Not to mention a bit of heat, you would definitely get that by throwing Europa onto Mars!
By the way, Europa is the home of my namesake Mahnmut and among the top candidates for life in the solar system, so I would recommend using another snowball.
Concerning the pros and cons of hard and soft terraforming I can really recommend the Mars Trilogy by Kim Stanley Robinson, if you are into Mars, don´t miss these great books!
And If you aren´t, read them anyway, after reading you will be.
Oh, I really was glad that my work didn´t annoy you, no sarcasm.
Thanks,
Best regards,
Jan