  Eta Carinae shows broad peaks in near-infrared (IR) JHKL photometry, roughly
correlated with times of periastron passage in the eccentric binary system.
After correcting for secular changes attributed to reduced extinction from the
thinning Homunculus Nebula, these peaks have IR spectral energy distributions
(SEDs) consistent with emission from hot dust at 1400-1700 K. The excess SEDs
are clearly inconsistent, however, with the excess being entirely due to
free-free wind or photospheric emission. One must conclude, therefore, that the
broad near-IR peaks associated with Eta Carinae's 5.5 yr variability are due to
thermal emission from hot dust. I propose that this transient hot dust results
from episodic formation of grains within compressed post-shock zones of the
colliding winds, analogous to the episodic dust formation in Wolf-Rayet binary
systems like WR140 or the post-shock dust formation seen in some supernovae
like SN2006jc. This dust formation in Eta Carinae seems to occur preferentially
near and after periastron passage; near-IR excess emission then fades as the
new dust disperses and cools. With the high grain temperatures and Eta Car's
C-poor abundances, the grains are probably composed of corundum or similar
species that condense at high temperatures, rather than silicates or graphite.
Episodic dust formation in Eta Car's colliding winds significantly impacts our
understanding of the system, and several observable consequences are discussed.
