According to the homeland security secretary Janet Napolitano, the only branch of government that is able to initiate a reform bill is the Congress. She was asked about this during a press conference in 2010 in the context of moving forward on comprehensive immigration reform.
There could have been a water source there a long time ago. The temperatures get higher as the years progress.
The answer is: just noticeable difference
In psychology, just noticeable difference refers to a sudden change that can make people's sense to perceive a certain thing differently.
In the case above, the soldier aware that if he move, he would create a movement that cannot be done by a simple snow. He's concerned that the enemy that see it would automatically notice it with their vision and directly aware of the camouflage.
