What made Marie Curie unique among Nobel winners?

Answer

She shared the 1903 Physics prize and won the 1911 Chemistry prize alone. She is still the only person to win Nobel Prizes in two different sciences.

Context

Curie's first Nobel, in 1903, was in Physics, shared with her husband Pierre Curie and Henri Becquerel for their work on radioactivity, the phenomenon Becquerel had found in uranium salts and the Curies had studied in detail. Her second, in 1911, was in Chemistry, awarded to her alone for the discovery of polonium and radium and for isolating radium and studying its properties. Marie coined the term radioactivity, and the work on pitchblende involved processing tonnes of ore by hand.

Others have won twice. Linus Pauling won the Chemistry prize in 1954 and the Peace prize in 1962, and John Bardeen won Physics twice, in 1956 and 1972. Frederick Sanger won Chemistry twice. Curie remains the only person to have received Nobel Prizes in two different scientific fields, and she was also the first woman to win any Nobel Prize and the first person to win two.

Her story also includes the controversy that surrounded the 1911 prize, when press coverage of a personal relationship nearly overshadowed the announcement; she nevertheless accepted the award. The Curie family continued the tradition: her daughter Irène Joliot-Curie won the 1935 Chemistry Nobel with her husband Frédéric. Marie's long exposure to radiation likely contributed to her death in 1934 from aplastic anemia, a conclusion generally drawn by historians.