what is the brightness of mars as seen form Earth?

Answer 1

Mars varies more in brightness than any of the other planets. It's about magnitude -0.8 right now, and will reach -1.6 at opposition in December. On the other side of its orbit, Mars gets down to about +2, while at its close approach (perihelic opposition) in 2003 it reached -2.9, brighter than Jupiter.

Answer 2

Mars at maximum brightness shines at apparent magnitude -2.9.
This is just a little bit brighter than Jupiter at its maximum brightness (-2.8). The only objects brighter than Mars are Venus (-4.7), the moon (-12.6) and the sun (-26.73).