Katsuko Saruhashi's interest in water led her to be the first woman to earn a doctorate in chemistry from the University of Tokyo in 1957.

The groundbreaking geochemist developed methodology to accurately determine the carbonic acid substances in natural waters based on water temperature, pH level and chlorinity. The measurements could be made with the help of "Saruhashi's Table," which served oceanographers for three decades before being replaced by computers.

To honor Saruhashi's contributions to the understanding of carbon dioxide in seawater, Google dedicated its doodle Thursday to her memory on her 98th birthday.

After the nuclear testing in the Pacific Ocean in the 1950s, Saruhashi began measuring artificial radioisotopes in seawater. Her research demonstrated that radionuclides could be used to trace ocean currents. In later years, she would go on to study acid rain.

During a career spanning 35 years, Saruhashi became the first woman elected to the Science Council of Japan in 1980, and the first woman honored with the Miyake Prize for geochemistry in 1985.

She died in 2007 at the age of 87.

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