Absolute zero is about -459 Deg F. very difficult to reach even under extreme lab conditions, but you can get "close" to that.
Liquid nitrogen is about -320 Deg F (77 Kelvin).
They use Liquid Nitrogen for Cryo. Close enough to "zero" for Goverment work.
The surface of Pluto is about -370 to -390 Deg F, not sure about Mars.
Link to cryo treatment site:
http://www.300below.com/site/home.html
The information presented there may be some what "bias".