Water, water every where,
And all the boards did shrink;
Water, water, every where,
Nor any drop to drink
Words from Coleridge’s Rime of the Ancient Mariner written in 1798.
Welcome to Episode 2 of Season 2 of the Paul Kristoffer Show. Thank you for joining. To To join the conversation, Please tweet me @Kristoffershow or visit Paul Kristoffer.com
Listen to the podcast, here:
In this episode, you’ll learn about water and the origins of life, including:
- What is water?
- What are the properties that make water so special?
- Why is water needed for all life on earth?
- How abundant is water in the Solar System? In the Universe as a whole?
- How did water get here?
Its not an exaggeration to say that water is life! We all know that we need water to survive, and without it, we can die in a matter of days. Water is required for all life processes, but for most of us, we take it for granted.
Specifically, water molecules are formed when two hydrogen atoms bond with one oxygen atom, with the well known chemical formula of H2O. The atoms share electronss in a special bond called a covalent bond.
Water is a relatively lightweight molecule, but is liquid at room temperature. Most lightweight compounds are gasses at room temperature.
Water has the rare property of expanding and becoming lighter, less dense, when it freezes. Most compounds become more compact, and denser, when moving from liquid to a solid state.
Ready for more? Water’s solid, liquid and gaseous states exist within a relatively narrow temperature range that we regularly experience on earth. In fact, water vapor is a major greenhouse gas.
Solid water, ice, floats on liquid water. This is a relatively rare occurrence among compounds, but brings significant advantages to life. The first being that aquatic life can remain relatively warm under lake or sea ice, and thus flourish under harsh atmospheric conditions.
Another important property of water is that it absorbs a lot of heat before it warms up. The scientific term for this is specific heat capacity. The concept is expressed as the amount of heat need to raise one gram of substance by 1 degree Celsius. The specific heat of water is higher than many other substances, including metals, sand, rock or the land in general. In fact water has one of the highest specific heat of natural substances.
Water does a lot to help regulate temperatures on earth by smoothing out atmospheric temperature changes. This is a major factor that explains why coastal areas remain cooler in the summer, and warmer in the winter. The ocean absorbs heat during the summer, and releases it over winter.
Water is required all life on Earth. Most scientists agree that living organisms are defined by their common attributes, such as the ability to grow, reproduce, maintain an internal homeostasis, respond to stimuli and carry out metabolic processes. All of these processes require water, whether the organism is a single celled bacterium, fungi or a blue whale.
Why is water so critical to many biological processes? It’s because of another property of water. Known as “the universal solvent”, water dissolves more substances than any other liquid. Solvent is the scientific word for a substance, usually a liquid, that other materials dissolve into. Like when salt or sugar dissolves in water. This is an important property to life, because wherever water goes, important chemicals, nutrients and minerals are brought along with it. The chemistry of life, the processes in our bodies and almost all biological processes, cannot take place without it. This is true for all life on earth.
Why does water have all of these unique properties? The answer is simple. Hydrogen bonds. Hydrogen bonds come into play because of the structure of the water molecule. Water has a unique shape and polarity. This is because of the way the Oxygen and two Hydrogen atoms bond together to form the molecule. Oxygen has 6 electrons in its outer shell, but it wants to have 8 to form a complete shell to achieve stability. Hydrogen has one electron, but wants two in its outer shell.
The Hydrogen atoms need to achieve stability by sharing one of its electrons with the oxygen, and recieves one from the Oxygen atom, to achieve two electrons in its outer shell.. The Oxygen atom, achieves stability by sharing two of its electrons with the two Hydrogen atoms. In turn, the Oxygen atom “receives” one electron from each Hydrogen atom, leaving the Oxygen atom with 8 electrons in its outer shell. Now all the atoms are happy with complete electron shells – 2 for each Hydrogen atom, and eight for the Oxygen.
These are very strong bonds, called covalent bonds
Simple right? That’s where the story ends for most of us, but there is a lot more to water than meets the eye. Understanding how water molecules interact with each other, and other substances can help us to understand this wondrous chemical compound and its properties.
Hydrogen bonds are formed in water because Oxygen is highly electo-negative. Electronegativity is a scientific word to describe how attractive an atom is to electrons. Oxygen is the second most electronegative element in the Periodic Table. Fluorine is the highest. Oxygen has 8 protons in its nucleus, which attract electrons and causes this high electronegativity.
The Oxygen nucleus attracts the shared electrons from the Hydrogen atoms towards itself. This results in a di-polar molecule, where one end of the molecule, the oxygen “end,” is more negatively charged, and the other “end”, where the Hydrogen atoms are, is more positively charged. Sort of like a magnet.
Hydrogen bonds are weak bonds, never more than 1/12 the strength of the covalent bond. These weak bonds continually form and reform in liquid water. when water molecules bond to each other (positive to negative), and to other substances.
In ice, each water molecule can form four permanent hydrogen bonds. The oxygen atom can attract two Hydrogen atoms from a neighboring molecule. Each hydrogen, likewise, can bond with the oxygen of two neighboring molecules. The molecules form a hexagonal structure.
As ice warms and becomes liquid, meaning that there is enough heat energy to break the hexagonal crystal structures, the hydrogen bonds are continuously broken and reformed. In liquid water, each water molecule forms at least one Hydrogen bond and there are effectively no free molecules in your glass of water.
This is the reason why liquid water is more dense than solid ice. Ice is made up of a hexagonal structure of molecules, due to the four permanent hydrogen bonds that form. 5 water molecules are bonded together in a repeating hexagonal structure. Molecules in liquid water bond with at least one partner, but the structure is not as rigid and open. More molecules can fit into a smaller space. This means that there are more water molecules into any given volume – higher density – then the solid form.
Water is actually most dense at 4 degrees C, and then gradually becomes less dense as the water cools into a crystalline solid. This property is very helpful to aquatic life, as the warmest water in winter may be found at the bottom of a pond, where the 4 degree celsius water has settled to the bottom of the pond, and cooler water will rest on top in layers.
Water is such a good solvent because of? Yes, you got it. Hydrogen bonds. The dipolar molecule, water, dissolves many ionic compounds readily, because the positive ions are attracted to the negatively charged, Oxygen, end of the molecule, and the negative ions are likewise attracted to the negative end. This attractive force is stronger than the ionic bond itself. However, this is not universally true. Before you run out and try to dissolve Calcium Carbonate in water, you may be disappointed to learn that there are many ionic compounds that do not dissolve in water. This is because the attractive force of the hydrogen bonds is less than the strength of the compounds ionic bond, or lattice energy.
How abundant is water in the universe? Is our Earth, largely a water planet, unique, unusual or rare?
According to NASA, Hydrogen and Oxygen are among the most abundant elements in the Universe. Astronomers can detect water signatures as light, and other EM waves, pass through interstellar clouds, protoplanetary disks (the nurseries of new solar systems and planets), and in the atmospheres of giant planets orbiting other stars.
Scientists use radio telescopes to pick up water signals in early galaxies, as far back in time as 11 billion years ago, when the universe was one fifth of its current age.
In our solar system, water is found almost everywhere astronomers look: in three of the rocky inner planets, Mercury, Mars and Earth. (Venus has lost almost all of its water to space, due to runaway greenhouse gas effects and Venus’ lack of a protective magnetic field). Water is also found in asteroids, comets, moons, and dwarf planets like Ceres. Water is thought to exist in massive quantities within in the gas giants, Jupiter, Saturn, Uranus and Neptune.
On a Paul Kristoffer Show side note, Ceres is located in the asteroid belt between Mars and Jupiter. Ceres plays a role in the book series, “The Expanse” written by James S. A. Corey (a pseudonym for the two authors, Daniel Abraham and Ty Frank). The Expanse was made into a television series released by SyFy in 2015 and later picked up by Amazon in 2019. The Paul Kristoffer Show highly recommends.
How did water get on Earth?
Scientists believe that the inner rocky planets would have been too hot for water to condense in the early stages of our solar system’s formation. Temperatures would have been much warmer than the melting and boiling point of water. The earth also did not have an atmosphere – meaning any water droplets in the would have been blown into space by the solar wind. The solar wind is a continuous stream of charged particles cast off from the sun’s corona. The particles are mostly electrons, protons and alpha particles with enough energy to blow our atmosphere, including water vapor, into space. Our magnetic field deflects these particles around the atmosphere, and ejects them around the magnetic poles, causing the stunning aurora borealis, or northern and southern lights.
The magnetic field extends around 10 earth radii on the dayside of the earth (facing the solar wind) and hundreds of earth radii beyond the earth to the nightside.
Back to our story of the Earth’s formation and how water got here. During the early period, known as the Hadean , many impacts occurred that resulted in surface temperatures hot enough to melt rock. The earth was in the process of clearing its orbit – and there was a lot more matter in the area that eventually cooalesed into the rocky planets and moons. It is thought that a sister planet to ours collided with the earth, discharging about one third the mass of each planet into space, releasing enormous amounts of energy. The resultant cooling and gravitational forces formed the planet earth and our moon. As you can imagine, no water could have existed in such an environment, so water had to have been brought here. In huge quantities. But from where?
what are the likely sources?
We know that Earth has been subjected to many strikes from Asteroids (rock debris left over from the dust that formed the rocky, inner planets) and Comets (snowballs of ice and dirt from the most distant, outermost edges of the Solar System known as the Oort cloud, or closer in from the area known as the Kuiper belt, which is located beyond the orbit of Neptune. The kuiper belt is where the dwarf planet Pluto is in orbit around the sun).
Its is theorized that asteroids and comets brought water to earth, via impact. Scientists have sent probes to measure the ratio of isotopes in the water on asteroids and comets to compare them to those found on earth. Isotopes naturally occur when atoms, such as Hydrogen, have one or more additional neutrons, but same number of protons and electrons. “heavy water” is water containing deuterium. Deuterium is a Hydrogen atom with a neutron and proton in its nucleus, instead of the most common configuration of Hydrogen, called protium, whose nucleus contains only a proton.
One of the more infamous naturally occurring isotopes, Uranium 235, can sustain a nuclear chain reaction. Uranium 235 occurs 0.72% of the time. Uranium 238 is the more predominant isotope found in nature.
Getting back to water, and how it arrived here on earth, When the ratios of isotopes from samples gathered from asteroids and comets are compared to those found in the water of our oceans, lakes and rivers, we find the ratios to be similar, although not always exact.. Scientists generally conclude that this is how water arrived on Earth, through comets and asteroids.
Let’s take off our tin foil hats for a minute. I want to discuss why its important to know that water was brought to earth by bodies such as asteroids and comets. It has to do with how life may have begun. All life on earth started once. The amazing diversity of life we see today, is from that first, ancestral organism.
But there is a problem with the amount of time. There is not enough for the required building blocks of life, as we know it, to have formed and to have become self replicating. We know that our solar system is around 4.6 billion years old. Dating of rocks and minerals on earth is done by measuring the lead isotopes found in the oldest rock formations. Lead is a reliable “clock” for dating rocks because there are two lead isotopes, PB 207 and PB206, that are the end result of the decay process of U238 and U235.
By knowing the radioactive decay process and half lives, reasonably accurate dating of rock formations can take place. What is radioactive decay? Radioactive decay is what happens when an unstable nucleus loses its energy by emission of radiation or a particle. Material containing an unstable nucleus is considered “radioactive”.
This fact relates to how life may have originated on planet earth, as well as answer the question about life on other worlds (planets, and moons). Life originated once. And from that one spark, the entire diversity of life on earth sprang.
The best theories on how life may have originated has been discussed and promoted by evolutionary Biologists, such as Richard Dawkins. One idea is that comets may have brought the building blocks of life to earth. These would be self-replicating structures that hitchhiked on celestial bodies that crash landed. This could answer the question of how self replicating proteins RNA could have developed so quickly and evolved onto DNA. I am speaking in geological terms when I say quickly. The earliest known fossils of life on earth are dated to 3.42 Billion years ago. Since scientists estimate that the earth is 4.6 Billion years old, that means life emerged in a time frame of less than 1.18 Billion years. Remember, there was no water on earth at first, and all life here relies on water. By most scientific models, that is not enough time for self replicating structures to form RNA and then DNA and single celled organisms.
These self-replicating structures could, conceivable, have sprung into existence through chance. Given the number of possible habitable worlds in the universe, something that is so unlikely that most of us would say “impossible” actually becomes possible given the age of the universe and the number of habitable worlds with water.
However, most scientists are not satisfied with such an explanation.
Do you think that this is an outlandish idea? Are there other structures that replicate, but do not have life? We are all familiar with crystals, which replicate a pattern based upon the underlying structure of the material.
There are also self-replicating proteins called prions, that are responsible for Mad Cow Disease and Jacob-Creuzfeld disease in humans. Prions are not alive, but are protein structures that cause the protein structures in our cells to deform, these deformed proteins then cause other normal proteins in our body to deform and so on.,..and that is how the disease progresses with 100% fatality rates. What other self-replicating structures will we discover in the future? I am sure many….
This exciting insight means that life very well can be more common than thought. That life may exist in other worlds, Mars, the moons of Jupiter and Saturn where salty oceans may exist, warmed by the massive tidal forces of those gas giants.
If comets could seed the earth with the building blocks of life, then why not these other worlds?
Of course, these theories need to be validated by evidence.
NASA has several missions underway to attempt to gather evidence, including:
Perseverance Mars Rover, which landed on the red planet on February 18, 2021. Perseverance can drill and collect soil cores that can be returned to earth for analysis in a future mission.
The Europa Clipper Mission, targeted to launch in 2024 will visit Europa, a moon of Jupiter, to determine whether conditions to sustain life exist on the frozen world.
“The Dragonfly mission will deliver a rotorcraft, an aircraft with rotary wings or rotors, to visit Saturn’s largest and richly organic moon, Titan. Slated for launch in 2027 and arrival in 2034, Dragonfly will sample and examine dozens of promising sites around Saturn’s icy moon and advance our search for the building blocks of life. This revolutionary mission will explore diverse locations to look for prebiotic chemical processes common on both Titan and Earth. Titan is an analog to the very early Earth, and can provide clues to how prebiotic chemistry under these conditions may have progressed”
I hope that you have enjoyed this episode of The Paul Kristoffer Show podcast. Many of us often take water for granted, me included, and overlook its special qualities, properties and beauty. Next time you take a drink, think about the amazing journey of the water in your glass, and the miracle of hydrogen bonds. Water is the reason why the Earth is known as the Blue Planet, and I hope it stays that way for millennia to come.
Sources:
USGS: https://www.usgs.gov/special-topics/water-science-school/science/water-universal-solvent
The Journal Nature: https://www.nature.com/articles/356428a0
NASA: https://www.nasa.gov/jpl/the-solar-system-and-beyond-is-awash-in-water
https://www.scientificamerican.com/article/how-did-water-get-on-earth/
https://www.nps.gov/subjects/geology/age-of-the-earth.htm
https://www.ncbi.nlm.nih.gov/books/NBK6360/
Music by Zapslat