Could Aliens Live Here?

At first glance, Saturn’s moon Enceladus doesn’t seem like a great place to live. Its entire surface is covered in ice, and temperatures hover at a bone-chilling -201°C (-330°F). It also has more than 100 active ice volcanoes, which blast a never-ending spray of ice, dust, and gases into the air.

Deep below Enceladus’s icy crust lies a totally different environment: a warm underground ocean (see Hidden Sea). Scientists have discovered that this vast sea has an abundance of organic molecules. These molecules contain the element carbon (C), which is the main building block for all living things on Earth. Researchers studying the ocean on Enceladus have also detected compounds that contain the elements hydrogen (H), nitrogen (N), oxygen (O), sulfur (S)—and, most recently, phosphorus (P).

Scientists consider these six elements essential for life as we know it. That’s led many researchers to believe Enceladus might be the best place to search for alien life in our solar system.

At first glance, Enceladus doesn’t seem like a great place to live. This moon of Saturn is completely covered in ice. Temperatures stay around a bone-chilling -201°C (-330°F). It also has more than 100 active ice volcanoes. They blast a never-ending spray of ice, dust, and gases into the air.

A totally different environment lies deep below Enceladus’s icy crust. It’s a warm underground ocean (see Hidden Sea). Scientists have discovered an abundance of organic molecules in this vast sea. These molecules contain the element carbon (C). It’s the main building block for all living things on Earth. Researchers have also detected other compounds in Enceladus’s ocean. They contain the elements hydrogen (H), nitrogen (N), oxygen (O), and sulfur (S). And recently, researchers have detected phosphorus (P).

Scientists say these six elements are necessary for life as we know it. That makes Enceladus interesting to many researchers. They believe it might be the best place to search for alien life in our solar system.

“We learned a lot from Cassini,” says Frank Postberg, a planetary scientist at the Free University of Berlin in Germany. For example, Enceladus’s ocean is salty, like Earth’s oceans. But in addition to sodium chloride, or table salt, the water on Enceladus is rich in sodium bicarbonate. This type of salt is also known as baking soda. The samples collected by Cassini also provided evidence that Enceladus’s ocean is heated by hydrothermal vents. These cracks in the seafloor release water that’s been heated within the moon. In Earth’s deep oceans, these same types of vents provide heat and nutrients for many marine creatures.

It’s these similarities with oceans on Earth that first made Enceladus a strong candidate for harboring life. The idea was further strengthened by the fact that Enceladus’s ocean also contains many elements necessary for life. There was only one problem: A key element—phosphorus—was missing. But then, in 2023, Postberg and his team used more advanced techniques to analyze Cassini’s water samples. They found phosphorus, which had previously gone undetected.

“We learned a lot from Cassini,” says Frank Postberg. He’s a planetary scientist at the Free University of Berlin in Germany. For example, Enceladus’s ocean is salty. Like Earth’s oceans, it contains sodium chloride, or table salt. But the water on Enceladus is rich in sodium bicarbonate too. This type of salt is also known as baking soda. The samples collected by Cassini also showed that Enceladus’s ocean is heated by hydrothermal vents. These cracks in the seafloor release hot water. The water was heated within the moon. Earth’s deep oceans have these same types of vents. They provide heat and nutrients for many sea creatures.

These similarities with Earth’s oceans sparked the idea that life could exist on Enceladus. Then researchers found that Enceladus’s ocean also contains many elements necessary for life. That strengthened the idea. There was only one problem. A key element was missing. It was phosphorus. But Postberg and his team analyzed Cassini’s water samples again in 2023. This time, they used more advanced techniques and found phosphorus. It had gone undetected before.

This year, NASA plans to send an orbiting spacecraft to study another lunar ocean on Jupiter’s moon Europa. The Europa Clipper will arrive at the moon in 2030. It’s equipped with instruments that will allow scientists to see if the moon’s ocean also has conditions that are suitable for life. There are hints that Europa, like Enceladus, has ice volcanoes that shoot up ocean particles. If it does, Clipper will be able to collect samples. “Of course, we’ll be checking for phosphorus,” says Postberg.

NASA and the European Space Agency have also flagged Enceladus for another major space mission in the future. But it will take time to design and build a spacecraft—and then almost 10 years for it to travel to faraway Saturn. “That means if you’re a kid reading this now who decides to become a planetary scientist, the mission to Enceladus will be arriving just when you are beginning your scientific career,” says Postberg. Who knows: You could be the first person to discover alien life on another world!

This year, NASA plans to send an orbiting spacecraft to Jupiter’s moon Europa. The Europa Clipper will arrive at that moon to study its ocean in 2030. Are conditions on Europa suitable for life? The spacecraft’s instruments will allow scientists to examine that question. Enceladus has ice volcanoes that shoot up ocean particles. It looks like Europa has them too. If it does, Clipper will collect a sample. “Of course, we’ll be checking for phosphorus,” says Postberg.

NASA and the European Space Agency are planning another major space mission to Enceladus. But it will take time to design and build a spacecraft. Then the spacecraft will need almost 10 years to reach faraway Saturn. “That means if you’re a kid reading this now who decides to become a planetary scientist, the mission to Enceladus will be arriving just when you are beginning your scientific career,” says Postberg. Who knows? You could be the first person to discover alien life on another world!