The laboratory ocean
Methanothermococcus okinawensis, isolated from a hydrothermal vent in the Okinawa Trough, lives by turning hydrogen and carbon dioxide into methane. The same organism grew up to pH 11 in a brine meant to mimic Enceladus's alkaline ocean. That is past its known pH limit. The experiment lasted days.[1]
This growth widens the chemical window for this metabolism. A counter-reading also stands: the species may be an Earth specialist, and the simulant's hydrogen and carbon may not carry a real seafloor longer than the experiment.[1]
The decision to look
In a second paper, ice grains in the plumes freeze and fragment while ocean material separates. If a droplet carried microbes, the trace may concentrate in a small share of the grains. Frank Postberg says looking at individual grains makes the trace easier to tell apart.[1]
ESA's proposed L4 mission carries a lander for the south pole and a launch aim of about 2042. Institutions make that choice. The experiment's days do not cover the moon's geological span.[1]