Deciphering the Origin and Evolution of the Early Solar System by Isotopes

The origin of our solar system has long been a focus of both human curiosity and scientific exploration. Interest has recently been heightened by the discovery of extrasolar planets, suggesting the exciting possibility of extrasolar siblings of the Earth and hence, perhaps, extraterrestrial life. Valuable information about the initial conditions from which habitable planets evolve can be obtained from our own solar system but several fundamental issues have to be tackled: To understand the circumstances of the birth of our solar system we need to find and examine samples that resemble the original material that was present during the formation of our solar system. To understand the processes that governed the evolution of the solar system we can compare various bodies and regions in the solar system, e.g., the comets in the cold outer solar system with the asteroids and the terrestrial planets in the inner solar system. We furthermore need to asses the transport and exchange mechanisms that have occurred between these regions. For instance, comets might have delivered most of the nitrogen to the Earth's atmosphere, but only a small fraction of the water. On the other hand, materials that were expected to have formed only in the hot inner regions of the early solar system have been detected in dust from comet Wild 2 that has been returned with the 'Stardust' mission. Also, it might well be that the composition of the comets in the outer solar system largely vary, and it is thus necessary to sample more comets to better understand this important source that may have delivered water and other volatile elements to Earth. However, sample return missions are expensive and thus limited. A unique alternative that I work on is the study of 'interplanetary dust particles' (IDPs) that are collected in the Earth's upper atmosphere. These dust grains are believed to originate mostly from comets. Here I propose to study noble gases, mainly krypton and xenon, in Stardust samples, IDPs and primitive meteorites from a large number of asteroids, to shed light on the above fundamental issues. Noble gases are uniquely suited to tackle these questions as they are rare on Earth, chemically inactive and hence do not lose their characteristic (isotopic and elemental) compositional signatures. This allows us to use noble gas signatures to trace materials back to their original reservoirs. Meteorites, e.g., show different signatures than the original nebula gas that is now in preserved the Sun. However, the detection of the heavy noble gases in cometary materials is extremely challenging. IDPs are very small and therefore a cutting-edge high-sensitivity instrument is needed. Cometary Stardust has been closely intermingled with the collector material during sampling and a particularly selective detection technique is required to separate cometary noble gases from those originating from collector contamination. These techniques are now available at the University of Manchester and I plan to combine, for the first time, these two state-of-the-art techniques to study the noble gas contents of comet Wild 2 dust, IDPs and primitive meteorites. With these studies, we will better understand the original inventory of protosolar cloud materials that accreted to form the solar system bodies and that were stored ever since in comets and primitive meteorites. I will constrain the contribution of volatile materials from comets to the terrestrial planets and their atmospheres, will be able to compare materials from different comets sampling the Kuiper belt and will assess transport mechanisms and the degree of mixing that must have occurred throughout the whole early solar system. Finally I might also be able to set chronological constraints on these processes.