  We explore the likelihood that early remains of Earth, Mars, and Venus have
been preserved on the Moon in high enough concentrations to motivate a search
mission. During the Late Heavy Bombardment, the inner planets experienced
frequent large impacts. Material ejected by these impacts near the escape
velocity would have had the potential to land and be preserved on the surface
of the Moon. Such ejecta could yield information on the geochemical and
biological state of early Earth, Mars and Venus. In order to determine whether
the Moon has preserved enough ejecta to justify a search mission, we calculate
the amount of Terran material incident on the Moon over its history by
considering the distribution of ejecta launched from the Earth by large
impacts. In addition, we make analogous estimates for Mars and Venus. We find,
for a well mixed regolith, that the median surface abundance of Terran material
is roughly 7 ppm, corresponding to a mass of approximately 20,000 kg of Terran
material over a 10 x 10 square km area. Over the same area, the amount of
material transferred from Venus is 1-30 kg, and material from Mars as much as
180 kg. Given that the amount of Terran material is substantial, we estimate
the fraction of this material surviving impact with intact geochemical and
biological tracers.
