EXPLORATION OF THE SOLAR SYSTEM VIA SAMPLE RETURN MISSIONS
Meenakshi Wadhwa is a planetary scientist interested in the time scales and processes involved in the formation and evolution of the Solar System and planets. She is director of the School of Earth and Space Exploration at Arizona State University, where she is also appointed as Foundation and Regents Professor. She additionally holds an appointment as Distinguished Visiting Scientist at the Jet Propulsion Laboratory (Pasadena, CA) and serves as the Principal Scientist for the Mars Sample Return Program. Wadhwa received her doctorate in Earth and Planetary Sciences from Washington University in St. Louis and was a postdoctoral researcher at the University of California at San Diego. She was subsequently Curator at the Field Museum in Chicago before moving to ASU in 2006. She has served on numerous advisory committees for NASA and the National Academies of Science, Engineering, and Medicine. She is a recipient of the Fulbright-Nehru Academic and Professional Excellence Award (2015), the Guggenheim Fellowship (2005), and the Nier Prize of the Meteoritical Society (2000). She was awarded an American Council on Education Fellowship (2018-2019) and became a Fellow of the American Geophysical Union in 2019. She became a Geochemistry Fellow of the Geochemical Society and the European Association of Geochemistry and was awarded the J. Lawrence Smith Medal of the National Academy of Sciences in 2021. She was elected as a member of the National Academy of Sciences in 2023. Asteroid 8356 has been named 8356 Wadhwa in recognition of her contributions to meteoritics and planetary science.
Extraterrestrial samples have taught us some fundamental things about ourselves, our planet, and our Solar System. The analysis in Earth-based laboratories of lunar samples returned by NASA astronauts during the Apollo program and by the robotic Soviet Luna program in the late 1960s and early 1970s not only revolutionized our understanding of the Moon and the Earth- Moon system but also provided broader insights into planet formation processes in the inner Solar System. For example, it is because of the chemical and isotopic characteristics of these lunar samples that we know that the Moon was likely formed when a Mars-sized planet smashed into Earth nearly 4.5 billion years ago. The recent return of unique lunar samples by the Chang’e 5 and 6 missions are also adding valuable insights to our understanding of lunar evolution.
Over the past two decades, our understanding of how the Solar System and planets formed has been improved by other robotic sample return missions: NASA’s Genesis mission that spent two years collecting samples of the solar wind, then delivered them to Earth in 2004; the NASA Stardust mission that collected particles from the tail of comet Wild-2 and returned these to Earth in 2006; fragments of the asteroids 25143 Itokawa and 162173 Ryugu that were delivered by the Japan Aerospace Exploration Agency’s Hayabusa and Hayabusa2 missions in 2010 and 2020; and finally, NASA’s OSIRIS-REx mission that returned samples of asteroid Bennu in September of 2023, and provided the largest sample mass (~122 grams) yet returned from any asteroidal body.
Chemical, isotopic, and mineral analyses of these samples returned by various spacecraft missions are contributing immensely to addressing questions about conditions and dynamics in the solar nebula, how the rocky planets formed in the early Solar System, and how life may have originated on at least one planet (i.e., Earth). In this talk, I will discuss the results and implications of the isotopic analyses in my laboratory of samples from asteroid Ryugu returned by the recent Hayabusa 2 mission. I will additionally touch on future plans to return carefully selected and documented samples from the planet Mars.