Abstract Details
| Name: GURPREET KAUR Affiliation: PANJAB UNIVERSITY, CHANDIGARH Conference ID: ASI2016_452 Title : Modelling the thermal evolution and differentiation of interior of Mars and Mercury Authors and Co-Authors : Prof. Sandeep Sahijpal, Panjab University, Chandigarh Abstract Type : Oral Abstract Category : Sun and the Solar System Abstract : The small size of Mars and Mercury as compared to other terrestrial planets is a big puzzle in terms of theories developed earlier to study planet formation processes. Despite of small size of Mercury (radius ~ 2440 km), its unusual high density (~5.44 g cm-3) as compared to other terrestrial planets like Earth (~4.1 g cm-3) and Mars (~3.7 g cm-3) is still a mystery. The recent results of MESSENGER mission to Mercury have challenged the results of theories developed earlier to understand the high density of Mercury with large iron core at the center. In the present work, we have studied the thermal evolutionary criteria of Mars and Mercury in the initial 50 Ma (million years) of the formation of solar system by incorporating the heat produced due to short lived radio-nuclides 26Al and 60Fe along with long-lived radionuclides 40K, 235U, 238U and 232U. To study the thermal evolution of Mars, we assumed Mars to be formed from planetesimals with H-chondritic composition. Partial differential equation of heat transfer was solved numerically assuming radiogenic heat along with the accretion heat produced during the growth planet. The pressure dependent liqidus and solidus temperature of iron and silicate were calculated at each spatial point inside Mars. Stoke’s law was used to calculate the descend velocity of metallic blobs to form iron core at the center. Apart from radiogenic and accretion heat, we have also parametrically incorporated the heat produced due to gravitational energy released during the core-mantle differentiation inside Mars. We also performed one simulation to understand the thermal evolution of Mars assuming a low value of (26Al/27Al)initial due to recent results showing the possibility of heterogeneity of 26Al in the solar nebula. From the results of thermal evolutionary study of Mars, we conclude that accretion energy alone cannot produce large scale heating, melting and differentiation of Mars. The results show that 26Al played the major role among all the heat sources in planetary scale differentiation of Mars within the initial ~1.5 million years. This seems to be consistent with the chronological records of Martian meteorites found on Earth. To study the thermal evolution of Mercury, we considered two types of models. In first type of model (Model A), we considered Mercury to be formed from accretion of planetesimals having Enstatite composition with final radius 2440 km. In the second model (Model B), we considered Mercury to be having radius comparable to radius of Mars(~3440 km) accreted from planetesimals with H-chondritic composition which subsequent to differentiation into iron core and silicate mantle, suffered impact induced stripping of its mantle leaving a large iron core at the center. The results of numerical simulations of Mercury show that heat produced due to short-lived radionuclides along with accretion energy could have resulted in the large scale heating and melting inside Mercury if Mercury accreted early during the formation of solar system. Acknowledgements: This work is supported by PLANEX (ISRO) research grant. |