Which characteristic makes certain components more likely to survive atmospheric re-entry?

High mass-to-surface-area ratios

The likelihood of a piece of space debris surviving the intense thermal stress of re-entry and reaching the Earth's surface depends critically on its physical properties relative to the heat generated by hypersonic atmospheric friction. Objects with a high mass-to-surface-area ratio are substantially more likely to survive intact. This means that thick, dense components—such as heavy titanium fuel tanks or robust sections of steel structure—retain their structural integrity against the rapid thermal ablation better than objects made of lighter materials like aluminum, which are designed to vaporize easily. Conversely, objects decaying from very high orbits, like GEO, often take decades to decay fully, giving time for maneuver or gradual orbital decay.