Earth-orbiting satellites can measure atmospheric opacity, but only for a small part of the atmosphere at any given time. A lunar eclipse, on the other hand, conveniently gives an average over all ...

Earth-orbiting satellites can measure atmospheric opacity, but only for a small part of the atmosphere at any given time. A lunar eclipse, on the other hand, conveniently gives an average over all ...

The space agency measures the atmospheric opacity, known as "tau," to determine how much dust is swirling around in the Martian sky. It's at a level of 0.8, down from 10.8 on June 10, ...