Readers marvel over moon mementos and more

Your comments and questions on the July 6, 2019 & July 20, 2019 issue of Science News

Bygone boot print?

No nation governs the moon’s surface, but NASA has issued guidelines for protecting artifacts still there from the Apollo missions, Maria Temming reported in “Apollo astronauts left trash, mementos and experiments on the moon” (SN: 7/6/19 & 7/20/19, p. 26). NASA outlines how far future spacecraft should land from the Apollo sites so that rocket exhaust doesn’t, for example, “wipe Neil Armstrong’s first boot print off the face of the moon,” Temming writes.

Reader Robert Struble wondered if the first boot print is even still there. “Wouldn’t that print have been obliterated when the lunar module blasted off?” he asked.

The descent stage served as a launchpad for the returning module and could have helped shield nearby footprints from the most violent gas flow, as well as keeping most of the exhaust high off the ground, says Philip Metzger, a planetary scientist at the University of Central Florida in Orlando. But since the first footsteps were at the base of the ladder, they would’ve been walked over repeatedly by the Apollo 11 astronauts. “It is likely that the very first footstep onto the moon was destroyed before they left the moon,” Metzger says.

Packaging problems

Biodegradable food packaging that contains industrial compounds called per and polyfluoroalkyl substances, or PFAS, could introduce those persistent chemicals into compost, Carolyn Wilke reported in “Chemicals in biodegradable food containers can leach into compost” (SN: 7/6/19 & 7/20/19, p. 7).

Online reader Mark S. was more concerned about PFAS leaching into food.

PFAS can move from containers to food. A 2008 study in Food Additives & Contaminants: Part A showed that the compounds entered microwave popcorn from packaging. “Temperature, if food is oily or water-based, and how long food touches the material play a role in the amount of PFAS that end up in food,” Wilke says. It’s unknown if compostable containers release enough PFAS into food to cause health concerns.