In a universe with uncountable planets and solar systems, it seems unlikely that Earth is the only one that can support life. When people think ‘alien’ they usually imagine a weird humanoid being or some other wildly strange creature. However, it is important to note that bacteria count as life, and if we’re going to find life on other planets, it’s going to be some kind of single-celled organism.
From our vantage point on Earth, it is difficult to discern whether there are signs of life on far-away planets. We have limited technology, and we only know what signs of life look like in terms of our home. So, what if we looked a little closer? Life probably doesn’t live on any of the gas giants, but what about Mars, Venus, or some of the larger moons in our solar system? Plenty of the moons in our solar system likely have subterranean oceans that could shelter various bacteria.
Just to get it out of the way, it’s more likely that there is life on a moon than on Mars or Venus. Our neighboring planets could have once held life; Venus may have had oceans, but they have since burned away. Mars has the opposite problem of Venus; it was once covered in water and had a strong magnetic field, but since then, the field has withered away, and the planet has frozen over. The most we can expect to find on Mars would be fossils.
By looking at the Earth from a distance, we can better understand what signs of life we might be able to see on other planets or moons. Some possible signs of life are unbalanced gasses. Some gases naturally cancel out; however, when you look at Earth from afar, you would see methane and oxygen. Of course, some planets have vents that are constantly producing such gasses, so looking out for other signs is crucial. Earth has what’s called a “red edge,” which exists because of our plant life. Earth also emits a techno signature of radio waves that indicates intelligent life. The biggest sign that a planet could host life, though, is the presence of water, an energy source (such as light or chemical vents), and changes in the planet over time, like plate tectonics.
One celestial body that is considered to have a high chance of containing life is Jupiter’s moon Europa. Europa vents water high into the atmosphere, high enough to hit satellites traveling close enough. The water freezes in the air and drifts to the ground as snow. This is evidence of a liquid ocean lying beneath the moon’s surface. Hydrothermal vents possibly exist below the surface, keeping the ocean warm. They could also serve as an energy source for life.
Some other moons in our solar system that could harbor alien life are Ganymed, Callisto, and Enceladus. Ganymed has an aurora, meaning it has a magnetic field. It also likely has a subterranean saltwater ocean that could be a home for life. Callisto is beyond Jupiter’s radiation and also has the potential for water beneath its surface. However, there could be another frozen ocean beneath the liquid one, making a sandwich of sorts, which isn’t ideal for life. Enceladus, one of Saturn’s moons, has shown evidence of hydrothermal vents that help create Saturn’s rings. These hydrothermal vents have materials that could promote life in the underground ocean. It also could be geologically active, which would mean that the moon is changing over time, something that helps life.
A final interesting prospect is Saturn’s moon Titan. Titan has rivers, lakes, and oceans of frozen methane and ethane all over its surface. There could very well be liquid methane hiding beneath the surface. We don’t know of any methane-based life, but if there could be, there is a chance of it being found on Titan. Even if life based on methane can’t exist, there is a possibility that the moon has underground water that could contain life.
Refferences: science.nasa.gov/universe/search-for-life, learn.genetics.utah.edu, scientificamerican.com, science.nasa.gov/universe/exoplanets; Photos: Canva
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