HI there 
the most reasonable answer is 
saturation of surface materials with water 
hope this has helped you
 
        
                    
             
        
        
        
Answer:
so you can tell its daytime on earth from space if from space, earth looks "normal" basically normal just means no shine or darkness or anything it just looks the same if you were to look at a picture of earth on google. When its nighttime, it appears as dark, makes sense...? 
Explanation:
I mean i've never been to space before soooo... the sun and/or the moon may be to big to even see to be honest..