Statement 1: If the mass of a boy on earth is 50 kg, suddenly if he is taken to mars then mass of the boy would decrease by some factor.
Statement 2: Mass is the measure of quantity of matter contained in an object.
Mass is the quantity of matter contained in any object and is constant everywhere. So, mass of the boy would still be 50 kg when taken to mars. Only weight can change as it depends upon the value of acceleration due to gravity of a planet.