Spitzer Space Telescope - General Observer Proposal #80116


IRAC Reflectances of Resonant KBOs and Scattered Disk Objects

Principal Investigator: Joshua Emery
           Institution: University of Tennessee 

     Technical Contact: Joshua Emery, University of Tennessee 

Co-Investigators: 
Michael Brown, Caltech                                                
Dale Cruikshank, NASA Ames Research Center                            
Cristina Dalle Ore, SETI Institute                                    
Yanga Fernandez, Univsersity of Central Florida                       
Wesley Fraser, Caltech                                                
John Stansberry, Univserity of Arizona                                
David Trilling, Northern Arizona University                           
Daine Wright, University of Tennessee                                 

Science Category: Kuiper belt objects 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 138.1 

Abstract:
We propose to measure broadband reflected fluxes of 25 Resonant Kuiper Belt
objects (KBOs), 16 scattered disk objects, and 6 Centaurs with IRAC in order to
determine surface compositions. The small bodies of the outer Solar System
provide probes of the statistical conditions, history, and interactions in the
Solar System. We focus in this proposal on two groups in order to extend our
previous observations to address the origin of the hot vs. cold classical
populations, the source and fate of Centaurs, and the overall spectral diversity
among KBOs. Many objects have been found occupying mean-motion resonances (MMRs)
with Neptune. The existence of these resonant populations led to the
understanding that Neptune had migrated outward during its history. Different
styles of migration have been suggested for Neptune, with distinct implications
for the distribution of the physical properties of resonant objects. We will
test which scenario is best explains the origin of resonant objects by searching
for the strong 3.6-micron absorption, further characterizing composition with
the 4.5-micron channel, and searching for trends among the various resonances
(i.e. with distance). Objects in the scattered disk have been or are currently
being gravitationally scattered by Neptune. The overall range of compositions
should be similar to that among the resonant population as a whole, since the
two groups sample the same primordial population, but the scattered disk objects
should be more well-mixed. We will use this group to identify endmember
compositions for the resonant bodies. This proposal directly builds on the
success of previous Spitzer observations that have characterized a small
sampling of the KBO diversity and obtained a deeper view of the other major
dynamical populations.