THE ABILITY OF CLATHRATE HYDRATE TO HOST VOLATILE MOLECULES AND ATOMS IN SIGNIFICANT CONCENTRATION MIGHT HAVE CONSIDERABLY DIVERSIFIED THE NEAR-SURFACE PHYSICO-CHEMICAL CONDITIONS OF PLANETS AND SATELLITES. ACCURATE INFORMATION CONCERNING THE CHEMICAL AND ISOTOPIC FRACTIONATION DURING THE PROCESSES OF GAS TRAPPING AND RELEASE ALONG PHASE TRANSITIONS (AMORPHOUS - CLATHRATE HYDRATE - CRYSTALLINE) OF SOLID WATER WOULD SHED LIGHTS ON THE EVOLUTION HISTORY OF ATMOSPHERES AND SURFACE ENVIRONMENTS OF PLANETARY BODIES IN THE SOLAR SYSTEM. THE PROPOSED PROJECT IS A PILOT STUDY FOR A DURATION OF TWO YEARS TO DEVELOP AND DEMONSTRATE THE PERFORMANCE OF A NEW EXPERIMENTAL SYSTEM WHERE MG CLATHRATES ARE FORMED AND THEIR CHEMICAL SELECTIVITY IS DETERMINED USING A QUADRUPOLE MASS SPECTROMETER (QMS). THE STRUCTURE OF THE CLATHRATES WILL BE DETERMINED BY X-RAY POWDER DIFFRAC- TION METHOD USING THE ADVANCED PHOTON SOURCE (APS) AT ARGONNE NATIONAL LABORATORY (ANL) AS DESCRIBED BELOW. WE START EXPERIMENTS WITH A SIMPLE BINARY SYSTEM OF N2-CH4 MIXTURE UNDER CONDITIONS RELEVANT TO THE SURFACE OF TITAN. SUBSEQUENTLY NOBLE GASES WILL BE ADDED TO EXPERIMENTS OF THE BINARY SYSTEM. THE TARGET QUESTIONS ARE: 1. WHAT IS THE GUEST CHEMICAL COMPOSITION OF CLATHRATE HYDRATE AT THE SURFACE OF TITAN? AT THE SURFACE TEMPERATURE OF 94K THE EQUILIBRIUM PRESSURE OF AN N2- DOMINATED CLATHRATE (STRUCTURE II) IS ABOUT 10-3 BAR. THE SURFACE PRESSURE OF ~1.3 BAR DOMINATED BY N2 GREATLY EXCEEDS THE EQUILIBRIUM PRESSURE SO THAT THE N2- DOMINATED CLATHRATE MAY BE PRESENT AT THE SURFACE OF TITAN [MOUSIS ET AL. 2011]. HOWEVER THE PREFERRED STRUCTURE OF CH4-DOMINATED CLATHRATE IS TYPE I. HOW DOES THE STRUCTURE OF THE CLATHRATE LOOK WHEN THEY ARE MIXED? HOW DOES IT LOOK AT THE ESTIMATED DISSOCIATION TEMPERATURE OF ~170 K? 2. WHAT IS THE CONCENTRATION OF NOBLE GASES IN THE CLATHRATE HYDRATE STABLE AT THE SURFACE OF TITAN? COULD IT BE A SIGNIFICANT SINK OF KR AND XE WHICH WERE NOT DETECTED BY CASSINI-HUYGENS PROBE? THE CHEMICAL COMPOSITIONS OF MG CLATHRATES FORMED IN THE LABORATORY UNDER TITAN'S SURFACE CONDITION WILL BE COMPARED WITH THE MODEL COMPOSITIONS FROM THE LITERATURE TO ADDRESS THE ACCURACY OF THERMODYNAMIC CLATHRATE MODELS AND THE GEOCHEMICAL IMPLICATION ON TITAN WILL BE CONSIDERED.