  We comment on the first indication of geo-neutrino events from KamLAND and on
the prospects for understanding Earth energetics. Practically all models of
terrestrial heat production are consistent with data within the presently
limited statistics, the fully radiogenic model being closer to the observed
value ($\approx 9$ geo-events). In a few years KamLAND should collect
sufficient data for a clear evidence of geo-neutrinos, however discrimination
among models requires a detector with the class and size of KamLAND far away
from nuclear reactors. We also remark that the event ratio from Thorium and
Uranium decay chains is well fixed $N(Th)/N(U) \simeq 0.25$, a constraint that
can be useful for determining neutrino oscillation parameters. We show that a
full spectral analysis, including this constraint, further reduces the
oscillation parameter space compared to an analysis with an energy threshold
$E_{vis}>2.6 MeV$.
