Table 1: Close approach circumstances of comet 79P/du-Toit-Hartley's orbit to that of Mars.
  $L_{\rm S}$ $\Delta$ ${v}_{\rm imp}$ Radiant (J2000)
  (deg) (AU) (km ${\rm s}^{-1}$) $\alpha$(deg) $\delta$(deg)
L1 173.7 0.0340 14.3 93.2 +18.4
L2 44.2 0.0547 14.3 119.7 +26.8
These were calculated as in Christou & Beurle (1999) using the cometary orbit in Table 2 and osculating orbital elements of Mars's orbit at the same epoch from HORIZONS. Here $\Delta$ is the orbit-to-orbit minimum distance, ${v}_{\rm imp}$ the velocity at the top of the Martian atmosphere and $\left(\alpha, \delta \right)$ the right ascension and declination of the theoretical radiant in the usual Earth-based (i.e. not Mars-based) reference frame.

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