On February 11, just four days short of her 101st birthday, Mildred Shapley Matthews passed away peacefully at her home in California with her family present. Mildred was the daughter of Harvard College Observatory Director Harlow Shapley and she held the interesting distinction of being “lost in the solar system” for 75 years. As a commemoration of his newborn daughter, Shapley bestowed the name Mildred to asteroid 878 discovered in 1916. Unfortunately the initial observations of the asteroid were limited, and the object was “lost” with highly uncertain orbital elements until recovered in 1991. Friends and colleagues seeing Mildred over the years would always ask, “are you found yet?” Matthews’ foundational contributions to planetary science began around the time of her nominal retirement age, when in the 1970s she began working as the production editor in the inaugural years of the Space Science Series created by Tom Gehrels. Her role became most prominently recognized as co-editor on more than a dozen volumes extending in to the 1990s. Overall for more than 20 Space Science Series volumes she edited, operating through friendly (then increasingly stern, but always polite) post cards and phone calls to delinquent authors, it was Matthews who brought the books into their final published form. Matthews leaves behind a legacy of books that have served as the gateway for countless planetary science careers and insights toward future advancements in our field. In 1993, Matthews received the DPS' Harold Masursky Award for Meritorious Service to Planetary Science.