June Book. Mission Of Gravity by Hal Clement

Mesklin is a vast, inhospitable, disc-shaped planet, so cold that its oceans are liquid methane and its snows are frozen ammonia. It is a world spinning dizzyingly, a world where gravity can be a crushing 700 times greater than Earth''s, a world too hostile for human explorers.

But the planet holds secrets of inestimable value, and an unmanned probe that has crashed close to one of its poles must be recovered. Only the Mesklinites, the small creatures so bizarrely adapted to their harsh environment, can help.