Vol. 618
In section 1. Letters to the Editor

Radial and vertical dust transport inhibit refractory carbon depletion in protoplanetary disks

by L. Klarmann, C. W. Ormel, and C. Dominik A&A 618, L1


How to explain the lack of carbon in the inner solar system? Carbon is abundant in the Sun and in the interstellar medium but it is depleted by a factor of 100 (compared to e.g., Si) in carbonaceous chondrites and by a factor of 10,000 in the Earth. More than half of the carbon in the interstellar medium is in the form of refractory material that would not vaporize in normal conditions at the Earth's distance from the Sun. It had been proposed that carbon could be extracted by UV radiation on small grains in the atmosphere of protoplanetary disks. Klarmann, Ormel, and Dominik show that in fact, when including radial migration of grains, this mechanism cannot explain the observed depletion. This seems to imply the existence of widespread (in time and location) high temperature (over 1000K) regions in the inner solar system combined with the quick formation of a giant planet core to form a barrier to incoming carbon-rich grains.