The universe is vast — in our Milky Way alone, there are an estimated more than 100 billion stars. This raises a fascinating question: what are the conditions for extraterrestrial life? In this blog, we dive into the latest insights from astronomers and astrobiologists, and explain which factors are essential for life as we know it.
1. Water: the Absolute Foundation
The most important condition for life as we know it is liquid water.
Water is a unique solvent in which essential chemical reactions can occur. Without water, life as on Earth is virtually impossible.
In the search for extraterrestrial life, scientists therefore first look for signs of liquid water, such as:
- Planets in the habitable zone of their star (not too hot, not too cold).
- Evidence of oceans beneath ice crusts (like on Europa or Enceladus in our solar system).
2. Stable and Suitable Atmosphere
A planet must have an atmosphere that:
- Has sufficient pressure to support liquid water.
- Provides protection against harmful radiation from the star.
- Contains gases potentially associated with biological activity, such as oxygen, methane, or carbon dioxide.
Too little atmosphere (like on Mars) or a toxic atmosphere (like on Venus) makes life extremely difficult.
3. Energy Source: Light or Chemical Reactions
All life needs energy. On Earth, it mainly comes from the sun (photosynthesis), but in extreme environments, like around deep-sea volcanoes, life exists on chemical energy (chemosynthesis).
Therefore, scientists look for planets:
- With access to solar energy (through light from their star).
- Or with internal geological activity (such as volcanoes or tidal heating).
Even in dark oceans, life can emerge if there are sufficient chemical energy sources.
4. Essential Chemical Elements
Certain elements are fundamental to life:
- Carbon (C) – the building block of organic molecules.
- Hydrogen (H) – present in water and many compounds.
- Oxygen (O) – essential for energy production.
- Nitrogen (N) – building block of proteins and DNA.
- Phosphorus (P) and sulfur (S) – necessary for biological processes.
Planets or moons where these elements are present, like on Earth, are considered more promising for supporting life.
5. Stability over Long Time Scales
Life needs time to emerge and develop. Therefore, a planet must:
- Have a stable climate over millions to billions of years.
- Be protected from too many asteroid impacts.
- Not undergo extreme changes, such as star explosions or planetary migration.
Stars that remain stable for long periods (like our sun) are therefore favorites in the search for life.
Could other Forms of Life Exist?
Although we search for life similar to ours, it’s theoretically possible that alternative life forms exist, for example based on:
- Ammonia instead of water.
- Silicon instead of carbon.
However, scientists primarily focus on water- and carbon-based life, as it’s the only form we know for certain can exist.
Examples from our Own Solar System
Even within our own solar system, there are places that meet some conditions:
- Europa (moon of Jupiter): ocean beneath an icy crust.
- Enceladus (moon of Saturn): geysers of hydrogen-rich fluids.
- Titan (moon of Saturn): lakes of liquid methane and ethane.
While these worlds aren’t identical to Earth, they show that life might emerge under very different conditions.
Smart Telescopes and the Search for Extraterrestrial Life
To study distant worlds, scientists use advanced space telescopes like James Webb and Hubble.
As an amateur, you can also contribute: smart telescopes like the Seestar S50 or the DWARF 3 enable enthusiasts to observe galaxies and planetary systems.
With a smart telescope, you can:
- Measure variations in star brightness (exoplanet transits).
- Take better photos of deep-sky objects.
- Participate in citizen science projects, like Exoplanet Watch.
Explore the capabilities of the DWARF 3 smart telescope here.
Conclusion: the Search Continues
The conditions for extraterrestrial life seem clear, but the universe keeps surprising us.
With each new discovery, such as the k2-18b planet, we get closer to answering one of the biggest questions ever: are we alone?
Science is still at the beginning of this journey.
Every telescope scanning the stars, every molecule found in a distant atmosphere, brings us one step closer.
So keep looking at the stars – who knows what we’ll find.
