We estimate heterotrophic respiration (R_h) – the respiration from microbes in the soil – using satellite estimates of the net carbon flux and other quantities. R_h is an important carbon flux but is rarely studied by itself. Our method is the first to estimate how R_h varies in both space and time. The resulting new estimate of R_h is compared to the best currently available alternative, which is based on interpolating field measurements globally. The two estimates disagree and are both uncertain.