The early impact histories of meteorite parent bodies

We have developed a statistical framework that uses collisional evolution models, shock physics modeling, and scaling laws to determine the range of plausible collisional histories for individual meteorite parent bodies. It is likely that those parent bodies that were not catastrophically disrupted sustained hundreds of impacts on their surfaces—compacting, heating, and mixing the outer layers; it is highly unlikely that many parent bodies escaped without any impacts processing the outer few kilometers. The first 10–20 Myr were the most important time for impacts, both in terms of the number of impacts and the increase of specific internal energy due to impacts. The model has been applied to evaluate the proposed impact histories of several meteorite parent bodies: up to 10 parent bodies that were not disrupted in the first 100 Myr experienced a vaporizing collision of the type necessary to produce the metal inclusions and chondrules on the CB chondrite parent; around 1–5% of bodies that were catastrophically disrupted after 12 Myr sustained impacts at times that match the heating events recorded on the IAB/winonaite parent body; more than 75% of 100 km radius parent bodies, which survived past 100 Myr without being disrupted, sustained an impact that excavates to the depth required for mixing in the outer layers of the H‐chondrite parent body; and to protect the magnetic field on the CV chondrite parent body, the crust would have had to have been thick (approximately 20 km) to prevent it being punctured by impacts.     

International students as urban agents: International education and urban transformation in Auckland,New Zealand

This paper discusses connections between the internationalisation of education, and in particular the growth in international students, and processes of urban transformation. The research is centred in Auckland, New Zealand, a city where the number of international students has grown rapidly over the last decade leading to significant impacts on the urban form and experience of the city’s CBD. This includes growth in educational services such as language schools and other private training establishments, new residential geographies characterised by low-cost and low-quality high-rise developments, and new ethnic economies of food, service and entertainment businesses that explicitly target international students. The paper draws on research with South Korean international students and a range of secondary materials to interrogate the connections between student mobilities and changing urban form. In doing so the paper contributes to emerging scholarship on student geographies and the role of students as urban agents through the inclusion of an international dimension that has largely been absent in the extant literature. The findings illustrate that while international students themselves clearly play a significant role in the transformation of urban spaces their influence cannot easily be separated from the contribution of a range of other actors including educational businesses, property developers, transnational migrants and local and national state actors.