Caption: 
A Southwest Research Institute-led study used NASA’s James Webb Space Telescope to examine ice grains in the coma of interstellar comet 3I/ATLAS, only the third interstellar object ever identified. In some previously studied comets, ice grains have been interpreted as relatively pure ice, with dust in separate grains (left). Webb’s spectra of 3I/ATLAS are best explained by tiny aggregates of water ice mixed with dust (right). Both types of grains are about a micron or smaller. The comet’s spectra resemble those of some icy worlds beyond Neptune. The results suggest that icy building blocks here and around other stars may share a common range of grain properties.