The Chicxulub impact crater, Mexico, is unique. It is the only known terrestrial impact structure that has been directly linked to a mass extinction event, and the only terrestrial impact with a global ejecta layer. Of the three largest impact structures on Earth, Chicxulub is the best preserved. Chicxulub is also the only known terrestrial impact structure with an intact, unequivocal topographic "peak ring". Chicxulub's role in the K-Pg mass extinction and its exceptional state of preservation make it an important natural laboratory for the study of both large impact crater formation on Earth and other planets, and the effects of large impacts on the Earth's environment and ecology. Our understanding of the impact process is far from complete and, despite over 30 years of intense debate, we are still striving to answer the question as to why this impact was so catastrophic. Expedition 364 is the first drill hole into an intact topographic peak ring, and the first to penetrate the offshore portion of the Chicxulub crater. Peak rings are a ring of hills that protrude through the crater floor within large impact basins on the terrestrial planets, and there is no consensual agreement on either their formational mechanism or the nature of the rocks that form them. Geophysical data indicate that the peak ring at Chicxulub is formed from rocks that have a low velocity and density, and one explanation for this is that they are highly fractured and porous. Immediately after impact the peak ring was submerged under water, and located adjacent to a thick pool of hot melt rocks. Hence, we would expect intense hydrothermal activity within the peak ring. This activity may have provided a niche for exotic life forms, in a similar way that hydrothermal vent systems do in the oceans. Drilling the peak ring will determine the origin, lithology, and physical state of the rocks that form it, allow us to distinguish between competing models of peak-ring formation, as well as document the hydrothermal systems and any associated microbiology. Immediately after impact the ocean is, locally, likely to have been sterile. We will use core through the post-impact sediments to examine the recolonization of the ocean, including: what biota came back first (benthic, dinoflagellates, specialists vs generalists), and how long did it take to return to normal conditions? The proposed drilling directly contributes to IODP goals in the: Deep Biosphere and the Subseafloor Ocean and Environmental Change, Processes and Effects, in particular the environmental and biological perturbations caused by Chicxulub.

How did dust and gas produce a planet capable of supporting life? This is one of the most fundamental of questions, and engages everyone from school children to scientists. Our planet formed 4.5 billion years ago along with the Sun and the other planets and minor bodies in our Solar System, and it is the only habitable world yet discovered on which life evolved. By understanding the details of how our Solar System formed we can hope to find an answer. We now know much about how stars and their accompanying planetary systems form in general. We know that stars form by the collapse of interstellar clouds of dust and gas. Planets are constructed in disks known as planetary nebula formed by the rotation of the collapsing gas cloud. It was in the solar nebula, surrounding the young Sun, that all the objects in our Solar System were created through a process called accretion. There is, however, a long list of details we don't know about how our Solar System formed. Why, for example, are all the planets so different? Why is Venus an inferno with a thick carbon dioxide atmosphere, Mars a frozen rock with a thin atmosphere, and Earth a haven for life? The answer lies in events that predated the assembly of these planets, it lies in the early history of the nebula and the events that occurred as fine-dust stuck together to form larger objects known as planetesimals, and as those planetesimals changed through collisions, heating and the effects of water to become the building blocks of planets. Our research intends to follow the evolution of planetary materials from the sources of dust prior to solar system formation, through the assembly of precursor objects within the solar nebula to the alteration of these objects as they became planets. The source of presolar dust provides a context to our solar system. From what types of star was dust derived and how did dust from these different sources mix and change in the solar nebula? These questions can be answered by analysis of isotopes of high temperature, refractory elements, within meteorites - rocks from asteroids that preserve a history of the early solar system. Meteorites, together with cosmic dust particles, also retain the fine-dust particles from the solar nebula. These dust grains are smaller than a millionth of a metre but modern microanalysis can expose their minerals and compositions. We will study the fine-grained components of meteorites and cosmic dust to investigate how fine-dust began accumulating in the solar nebula, how heating by an early hot nebula and repeated short heating events affected aggregates of dust grains, and whether magnetic fields helped control the distribution of dust in the solar nebula. In addition to the rocky and metallic materials that make up the planets, our research will examine the fate of organic materials that were crucial to the origins of life. Through newly developed methods we can trace this history of organic matter in meteorites from their formation in interstellar space, through the solar nebula and into planetesimals. This research will examine the effect of events also recorded in rocky and metallic fine-dust on the organic components of the early planetary materials from which the first living things on Earth were constructed. Once the planets finally formed, their materials continued to change. Our research focuses on the planet Mars, which provides a second example of a planetary body on which life could have appeared. We will trace the evolution of water and organics from planetary formation to the present day. Research on landforms on Mars will examine a crucial period in the planet's history, when global climate change transformed the planet into an arid wasteland, to evaluate the opportunity for organisms to adapt and survive. Research on the survival or organic compounds in martian soil will test whether the signature of life can still be detected on the planet.