Would Europa be an ocean planet if it were in the habitable zone?
According to Arnscheidt et al. (2019) &quot;Atmospheric Evolution on Low-Gravity Waterworlds&quot;, the transition between &quot;planet-like&quot; and &quot;comet-like&quot; (escaping) atmospheres occurs at a surface gravity of around 1.48 m/s2. As a caveat, the waterworlds being considered in the paper are objects which have water reservoirs of 40% of the total mass, which is a much higher fraction than Mars or Europa, such worlds would be more like scaled versions of Ganymede.
The surface gravity on Europa is 1.315 m/s2, putting it on the comet-like side of the transition. According to this, it seems unlikely that Europa would be able to maintain long-term habitable conditions in the face of atmospheric escape.
Martian gravity is 3.71 m/s2, putting it on the planet-like side of the transition, so a &quot;super-Ganymede&quot; with Mars-like gravity would likely be able to maintain long-lived habitable conditions.
They also note that the high albedo of ice means that deglaciating ice worlds tend to skip the long-lived habitable state entirely, going straight from frozen to runaway greenhouse/atmospheric escape:

The ice-albedo feedback can hamper transitions from snowball states to temperate states: this has
already been demonstrated for terrestrial-mass worlds
(Yang et al. 2017). We can incorporate the ice-albedo
feedback into our model using the simple albedo step
function
$$
A(T_s) = \begin{cases}
\alpha_I &amp; T_s &lt; 273\,\mathrm{K} \\
\alpha_L &amp; T_s \ge 273\,\mathrm{K}
\end{cases}
$$
where $\alpha_I$ is the albedo of the icy (snowball) state, and
$\alpha_L$ is the albedo when there is surface liquid water. Hysteresis plots for different choices of $\alpha_I$ are shown in Figure 5. We observe that a snowball state experiencing
a stellar flux-driven deglaciation generally bypasses the
long-lived state entirely, except for very low $\alpha_I$ values.
Although the mechanism setting the inner edge of the
habitable zone is different, the conclusion of the habitable state likely being bypassed upon stellar flux-driven
deglaciation is the same as that of Yang et al. (2017).

(emphasis mine)