The science “is very clear” that stratospheric black carbon emissions could lead to ozone depletion, said Ross, comparing the effect to a “thin black umbrella that shades the Earth’s surface and warms the stratosphere.”

While jet aircraft also use kerosene, Ross notes that soot from airplanes dissipates within a few weeks. But black carbon from rocket engines lasts years. Rockets also emit black carbon directly into the stratospheric ozone layer, whereas most jets fly lower in the stratosphere, below the ozone. Finally, Ross points out that rocket engines produce black carbon at much greater magnitude per kilogram of fuel burned than airplanes – up to a factor of 1,000.