When Asterius reaches orbit around Europa, it will remain to scan the surface with radar, attempting to find the thinnest spot. Once the site is selected, the SOM will jettison the OOM and perform the landing maneuver.
Due to the tenuousness of Europa's atmosphere, it is not feasible to do a ballistic entry. The landing rockets will provide all the force necessary to safely land Asterius on Europa. To minimize fuel, the landing maneuver is a Hohmann transfer to the surface. Asterius holds enough fuel for the Hohmann transfer from a 200 km altitude circular orbit, braking to zero velocity at the landing site, with a 20% reserve.