Ground-based spectroscopy of Jupiter's moon Europa, combined with gravity data, suggests that the satellite has an icy crust roughly 150 km thick and a rocky interior. In addition, images obtained by the Voyager spacecraft revealed that Europa's surface is crossed by numerous intersecting ridges and dark bands (called lineae) and is sparsely cratered, indicating that the terrain is probably significantly younger than that of Ganymede and Callisto. It has been suggested that Europa's thin outer ice shell might be separated from the moon's silicate interior by a liquid water layer, delayed or prevented from freezing by tidal heating; in this model, the lineae could be explained by repetitive tidal deformation of the outer ice shell. However, observational confirmation of a subsurface ocean was largely frustrated by the low resolution (>2 km per pixel) of the Voyager images. Here we present high-resolution (54 m per pixel) Galileo spacecraft images of Europa, in which we find evidence for mobile 'icebergs'. The detailed morphology of the terrain strongly supports the presence of liquid water at shallow depths below the surface, either today or at some time in the past. Moreover, lower-resolution observations of much larger regions suggest that the phenomena reported here are widespread.

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OBJECTIVES Early thrombosis (ET) contributes to autogenous arteriovenous fistula (AVF) failure. We studied patients undergoing AVF placement in the Hemodialysis Fistula Maturation (HFM) Study, a prospective, observational cohort study, using a nested case-control analysis to identify pre-operative and intra-operative predictors of ET. METHODS ET cases were compared to controls who were matched on gender, age, diabetes, dialysis status, and surgeon fistula volume. ET was defined as thrombosis diagnosed by physical exam or ultrasound within 18 days of AVF creation. Conditional logistic regression models were fit to identify risk factors for ET. RESULTS Thirty-two ET cases (5.3%) occurred among 602 study participants; 198 controls were matched. ET was associated with female gender (OR=2.75, CI 1.19–6.38, P=0.018), fistula location (forearm vs. upper arm) (OR=2.76, CI 1.05–7.23, P=0.039), feeding artery (radial vs. brachial) (OR=2.64, CI 1.03–6.77, P=0.043) and arterial diameter (OR=1.52, CI 1.02–2.26, P=0.039, per mm smaller). Draining vein diameter was nonlinearly associated with ET, with highest risk in 2–3 mm veins. Surprisingly, ET risk was lower in diabetics (OR=0.19, CI 0.07–0.47, P=0.0004), lower with less nitroglycerin-mediated brachial artery dilatation (NMD%) (OR=0.42, CI 0.20–1.92, P=0.029 for each 10% lower) and higher with lower carotid-femoral pulse wave velocity (OR=1.49, CI 1.02–2.20, P=0.041, for each m/sec lower). Intraoperative protamine use was associated with a higher ET risk (OR 3.26, CI 1.28-∞, P=0.038). Surgeon’s intraoperative perceptions were associated with ET: surgeons’ greater concern about maturation success (likely, marginal, unlikely) was associated with higher thrombosis risk (OR 8.09, CI 4.03-∞, p<0.0001, per category change), as were absence vs. presence of intraoperative thrill (OR 21.0, CI 5.07-∞, P=0.0002) and surgeons’ reported frustration during surgery (OR 6.85, CI 2.70-∞, P=0.0004). Reduced extent of intraoperative thrill (proximal, mid or distal third of the forearm or upper arm, based on AVF placement) was also associated with ET (OR 2.91, CI 1.31-∞, P=0.014, per diminished level). Oral antithrombotic medication use was not significantly associated with ET. CONCLUSIONS ET was found to be associated with female gender, forearm AVF, smaller arterial size, draining vein diameter of 2–3 mm, and protamine use. Paradoxically, diabetes and stiff, noncompliant feeding arteries were associated with lower frequency of ET. Absent or attenuated intraoperative thrill, and both surgeon frustration and concern about successful maturation during surgery, were strongly correlated with ET.