  A recent X-ray observation has shown that the radio pulsar PSR B0943+10, with
clear drifting subpulses, has a much smaller polar cap area than that of
conventional pulsars with mass of $\sim\msun$ and radius of $\sim10$ km. Zhang
et al. (2005) addressed then that this new result conflicts with the standard
vacuum gap model. Nonetheless, the discrepancy could be explained if PSR
B0943+10 is actually a low-mass quark star. It is found that the potential drop
in the open-field-line region of oblique pulsars (i.e., inclination angle
$\alpha\neq 0$) might be $\sim 10^2$ times that of aligned pulsars, and that
PSR B0943+10 with $\alpha = 12.4^{\rm o}$ could be well above the deathline. We
thus conclude that the Ruderman-Sutherland-type vacuum gap model still works
well for this pulsar if it is a bare quark star with a mass of $\sim
0.02M_\odot$ and a radius of $\sim 2.6$ km.
