A new listing of the 50 most concerning pieces of space debris in low-Earth orbit is dominated by relics more than a quarter-century old, primarily dead rockets left to hurtle through space at the end of their missions. //

Russia and the Soviet Union lead the pack with 34 objects listed in McKnight's Top 50, followed by China with 10, the United States with three, Europe with two, and Japan with one. Russia's SL-16 and SL-8 rockets are the worst offenders, combining to take 30 of the Top 50 slots. //

The list published Friday is an update to a paper authored by McKnight in 2020. This year's list goes a step further by analyzing the overall effect on debris risk if some or all of the worst offenders were removed. If someone sent missions to retrieve all 50 of the objects, the overall debris-generating potential in low-Earth orbit would be reduced by 50 percent, according to McKnight. If just the Top 10 were removed, the risk would be cut by 30 percent. //

China, on the other hand, frequently abandons upper stages in orbit. China launched 21 of the 26 hazardous new rocket bodies over the last 21 months, each averaging more than 4 metric tons (8,800 pounds). Two more came from US launchers, one from Russia, one from India, and one from Iran. //

Since 2000, China has accumulated more dead rocket mass in long-lived orbits than the rest of the world combined, according to McKnight. "But now we're at a point where it's actually kind of accelerating in the last two years as these constellations are getting deployed."