Dr. Julie Stopar
More About Dr. Stopar’s Research
The Lunar Reconnaissance Orbiter Camera (LROC) images have revealed paths where rivers of once-molten rock flowed on the Moon. Some of these rock-rivers are surprising because they occurred on the rims of small, young impact craters. Rock can be melted during the extreme pressures and temperatures associated with an impact cratering event, but craters less than about 5 km in diameter were once thought to not produce enough melted rock in order to initiate flows. Ponds of melted rock can now also be seen in the floors of craters only a few hundred meters in diameter.
Meyer, H. M., J. D. Stopar, S. S. Bhiravarasu, B. W. Denevi, M. S. Robinson (2019) Morphology and physical properties of Orientale light plains and associated flow features on the Moon, 50th Lunar and Planetary Science Conference, abstract 2581.
Meyer, H., M. S. Robinson, J. D. Stopar (2017) A new look at Surveyor VII from the Lunar Reconnaissance Orbiter Camera, Lunar and Planetary Science Conference 48, abstract 2631.
Cohen B. A., Lawrence S. J., Petro N. E., Bart G. D., Clegg-Watkins R. N., Denevi B. W., Ghent R. R., Klima R. L., Morgan G. A., Spudis P. D., and Stopar J. D. (2016) Identifying and Characterizing Impact Melt Outcrops in the Nectaris Basin. 47th Lunar and Planetary Science Conference, abstract 1389.
Giguere T. A., Hawke B. R., Peterson C. A., Lawrence S. J., Stopar J. D., and the LROC Science Team (2015) Impact Melts At Glushko Crater – LROC Revelations. 46th Lunar and Planetary Science Conference, abstract 1308.
Stopar J. D., Hawke B. Ray, Robinson M. S., Denevi B. W., Giguere T. A., and Koeber S. D. (2014) Occurrence and mechanisms of impact melt emplacement at small lunar craters. Icarus, 243: 337-357, http://dx.doi.org/10.1016/j.icarus.2014.08.011
The shapes and depths of impact craters, determined from LROC NAC stereo-derived topography (digital terrain models), indicate that craters less than about 400 meters in diameter are usually relatively shallow (lower depth-to-diameter ratios) compared to their larger (simple) crater counterparts. This was an unexpected discovery in the LRO/LROC data! Various factors can affect the morphologies and relative depths of small craters – including impactor and target properties, impact angle and velocity, and degradation (such as landslides). However, these small and shallow craters are consistent with formation in a regolith target and reflect local regolith thickness and evolution.
Stopar, J. D., M. S. Robinson, O. S. Barnouin, A. S. McEwen, E. J. Speyerer, S. Sutton, M. R. Henriksen (2017) Relative depths of simple craters and the nature of the lunar regolith. Icarus 298: 34-48,doi:10.1016/j.icarus.2017.05.022Clegg-Watkins R. N., Jolliff B. L., Boyd A., Robinson M. S., Wagner R., Stopar J. D., Plescia J. B., and Speyerer E. J. (2016) Photometric characterization of the Chang’e-3 landing site using LROC NAC images. Icarus, 273: 84-95, http://dx.doi.org/10.1016/j.icarus.2015.12.010.
Localized Volcanic Deposits
A variety of relatively small-area volcanic deposits have erupted onto the Moon’s surface over time. These deposits include silicic lava flows and domes, irregular mare patches (or IMPs), and pyroclastics.
Small, cinder-cone-like, volcanic vents, each less than 3 km in diameter and a few hundred meters in height, have been recently resolved in the high-resolution LROC images. We can now resolve individual layers including spatter and lava flows. Enhanced concentrations of small volcanic vents superposed on several large topographic rises suggest mantle hot-spots, where volcanism may have occurred intermittently over billions of years.
LROC images also reveal the crisp, fresh morphologies of the IMPs that signify recent eruptions, and that the Moon could have been volcanically active in the last 100 million years. A discovery that is surprising because most scientists thought that the Moon’s interior had cooled long ago (nearly one billion years ago)!
Some steep-sided topographic rises, or domes, are associated with unusual compositions. Using recent LROC images, flow fronts and stratigraphic relationships of these domes have finally been revealed. Several of the steep-sided rises, such as the Lassell Massif, are composed of erupted silicic lava flows, pyroclastics, and other volcanic deposits.
Stopar J. D., L. R. Gaddis, B. H. N. Horgan, M. J. McBride, S. J. Lawrence, K. A. Bennett (2019) Outcrop-scale investigations of the pyroclastic deposits in J. Herschel crater. 50th Lunar and Planetary Science Conference, abstract 1937.
Madrid M. and Stopar J. (2018) The age of volcanism north and east of the Aristarchus crater. 49th Lunar and Planetary Science Conference, abstract 1071.
Stopar J. D., Lawrence S. J., Robinson M. S., Gaddis L. R., Giguere T. A., Sutton S., and the LROC Team (2016) Proximal Volcanic Deposits: Roughness and Implications for Lunar Volcanism. 47th Lunar and Planetary Science Conference, abstract 2555.
Ashley J. W., Robinson M. S., Stopar J. D., Glotch T. D., Hawke B. Ray, van der Bogert C. H., Hiesinger H., Lawrence S. J., Jolliff B. L., Greenhagen B. T., Giguere T. A., and Paige D. A. (2016) The Lassell massif—A silicic lunar volcano. Icarus, 273: 248-261, http://dx.doi.org/10.1016/j.icarus.2015.12.036.
Braden S. E., Stopar J. D., Robinson M. S., Lawrence S. J., van der Bogert C. H., and Hiesinger H. (2014) Evidence for basaltic volcanism on the Moon within the past 100 million years. Nature Geoscience 7: 787–791 http://dx.doi.org/10.1038/ngeo2252
Lawrence S. J., Stopar J. D., Hawke B. Ray, Greenhagen B. T., Cahill J. T. S., Bandfield J. L., Jolliff B. L., Denevi B. W., Robinson M. S., Glotch T. D., Bussey D. B. J., Spudis P. D., Giguere T. A., and Garry W. B. (2013) LRO observations of morphology and surface roughness of volcanic cones and lobate lava flows in the Marius Hills. J. Geophys. Res. Planets, 118: 615–634, http://dx.doi.org/10.1002/jgre.20060
There are presently no known samples of small-area volcanic deposits in our sample collection. Such deposits, due to their potential to inform interior processes and volatile inventories, are high-priority exploration targets. Other areas of the Moon are important destinations, too, because of their unusual compositions, unique solar illumination conditions (e.g., shaded polar regions), or their potential to constrain the sequence and timing of key events on the Moon (for example, earliest basin formation, or youngest lava flow). By using geologic knowledge gained by studying data from LRO and other spacecraft, we can better plan successful and useful forays to the lunar surface in the years to come.
Stopar J. D., S. J. Lawrence, L. Graham, J. Hamilton, B. Denevi, K. K. John, H. M. Meyer, J. E. Gruener, J. Nunez, D. S. Draper, B. J. Mass, J. M. Greenberg (2019) Ina, Moon: geologic setting, scientific rationale, and site characterization for a small planetary lander concept. Planetary and Space Sciences 171: 1-16, doi:10.1016/j.pss.2019.04.003
Stopar J. and Meyer H. (2019) Topographic Map Series of the Moon’s South Pole. Lunar and Planetary Institute Regional Planetary Image Facility, LPI Contributions 2169 to 2182. Lunar South Pole Atlas (maps).
Speyerer E. J., Lawrence S. J., Stopar J. D., Gläser P., Robinson M. S., and Jolliff B. L. (2016) Optimized traverse planning for future polar prospectors based on lunar topography. Icarus 273: 337-345, http://dx.doi.org/10.1016/j.icarus.2016.03.011
Stopar J. D., Lucey P. G., Sharma S. K., Misra A. K., and Hubble H. W. (2004) A remote Raman system for planetary exploration: Evaluating remote Raman efficiency. Instruments, Methods, and Missions for Astrobiology VII. Edited by Hoover, Richard B.; Rozanov, Alexei Y. Proceedings of the SPIE, Volume 5163, pp. 99-110
Other Research Interests
My other research is focused on determining the results of water-driven chemical reactions throughout the Solar System, including low-temperature mineralization on Mars and water-mineral interfaces at the poles of the Moon.
Stopar, J. D., B. Jolliff, E. Speyerer, E. Asphaug, M. Robinson (2018) Potential Impact-induced Water-solid Reactions on the Moon. Planetary and Space Sciences 162: 157-169, doi:10.1016/j.pss.2017.05.010
Stopar J. D., Taylor G. J., Velbel M. A., Norman M. D., Vicenzi E. P., and Hallis L. J. (2013) Element abundances, patterns, and mobility in Nakhlite Miller Range 03346 and implications for aqueous alteration. Geochimica et Cosmochimica Acta 112: 208-225, http://dx.doi.org/10.1016/j.gca.2013.02.024
Stopar J. D., Taylor G. J., Hamilton V. E., and Browning L. (2006) Kinetic model of olivine dissolution and extent of aqueous alteration on Mars. Geochimica et Cosmochimica Acta 70: 6136-6152, http://dx.doi.org/10.1016/j.gca.2006.07.039
Taylor G. J., Stopar J. D., Boynton W. V., Karunatillake S., Keller J. M., Brückner J., Wänke H., Dreibus G., Kerry K. E., Reedy R. C., Evans L. G., Starr R. D., Martel L. M. V., Squyres S. W., Gasnault O., Maurice S., d'Uston C., Englert P., Dohm J. M., Baker V. R., Hamara D., Janes D., Sprague A. L., Kim K. J., Drake D. M., McLennan S. M., and Hahn B. C. (2006) Variations in K/Th on Mars, Journal of Geophysical Research 111: http://dx.doi.org/10.1029/2006JE002676