  Ultra High Energy (UHE) Cosmic Rays, UHECR, may graze high altitude
atmosphere leading to horizontal upward air-showers. Also PeVs electron
antineutrino hitting electron in atmosphere may air-shower at W boson resonant
mass. On the other side ultra high energy muon and electron neutrinos may also
lead, by UHE neutrinos mass state mixing, to the rise of a corresponding UHE
Tau neutrino flavor; the consequent UHE tau neutrinos, via charge current
interactions in matter, may create UHE taus at horizons (Earth skimming
neutrinos or Hor-taus) whose escape in atmosphere and whose consequent decay in
flight, may be later amplified by upward showering on terrestrial, planetary
atmospheres. Indeed because of the finite terrestrial radius, its thin
atmosphere size its dense crust, the UHE tau cannot extend much more than 360
kilometers in air, corresponding to an energy of about 7.2 EeV, near but below
GZK cut-off ones; on the contrary Jupiter (or even Saturn) may offer a wider,
less dense and thicker gaseous layer at the horizons where Tau may loose little
energy, travel longer before decay and rise and shower at 4-6 10^{19} eV or ZeV
extreme energy. Titan atmosphere may open a rare window of opportunity for
Up-ward Taus at PeVs. Also solar atmosphere may play a role, but unfortunately
tau-showers secondaries maybe are too noisy to be disentangled, while Jupiter
atmosphere, or better, Saturn one, may offer a clearer imprint for GZK (and
higher Z-Burst) Tau showering, well below the horizons edges.
