Found 55 talks archived in Planetary systems

The role of asteroids and comet impacts on the origin of Earth’s water and organic molecules is reviewed. Earth is believed to have formed dry, and magma oceans probably destroyed any primordial organics on Earth. The oldest clear evidence for water on Earth is about 3.85 Ga, right after the “Late Heavy Bombardment” (LHB). Asteroid and comet impacts during the LHB probably contributed significantly to Earth’s water and organic inventory. Evidence for this contribution is found in the D/H isotopic ratios of meteorites and comets. The abundance and variety of organic solids in asteroids and comets also point at a significant contribution to the organic inventory of the early Earth. However, the pieces of this puzzle do not all fit into a neat picture and several questions remain unanswered.

Radar observation of near-Earth asteroids (NEAs) reveal the size, shape, spin characteristics of the population of small bodies near the Earth. Although spacecraft missions may give higher resolution images, they are infrequent and expensive. Only through ground based observations can we hope to understand the diverse population of NEAs. Radar imaging reveals surface features and shape at up to 7.5-m resolution. We see a surprising variety of object shapes, which tells us about their formation and evolution. Binary NEAs are easily detected using radar regardless of viewing geometry, the characteristics of which have led to new ideas about NEA evolution and internal structure. Craters and other surface concavities are often visible in radar images, unlike lightcurve-based shape models. Although opportunities to observe comets with radar are rare, more than ten comet nuclei have been detected to date, three with high resolution imaging. Radar observations have played an important role in a number of key areas in small body science, some of which will be discussed in this talk.