Thomas H. Prettyman, Senior Scientist at the Planetary Science Institute, has been awarded funding from the NASA Innovative Advanced Concepts (NIAC) Program to develop a groundbreaking way to study the deep interiors of asteroids and comets using high-energy muons and other particles generated by galactic cosmic rays.

For comets, muon imaging could determine how volatiles are transported from the interior of the nucleus by directly imaging the vent system and related structures. And information on the porosity, density distribution and internal structure of small asteroids would provide data on their formation, evolution and impact history as well as providing information needed for developing planetary defense strategies.

"Our objective is to develop new types of spacecraft instrumentation and methods to map the deep interior of asteroids and comets with unprecedented detail - particularly those in near-Earth orbits," Prettyman said.

Prettyman, along with Steven L. Koontz of NASA Johnson Space Center and Lawrence S. Pinsky of the University of Houston will investigate the use of muons, pions and other subatomic particles formed when galactic cosmic rays strike the surfaces of these objects.

"High-energy muons, which can penetrate rocks hundreds of meters, could enable sampling of the inside of asteroids and comets to great depth and with high spatial resolution," Prettyman said.

"Muon imaging could also be applied to near-surface features of large planetary bodies, and would enable a better understanding of many aspects of their structural, chemical and physical properties."

Secondary muons produced by galactic cosmic ray collisions with Earth's atmosphere have already found application in volcanology, archeology, and national security.

Application to planetary science requires a thorough understanding of how these particles are produced and transported in planetary atmospheres and rocky soils, as well as the development of compact instrumentation suitable for flight, he said.

"Our team will determine whether there is a feasible path to the development of a new generation of nuclear instrumentation for deep imaging of asteroids and comets," Prettyman said. "Muon imaging could also be used to image layered deposits on Mars, as well as volcanic structures, and search for and characterize subsurface ice and other deposits there."

NIAC Phase I grants, like the one announced today funding Prettyman's project, aim to turn science fiction into fact. The Phase I awards are about $100,000 to conduct nine-month initial definition and analysis studies of a concept.

If the basic feasibility studies are successful, proposers can apply for Phase II funding of as much as $500,000 for two more years to mature the concept.