Context : Main belt comets ( MBCs ) are a peculiar class of volatile-containing objects with comet-like morphology and asteroid-like orbits .
However , MBCs are challenging targets to study remotely due to their small sizes and the relatively large distance they are from the Sun and the Earth .
Recently , a number of weakly active short-period comets have been identified that might originate in the asteroid main belt .
Among all of the known candidates , comet 66P/du Toit has been suggested to have one of the highest probabilities of coming from the main belt .

Aims : The main goal of this study is to investigate the physical properties of 66P via spectroscopic and imaging observations to constrain its formation conditions .
In particular , the isotopic abundance ratio and the ortho-to-para ratio ( OPR ) of gaseous species can be derived via high-resolution spectroscopy , which is sensitive to the formation temperature of the nucleus .

Methods : We obtained medium and high-resolution spectra of 66P from 300-2500 nm with the X-shooter and the UVES instruments at the Very Large Telescope in July 2018 .
We also obtained a series of narrow-band images of 66P to monitor the gas and dust activity between May and July 2018 with TRAPPIST-South .
In addition , we applied a dust model to characterize the dust coma of 66P and performed dynamical simulations to study the orbital evolution of 66P .

Results : We derive the OPR of ammonia ( NH _ { 3 } ) in 66P to be 1.08 \pm 0.06 , which corresponds to a nuclear spin temperature of \sim 34 K. We computed the production rates of OH , NH , CN , C _ { 3 } , and C _ { 2 } radicals and measured the dust proxy , Af \rho .
The dust analysis reveals that the coma can be best-fit with an anisotropic model and the peak dust production rate is about 55 kg s ^ { -1 } at the perihelion distance of 1.29 au .
Dynamical simulations show that 66P is moderately asteroidal with the capture time , t _ { cap } \sim 10 ^ { 4 } yr .

Conclusions : Our observations demonstrate that the measured physical properties of 66P are consistent with other typical short-period comets and differ significantly from other MBCs .
Therefore , 66P is unlikely to have a main belt origin .