Experimental investigation of the formation of dipeptides in the ices of Kuiper Belt Objects

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How did there come to be organic molecules on early Earth? Did they develop here or arrive from elsewhere in the Solar System? One possible source is the Kuiper Belt beyond Neptune, where over 70,000 objects with a diameter larger than 100km have been identified to date. Most of these Kuiper Belt Objects, or KBOs, consist mainly of ice of varying compositions of CHON, the most common elements in living organisms. For example, the ice on Quaoar includes nitrogen, methane, ethane, and water. Because KBOs have existed since the early stages of the Solar System's development, these ices have been exposed to the ionizing solar radiation for billions of years. Such radiation can trigger chemical reactions in the ice matrix, possibly resulting in the formation of dipeptides. Dipeptides play a key role in the development of prebiotic molecules, not only as a building block of proteins but a catalyst of polypeptides and enzymes. Because KBOs are considered to be a key source of short period comets, they may have delivered these biologically relevant molecules to the early Earth.The goal of this project is to experimentally simulate the physical and chemical conditions and processes on KBOs, to determine if, and under what conditions, dipeptides can form there.To do this, we will synthesize ices analogue to KBO ices in composition and temperature, using a novel ultra-high vacuum machine. We will then expose the ices to ionizing radiation that simulates the naturally occurring radiation on KBOs (protons and photons). Both during and after the radiation of the ices, we will use an array of specially developed detection mechanisms to probe for complex organic molecules and for the dipeptide bond in particular. In the first phase, to rule out detection artifacts, we will first synthesize the pure ices and obtain measurements for later comparison. Then, in a second phase, the ices will be treated separately with each type of ionizing radiation, then treated with both photons and proton radiation simultaneously, as interactions are possible. Finally, in a third experimental phase, the ice will be doped with the mineral olivine (one of several similar minerals found on comets) before irradiation, to test for possible catalytic effects.