On reading about the interesting research on droplets in this article, I noticed that the two droplets shown in the photos at the moment of first contact have different shapes. In air at normal pressure, the droplet has the characteristic hamburger-bun shape. In contrast, the droplet at reduced pressure is spherical, or nearly so. Can this difference be responsible for all or most of the difference in the splatter patterns?

Daniel Lipp
Fort Collins, Colo

The nonsplash in thin air occurs even in tests in which only “hamburger-bun” droplets hit the surface, says Sidney R. Nagel of the University of Chicago .—P. Weiss