Can life exist on earth wihout light?

Question

we entered a debate about whether life can exist on earth without light...we thought of bacteria, bats or fish deep into the oceans...but we couldn't come to a very clear cut conclusion.

Answer 1

Yes, there are bacteria in the very deep ocean ridges which use hydrogen sulphide from thermouclear vents to produce energy and then they form an ecosystem of strange creatures.

Answer 2

Yes, if there would be another energy source. Problem is that it is really hard to find energy source that is so easy absorbable, not too dangerous for life, and so long-therm, that the life-form would evolve into intelligent life. Chemical energy is not enough. Light, in contrast, is transporting energy which was created in a thermonuclear, self-modulating process, which will last for much longer, than e.g. chemical, it's easily absorbable mainly by plants, common, so You don't have to dig deeply to find your dinner :P, and not very dangerous (you can just get sunburn; except if the planet is too close to it's sun). While chemical... how many organism live there? And, what can be tricky, they live there, because sun is warming us - without light from sun, our planet would be extremely cold, so cold, there would be hardly any chemical reaction, which could take place. Chemical energy is just supporting light energy, but is not enough to warm the planet for long and "to power up the life".
And for those, who write that deep in a ocean there is no light and as a conclusion say it means, that life can handle without light - don't forget, organic substances which are used as energy source down there, are created with the energy of light!
One more thing - when one of Us told, the life can handle without light, because inside our bodies is dark... I hope he was joking?

Answer 3

I remember going on a marine biology lecture where it was stated that the entire ocean is dependant on the first 3 feet (or perhaps 6 feet or more) from the surface. This is where the lifeforms rely on their survival from light. The entire depths and all of its life relies on the continuing survival of these light 'feeding' organisms - they are an integral part of the food cycle. I believe that the same rule applies for land, where plants require light and are subsequently eaten by herbivores, which are in turn eaten by carnivores. So everything requires light, though indirectly in most cases. If the light was blanketed out and all life perished, perhaps new lifeforms could evolve to live in those conditions.

Answer 4

Life requires some form of external energy. Sunlight is the most common source. Plant life uses sunlight as its main source of energy. Animals get their energy by eating plants or other animals. In theory animals could live in total darkness, but they would need a source of food - and that would normally need light.

There are some primitive forms of life that do not require light, but instead rely on geothermal heat. If there was no light on earth, but a ready source of heat, it's likely that these lifeforms could have evolved into something more advanced. The world would be a very different place.

Answer 5

All energy on earth must come from somewhere. For the most part this is from sunlight, but there are some bacteria that use sulphur from deep underwater volcanoes.

All life that ultimately depended on light (including bats for example) couldn't survive without light. But food chains based on these non-light dependent bacteria could.

Answer 6

Yes but light can't initially develop without an outside energy source, in the Earth's case this came in the form of light from the Sun.

Once life has developed other methods of generating energy it can survive without light.

You'll probably get some idiots saying that it can survive for about 12 minutes (or however long it takes for light from the Sun to reach us) but that's a load of nonsense, kinda like an urban-legend.

Answer 7

In the sense that life can exist in places without any light, for example, the rock-eating bacteria that are thought to total more biomass than all other life on earth as well as cave dwellers etc., then yes, it can.

In the sense that without the sun as a source of a light, the earth wouldn't be able to support any life as we know it, then no.

Answer 8

I suppose it is theoretically possible, but seems very unlikely to me. Even the bacteria or fish that don't depend on light at the bottom of the ocean have an indirect dependency on light...as a means to warm the earth, since light is linked to heat in the sun. Therefore, the discussion could be moot.

Answer 9

Yes it can. Thermal vents in the deep ocean treches , smokers, provide a habitat in which many strange life forms exist totally devoid of sunlight.

At a depth of between 3700 and 5500m, the abyssal plains begin – no sunlight penetrates here and only sea creatures that can handle the darkness and pressure and can take advantage of the process of chemosynthesis can survive.


In 1977 scientists discovered hot springs at a depth of 2.5km on the Galapagos Rift off the coast of Ecuador. These hot springs, also called geothermal vents, or smokers because they resemble chimneys, spew out dark mineral-rich fluids, heated to temperatures of up to 380 degrees C by contact with the newly-formed ocean crust at the spreading ridge. The water does not boil because it is under so much pressure from the tremendous weight of the ocean above and when the pressure on a liquid is increased, its boiling point goes up. Smokers can be black, white, grey or clear, depending on the type of material ejected.

Exploration in the pitch-black environment has revealed extraordinary forms of marine life that thrive around hot springs. The primary producers5 in these areas use the hydrogen sulphide contained in the volcanic gases that are spewed out of hydrothermal vents to live. They are called chemoautotrophs. Thus the energy source that sustains this deep-sea ecosystem is not sunlight (photosynthesis) but energy from chemical reaction (chemosynthesis). Many bizarre creatures such as giant tube worms, blind shrimp, angler fish, lantern fish, giant clams, pink sea urchins and sea cucumbers manage to survive here without sunlight in conditions of high pressure, steep temperature gradients and levels of minerals that would be toxic to animals on land. This alien underwater environment may well resemble the places where life on earth first began.

However, deep sea creatures are not only found at hydrothermal vents and scientists have long wondered what might be sustaining them at other areas of the ocean floor. The answer may lie in whale carcasses which fall to the ocean floor from above when the creature dies. Whale bones are rich in sulphur so once the flesh has been stripped by scavengers such as hagfish (primitive, eel-like fish) which can take less than six months, the chemoautotrophs can use the sulphur for years to come. One square yard of bones can sustain over 5000 animals representing over 170 species.

Answer 10

My initial thoughts were, no it could not simply from the food chain argument. Plants need light, animals need plants and we need animals (to put it very crassly!). However, on second thoughts I believe we can. There are animals that exist in the deepest darkest caves on earth. As for human beings, I believe we could survive too, simply because we are amazingly adaptive and our instinct for survival would find a way of continuing. Hopefully we never need to find out the answer to this question. I seem to remember learning in school that the sun is going to outlive planet earth, so we should be alright from that perspective. Good question though.

Answer 11

Goodness gracious, people, think outside the box!!! Lack of light would be a far bigger problem for this planet than just making it dark! Plants are the source of ALL life on this planet, not because of food chains, but because of the vital process that takes place in them. Plants need light in order for photosynthesis to take place. Photosynthesis produces oxygen which allows all other living things to breathe, therefore exist. So, if there was no light, there would be no life at all (including sea life, they are as reliant on oxygen in the water as we are reliant on oxygen in the air)