A New and Improved Model of the Near-Earth Object Population

Abstract:

This is a golden age for near-Earth Object (NEO) research. We have discovered some 90% of the most threatening NEOs, while ongoing surveys are finding many sub-km NEOs as well. NEO physical characterization studies by missions, space- and ground-based observatories are also revolutionizing our ideas about what NEOs are like. President Obama announced on April 15, 2010 that NASA would send astronauts to an NEA by 2025; this remains Administration policy. The Feb. 15, 2013 explosion of an NEO over Chelyabinsk, Russia, has further boosted interest in NEOs.

This increasing interest, and a vast array of new data, have led us to re-investigate the debiased orbital and absolute magnitude distribution of the NEO population. Such models are asboluetly needed to make accurate predictions about NEOs that are likely exploration targets for human and robotic spacecraft.

Using the methods of Bottke et al. (2002), we numerically tracked a large unbiased sample of asteroids escaping the main belt and TNO populations in order to locate all possible NEO source regions. From here, we recorded the orbital evolution of the bodies that entering the NEO region; their evolutionary pathways were used to create so-called NEO residence-time distributions. They were combined with the calculated observational selection effects for the Catalina Sky Survey, with the model fit to 4,550 NEOs (15 < H < 25) detected by the Catalina Sky Survey’s Mt. Lemmon (G96) and Catalina (703) stations between 2005–2012. Our best fit case beautifully reproduces observations and provides us with a new and improved NEO model population.

We find our results are in good agreement with the Bottke et al. (2002) model, but we also find many intriguing differences as well: (i) There is an increasing preference for small NEOs to come from the central main belt; (ii) Many low-perihelion-distance NEOs are apparently missing -- we suspect many were removed by a physical destruction mechanism; (iii) We are largely complete in H < 18 Atens and Amors, but we are still missing a good fraction of Apollo NEOs. In our talk, we will discuss our latest findings and will describe the nature of the NEO populations accessible by both ARM and human missions.