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Igor Lvovich Khodakovsky (1941 - 2012)

Igor Khodakovsky, the famous Russian geoscientist, principal senior scientist of Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, (GEOKHI RAS), Moscow, doctor of chemical sciences, professor, passed away on 29 July 2012 in a drowning accident at Raystown Lake, Pennsylvania, USA. He was 71. Igor was traveling with his youngest son Andrei and was visiting his many friends and scientific colleagues across the USA. Igor is survived by his wife, Tatiana Ivanova, his sons Gleb Khodakovsky and Andrei Khodakovsky, his daughter, Julia Rostovtseva (Khodakovskaya) and his grandchildren Nikita, Boris and Elisabeth.

Born in Moscow, Russia, on 4 April 1941, Igor earned his BS in geochemistry from Moscow State University, Geological Faculty, 1963, his PhD, 1969, and relatively soon thereafter his Doctoral Habilitation Degree, 1976, from GEOKHI RAS. In 1977 - 1988 Igor was the head of the laboratory of Thermodynamics of Natural Processes founded by him. He received his professorship in 1983.

He wrote in his memoirs that his interest to study cosmochemistry was greatly motivated by his secret hope to be the first geochemist to step on the Moon. In 1962 while still an undergraduate student, he was invited to meet with the Head of the Geochemistry Chair - Academician Alexander Vinogradov. Professor Vinogradov wished to know whether Igor would be willing to participate in a flight to the Moon as a geochemist. Igor agreed to participate and was very excited by this prospect. He promised and for a long time kept this proposition a deep secret. He did not know that the Soviet Moon Program had been changed in favor of automatic probes flights (Luna -10, -16, and -20).

Shortly after beginning his work in GEOKHI RAS, Igor demonstrated that he was a talented experimentalist and gifted theoretician in geochemistry, cosmochemistry and thermodynamics of geological systems. During the 1960's, Igor became one of the initiators and an active participant in the calorimetric measurement of mineral heat capacities in GEOKHI RAS. In those years, his developments of thermodynamics in geochemical processes became one of the mainstays of the fundamental basis for geochemistry. An investigation into correlations between partial molal entropies and partial molal heat capacities of aqueous species was the topic of his PhD. The prediction of equilibrium constants for geochemical reactions in hydrothermal systems was found to be reliable enough for wide applications. Consequently, Igor became a leader of thermodynamic investigations in national and international geoscience. He developed both theoretical and empirical correlations for calculations of the heat capacities of ionic and neutral substances as a function of temperature. Those methods were applied broadly in the well known Handbook of Thermodynamic Data by Naumov, G.B., Ryzhenko, B.N. and Khodakovsky, I.L. (in Russian - Atomizdat, 1971; in English - Springfield, 1974).

Methods of extrapolation to high temperature of heat capacities, molar volumes and enthalpies of aqueous electrolyte solutions at infinite dilution, the corresponding extrapolation of equilibrium constants and thermodynamic properties of aqueous solutes up to 300°C were described and analyzed in Igor Khodakovsky's publications of those years. Igor contributions to establishing the self-consistency of ion thermodynamic properties with critical evaluations of large experimental data sets became benchmarks in this field of geosciences.

He also compiled standard thermodynamic properties for large numbers of mineral compounds including the radionuclides. These key data became decisive for many thermodynamic calculations and for solution of physico-chemical problems of toxic elements and radionuclide migration in the earth's environment.

Igor was very active in the expansion of an accelerating science - cosmochemistry. He led innovative modeling of several planetary atmospheres (Venus, Mars, Jupiter, Saturn), of crust formation on Venus and Mars, and of the role of volatiles in the formation of meteorites and planets of the Solar system. In cooperation with astrophysicists the pioneering modeling computations were used for the prediction of composition and chemical forms of volatile elements at different stages of the protoplanetary disk evolution. This approach was recently successfully applied by colleagues of Igor to the data obtained during exploration of Jupiter, Saturn and their satellites.

He was a pioneer of chemical thermodynamic applications in the computer modeling of the chemical composition of Venus' atmosphere as well that of Venus' and Martian surface rocks. He and his colleagues originated a model of the atmosphere of Venus. The model was successfully used in both planning of cosmic experiments and for their interpretation (Venus-13, -14; Vega-1, -2). For instance, he concluded that the chemical composition and physical properties of surface rocks on Venus are probably determined by the oxidation and sulfate formation governed by the rock-atmosphere interaction. This conclusion was found to be in agreement with the experimental data obtained by (Venus -13, -14; Vega -2). That thermodynamic approach was also very useful in assessing possible cloud particle compositions in Venus' atmosphere. In 1983, he was awarded the Order of the Red Banner of Labour for his contributions to cosmic space research.

He creatively participated in the development of national and international thermodynamic data bases (RAS, CODATA, MAGATE) and their publication as handbooks.

One of his last achievements in mineral thermodynamics was the development of an improved heat capacity equation. The improved semi-empirical equation models with good accuracy from zero K to high temperatures. The applicability of this new equation at very low temperatures is indispensable in cosmochemistry and planetary science.

In 1994 - 2007, he held the Chemistry, Geochemistry and Cosmochemistry chair in Dubna University. He taught courses on inorganic and physical chemistry, thermodynamics of natural and technogenic systems, general geochemistry and cosmochemistry, geochemistry of the biosphere, and the history of chemistry. His work ethic, energy, outstanding organizational abilities, deep enthusiasm and joint collaboration with leading specialists in different fields of science contributed to his productivity. In 2012 he was awarded the distinguished title of Honored Scientist of Moscow Oblast.

A dedicated scientist, Igor spent many hours in libraries working on data storage. In his files he stored thousands of papers for hundreds of known thermosystems. During the 1960's through the 1980's, his card system held thermodynamic references to more than 10,000 solid compounds and components of aqueous solutions. With time, these data found their place into computer storage. This work on data collection and analysis continued until his last days.

Under his supervision, 20 PhDs and many Bachelor degrees were successfully defended. He was always sensitive to younger specialists. He treated them with respect, trust and often with good humor. He did for them more than was expected . He always could feel and see the scientific perspective, and support able workers on the scientific frontier. People who worked with him truly appreciated and respected him.

Igor L. Khodakovsky was a lead scientist in the field of process modeling in geochemical and cosmochemical systems. He authored and co-authored more than 300 scientific publications, including sets of monographs. He was presented with the high distinction of the A.P.Vinogradov Award. He was a constantly active member of many Science Councils: in geochemistry (GEOKHI RAS) and in chemical thermodynamics and thermochemistry (RAS). He organized many national and international symposia on thermodynamics in geology and thermodynamics of natural processes. He encouraged and arranged for many extended visits to his country by scientists and their family members, enriching important international scientific and cultural exchange for those involved. Those colleagues are among those who are saddened by his passing.

The name of Igor Khodakovsky is forever written in the history of thermodynamic modeling in geochemistry and cosmochemistry. Igor's memory persists in the hearts of his immediate family, his colleagues and friends.

Boris N. Ryzhenko and V.P. Volkov, GEOKHI RAS; Dubna University; Gleb Khodakovsky; Tatiana Ivanova; Andrei Plyasunov, IEM RAS, Chernogolovka, Moscow Oblast, Russia; Hu Barnes, EMS PSU; Estelle Parizek; Richard Parizek, EMS PSU; Victor Balashov, EESI PSU, University Park, PA, USA