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Credit: NASA Sources: Lodders & Fegley (2011). of the , Cambridge: Royal Society of Chemistry. Lodders & Fegley (1994). Icarus, Vol. 112. DR.Washington KATHARINA University LODDERS Neptune, the eighth most distant from the , was named after the Roman god of the seas, but by fortuitous accident since nothing was known about its composition when it was discovered in 1846. Neptune is often called an -, and it may have up to 640 times more oxygen in the form of water than expected if Neptune had formed from material in the same Dr. Katharina Lodders is a research proportions found in the Sun. Neptune’s , along with professor in the Department of from and Earth-based observations, reveal that its outer, observable and Planetary Sciences and the atmosphere contains ~80% hydrogen, 19% helium, and 1.5% . McDonnell Center for the Space Consequently, Neptune appears blue because methane absorbs the red Sciences at Washington University in wavelengths of visible light it St. Louis, Missouri. She obtained her receives from the Sun (the blue in from the light is reflected). The outermost Johannes-Gutenberg University in atmosphere is very cold, down 1990 and did her Ph.D. work at the to –50°C. Icy layers of Max Planck Institute for Chemistry in methane, , and water Mainz, Germany. From 2010 to 2013 occur with increasing depth in she worked as Program Director in Neptune’s atmosphere, which the Division of Astronomical Sciences gets hotter and denser inward. at the National Science Foundation in Chemical reactions between Arlington, Virginia. Lodders is the and hydrogen author of two books written with Bruce Fegley Jr., The Planetary Scientist’s provide a window into the Companion (Oxford University Press, 1998) and Chemistry of the Solar System composition of Neptune’s interior. (Royal Society of Chemistry, 2011), and has contributed to over 90 refereed This false-color from Voyager 2 reveals Deeper in the hot and dense scientific papers. Her research in , , and planetary features at different depths in the atmosphere of portions of the atmosphere, sciences focuses on experimental and theoretical studies of abundances of Neptune: Blue objects are deeper, while white the chemical elements, formation of dust from evolved , chemical features are at higher . oxygen is bound in carbon Credit: NASA/JPL. monoxide and water, but in the processes in the solar nebula and disks, formation of cooler and less dense upper parent bodies, planetary accretion and differentiation, and chemistry in oxygen is mainly bound in water. The observed carbon monoxide and substellar environments such as giant , , brown dwarfs, rising from the deep interior tells us about the high water content of the and low- stars. deep atmosphere of Neptune — which is indeed another water-rich planet and blue dot in the solar system.

Founded at the height of the Apollo program in 1968, the Lunar and Planetary Institute (LPI) is an The year 2019 marks the 150th anniversary of Dmitri Mendeleev’s development of the Periodic intellectual leader in lunar and . LPI’s mission is to advance understanding of the System and has been proclaimed the “International Year of the of Chemical solar system by providing exceptional science, service, and inspiration to the world. The research Elements” (IYPT2019). carried out at LPI supports NASA’s efforts to explore the solar system. www.iypt2019.org www.lpi.usra.edu