Pluto's lower atmosphere and pressure evolution from ground-based stellar occultations, 1988-2016

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere

Semmelweis' discovery and its Finnish follow-up

Professor Ignác Semmelweis (1818-1865) is one of the great personalities of medical history. He insisted on washing hands with chlorine water before any obstetrical intervention, he was the first to demonstrate its importance in preventing puerperal fever. Thus, the principle of asepsis was introduced prior to the discovery of bacteria and bacterial diseases. Semmelweis carefully documented his findings and in this way pioneered the scientific analysis of clinical data. Medical community of that time misinterpreted Semmelweis' great ideas, he died abandoned and forgotten. A Finnish doctor Josef Adam Joachim Pippingsköld was one of the first obstetricians who had realized the importance of Semmelweis' work. In 1861, in his letter to Semmelweis he reported about his own findings and favorable results in prevention of puerperal fever in Helsinki. Two decades earlier, Dr. Ehrström in the University of Helsinki had submitted his thesis on pathophysiology of puerperal fever that was similar to the ideas of Semmelweis. Long before modern times in Finland, mothers traditionally had their babies delivered in smoke saunas, where heating and smoke of bactericidal phenols created a clean, rather aseptic environment. Hand washing was self-evident necessity. However, the situation was quite different in the Central European universities and departments of obstetrics, where the medical training and clinical practice took place side by side. Semmelweis' life and his contribution to medicine was appreciated even in the theatrical circles of Finland. The piece “Semmelweis” of Norwegian playwright Jens Bjørneboe got its World Premier in the Swedish Theatre in Turku, former capital of Finland, in September 1969