We study the space of rational curves on del Pezzo surfaces in positive characteristic. For most primes
p
p
we prove the irreducibility of the moduli space of rational curves of a given nef class, extending results of Testa in characteristic
0
0
. We also investigate the principles of Geometric Manin’s Conjecture for weak del Pezzo surfaces. In the course of this investigation, we give examples of weak del Pezzo surfaces defined over
F
2
(
t
)
\mathbb F_2(t)
or
F
3
(
t
)
\mathbb {F}_{3}(t)
such that the exceptional sets in Manin’s Conjecture are Zariski dense.