Credit: NASA/JPL-Caltech/T. Pyle (IPAC)

Observations from NASA's Spitzer Space Telescope reveal new information about the structure of 2011 MD, a small asteroid being considered by NASA for its proposed Asteroid Redirect Mission, or ARM. Spitzer's infrared images helped reveal that this asteroid consists of about two-thirds empty space. One possible structure for such an asteroid is illustrated here: a loosely clumped group of boulders.