Goals: Leonid MAC, NASA's first astrobiology mission, was a series of five missions that took flight in aircraft during the years 1998, 1999, 2000, 2001, and 2002. By observing and studying meteor showers the mission looked to learn how extraterrestrial materials may have been brought to Earth at the time of the origin of life. In addition, the interaction of meteoroids with the atmosphere generates molecules that may have played a role in the origin of life on Earth.

Accomplishments: The Leonid Mac missions observed, studied, imaged, and made measurements of the Leonid meteors. Among the discoveries and firsts made were: The ability to weigh meteors by measuring the amount of iron atoms that ablate from the meteor. The measurement of the properties and characteristics of meteor dust trails. The first detection of mid-infrared emissions from relatively faint meteors and the first mid-infrared spectroscopy of persistent meteor trains. Leonid MAC also detected, and later confirmed, the existence of a halo and shadow surrounding the head of bright Leonid meteors.