Dr. Galen Gisler, retired LANL astrophysicist and community volunteer, spoke Tuesday at the Rotary Club of Los Alamos weekly meeting at Cottonwood on the Greens about the threat of near-Earth asteroids.  He described the impacts of the Chicxulub impact n present-day Yucatan that is responsible for the extinction of the dinosaurs 65 million years ago, as well as those impacts in our modern age:  Tunguska, Siberia in 1908 and Chelyabinsk, Russia in 2013.  To study the threat, scientists find potentially hazardous asteroids, calculate their orbits, monitor and characterize them, and if necessary, develop and execute a deflection mission.  The intent of the deflection is to alter the asteroid’s orbit away from Earth.  Methods considered include a gravity tractor, kinetic impact, a nuclear explosive device, and a spacecraft swarm with lasers, ion beams, or solar mirrors.  For more information, visit the Minor Planet Center, www.minorplanetcenter.net, which operates at the Smithsonian Astrophysical Observatory. Photo by Linda Hull