Defending the Earth with a Telescope: Mitigating Impact Hazard through Studies of Near-Earth Asteroids
Nicholas Moskovitz, Massachusetts Institute of Technology
An asteroid impact is the only natural catastrophe that we can accurately predict and attempt to mitigate. Fortunately, the odds of a large (km-scale) asteroid impacting the Earth are very small, and have almost entirely been eliminated thanks to efforts over the past decade to discover and track the largest asteroids in near-Earth space [1,2]. However, small (10‘s to 100‘s of meter) asteroids are far more numerous than their larger counterparts, are challenging to detect due to their small sizes and intrinsic faintness, and are not well understood in terms of their physical properties. Objects of this size can be dangerous as we saw with the impact of an approximately 15-meter object over Chelyabinsk, Russia in February 2013, an event that injured nearly 1000 people.
Characterizing the basic physical properties of asteroids is essential to understanding and mitigating impact hazard. Properties like density, internal structure, size, rotation state, and morphology inﬂuence estimations for the frequency and severity of impact events . Quite conveniently, these are exactly the same properties as those that areof interest for addressing fundamental science questions related to planet formation and evolution, meteoritics, gravitational dynamics, and radiative processes.
I will discuss recent progress in our ability to telescopically characterize the physical properties of near-Earth asteroids. Recent advances have been driven by an exponentially increasing discovery rate of near-Earth asteroids over the past decade , which has and will continue to provide abundant opportunities for conducting a variety of novel investigations. I will highlight the types of observations that are used to characterize this population, the development of next-generation telescopic surveys that are allowing us to study objects down to a few meters in size within hours of discovery, and the unique research opportunities provided by those objects that ﬂyby the Earth but narrowly avoid impact . The study of near-Earth asteroids is a rapidly evolving ﬁeld that in the coming years will yield new insights relevant to impact hazard while simultaneously providing information about the origin and evolution of small planetary bodies in the Solar System.
 Jewitt D. Eyes wide shut. Nature 403, 145 (2000).
 Chapman C. The hazard of near-Earth asteroid impacts on Earth. Earth and Planetary Science Letters 222, 1 (2004).
 Chapman C. Asteroids: Stripped on passing by Earth. Nature 463, 305 (2010).