Its because in space there is no air to breathe and more over no pressure. When we live on earth we can feel atmospheric pressure which is nornmal to us . Just think what will happen if the pressure is gone our body will not react that it should have react.
So, they wear a special suits.
le chatlier's principle (also known as "chatelier's principle" or "the equilibrium law") states that when a system experiences a disturbance (such as concentration, temperature, or pressure changes), it will respond to restore a new equilibrium state.
le chatelier's principle is an observation about chemical equilibria of reactions. it states that changes in the temperature, pressure, volume, or concentration of a system will result in predictable and opposing changes in the system in order to a new equilibrium state.
le chatelier’s principle can be used to predict the behavior of a system due to changes in pressure, temperature, or concentration.
le chatelier’s principle implies that the addition of heat to a reaction will favor the endothermic direction of a reaction as reduces the amount of heat produced in the system.
increasing the concentration of reactants will drive the reaction to the right, increasing the concentration of products will drive the reaction to the left.