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Comic-style illustration showing a ribosome translating an mRNA strand, with labeled nucleotide sequences and emerging protein chains. Background is dark and light shades of orange rays spreading from the center of the strand.

4.2. What are the sources of life's building blocks within the Earth?

A core learning question from the Astrobiology Learning Progressions

Astrobiology Learning Progressions Navigation

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4.1. Where do life's building blocks come from?

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4.3. What are the sources of life's building blocks outside the Earth?

Grades K-2 or Adult Naive Learner

If you want to make a meal using a recipe, then you’ll have to use all of the right ingredients. Well, just like that, living things all over Earth need to be able to get the right ingredients for their survival. Living things have been on Earth for a really long time so it makes sense that the ingredients for life have also been available the entire time, just like having the right ingredients available at the grocery store.

Portrait photo of Comic-style illustration showing a ribosome translating an mRNA strand, with labeled nucleotide sequences and emerging protein chains. Background is dark and light shades of orange rays spreading from the center of the strand.
Nucleobases—the molecular components of DNA—can be formed on Earth in hydrothermal ventsand volcanic reactions with the atmosphere,drivingcomplex organic chemistry.
NASA/Aaron Gronstal

Grades 3-5 or Adult Emerging Learner

A family might go to the grocery store in order to find the right ingredients for the meals of the week. Similarly, living things all over Earth need to have certain ingredients to survive, but those ingredients can be found all over. For instance, plants need water and air and the nutrients in the soil. Living things have also been on this Earth for many years, therefore it must mean that the ingredients needed for living things have also been here for many years.

Portrait photo of Comic-style illustration showing a ribosome translating an mRNA strand, with labeled nucleotide sequences and emerging protein chains. Background is dark and light shades of orange rays spreading from the center of the strand.
Nucleobases—the molecular components of DNA—can be formed on Earth in hydrothermal ventsand volcanic reactions with the atmosphere,drivingcomplex organic chemistry.
NASA/Aaron Gronstal

Grades 6-8 or Adult Building Learner

Investigating life on Earth has shown us that all living things need certain elements for their cellular processes, such as growth and metabolism (getting and using energy). For instance, the CHNOPS elements (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur) are known to be part of every living thing. These ingredients for life as we know it work kind of like a recipe, where you have to put the ingredients together in the right way to make the recipe work. So if we want to understand how life works, it’s important for us to know where the ingredients are at and when they’re put together in the right way for life.

Fossil evidence shows life thriving well over 3.5 billion years ago. This implies that the ingredients for life were available very early in the history of Earth. We know that water, with both hydrogen and oxygen, was available back then based on the evidence left in the rock record. Also, the CHNOPS elements along with a lot of metals and other important elements for life were present in the rocks of the crust and mantle of Earth, back then as well as now. This tells us that the ingredients for life have always been available on Earth.

We also know that Earth is pretty good at recycling the elements that are present at the surface through processes like plate tectonics and volcanism. Plate tectonics are when the large plates of rock that make up the crust shift around and sometimes create new mountains or drive old rock down into the mantle. Volcanism includes all of the processes that make volcanoes and cause them to erupt. While plate tectonics can send some elements down into the mantle and bring new elements up when forming mountains, volcanism can bring some elements back to the surface as well as to the atmosphere. We also know that the breakdown of rocks, known as weathering, is important for getting the ingredients for life out of rocks and into the soil and the oceans.

The next important thing is finding the places where the ingredients for life are brought together in the right ways. We’re really lucky to have an active planet, because having lots of different kinds of environments means there’s lots of places where different ingredients can be brought together and made useful for life. For instance, high temperature places like hot springs and hydrothermal vents can make a lot of metals available for life. Glaciers breaking down rocks as they move can make nutrient rich soils. The oxygen in the atmosphere can actually react with the rocks at the surface to make chemical molecules that are useful for life. sunlight itself can cause a lot of the ingredients for life to come together in a way that make them more useful for living things.

Portrait photo of Comic-style illustration showing a ribosome translating an mRNA strand, with labeled nucleotide sequences and emerging protein chains. Background is dark and light shades of orange rays spreading from the center of the strand.
Nucleobases—the molecular components of DNA—can be formed on Earth in hydrothermal ventsand volcanic reactions with the atmosphere,drivingcomplex organic chemistry.
NASA/Aaron Gronstal

Grades 9-12 or Adult Sophisticated Learner

Investigating life on Earth has shown us that all living things need certain elements for their cellular processes, such as growth and metabolism. For instance, the CHNOPS elements (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur) are known to be part of every living thing. They make up most of the proteins, fats, nucleic acids, and carbohydrates that life uses. There are also lots of other elements, especially lots of the metals, that are needed by living things. All of these ingredients for life as we know it work kind of like a recipe, where you have to put the ingredients together in the right way to make the recipe work. So if we want to understand how life works, it’s important for us to know where the ingredients are and when they’re put together in the right way for life.

Fossil evidence shows life on Earth thriving well over 3.5 billion years ago. This implies that the ingredients for life were available very early in the history of Earth. We know that water, with both hydrogen and oxygen, was available back then based on the evidence left in the rock record. The CHNOPS elements along with a lot of metals and other important elements for life were present in the rocks of the crust and mantle of Earth, back then as well as now. This tells us that the ingredients for life have always been available on Earth.

We know that Earth is pretty good at recycling the elements that are present at the surface through processes like plate tectonics and volcanism. Plate tectonics are when the large plates of rock that make up the crust shift around and sometimes create new mountains or drive old rock down into the mantle. Volcanism includes all of the processes that make volcanoes and cause them to erupt. While plate tectonics can send some elements down into the mantle and bring new elements up when forming mountains, volcanism can bring some elements back to the surface in lava as well as to the atmosphere through the gases that come out during eruptions. We also know that the breakdown of rocks, known as weathering, is important for getting the ingredients for life out of rocks and into the soil and the oceans. A lot of things drive weathering, but the movement of water (in the hydrological cycle) is one of the most powerful on Earth. Elements like carbon and phosphorus become available for life due to water breaking down rocks.

The next important thing is finding the places where the ingredients for life are brought together in the right ways. We’re really lucky to have an active planet, because having lots of different kinds of environments means there’s lots of places where different ingredients can be brought together and made useful for life. For instance, high temperature places like hot springs and hydrothermal vents can make a lot of metals available for life. Glaciers breaking down rocks as they move can make nutrient rich soils. The oxygen in the atmosphere can actually react with the rocks at the surface to make chemical molecules that are useful for life. sunlight itself can cause a lot of the ingredients for life to come together in a way that make them more useful for living things.

Portrait photo of Comic-style illustration showing a ribosome translating an mRNA strand, with labeled nucleotide sequences and emerging protein chains. Background is dark and light shades of orange rays spreading from the center of the strand.
Nucleobases—the molecular components of DNA—can be formed on Earth in hydrothermal ventsand volcanic reactions with the atmosphere,drivingcomplex organic chemistry.
NASA/Aaron Gronstal