Space debris as human pollution By Julie Peller Ph.D.

Green Junction

Human pollution is far-reaching. Space debris is defined as any piece of machinery or debris left by humans in space (100 km + above the Earth’s surface). Satellites or space debris at high altitudes (~36,000 km) are expected to circle Earth for hundreds or even thousands of years. If satellites collide (a rare incident), vast amounts of debris can form. Hundreds of space maneuvers are performed every year to avoid these collisions. According to NASA, there are at least 26,000 pieces of space junk orbiting the Earth, the size of a softball or larger, that could potentially destroy a satellite on impact. Over 500,000 pieces are the size of a marble, and more than 100 million pieces are the size of a grain of salt in space.

An uninhabited area in the South Pacific Ocean, known as Point Nemo, approximately 3,000 miles from the eastern coast of New Zealand, is referred to as the “spacecraft cemetery.” (It was named after Captain Nemo of the submarine Nautilus from the 1870 Jules Verne story “Twenty Thousand Leagues Under the Sea.”) When the International Space Station is retired in 2031, it will join the other decommissioned space stations, satellites, and space debris here on Earth. This large, remote ocean area is considered the safest place for long-term fallout of debris after re-entry into Earth’s atmosphere. Interestingly, while humans do not occupy this remote area of the Earth, the seafloor is littered with space garbage. Not surprisingly, microplastics were found here in 2018.

While space debris from old satellites re-enters the Earth’s atmosphere daily, most of it burns up long before it hits the Earth’s surface. Larger space debris from spacecraft and rocket parts poses a very small risk to humans and infrastructure on the ground. Scientists must plan well in advance to ensure that the debris lands in the spacecraft cemetery. The bigger problem, according to Holger Krag, Head of the Space Safety Programme Office at the European Space Agency (ESA), “is chunks of metal rocket stages and spacecraft making what’s known as an ‘uncontrolled reentry’ into the Earth’s atmosphere.” As part of ongoing safety efforts, the ESA is working to make equipment “with materials that would melt during reentry.”

Julie Peller, Ph.D., is an environmental chemist (Professor of Chemistry at Valparaiso University). She has been writing a weekly column called The Green Junction for the past seven years and is helping to move the call of Laudato Si to action forward. Her Research Interests are advanced oxidation for aqueous solutions, water quality analyses, emerging contaminants, air quality analyses, Lake Michigan shoreline challenges (Cladophora, water, and sediment contaminants), and student and citizen participation in environmental work.