The collector did not send the sample to the laboratory until Monday, thinking it would be more secure at home than at a Federal Express office during the weekend.
Kepler is searching for Earth-like planets around far-flung stars, and the Mars Science Laboratory will sample the Red Planet's geology looking for the building blocks of life - though it will not explicitly look for life itself.
"This is the first time any robot has drilled in any rock on Mars" or anywhere else beyond Earth, said Louise Jandura, chief engineer for Curiosity's sample system at the Jet Propulsion Laboratory in Pasadena, Calif.