Enceladus Might Have Life. All It Takes Is One Launch.Alien Life Can Survive on This Tiny Moon—We Just Need to Go Find It

Two new studies show that Enceladus's alkaline ocean could support methane-making microbes and that its ice grains pre-sort organic molecules, so a single sampling mission could settle the question.

Enceladus is a small moon of Saturn, less than 500 kilometres across. Under its ice shell sits a whole ocean, and on that seafloor are hydrothermal vents — on Earth, exactly the kind of place life clusters around.

Better still, that ocean sprays plumes of water out through cracks in the surface, and any probe passing by can catch a mouthful. Cassini flew through them several times, giving humanity its first taste of an alien sea. The spacecraft just wasn't carrying the instruments to look for life.

First, brew it in the lab

The first study rebuilt Enceladus's 'soda ocean' in the lab — alkaline and rich in carbonate. Then researchers dropped in a heat-loving microbe that normally lives at deep-sea vents in the Pacific.

It did better than expected. The range of conditions that ocean could support life in, it turns out, is wider than anyone had assumed.

The second study went back over Cassini's ice grains. They found that these droplets freeze slowly in space, and as they do, similar organic molecules clump together.

Good news: the molecules sorted themselves

If the grains do contain traces of life, they come pre-sorted: each class of molecule ends up concentrated in a small number of grains rather than spread thin. A future probe that examines grains one at a time will have a much easier job than one that measures them all mixed together.

Mission concepts for Enceladus have been floated for years — NASA's Enceladus Life Finder, the European Space Agency's L4 — and none has been approved.

In astrobiology, Enceladus is low-hanging fruit. The trouble is that the fruit has been hanging there for nearly twenty years and nobody will pick it.