  We study the efficiency of the noble gases sequestration by the ion H3+ in
the form of XH3+ complexes (with X = argon, krypton or xenon) in gas phase
conditions similar to those encountered during the cooling of protoplanetary
disks, at the epoch of icy planetesimals formation. We show that XH3+ complexes
form very stable structures in the gas phase and that their binding energies
are much higher than those involved in the structures of X-H2O hydrates or pure
X-X condensates. This implies that, in presence of H3+ ions, argon, krypton or
xenon are likely to remain sequestrated in the form of XH3+ complexes embedded
in the gas phase rather than forming ices during the cooling of protoplanetary
disks. The amount of the deficiency depends on how much H3+ is available and
efficient in capturing noble gases. In the dense gas of the mid-plane of solar
nebula, H3+ is formed by the ionization of H2 from energetic particles, as
those in cosmic rays or those ejected by the young Sun. Even using the largest
estimate of the cosmic rays ionization rate, we compute that the H3+ abundance
is two and three orders of magnitude lower than the xenon and krypton
abundance, respectively. Estimating the ionization induced by the young Sun, on
the other hand, is very uncertain but leaves the possibility to have enough H3+
to make krypton and xenon trapping efficent. Finally, additional source of H3+
formation may be provided by the presence of a nearby supernova, as discussed
in the literature. Recent solar system observations show a deficiency of Ar,
and, even more, of Kr and Xe in Titan and in comets. In this article, we
consider the possibility that this deficiency is caused by the afore-mentioned
process, namely trapping of those noble gases by H3+ ions in the solar nebula.
