The relativistic factor is:
1
gamma = ------------- = 70.7
2 1/2
( 1 - (v/c) )
and the total energy is then
2
E = gamma x m c
A marshmallow weighs about 10 grams, so the total energy is about
70.7 x 10 x ( 30,000,000,000)^2 = 6.4 x 10^23 ergs. I think this is equal
in energy to a few dozen good-sized hydrogen bombs. It makes a mess
on the surface, but has no effect on the orbit of the earth.
Please, do not attempt this experiment yourself. Consult professionals first!!