The absence of CO from the dust peak around Eri

We have searched for the J = 2–1 emission of carbon monoxide (CO) from the brightest peak in the epsilon Eridani ( Eri) dust disc – without success. The non-detection sets 3σ upper limits to the mass of CO gas in the dust peak of 3.3 × 1016 kg and to the total amount of (H2) gas in the disc of 8 × 1019 kg. The paucity of gas in the disc (there is ∼1000× more dust) constrains the composition of orbiting comets or icy planetesimals. If these comprise the pre-eminent reservoir of dust and gas in both the Edgeworth–Kuiper Belt (EKB) and the Eri disc then it seems unlikely that the Eri planetesimals can be as rich in volatiles as their EKB counterparts.