arose 

Why are hydrothermal vents considered a possible location for the origin of early life? 

To determine a planet’s average density, we can use 

How far is the Virgo cluster from our Galaxy? 

What is the reason for the fact that we look back in time when observing distant objects? 

What

is the typical percentage (by mass) of elements other than hydrogen and

helium in stars that are forming right now in the vicinity of the Sun?

Why do disk stars bob up and down as they orbit the galaxy?