Archival observations of active asteroid 313P/GIBBS

We present prediscovery observations of active asteroid 313P/(2014 S4) Gibbs taken in 2003 and 2004. Sloan Digital Sky Survey observations from 2003 establish that, after 133P/Elst–Pizarro and 238P/Read, 313P is only the third main-belt active asteroid to show mass loss in different orbits. This repetitive activity is consistent with mass loss driven by the sublimation of ice. A Finson-Probstein model is used to analyze the morphology of the object, showing that the activity was continuous but declining steadily over two months of observation in 2003. Ejected dust particles are dominated by relatively large sizes with radii from ∼25 to ∼600 μm. We estimate from photometry the dust mass loss rate to be $\lesssim 0.2$ kg s⁻¹. In contrast, Subaru telescope observations from 2004 show no evidence for mass loss and suggest a bare nucleus. The color, nucleus size, and the mass loss rates of 313P measured in 2003 are consistent with published values obtained from data taken in 2014. However, the effective cross-section was larger than in 2014 by a factor of ∼2, indicating a decline in the activity between orbits. A new orbital solution gives a 5σ upper limit to the transverse non-gravitational parameter $A_2\lesssim 2.45\times {10}^{-8}$ AU day⁻².