Inefficient Collisions, Hit-and-Runs, and Splats

In pairwise accretion -- that is, the formation of bigger planets hierarchically from smaller ones -- the typical encounter speeds are comparable to the escape velocities of the dominant bodies, and the colliding bodies are of comparable size. This is a far cry from the two most commonly considered regimes: hypervelocity bullets hitting a much larger target (a.k.a. impact cratering), and the perfect mergers (sometimes with a disruption threshold) assumed in nearly every N-body simulation of planetesimal/planetary growth. The best studied case is the Moon's formation by a giant impact.

The Great Archean Bombardment, or the Late Late Heavy Bombardment

The early bombardment history of the Inner Solar System is recorded in a number of interesting places (e.g., the surprisingly high abundance of highly siderophile abundances found in the Earth, Moon, and Mars, the observed impact basins found on Mercury, the Moon and Mars, various properties of main belt asteroids and meteorites, etc.).

Tracking and Mitigating Meteoroid Threats to Spacecraft

Whether residing in low-earth orbit or traveling through interplanetary space, spacecraft must shield against environmental threats that could result in minor to catastrophic failure. One such threat is an impact by a meteoroid, which is a natural object ranging from 62 microns to meters in diameter that could cause either mechanical or electrical damage. In this presentation, Dr. Close will discuss current research into meteoroid and meteoroid plasma physics and how these tiny particles may offer insight into the formation of life on Earth.

EPOXI and Comet 103P/Hartley 2

The Deep Impact Flyby Spacecraft flew past comet Hartley 2 on 4 November 2010. Yet again a cometary flyby has led to numerous surprises that will yet again change our understanding of the role of comets in the formation of the solar system and our understanding thereof. This talk will highlight the new knowledge gained from the flyby. By the time of this talk, Stardust NExT will have flow past comet 9P/Tempel 1 (on 15 April PST) and the new data on the cometary nucleus onto which Deep Impact delivered its Impactor Spacecraft 5 years ago.

Near Earth Asteroids as Targets for Human and Robotic Exploration

Near-Earth Asteroids (NEAs) are both enemies (that can collide with our planet) and friends (future targets for human exploration missions). As the Spaceguard Survey nears its goal of finding 90% of NEAs larger than 1 km, public and government interest turns to the much more numerous sub-kilometer NEAs. These small asteroids are the most likely to hit Earth and are also the designated NASA target for astronaut visits in the late 2020s.

Arecibo Radar Observations of Near-Earth Asteroids

Radar observations are one of the only groundbased techniques to spatially resolve near-Earth asteroids. Images with up to 7.5-m resolution reveal a wide variety of shapes, surface features and helped to discover many binary objects. Our understanding of the nature and evolution of NEAs has changed radically in recent years, in a large part due to the information from radar images, and shape models derived from them. I will discuss current results and upcoming improved capabilities of the Arecibo planetary radar system.


Did the Late Heavy Bombardment end with a whimper? Evidence from 3.5-3.2 Ga rocks in Archean Barberton region of South Africa

 Lunar evidence of Late Heavy Bombardment has been interpreted to suggest that large-body impacting declined rapidly after about 3.8 Ga and that by 3.5 Ga the terrestrial bombardment rate was not much greater than the impact rates of today. In 1986 and 1989 Dr. Lowe and colleagues described four major layers of spherical particles in the 3.22-3.55 Ga Barberton greenstone belt (BGB), South Africa, ranging from 3,472 to 3,243 Ma, and interpreted them to represent the products of large terrestrial impacts of bolides 20-50 km in diameter.

Primordial Ice Reservoirs of the Solar System

We now know that ice in the solar system resides in at least three distinct reservoirs, known as the Oort cloud, the Kuiper belt and the main-belt comets. Dr. Jewitt will discuss the nature, distribution and significance of the ice, highlighting its connection to the formation epoch, in a style intended to be sweeping and broadly accessible.

The impact and recovery of asteroid 2008 TC3

For the first time, astronomers tracked an asteroid in space, observed its size, reflection properties and how it tumbled, then saw it crash in Earth's atmosphere over Sudan on October 7, 2008. At first, no pieces were expected to survive because the entry resulted in a massive explosion at 37 km altitude that left most of the asteroid in dust.

NEOs Ho!! The Asteroid Option

In late 2006, NASA's Constellation Program (CxP) sponsored a study to examine the feasibility of sending a piloted Orion spacecraft to a near-Earth Object (NEO).


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