Ordeal by Eshaar (1981)

An Adventure for Traveller.

From the back of the book:

As the Fifth Frontier War locks the Spinward Marches in mortal combat, a band of adventurers journeys outside the Imperium on a mission of vital importance. Their destination: ESHAAR, a dangerous and hostile world where temperatures average 150°C... where sulfuric acid takes the place of water . . . where enigmatic aliens hold the key to success or failure for the Imperium, The mission: discover - and secure control of - affas, a mineral compound that could turn the tide in the Fifth Frontier War. The opposition: the devious Zhodani, who will stop at nothing to ruin the Imperial cause.

Ordeal by Eshaar is a unique adventure that pits the travellers against a combination of hostile Zhodani, mysterious aliens... and the dangers of the planet itself. From subtle confrontations amidst the false gaiety of the diplomatic enclave to the struggle for survival on the world's surface, this is...Ordeal by Eshaar.

From the title and copyrights pages:

An Adventure for TRAVELLER by
J. Andrew Keith
William H. Keith, Jr.

Based on a concept by
Jordan Weisman
Marc Miller

Playtesters:
Tom Kokklenberg
Larry Gniadek
Jerry Betz
Jim Just
Mike Messenger
Wayne Budwick

Spiritual Advisor:
Marc Miller

Domes drawn by Ross Babcock