Destruction of molecular hydrogen ice and Implications for 1I/2017 U1 (`Oumuamua)

Abstract

The first interstellar object observed in our solar system, 1I/2017 U1 (`Oumuamua), exhibited a number of peculiar properties, including extreme elongation and acceleration excess. Recently, \cite{Seligman:2020vb} proposed that the object was made out of molecular hydrogen (H${}_2$) ice. The question is whether H${}_2$ objects could survive their travel from the birth sites to the solar system. Here we study destruction processes of icy H${}_2$ objects through their journey from giant molecular clouds (GMCs) to the interstellar medium (ISM) and the solar system, owing to interstellar radiation, gas and dust, and cosmic rays. We find that thermal sublimation due to heating by starlight can destroy `Oumuamua-size objects in less than 10 Myr. Thermal sublimation by collisional heating in GMCs could destroy H${}_2$ objects of `Oumuamua-size before their escape into the ISM. Most importantly, the formation of icy grains rich in H${}_2$ is unlikely to occur in dense environments because collisional heating raises the temperature of the icy grains, so that thermal sublimation rapidly destroys the H${}_2$ mantle before grain growth.

arXiv comment8 pages, 2 figures, accepted to ApJ Letters on July 31, 2020

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• Evidence Suggesting that 'Oumuamua is the ~30 Myr-old product of a Molecular Cloud
• Assessing the Formation of Solid Hydrogen Objects in Starless Molecular Cloud Cores
• On the Possibility of an Artificial Origin for `Oumuamua
• Numerical Simulations of Tidal Deformation and Resulting Light Curves of Small Bodies: Material Constraints of 99942 Apophis and 1I/`Oumuamua
• Observable Signatures of the Ejection Speed of Interstellar Objects from their Birth Systems
• Oumuamuas passing through molecular clouds
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• Constraining the orientation of the spin axes of extrasolar minor bodies 1I/2017 U1 (`Oumuamua) and 2I/Borisov
• Research Programs Arising from 'Oumuamua Considered as an Alien Craft
• Preliminary Evidence That Protoplanetary Disks Eject More Mass Than They Retain
• Implications of evaporative cooling by H${}_2$ for 1I/`Oumuamua
• Close Encounters of the Interstellar Kind: Examining the Capture of Interstellar Objects in Near Earth Orbit
• Machine Learning Methods for Automated Interstellar Object Classification with LSST