In Memoriam

Michael F. A’Hearn, 1940–2017 Leading researcher on structures and

compositions of comets Principal Investigators for Deep Impact

and EPOXI spacecraft missions Director of PDS’ Small Bodies node for more than 25 years Expert in mitigation of dangers from near-Earth objects

In Memoriam

Nathan Bridges, 1966–2017 Expert on sand movement, rock abrasion,

and ventifact formation on Earth and Mars Stalwart on the MER, MRO HiRISE, and

MSL science teams; co-I with Mars 2020 rover Active in planetary science societies; would have

been president of AGU Planetary Section

In Memoriam

Robert N. Clayton, 1930–2017 Discovered 17O anomalies; established oxygen

three-isotope geochemistry and taxonomy Pioneer of geothermometry from stable

isotope distributions Correctly predicted O isotope composition of the

Sun, confirmed by Genesis spacecraft samples Recipient of the Goldschmidt, Leonard, and Urey Medals;

elected to National Academy of Sciences

In Memoriam

John R. Holloway, 1940–2017 Pioneer in studies of volatiles and redox

conditions in magma systems Pathfinding experiments on Mars’ mantle

and formation of Mars’ basalts Early innovator in experimental trace element partitioning Inventor of the QuickPress, universally used for high-pressure

experimental petrology

In Memoriam

Elmar K. Jessberger, 1943–2017 Determined ages of lunar samples and

impact events by 40Ar-39Ar Chemistry and origins of solids from

Comet Halley (Giotto spacecraft) Analyses of Stardust samples (Comet 67P)

by TOF-SIMS

In Memoriam

Ursula B. Marvin, 1921–2018 Member of Apollo 17 Sample Preliminary

Examination Team Expert in lunar and meteorite petrology;

keen eye for the unusual and its explanation Member of early ANSMET expeditions, finder of

the first lunar meteorite Recipient of numerous awards, including “Service,” from

The Meteoritical Society; “Lifetime Achievement,” from Women in Science and Engineering; “History of Geology,” from GSA; “Sue Tyler Friedman,” from the Geological Society of London

In Memoriam

George E. McGill, 1931–2018 Pioneer planetary mapper of the Moon,

Mars, Venus, Mercury, Ganymede, and Earth Application of terrestrial analogs to explain

planetary geological structures Science team for Pioneer Venus and Magellan

In Memoriam

Tobias C. Owen, 1936–2017 Pioneer on origins and compositions of

planetary atmospheres Participant in NASA missions to the outer

solar system; a father to the Cassini mission Together with Carl Sagan, persuaded AAS to

form the Division of Planetary Sciences Author of seminal textbooks on the search for

extraterrestrial life

In Memoriam

Lawrence A. Taylor, 1938–2017 “Back Room” geologist supporting the

Apollo 17 Moon mission Hundreds of scientific contributions to

lunar geology and petrology Early contributor to lunar in situ

resource utilization (ISRU) Expert in terrestrial mantle petrology and

its diamonds