Astronomy and Astrophysics

Where do near-Earth Asteroids come from?
Kevin Walsh, Southwest Research Insitute

Near-¬Earth Objects (NEOs) are a transient population with lifetimes only a small fraction of the Solar System lifetime. We know the NEO's exit routes -¬chaotic orbits put them on a collision course with a planet or the Sun, while Jupiter can provide a one-¬way ticket out of the Solar System. Meanwhile, the size of the NEO population hasn't changed much over time (as determined by the cratering record on the Moon), and thus they can be considered a steady-¬state population. However, we don't fully understand their sources or where specifically they all originated.

Asteroids in the Main Asteroid Belt, orbiting between Mars and Jupiter, can make the jump to a near-¬Earth orbit if their orbit gets altered/excited if it resonates with an orbit of a giant planet [1]. One piece of essential physics is the mechanism to move asteroids into these resonant orbits, and with sunlight as the most important driver [2]. The key is the re-¬generation of small asteroids in the Main Asteroid Belt due to catastrophic collisions between large asteroids [3]. Combined, we can start to trace the history of the dominant source populations feeding the NEA population over time. This has helped make links between specific events here on Earth (see the Dinosaur extinction event) with events in the Asteroid Belt (formation of a specific asteroid family [4]). It can also provide context for asteroids that we might visit with a spacecraft [5]. I will discuss the evolving understanding of NEA delivery processes in light of rapidly improving knowledge of asteroid physical properties and orbital distributions, and new models of competing radiation-¬driven evolutionary effects [6].

[1] Chapman C. R., Nature 407, 573-¬576 (5 October 2000) nature.com/nature/journal/v407/n6804/full/407573a0.html

[2] scholarpedia.org/article/Yarkovsky_and_YORP_effects

[3] Richardson D. C., Nature 417, 697-¬698 (13 June 2002) nature.com/nature/journal/v417/n6890/full/417697a.html

[4] Claeys & Goderis, Nature 449, 30-¬31 (6 September 2007) nature.com/nature/journal/v449/n7158/full/449030a.html

[5] NASA’s New Frontiers OSIRIS-¬REx asteroid sample return mission Error! Hyperlink reference not valid.

[6] Binzel, R. P., Nature 425, 131-¬132 (11 September 2003), nature.com/nature/journal/v425/n6954/full/425131a.html

Background Review Article:
How to Deflect Killer Asteroids With Spray Paint, Adam Mann, 02.07.13, Wired. wired.com/wiredscience/2013/02/painting-asteroids/

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Astronomy and Astrophysics

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