Fossils are all over Mars, period.

There are two mainways, it is thought, by which
amino acids make their way into meteorite parent bodies. The
first is through the Strecker synthetic process in liquid water
(Peltzer et al. 1984) on the parent body itself. This process requires
HCN, which has a limited e-folding half-life (0.37-life,
or the time in which the concentration decreases to 1=e of its initial
value) in liquid water at 273 K of »104 years (Peltzer et al.
1984). Thus, the amino acids would have been formed within
»104 years within the parent body. After 104 years, the synthesis
would be over (barring some source of HCN), but liquid water
might persist.
The second method is incorporation of amino acids into the
parent body through accretion of previously synthesized molecules
from the interstellar medium (ISM). Spectroscopic observation
of grains in the ISM (Pendleton et al. 1994) reveals
features attributable to the C–H stretch in organic material.
Flores et al. (1977) and Norden (1977) showed experimentally
that amino acids could have an enantiomeric excess imposed
by selective destruction by circularly polarized ultraviolet radiation,
such as that from the poles of a neutron star (Bonner
1991) or an active star-forming region (Bailey et al. 1998). The
conditions for creating such excesses are not uncommon, and
chiral excesses of up to a few percent may be created. It is not
known whether or to what degree the molecular cloud that collapsed
to form our solar nebula experienced these conditions.
However, ample evidence exists for incorporation of supernova
ejecta into meteorites (Zinner 1998); consequently, exposure of
this material to circularly polarized radiation from a neutron
star, the supernova residuum, might be inferred.