  2009 MS9 is a trans-Neptunian object (TNO) whose perihelion brings it close
to the distance where some long period comets are seen to become active.
Knowing this, and the fact that this object appears to brighten in excess of
it's predicted nucleus brightness suggests that 2009 MS9 has a delayed onset of
activity brought on by the sublimation of a species more volatile than water.
In this paper we characterize 2009 MS9's physical properties and investigate
potential outgassing through composite images, sublimation models, and
measurements of spectral reflectivity. We find that deep composite images of
the object at various epochs along its orbit show no evidence of dust yet place
sensitive limits to the dust production. We estimate the nucleus radius to be
11.5 km $\pm 3.5$ km using thermal IR modeling from NEOWISE data and use this
and data pre-perihelion to estimate a geometric albedo of 0.25. We compare a
CO-sublimation activity model to its post perihelion heliocentric light curve
and find this data supports an active fractional area of $5 \times 10^{-6}$
assuming 2 $\mu$m sized grains and other typical comet parameters. The spectral
reflectivity of the surface materials obtained with the Gemini Observatory and
CFHT at different epochs shows a reddening spectral slope. We compare the
physical properties of 2009 MS9 to both TNO and comet populations, and
speculate that 2009 MS9's reddening may be due to the buildup of a dust mantle
on the surface and could be an explanation of why TNOs exhibit a color
bimodality.
