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MVP ARCHIVE NASA | Search for Life Phase 01-03 : Hydrothermal Vent Ecosystems / A World of Life Without Sunlight

2026年7月6日 07:06

A World of Life Without Sunlight

Life cannot exist without sunlight.
Many scientists once thought this to be true.
This was because ecosystems on Earth are based on photosynthesis by plants, and it was an unquestionable fact that sunlight is the starting point for biological activity.

Discovery in the Deep Pacific

However, in 1977, a discovery was made at a hydrothermal vent about 2,500 meters deep in the Pacific Ocean that overturned this conventional wisdom.
There, despite the fact that sunlight never reaches it, an independent ecosystem existed where diverse organisms gathered.

What supports this ecosystem is not light, but "chemical energy."
The high-temperature hydrothermal fluid gushing from the seafloor is rich in chemical substances such as hydrogen sulfide and methane.

Chemosynthetic bacteria use these chemical substances to obtain energy and produce organic matter.

These bacteria form the foundation of the ecosystem, and many organisms, such as tube worms, shrimp, crabs, and bivalves, live around them.
This is another life-support system, different from photosynthesis driven by sunlight.

Impact on Life Exploration

This discovery had a major impact not only on biology on Earth but also on the search for life in the universe.
If life does not require sunlight, there is a possibility that life could exist even in worlds covered by thick ice.

One of the reasons why Jupiter's moon Europa and Saturn's moon Enceladus are currently considered strong candidates for life exploration is thisdiscovery of hydrothermal vent ecosystems.

This is because if liquid oceans and seafloor hydrothermal activity exist underground, a chemosynthetic ecosystem similar to that on Earth could potentially be formed.

Hydrothermal vents are not just rare deep-sea environments.
They are an important discovery that caused us to rethink the long-held premise that "life needs the sun" and changed the very way humanity searches for life in the universe.