First International Conference on MOLDAVIAN RISKS – FROM ...

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<strong>First</strong> <strong>International</strong> <strong>Conference</strong> on MOLDAVIAN RISKS - FROM GLOBAL TO LOCAL SCALE 16-19 May 2012, Bacau, Romania THE HAZARD OF IMPACTS FROM SPACE Michael Purucker Planetary Geodynamics Laboratory, GSFC/NASA, Greenbelt, MD USA Corresponding author: Michael Purucker, Michael.E.Purucker@nasa.gov Abstract: Near-earth objects (NEOs) have been implicated in mass extinctions in Earth history. The most recent mass extinction occurred at the End-Cretaceous, and is associated with the Chixulub impact structure in Mexico and the Deccan traps in India. NEOs comprise both the much more abundant asteroid component, with orbits between 0.98 and 1.3 astronomical units, and the much rarer cometary component. NASA has now cataloged 90% of NEOs larger than 1 km (civilization ending) and has begun the task of identifying those larger than 140 m (city killers). NEOs are identified by earth-based telescope, but an infra-red space-based telescope in an orbit between the Earth and Venus would offer superior viewing geometry for these dim objects. NEOs have no substantial gravity well, and hence are ideal targets for both NASA’s robotic and human exploration program. The natural history of NEOs suggests that they originate via planetary resonances from the main asteroid belt and the trans-Neptunian disk, and that their dynamical lifetimes are on the order of 10 Myr. Once identified, their threat can be assessed via precise orbit determination, and steps might be considered to re-direct them away from Earth. However, the complex interaction of science, psychology, politics, and money has hindered attempts at an integrated global approach to the problem. The threat from NEOs was much more common in the deep past, in what is termed the Late heavy bombardment 4 billion years ago. This is a period when most of the Moon’s largest impact basins were formed, and by inference the largest impact basins on Mercury and Mars. Key words: impacts, hazard, extinction, planetary defense. 16
<strong>First</strong> <strong>International</strong> <strong>Conference</strong> on MOLDAVIAN RISKS - FROM GLOBAL TO LOCAL SCALE 16-19 May 2012, Bacau, Romania CLIMATE VARIABILITY AND COSMIC RAYS Eigil Friis-Christensen Techncal University of Denmark, National Space Institute Eigil Friis-Christensen, efc@space.dtu.dk Abstract: Our Climate is changing all the time due to a number of various causes, internal as well as external, natural as well as anthropogenic. In addition to the ice ages, which are believed to be caused by variations of the Earth’s orbit, paleoclimate records indicate significant changes of regional climate that are strongly correlated with solar activity variations - both the 11-year period and longer periods. Various hypotheses regarding the physical mechanism have been proposed. In this presentation the hypothesis of an effect on global cloud cover of cosmic rays modulated by solar activity will be discussed, based on results from observations, laboratory experiments and theoretical considerations. A much better understanding of the natural variations of climate is a fundamental requirement for a credible assessment of the human contribution to climate change, now and in the future. Key words: climate, cosmic rays, clouds, atmosphere, observations, experiments. 17
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Sponsors of the conference Sodexo P
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