A plume ejects water ice from a location near the south pole of Saturn’s moon Enceladus
NASA/JPL/Space Science Institute
Below is an excerpt from our monthly Launchpad newsletter. In this newsletter, resident space expert Leah Crane travels through our solar system, 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 could be used to search for potential life. It is an attractive destination. Let’s dive in.
As far as we know, there are three main ingredients necessary for life. Liquid water, an energy source, and complex chemistry. Liquid water is the easiest to determine. As shown in the image above, Enceladus is actually spewing liquid water into space, and Europa likely does the same. I mean, it’s pretty cut and dry. Although salty, both are definitely watery.
On Earth, the main source of energy is sunlight, but in worlds like Europa and Enceladus, where potentially habitable environments lie beneath kilometers of ice, energy must come from elsewhere. . In Earth’s deep oceans, much of the energy comes from hydrothermal vents, where molten rock beneath the seafloor heats and expels water. Near these hot vents, microorganisms 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 – the tiny particles spewed into space from Enceladus’ oceans seem to have been tempered by high temperatures – but they do exist in space. Unless you send the ship out to sea, you can’t be sure. . However, Enceladus and Europa may have one advantage over Earth when it comes to underwater energy sources. It’s that they orbit a small, very huge planet.
That means the tides are much more extreme than on Earth. As the gravitational forces of Saturn and Jupiter stretch and bend the moons, the cores of these natural moons heat up, potentially causing their destruction. Not only does this provide energy to any microbes that may be there, the cracks can be doubly important. Many of the chemical constituents of life are produced through the interaction of water and rock, and cracks and pores provide an opportunity for water to penetrate fresh stone and undergo chemical reactions.
But planetary scientists are divided on whether these submarine energy sources actually exist on Europa and Enceladus. I think everyone would like to be there, but new research published this month suggests that the seafloor may not have enough stress to cause cracks. Alternatively, even if there was sufficient stress early in the satellite’s history, it may no longer exist. .
That leads to the final requirement of life: complex chemistry. Chemistry requires gradients in material composition, temperature, acidity, charge, etc. You cannot proceed in equilibrium. Enceladus, at least, contains all the chemical elements important to life, but without some kind of gradient, it’s like putting flour, sugar, and baking powder in separate piles, and they’ll never make a cake on their own. it won’t work. The tides on Europa and Enceladus probably cause giant waves to mix under the ice, so if there is indeed a section of the ocean with some kind of gradient, there’s no problem getting chemical reactions going. must.
And then comes the final problem in the search for extraterrestrial life. That is, we have no accepted idea of how life began. We know a lot about the chemistry and biochemistry of prebiotics, but how the former turns into the latter is inherently a big question mark. So, unless life stands up and waves at us, we cannot know if there is life in these strange worlds (metaphorically, of course, if it does, I think it is microbes). I’m pretty sure).
However, it is more than just an obstacle. Studying such worlds with the potential for life helps us learn how and whether life originated. It helps us understand how life would have arisen in the universe, if it had originated, and if it hadn’t. This indicates that something is missing in the recipe.
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