What are the Essential Ingredients of Life?
Wherever we have found life on Earth, it has had these key ingredients:
Energy + Water + Chemical Raw Materials = Life
As scientists look for life on other worlds, they are looking for places that might have liquid water and some form of energy.
What Kinds Of Energy Support Life?
All organisms require energy to fuel their life processes of growth, maintenance and reproduction.
The known forms of life use two forms of energy - light and chemical. Plants, algae and some bacteria photosynthesize and therefore fall into the first category. Animals, fungi and non-photosynthesizing bacteria fall into the second. Most chemical eaters ultimately depend on photosynthesis to obtain their organic matter and oxygen.
Until recently, we thought that all life cycles were directly dependent on light for their energy. Then in 1977, we discovered deep sea ecosystems that are sustained almost entirely by chemical energy, such as those that flourish around the black smokers in the picture above.
Black smokers dump large amounts of hydrogen sulfide into the surrounding water, which sulfur eating bacteria metabolize. These bacteria form symbiotic relationships with other life forms, such as tubeworms, allowing them to survive where other life forms cannot.
Black smokers dump large amounts of hydrogen sulfide into the surrounding water, which sulfur eating bacteria metabolize. These bacteria form symbiotic relationships with other life forms, such as tubeworms, allowing them to survive where other life forms can not.
Water (H2O)
Liquid water is required by all known forms of life. It is the only liquid that has been found to facilitate the processes that are the basis of life. Liquid water can dissolve many, but not all compounds. As a result, it can provide a medium for cells (built out of non-dissolving material), and a means of transporting materials in and out of them. Consequently, NASA scientists are "following the water," looking for life on planets that have signs of water.Water (H2O)
Liquid water is required by all known forms of life. It is the only liquid that has been found to facilitate the processes that are the basis of life. Liquid water can dissolve many, but not all compounds. As a result, it can provide a medium for cells (built out of non-dissolving material), and a means of transporting materials in and out of them. Consequently, NASA scientists are "following the water," looking for life on planets that have signs of water.
Martian Ice Cap Courtesy NASA/JPL-Caltech
Mars has features that appear to have been created by flowing water, which makes it a prime candidate for exploration in our solar system.
Some scientists believe that the gully-like features running down the crater walls above were formed by water. Other scientists have suggested that the channels were caused by a process that did not involve water, such as wind or landslides
Courtesy NASA/JPL/ASU
This sinuous channel snakes its way across 1000 km. It is likely that it was carved by either lava or water.
In conclusion, we must offer two caveats about life and water. First, although life has always been found in the presence of water, water alone is not enough to support life because other limitations can come into play. These include extreme temperatures such as those found inside hydrothermal vents, where water can be 350°C. That is too hot for life to exist.
Finally, it is also possible that a chemical other than water could be the solvent that supports life, but we have not found it yet. Hydrogen
Hydrogen is the simplest atom. It is a fundamental building block of many molecules including water. Molecules are chains of atoms. Methane (CH4) is a common molecule found throughout the throughout our solar system, and has been demonstrated to support life.
Oxygen
Oxygen is highly corrosive when not in a stable molecular arrangement. It rapidly destroys materials through a process called oxidation. Many people are familiar with this process. It is the reason an apple that is cut open quickly turns yellow. It is why your blood is red, the iron in it is oxidizing.
Free radicals, oxygen molecules that aren't trapped in a stable chemical bond, can damage a body, which is why we are encouraged to eat anti-oxidants such as Vitamin C. Vitamin C scoops up the lone oxygen molecules and transport them safely out of the body.
Likewise oxygen can be extremely destructive to bacteria. Some bacteria are anaerobic, meaning they can't survive exposure to oxygen because they have no protective mechanisms for getting rid of free floating oxygen radicals.
Fortunately oxygen loves to hang out with hydrogen, where it forms water, and water is a very stable molecular configuration that is essential to all life.
Carbon
Carbon is an diverse atom that is a fundamental building block of life and the essential ingredient of any organic molecule. Methane, which is common throughout the solar system, contains one carbon molecule and four hydrogen molecules.
Carbon is also present in carbon dioxide(CO2), a common biproduct of animal respiration which is breathed in by plants. Plants collect the carbon molecules to build their bodies, then release oxygen back out into the atmosphere.
Heat
Although large amounts of heat are not necessary for life to exist, it does speed up chemical reactions, and, as a result, evolution. Heat can be generated from light, friction(tidal forces) or geothermal activity.
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compiled by aritri
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