Can alien life exist only on Earth-like planets?
Is alien life only possible on Earth-like planets, or could worlds completely covered with oceans hold the key to finding life beyond our solar system?
The discovery of exoplanets has completely changed our understanding of the universe and our place within it. Astronomers have been rushing to find exoplanets light years from Earth, often hoping to find alien life among the stars. Among the many types of planets found orbiting these distant stars, a new kind of planets are becoming the talk of the town; Hycean worlds.
Hycean worlds are a unique blend of planet wide oceans and hydrogen filled airy atmospheres. The word “Hycean” reflects this combination of “Hydrogen” and “oceans”. Hycean plants are typically bigger than Earth and smaller than Neptune, and are very interesting for astronomers studying habitable exoplanets. Firstly, they have liquid water at the surface, a key ingredient for life. Then, their hydrogen atmospheres are also able to support just the right temperature for reactions to happen, another important factor for the success of life.
Scientists theorise that these large ocean worlds are a viable candidate for finding alien life. Similar to the ancient oceans of Earth, these planet wide oceans could serve as the base for life to develop in. The hydrogen rich atmospheres can also create warm conditions that are very conducive to life. Hycean worlds are able to maintain liquid water at a greater range of environmental conditions, making them all the more interesting to study. Scientists are using other indicators for life, such as organic molecules, to search for habitability and Hycean worlds are at the top of this list as well. The combination of hydrogen atmosphere and large body of water provide a petri dish for the simple unicellular life that will one day lead to the civilisation we have today.
In recent years, the astronomy community has used telescopes like TESS to find thousands and thousands of exoplanets, like TOI-270 d, a Hycean world 73 light-years away. The system houses 4 other planets orbiting a red dwarf star much smaller than the Sun, being only 38% of the Sun’s size. The system is also very tightly packed together, with more than 4 planets closer to the star than Mercury is to the Sun.
Despite the planet’s close orbit, the hydrogen-ocean combination has motivated scientists to search the planet for signs of methane and carbon dioxide. In March of 2024, the James Webb telescope was used to confirm the presence of these molecules on TOI-270 d. Scientists were also able to find out that the planet boasts a very cool 23 degree surface temperature and shows lots of similarities to Neptune.
These Hycean worlds show us that alien life may not be on Earth-like planets and might be found in stranger places than we ever thought. They challenge our understanding of habitability and suggest that life may exist in a broader range of environments, even on planets that don’t resemble Earth. They remind us that the universe is full of surprises and studying these planets brings us closer to answering one of humanity’s most profound questions: are we alone in the universe?