This would never happen. The disk of the Earth subtends the same angular size as the Sun about 1.5 million kilometers from the Earth. At the distance of Mars, the angular diameter of the Earth at opposition (35 million miles) is about 48 arcseconds, while the Sun subtends 1400 arcseconds ( 35 + 93 million). Earth would not produce a full eclipse of the Sun, but would be seen as a small black spot transiting the bright disk of the Sun.