  We have observed well-sampled phase curves for nine Trojan asteroids in B-,
V-, and I-bands. These were constructed from 778 magnitudes taken with the
1.3-m telescope on Cerro Tololo as operated by a service observer for the
SMARTS consortium. Over our typical phase range of 0.2-10 deg, we find our
phase curves to be adequately described by a linear model, for slopes of
0.04-0.09 mag/deg with average uncertainty less than 0.02 mag/deg. (The one
exception, 51378 (2001 AT33), has a formally negative slope of -0.02 +- 0.01
mag/deg.) These slopes are too steep for the opposition surge mechanism to be
shadow hiding (SH), so we conclude that the dominant surge mechanism must be
coherent backscattering (CB). In a detailed comparison of surface properties
(including surge slope, B-R color, and albedo), we find that the Trojans have
surface properties similar to the P and C class asteroids prominent in the
outer main belt, yet they have significantly different surge properties (at a
confidence level of 99.90%). This provides an imperfect argument against the
traditional idea that the Trojans were formed around Jupiter's orbit. We also
find no overlap in Trojan properties with either the main belt asteroids or
with the small icy bodies in the outer Solar System. Importantly, we find that
the Trojans are indistinguishable from other small bodies in the outer Solar
System that have lost their surface ices (such as the gray Centaurs, gray
Scattered Disk Objects, and dead comets). Thus, we find strong support for the
idea that the Trojans originally formed as icy bodies in the outer Solar
System, were captured into their current orbits during the migration of the gas
giant planets, and subsequently lost all their surface ices.
