  The escape of hot O and C atoms from the present martian atmosphere during
low and high solar activity conditions has been studied with a Monte-Carlo
model. The model includes the initial energy distribution of hot atoms,
elastic, inelastic, and quenching collisions between the suprathermal atoms and
the ambient cooler neutral atmosphere, and applies energy dependent total and
differential cross sections for the determination of the collision probability
and the scattering angles. The results yield a total loss rate of hot oxygen of
$2.3-2.9\times 10^{25}\,{\rm s}^{-1}$ during low and high solar activity
conditions and is mainly due to dissociative recombination of O$_2^+$ and
CO$_2^+$. The total loss rates of carbon are found to be $0.8$ and $3.2\times
10^{24}\,{\rm s}^{-1}$ for low and high solar activity, respectively, with
photodissociation of CO being the main source. Depending on solar activity, the
obtained carbon loss rates are up to $\sim 40$ times higher than the CO$_2^+$
ion loss rate inferred from Mars Express ASPERA-3 observations. Finally,
collisional effects above the exobase reduce the escape rates by about
$20-30\,\%$ with respect to a collionless exophere.
