Etymology From yester- + sol (“Martian day”), by analogy with yesterday.
1
On the sol (Martian day) before the present one.
But yestersol he took Mother into the old middle-pressure greenhouse (the little one they built when they first arrived here) and got her involved in a long discussion.2001, Mary Turzillo, “Mars is No Place for Children”, in Robert Silverberg, editor, Nebula Awards Showcase 2001: The Year's Best SF and Fantasy Chosen by the Science Fiction and Fantasy Writers of America, Houghton Mifflin Harcourt, →ISBN, page 61:
yestersol
noun
Etymology From yester- + sol (“Martian day”), by analogy with yesterday.
1
The sol (Martian day) before the present one.
"We'll basically be waking up in the Mars morning, which will be 47 minutes later each day, and uploading our commands from 'yestersol,'" he said.2003 December 19, Sue Vorenberg, “Mars Central”, in Albuquerque Tribune: