On July 20,1969,Neil Armstrong became the first person to walk on the moon. The spacesuit Armstrong wore on his mission has come to symbolize courage and human achievement. In 1971, the Smithsonian's National Air and Space Museum (NASM) acquired Armstrong's suit. It stood proudly on display for visitors to admire, until there were changes in the suit's appearance."Over time，the suit started to show signs of deterioration （变坏），”Lisa Young says. She works at NASM and her job is to preserve historical and cultural treasures. Plastics are tricky to preserve. They tend to degrade （降解） over time. Neoprene is one type of plastic in Armstrong's suit. The material can turn brittle and break into tiny pieces. (77) This would ruin the spacesuit. NASM, seeking ways to preserve this historical treasure, removed it from display in 2006. Yet history can still be saved. Sunlight, water, humidity, and dust can cause plastics to degrade. Scientists have found that storing plastics in cooler temperatures, with lower humidity levels,can slow degradation.Young says Armstrong's suit is currently in storage at a temperature of 63°F and a lower relative humidity of 30%6.These conditions will be maintained when Armstrong's suit returns to a museum display casein time for this year's 50th anniversary（周年纪念日）of the moon landing. Plastic degradation affects art,too.Artist Claes Oldenburg created False Food Selection in 1966.(78)It consists of plastic food displayed in a wooden box. The plastic food used to look real. Now, some of it has flattened and yellowed. The artwork's wooden box produces an acidic gas that eats away at the plastic,which speeds up the degradation process.But Young is motivated to preserve this artwork and others like it."Plastics are a part of our history,"she says. “It’s important to preserve them so that future generations can understand the journey we've taken.”