  The region of heavy calcium isotopes forms the frontier of experimental and
theoretical nuclear structure research where the basic concepts of nuclear
physics are put to stringent test. The recent discovery of the extremely
neutron-rich nuclei around $^{60}$Ca [Tarasov, 2018] and the experimental
determination of masses for $^{55-57}$Ca (Michimasa, 2018] provide unique
information about the binding energy surface in this region. To assess the
impact of these experimental discoveries on the nuclear landscape's extent, we
use global mass models and statistical machine learning to make predictions,
with quantified levels of certainty, for bound nuclides between Si and Ti.
Using a Bayesian model averaging analysis based on Gaussian-process-based
extrapolations we introduce the posterior probability $p_{ex}$ for each nucleus
to be bound to neutron emission. We find that extrapolations for drip-line
locations, at which the nuclear binding ends, are consistent across the global
mass models used, in spite of significant variations between their raw
predictions. In particular, considering the current experimental information
and current global mass models, we predict that $^{68}$Ca has an average
posterior probability ${p_{ex}\approx76}$% to be bound to two-neutron emission
while the nucleus $^{61}$Ca is likely to decay by emitting a neutron
(${p_{ex}\approx 46}$ %).
