The mass of the meteorite will increase by the gamma factor , 1/root(1-v^2/c^2) , here v is the velocity of the object , in this case here it is meteorite and c is the velocity of light , use your calculator so find out the magnitude of gamma factor , here i found it as 1.4(approx) so the mass of the meteorite will there be in respect of your frame of reference , 1.4*1500=2100 kg and now you can apply the einstein's most famous equation of relating mass and energy , E=m*c^2 to find out the energy of the meteorite which is 2100*c^2 =1.89*10^20 joules when it is moving at the velocity of 0.700c and the rest energy when the meteorite is not moving , 1500*c^2= 1.35*10^20 ... hmm!! looks like you are gonna having 100000 of atomic bombs .