Hal Clement - Mission of Gravity

Mesklin is a very large and very dense planet. Its surface gravity varies greatly from 3g at the equator to 700g at the poles.

 
The oceans are liquid methane and  snow is frozen ammonia. Under these nightmarish conditions live mesklinitas, who have developed a culture and a society perfectly suited to the conditions of their environment. Barlemann, a bold mesklinita sailor agrees to undertake an impossible journey to save an expensive Earth probe broken on the pole of the planet. For mesklinitas the trip is a wonderful opportunity to discover science and progress in the path of knowledge, and this is the driving force that guides them through many adventures motivated by working and negociating with humans.



This is "hard" science-fiction, of the kind that pays special attention to scientific and technical details of the story. The most characteristic aspect of this book is the clarity of its approach.  Clement introduces his characters without further preamble, and in fact does not even bother to explain how humans managed to arrive to Mesklin and there's no hesitation, no doubt or speculation. The mesklinitas are remarkably intelligent, and therefore smart and cunning, basic characteristics of any self-respecting adventurer. In that sense, they can seem too human but that's part of the clarity of approach. 

Masterpiece and classic.  

Harry Clement Stubbs (May 30, 1922 – October 29, 2003) better known by the pen name Hal Clement, was an American science fiction writer and a leader of the hard science fiction subgenre. He went to Harvard, graduating with a B.S. in astronomy in 1943. His further educational background includes an M.Ed. (Boston University 1946) and M.S. in chemistry (Simmons College 1963).

During World War II Clement was a pilot and copilot of a B-24 Liberator and flew 35 combat missions over Europe with the 8th Air Force. After the war, he served in the United States Air Force Reserve, and retired with the rank of colonel. He taught chemistry and astronomy for many years at Milton Academy in Milton, Massachusetts.

He also painted astronomically oriented artworks under the name George Richard.

He created (below from wikipedia) a number of notably unusual fictional planets as settings for his works. They include:

• Abyormen – A planet circling a dwarf star (Theer), which in turn circles a blue giant. This produces a hot and a cold season, each of 65 years' duration. The native intelligent life forms undergo a seasonal mass death. From Cycle of Fire.
• Dhrawn – A high-gravity world settled by Mesklinites in Star Light.
• Habranha - A planet that is tidally locked with its sun, such that the far side is a mix of solid CO₂, solid methane, and ice, and the other side completely ocean, in Fossil.
• Hekla – An ice-age planet in Cold Front (short story, Astounding July 1946).
• Kaihapa – An uninhabited ocean planet, twin of Kainui, in Noise.
• Kainui – An inhabited ocean planet in Noise.
• Mesklin — A planet with ultra-high gravity (up to 700 g) in Mission of Gravity. Clement later corrected his model of Mesklin and determined that the maximum surface gravity would be "only 250 gravities".
• Sarr – An extremely hot planet with an atmosphere of gaseous sulphur ('air') and liquid copper sulphate ('water') in Iceworld
• Tenebra – A high-gravity world with a corrosive atmosphere in Close to Critical.
• Enigma 88 - A small planet near η Carinae in Still River. The interior of the object is honeycombed with caves, due to evaporation of accreted ice-rich planetoids. Unusually for Clement, Enigma's structure is not fully consistent with the laws of physics.