Researchers used molecular-rotor probes to map nanoscale viscosity inside marine-snow aggregates. Low-viscosity regions are easier for bacteria to penetrate; viscous regions act as barriers and slow degradation. In simulations, the viscous aggregates carried more than six times as much carbon to the deep ocean as low-viscosity ones. That does not remeasure the whole carbon budget—more than 10 gigatons leaves the surface annually and roughly 2 gigatons reaches long-term depth—but it identifies a microphysical property that climate models can represent more realistically. UC San Diego · Science