Department News

We hope you will join us in remembering our friend and colleague Adam Showman with a gift of any size for the Adam P. Showman Distinguished Visiting Lectureship. With your generous support, we plan to establish an endowed fund that will allow LPL to bring guest lecturers to campus in Adam's memory in perpetuity. We can think of no better way to honor him than to bring exceptional planetary scientists with similarly broad interests to engage with and inspire our students, just as Adam did. Thirty donors have already pledged a total of more than $10,000.

by Mikayla Mace, University Communications

Professor Alfred McEwen's mission proposal to one of Jupiter's moons is among the four finalists for the next $500 million Discovery mission. The Discovery Program funds midsize principal-investigator-led spacecraft missions designed to unlock the mysteries of the solar system and our origins.

The four finalists will now embark on a one-year study before NASA expects to make its final selection in 2021.

If selected, the Io Volcano Observer, or IVO, mission will orbit Jupiter and make 10 close flybys of its moon Io – the most volcanically active world in the solar system – to determine if the moon has a magma ocean hidden beneath its vibrant, pockmarked surface.

"IVO will revolutionize our understanding of a truly spectacular, volcanically active world, with volcanic eruption scales seen on Earth only during mass extinctions," said Alfred McEwen, IVO principal investigator and Regents' Professor of planetary sciences.

"To become a finalist for the next phase of the NASA Discovery Program is a tremendous accomplishment," said University of Arizona President Robert C. Robbins. "If we are selected in the final round, IVO will become the second University of Arizona-led Discovery mission following the Phoenix Mars Lander, and the third University of Arizona-led NASA planetary mission, following the current OSIRIS-REx mission. The University of Arizona has a long history of space research that began with mapping the moon and has included most NASA planetary missions. This is a phenomenal step for our continuing leadership in space exploration."

The mission would carry a suite of science experiments to map Io's surface, measure its heat flow, monitor volcanic activity, measure the composition of surface lavas and gases erupting from Io, and measure the magnetic and gravitational fields near Io that inform us about the internal structure and distribution of magma.

"Magma oceans were common among the terrestrial planets – Mercury, Venus, Earth, Mars and the moon – soon after the planets formed," McEwen said, "and are an integral piece of planet formation and evolution. They are responsible for the formation of metal cores and degassing to produce the planet's oceans and atmosphere."

These magma oceans cooled and solidified billions of years ago, but great quantities of magma are currently produced in Io from tidal heating as it is stretched and squished by its gravitational dance with the giant Jupiter and sister moons, changing its shape every 42-hour orbit.

The tidal heating could be so great that it sustains an entire magma ocean. Or Io may lack a continuous liquid layer and instead resemble the terrestrial planets soon after their magma oceans solidified. Either way, Io can inform us about ancient volcanic and tectonic processes on Earth and other worlds, and about countless exoplanets that may resemble Io, according to McEwen.

"The NASA Discovery Program enables universities like ours to make exquisite use of our remarkable scientists to peer into the formations and workings of planetary bodies, comets and asteroids and truly discover new knowledge that illuminates our place in the universe," said Senior Vice President for Research and Innovation Elizabeth "Betsy" Cantwell. "The discoveries resulting from this program also advance our ability to innovate broadly around space technologies and new entrepreneurial opportunities, opening many more doors for advances that benefit life on Earth."

The IVO spacecraft and several science instruments would be built and managed by the Applied Physics Laboratory. UArizona would lead science operations and the potential development of a camera in collaboration with students. Other key partners are the Jet Propulsion Laboratory for gravity science and spacecraft navigation, the University of California, Los Angeles for magnetometers, the German Aerospace Center for an infrared instrument and the University of Bern in Switzerland for a mass spectrometer. 

Adam P. Showman passed away unexpectedly on March 16, 2020, at his home in Tucson, AZ. His untimely passing has been felt widely in the international planetary science community which has lost an outstanding theorist, dedicated teacher of many graduate students, and a sought-after collaborator to a world-wide network of exoplanet astronomers.

Adam Showman was born on October 9, 1968 in Palo Alto, CA. He studied physics at Stanford University, where he earned a B.S. in 1991. He earned a Ph.D. at Caltech in 1999, with a dissertation on the atmosphere of Jupiter as well as the geophysics of its largest moon Ganymede. After two short postdoc stints at the University of Louisville and NASA Ames, Dr. Showman joined the Lunar and Planetary Laboratory at the University of Arizona as an Assistant Professor in 2001; he was named full Professor in 2012. He was recently named a Galileo Circle Fellow of the University of Arizona (2018) and a Fellow of the American Geophysical Union (2019).

During his career, Dr. Showman directly advised eleven graduate students and mentored many more across the disciplines of planetary science, atmospheric sciences and geosciences. He was a renowned teacher who enjoyed explaining to his students the complicated details of planetary physics and hammering out ideas to solve research problems. He developed eight different courses in the planetary sciences, including two completely new graduate courses, with course notes that are treasured by his students. His early pioneering research on the atmospheric dynamics of exoplanets (Showman & Guillot, 2002, Astron. & Astrophys. 385:166-180) has been the paradigm of hot gas giant atmospheric circulation models ever since. This work showed that the difference between the day and night side on hot Jupiters would drive strong eastward equatorial winds, comparable to or greater than the speed of sound in the medium. Showman and his collaborators worked out in detail the theoretical predictions that were spectacularly verified in subsequent observations, profoundly shaping the field. Showman extended his innovative theoretical models beyond hot gas giant planets, to tidally-locked and fast-rotating planets of smaller sizes and cooler temperatures as well as to the larger and warmer brown dwarfs. He was deeply involved in the exoplanet science community, collaborating with many observers to interpret their observations of exoplanet atmospheres and working with theorists to advance modeling techniques. He served the planetary science community in many professional roles, including as Editor of the international planetary science journal, Icarus.

Dr. Showman also made notable contributions to our understanding of atmospheric circulation in the four giant planets in our own solar system and of the geophysics of the Galilean satellites. Showman and collaborators (Kaspi, Flierl & Showman, 2009, Icarus 202:525-542) used an anelastic general circulation model to explore the deep winds on Jupiter, where density varies by more than four orders of magnitude from the atmosphere to the interior. They find that the winds are aligned with the rotation axis but decay gradually with depth. Their predictions were verified by the Juno mission, which has measured the higher harmonics of Jupiter’s gravity field and has shown that the zonal winds extend 3000 km below the visible clouds, a major breakthrough in planetary science. On the icy Galilean satellites, Europa, Ganymede and Callisto, Showman’s work encompassed interior thermal structures and their interplay with the orbital dynamics (the formation of a water ocean in Ganymede and implications for the magnetic field detected by the Galileo Orbiter, Showman et al., 1997, Icarus 129:367-383), the peculiar tectonics of Ganymede (graben formation, Showman et al., 2004, Icarus 172:625-640), the putative convection in Europa’s ice shell (Showman & Han, 2004, JGR-Planets 109:E01010), and the unstable lithosphere of Enceladus (Bland, Beyer & Showman, 2007, Icarus 192:92-105). Dr. Showman was equally in command of both gas giant atmospheric dynamics and geophysical fluid dynamics, an astonishing combination of expertise widely admired by his colleagues.

Students and colleagues alike knew Dr. Showman as a fount of knowledge and ideas which he shared generously and widely. He was a friend to many who fondly remember his spirit of adventure and abiding curiosity. In his teenage years, after a family trip to China, he developed a fascination for Chinese culture; he travelled frequently to China and became proficient in the Mandarin language. Dr. Showman is survived by his daughter, Arwen, his brother, Ken, and his parents, Pete and Dinah Showman.

Renu Malhotra⁽¹⁾ and Andrew P. Ingersoll⁽²⁾

^{(text prepared for Icarus)}

Fortney, J.J. Adam P. Showman. Nat Astron (2020)

In Memoriam: Adam Showman

Dr. Stefano Nerozzi joined LPL in January as a Postdoctoral Research Associate working with Professor Jack Holt. He is leading a NASA-funded project to study the geological evolution of outflow channel systems in Utopia Planitia, Mars. This project integrates several remote sensing techniques to unravel the history of water in this region, and especially how it shaped the surface and interacted with volcanic and impact processes. Stefano is also interested in the study of Mars' cryosphere, analyzing gamma ray spectrometer elemental concentration data at boulder halo sites and continuing his doctoral work on ancient icy sedimentary deposits in Planum Boreum using radar sounding and visible imagery.

Stefano grew up near Bologna, Italy. He earned his B.S. in Geological Sciences in 2011 and his M.Sc. in Geology and Land Management in 2014 at the University of Bologna. During the second half of his M.Sc. program, Stefano participated in an exchange program at the University of Texas at Austin, where he also received a Ph.D. in Geological Sciences in 2019 with Professor Jack Holt. His dissertation focused on unraveling the morphological and stratigraphic signature of global climate events within the Planum Boreum of Mars.

Aside from work, Stefano enjoys a large number of hobbies and interests, including DIY electronics, amateur radio, outdoor activities, role-play games, and building ecospheres.

Congratulations to Cecilia Leung, Hamish Hay, and Nathanial Hendler, LPL's newest alumni!

Cecilia defended her dissertation, Regional Atmospheric Dynamics of Water on Mars, on January 7. Regents' Professor Alfred McEwen served as her advisor. Cecilia is currently a NASA Postdoctoral Program Fellow at JPL, working with Dr. Leslie Tamppari.

On March 6, Hamish defended his dissertation, A Tale of Tides: Icy Satellites, Subsurface Oceans, and Tightly-Packed Planetary Systems. Hamish's advisor was Associate Professor Isamu Matsuyama. Hamish will begin a postdoctoral appointment at JPL with Dr. Robert Pappalardo.

Nathanial Hendler made department history by being the first LPL student to defend a dissertation via remote, on May 20. His dissertation was titled Evolution of Protoplanetary Dust-Disk Sizes. Nathanial was advised by Associate Professor Ilaria Pascucci.

We would like to thank all those who have donated to LPL in 2018 and 2019. Thanks to everyone for helping LPL accomplish things we would not be able to without you. 

by Dolores Hill

This fall, LPL staff and students were busy reaching out not only to the local community but all of Arizona as well. Several events centered around moonfest, the University of Arizona’s extended celebration of the Apollo moon landings and future lunar exploration. We were able to “multiply our impact” at many public events with engagement by the Space Imagery Center, LPL Graduate Student Outreach, and OSIRIS-REx, thereby allowing us to reach more than 7000 people.

Spacefest brought together astronauts, artists, and space aficionados from all over the world including quite a few LPL alumni and longtime “friends of LPL” who stopped by the STEAM tables to say hello! We provided educational activities and exhibits for a range of ages and backgrounds from the STEM Showcase at Ocotillo Ridge Elementary School to Southern Arizona Technology Council industry leaders at the Tucson Convention Center. We presented the OSIRIS-REx mission’s “Final Four” Candidate sites in UArizona’s Research Innovation and Impact (RII) tent during UArizona homecoming and the Mt. Lemmon SkyCenter Office and Science Shop open house that coincided with the transit of Mercury.

LPL and baseball? Sure! On July 20, LPL joined Raytheon for Space Day at the Arizona Diamondbacks baseball game in Phoenix and also provided an assortment of OSIRIS-REx hands-on activities and demonstrations for Goddard Space Flight Center’s STEM Education Day at Fenway Park in Boston. LPL Director Tim Swindle kindly volunteered to staff the Diamondbacks outreach event—double duty on July 20 after hosting LPL’s Summer Science Saturday Apollo anniversary celebration in Tucson. In addition to external community events, we conducted OSIRIS-REx and meteorite tours for Smithsonian Astrophysical Observatory volunteers and presentations for Kitt Peak docents, IEEE Tucson and Sierra Vista, Osher Lifelong Learning Institute, Prescott Astronomy Club, and the Huachuca Astronomy Club. Summer and fall were jam-packed with wonderful opportunities to showcase LPL and our contributions to planetary science, past, present, and future.

OSIRIS-REx engineer Josh Nelson answers questions from Space Shuttle astronaut Linda Godwin in the Spacefest STEAM area. (Godwin was a crewmate of LPL  alumnus astronaut Tom Jones on STS-59).

Graduate student Indujaa Ganesh, ready to share many worlds at Spacefest 2019.

by Christopher Hamilton

For the Fall 2019 semester (October 17–21), the Lunar and Planetary Laboratory (LPL) graduate student field trip class (PTYS 594A) ventured to the Zuni–Bandera Volcanic Field in New Mexico. The volcanic field is part of the Jemez Lineament, which extends from central Arizona to northeastern New Mexico. The Jemez Lineament includes approximately 100 volcanoes, which erupted during the past 16 Ma. This semester’s field trip primarily focused on lava tubes within the Hoya de Cibola lava flow-field, lava stratigraphy and inflation features within McCarty's lava flow-field, and Bandera Crater.

During the first day of the field trip, the group met with members of the National Park Service and travelled with Ranger Nicholas (“Nick”) Poister to the Haltun Cave. This provided students with a unique opportunity to explore an exceptional lava tube system within the El Malpais National Monument. On the second and third days, the class examined 20 m (65’) thick lava flow units within the McCarty's lava flow-field. This approximately 3000-year-old lava flow-field was emplaced over older Hoya de Cibola lava units as well as Holocene alluvial sediments. McCarty's lava flow units include outstanding examples of inflation features, which formed as the flows were supplied by lava through internal pathways and gradually swelled like a balloon. Similar structures are identified on Mars and provide valuable information about eruption timescales. Additionally, using ground-penetrating radar (GPR) and Global Positioning System (GPS) measurements, the class examined McCarty's lava units, estimating their thickness and identifying buried contacts with older materials (i.e., lava and sedimentary units) as analogs for imaging subsurface interfaces within volcanic terrains on Mars using the shallow radar (SHARAD) instrument. During the final day of the field trip, they visited Bandera Crater and an “ice cave” formed where meteoric water infiltrates into a cold lava tube to form perennial ice deposits.

This semester’s field trip involved the increased usage of high-tech (e.g., GPR and GPS) and low-tech (e.g., notebooks, measuring tape, compass, and hand lens) tools to develop detailed measurements and descriptions, with a focus on lava tube and other lava flow structures as analogs for volcanic terrains on the Moon and Mars, as well as elsewhere in the Solar System. Next semester, the field trip will explore a different region of the Southwest, with a trip to the Mojave Desert.