Mars Opposition Overview
An astronomical opposition occurs when an outer planet like Mars lies on a straight line drawn from the sun through the Earth to the planet. At this moment, the outer planet is the closest to Earth that it can get ignoring issues of orbital eccentricity. Mars will reach opposition this year on August 27.
Mars is a difficult planetary target for amateur astronomers due to its relatively small size. Since it typically presents a much smaller apparent size than either Jupiter or Saturn, it is a challenge to see much detail on its surface. In addition, huge sandstorms sometimes further obstruct our view of the surface. At this extremely rare close opposition, Mars will grow to an apparent angular size of about 25 arcseconds, which is similar to Jupiter.
Compounding the difficulty for observers at our latitude in the northern hemisphere is the fact that at opposition Mars will still be far to the south, and will not appear high in the sky. To observe Mars, we will be looking through extra atmosphere which can degrade our resolution. At best, we will have to look through twice the air mass as we would if looking straight up. Atmospheric turbulence which is common here in the Colorado front range can limit our ability to see surface detail on planets.