Reika Yokochi

Reika Yokochi (横地玲果, born November 9, 1975 in Saga, Kyushu Prefecture, Japan; died on February 17, 2024 in Chicago, USA) was a Japanese geochemist who worked on the origin and geological behavior of volatile elements.

Yokochi crafted a device capable of efficiently extracting krypton from vast quantities of groundwater, thus facilitating the accurate quantification of 81Kr using Atom Trap Trace Analysis (ATTA).

[10] In a study of the Nubian Sandstone Aquifer in Israel's Negev Desert, Yokochi and colleagues utilized radiokrypton (81Kr) to date groundwater, discovering two major water recharge events.

Yokochi also conducted experiments aimed at understanding how volatile elements are trapped in ices under conditions relevant to the formation of comets and icy moons.

[14][15] Yokochi received the Young Scientist Award from the Geochemistry Research Association of Japan in 2012; the same year, she was also named a NASA Planetary Science Early Career Fellow.

Reika Yokochi (in the center) and fellow scientists extracting gases from a water production well in the Negev Desert.
Variations in 136 Xe*/ 4 He* and 21 Ne*/ 4 He* in deep mantle samples from the Kola Peninsula reflect magmatic processes. By interpolating this correlation to the known 21 Ne*/ 4 He* production ratio of the mantle, Yokochi and Marty estimated the deep mantle 136 Xe*/ 4 He*, indicating that 33-60% of 136 Xe* comes from decay of 244 Pu (t 1/2 =81 Myr) while the rest comes from decay of 238 U (t 1/2 =4.5 Gyr). [ 4 ]
81 Kr forms in the atmosphere from cosmic ray interactions. In the Sinai, rainwater dissolves this isotope and stable krypton, infusing it into groundwater at recharge sites. As groundwater flows from these sites, 81 Kr decays. Analyzing the 81 Kr/krypton ratio in groundwater from the Negev indicates a recharge time of 360 kyr. [ 6 ]