In an alternate timeline, Garrett Tarses was a human male in the 23rd century native to Mars. His grandfather had been a member of the Human Loyalists, who opposed the Declarationists who wanted to make Mars independent of United Earth.
Tarses was an agent of Starfleet Intelligence from 2234 to 2253. During that period, he spent ten years at a covert listening post gathering and translating Vulcan communications. After 2253, he joined the United Earth Foreign Office, where he established himself as one of Earth's foremost experts on the Interstellar Coalition. In 2264, he took part in the mission to Babel where United Earth petitioned for membership into the Interstellar Coalition. (Star Trek: Myriad Universes novel: A Less Perfect Union)
- This character may have been intended to be an ancestor of Simon Tarses, given his Martian heritage, and the similarity of his name to the actor who portrayed Simon, Spencer Garrett. Even so, no "prime timeline" counterpart for this character has been established.