What are the prospects for life on the icy moons Europa and Enceladus?

Below is an excerpt from our monthly Launchpad newsletter. In this newsletter, space expert Leah Crane travels through the solar system, the galaxy and beyond. You can sign up for Launchpad for free here.

A staggering number of moons in our solar system, notably Jupiter’s moon Europa and Saturn’s moon Enceladus, are thought to have vast oceans beneath their ice, and those oceans look for potential life. attractive as a destination. Let’s dive in.

As far as we know, the three main ingredients necessary for life are liquid water, an energy source, and complex chemicals. Liquid water is the easiest to identify. As shown in the image above, Enceladus is actually spewing liquid water into space. Europa is probably doing the same. It’s pretty cut and dry. Both definitely have water, but they’re salty.

On Earth, the main source of energy is sunlight, but in worlds like Europa and Enceladus, where potentially habitable environments are several kilometers beneath the ice, sunlight must be sourced elsewhere. must be In the depths of Earth’s oceans, much of the energy is generated in hydrothermal vents. In hydrothermal vents, molten rock beneath the seafloor heats and ejects water. Near the hot vents, microbes convert carbon dioxide and hydrogen into methane for use as fuel.

There is some evidence that Enceladus may have hydrothermal vents similar to those on Earth. Small particles ejected from the ocean into space appear to have formed at high temperatures. Enceladus and Europa have one advantage over Earth as far as underwater energy sources are concerned. They are small and completely orbit giant planets.

This means that the tides are much more extreme than on Earth. As the gravitational pull of Saturn and Jupiter stretches and bends the moons, the cores of these natural moons heat up and can crack. Not only does this provide energy for the microbes that may be there, fractures can be doubly important. increase. Crevices and pores provide an opportunity for water to seep into fresh stone and undergo chemical reactions.

However, planetary scientists are divided on whether these submarine energy sources actually exist on Europa and Enceladus. I think everyone would like it to be there, but new research published this month suggests that the ocean floor may not be stressed enough to cause destruction. .

This leads to the complex chemistry that is the ultimate requirement of life. Chemistry requires gradients in matter composition, temperature, acidity, charge, etc. You cannot proceed in equilibrium. Enceladus, at least, contains all the chemical elements important to life, but without some sort of gradient, it’s like flour, sugar, and baking his powder piled up separately. They are never cakes on their own. The tides on Europa and Enceladus likely cause giant waves and mixing under the ice. So if there are actually some pockets of the ocean with some kind of gradient, it’s fine to have chemical reactions.

And then comes the final problem in the search for life beyond Earth. We have no accepted idea of ​​how life began. We know a lot about prebiotic chemistry, and we know a lot about biochemistry, but how the former turns into the latter is essentially a big question mark. We don’t know if there is life in a strange world until it stands up and waves at us (metaphorically of course, if there is life, I’m pretty sure it’s microbes. increase).

However, it is more than just an obstacle. Studying such worlds with the potential for life can help us understand how life originated and whether it originated there. It shows that there is something missing in our recipe.