The asteroid orbits the Sun at a distance of 2.1–2.8 AU once every 3 years and 11 months (1,419 days). Its orbit has an eccentricity of 0.13 and an inclination of 6° with respect to the ecliptic.
The spectrum of this object indicates that it is an S-type asteroid with both low and high calcium forms of pyroxene on the surface, along with less than 20% olivine. The high-calcium form of pyroxene forms 40% or more of the total pyroxene present, indicating a history of igneous rock deposits. This suggests that the asteroid underwent differentiation by melting, creating a surface of basalt rock.
The mass of Thetis has been calculated from perturbations by 4 Vesta and 11 Parthenope. In 2007, Baer and Chesley calculated Thetis to have a mass of 1.2×1018 kg[a] with a density of 3.21 g/cm3.
^ abMichalowski, T.; Velichko, F. P.; Di Martino, M.; Krugly, Yu. N.; Kalashnikov, V. G.; Shevchenko, V. G.; et al. (December 1995). "Models of four asteroids: 17 Thetis, 52 Europa, 532 Herculina, and 704 Interamnia". Icarus. 118 (2): 292–301. Bibcode:1995Icar..118..292M. doi:10.1006/icar.1995.1192.