What makes the Iditarod race so challenging?and why?

Question

Why is it challenging? what makes ppl want to race in sub below zero temp?

Answer 1

Considering the race is in Alaska in the snow, ice, wind, and sub zero temperatures, should be explanation enough for the challenge it presents.

Answer 2

The terrain, the competition, and the shear excitement

Answer 3

Just 1200-miles across Alaska, where at the time of the race, wind chills can reach 100 degrees below zero, outdoors on a dogsled.