“It dramatically changed the way we look at comets,” says Maryland astronomer Michael A’Hearn, who led the mission. Data from Deep Impact proved, for instance, that many comets are mostly porous, as fluffy as a bank of powdered snow. After the first mission ended, Maryland scientists convinced NASA to keep using Deep Impact rather than let it spin off into space. Its later missions led to discoveries about comets’ chemical makeup, formation locations and surface changes.
Credit: John T. Consoli/University of Maryland