What key idea does the text below suggest? it’s physical condition is still largely a mystery but we know now that even in its equatorial region the midday temperature barely approaches that of our coldest winter

The key idea in the text is that despite not knowing everything about it, the one thing they do know is that [they] live in a cooling place.

Breaking it down:

- It’s physical condition is still largely a mystery (meaning there are still gaps in their knowledge, hence they don't know everything about it)  but we know now that even in its equatorial region (where they live) the midday temperature barely approaches that of our coldest winter (their midday temperature is not nearly as cold as ours but its still cold/chilly).