Question: Is biology as universal as chemistry and physics?

Susan Cartwright answered on 23 Jun 2015:

We don’t really know, as we have not had chance to study extraterrestrial biology.

Some things probably are universal, such as evolution by natural selection: it’s hard to think of any case in which that would not work. Carbon-based molecules are also probably universal: there is no other element nearly so good at forming long, complex molecules as carbon.

Water may be universal. It has a number of special properties: it is an excellent solvent, is very good at storing heat, and – very unusually – gets less dense when it freezes (i.e. ice floats). This is very important, because it means that water oceans are unlikely ever to freeze solid: the floating ice insulates the water beneath.

Are DNA and proteins universal? They are very good at their respective jobs, but it is not clear whether something else could substitute. The same goes for other biochemical reactions.

So, there is no guarantee that biology is as universal as chemistry and physics. It would be very very interesting to find out. I do hope that there are living organisms underground on Mars!