Water was crucial for the evolution of life on our own beautiful blue planet--as well as for evaluating the possibility of life existing on other worlds.
Identifying the original source of Earth's water is central to our scientific understanding of how life-sustaining environments emerge and how likely they are to be discovered elsewhere.
In the September 25, 2014 issue of the journal Science, a team of astronomers announced their new findings suggesting the possibility that half of the water on Earth is older than the Solar System itself--perhaps originating in the very ancient, frigid, dark molecular cloud that gave rise to our Sun and its surrounding, nourishing planet-birthing disk composed of gas and dust.
Water can be found throughout our entire Solar System--not just on our own planet.
It also exists on the multitude of frozen comets that dwell in our Solar System's outer limits, as well as on the icy moons of the four giant gaseous planets of the outer Solar System--Jupiter, Saturn, Uranus, and Neptune.
Water has even been found secreted in the shadowed basins of Mercury, which is the closest planet to our Sun.
Indeed, water has been detected in mineral samples from meteorites, and on Earth's Moon and Mars.
Primitive objects like comets and asteroids are precious "time capsules" that tell of the long-vanished conditions that existed during the most ancient eras of our Solar System's existence.
Their tattle-tale ices can reveal to scientists information about the ice that surrounded our Star after its birth about 4.
56 billion years ago--the origin of which was an unanswered question, until now! When our Sun was a bouncy, sparkling young Star, it was surrounded by a solar nebula, from which the planets were born.
However, it was previously unclear to astronomers whether the ice in this primordial disk originated from the Sun's own parental interstellar molecular cloud, from which it was formed, or whether this interstellar water had been destroyed and was re-formed by the chemical reactions occurring in the solar nebula.
"Why is this important? If water in the early Solar System was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars.
But if our early Solar System's water was largely the result of local chemical processing during the Sun's birth, then it is possible that the abundance of water varies considerably in forming planetary systems, which would obviously have implications for the potential for the emergence of life elsewhere," explained Dr.
Conel Alexander in a September 25, 2014 Carnegie Institution of WashingtonPress Release.
Dr.
Alexander, a member of the research team, is of the Carnegie Institution which is located in Washington D.
C.
By reconstructing the mysterious conditions that existed in this primordial protoplanetary disk--composed of gas and dust--from which our Solar System was born, the astronomers have concluded that our planet, as well as other bodies that circle our Sun, must have received a large quantity of their water from the ancient cloud of gas from which our Star was born--instead of forming later.
The astronomers believe that such interstellar water would also be included in the formation of most other stellar systems, and perhaps of other Earth-like exoplanets dwelling in the distant families of stars beyond our Sun.
These very dense molecular clouds of gas and dust haunt our Milky Way Galaxy in huge numbers--floating like enormous, billowing dark ghosts through the space between stars.
These ghostly clouds also harbor abundant quantities of water, in the form of ice.
When a baby star first ignites, it heats up the cloud around it with its furious searing-hot fires, and it also floods it with radiation--thus vaporizing the ice and shattering some of the water molecules into their component oxygen and hydrogen atoms.
A Star Is Born Protostars form surrounded by a nourishing disk of gas and dust, termed the solar nebula or the protoplanetary accretion disk.
This dusty gaseous ring encircling the baby star harbors the material from which planets are born.
Planetary systems, such as our own Solar System, form when a relatively small, very dense blob, embedded within one of the many gigantic, dark, and frigid molecular clouds billowing ghost-like throughout interstellar space, collapses under its own heavy weight.
Most of the collapsing blob congregates at the center, eventually catching fire as a result of the process of nuclear fusion, thus giving birth to the protostar.
The leftover gas and dust becomes the accretion disk, from which planets, moons, and an assortment of smaller planetary system objects, may form.
These very thick, swirling disks are both extremely hot and very massive, and they can circle their stars for as long as 10 million years.
However, by the time the baby star has reached what is termed the T Tauri stage of its development, the thick encircling protoplanetary disk has cooled off quite a bit and thinned out dramatically.
A T Tauri is a youthful, variable Sun-like star, of the tender age of 10 million years--or less--that is also extremely active.
These stellar toddlers carry a mass that is about the same as that of our Sun, but they show diameters that are several times larger.
However, T Tauris are still in the process of shrinking.
Baby stars that are like our Sun shrink as they grow older.
By the time the stellar toddler has reached this active stage, less volatile materials have started to condense close to the center of its swirling, surrounding disk, producing a multitude of naturally sticky and very fine grains of dust.
The delicate, fragile dust motes carry crystalline silicates.
The very fine dust particles bump into each other and then stick together in the very dense disk environment.
Gradually, the merging dust motes create ever larger and larger objects--from pebble-size, to boulder-size, to mountain-size, to planet-size.
The dust particles "glue" themselves to one another to create objects that can reach several centimeters in size, and these objects gradually grow into what are termed planetesimals--which are the building blocks of major planets.
Planetesimals can attain sizes of 1 kilometer across--or even larger--and they are a very plentiful population within the disk environment.
Some planetesimals can even linger long enough to still be around literally billions of years after a mature planetary system has formed.
In our own Solar System, the asteroids and comets are remnant planetesimals--the leftovers of the ancient era of planet-building.
Water Most Ancient For a long time, astronomers have been uncertain about how much of the "old" disk water would be able to survive the turbulent process of planetary system formation.
If most of the "old", original water molecules had been broken up into hydrogen and oxygen, water would have had to reform in our ancient Solar System.
However, the environment that made this possible could be specific to our Solar System, in which case there may well be a large number of other, very distant stellar systems that were left dry--bereft of life-sustaining water, according to Ilsedore Cleeves, a doctoral student in astrochemistry at the University of Michigan's College of Literature, Science, and the Arts in Ann Arbor.
According to Cleeves, who led the new study, if some of the "old" water was able to survive the turbulent star-birthing process, and if our Solar System's example is typical of what occurs in other systems, it means that water is readily available as a universal ingredient at the time of planet-building.
Between 30 and 50 percent of the water originated in the very ancient billowing, cold, dark molecular cloud that gave birth to our Solar System, according to the new study, Cleeves went on to explain.
In order to arrive at that particular estimate, Cleeves and Dr.
Edwin Bergin, a professor of astronomy at the University of Michigan, simulated the chemistry that went on as our Solar System formed.
The two colleagues focused on the ratio of two slightly different varieties of water--the common kind and a more exotic heavier version.
In our Solar System today, comets and Earth's churning oceans contain particular ratios of heavy water--higher ratios than the Sun contains.
"Chemistry tells us that Earth received a contribution of water from some source that was very cold--only tens of degrees above absolute zero, while our Sun being substantially hotter had erased this deuterium, or heavy water, fingerprint," Dr.
Bergin explained in a September 25, 2014 University of Michigan Press Release.
To begin their Solar System supercomputer simulation, the astronomers went far back in time to zero in on heavy water.
They proceeded with their simulation, and then waited to see if eons of Solar System formation could lead to the ratios they were seeing today on our planet and in comets.
"We let the chemistry evolve for a million years--the typical lifetime of a planet-forming disk--and we found that chemical processes in the disk were inefficient at making heavy water throughout the Solar System.
What this implies is the planetary disk didn't make the water, it inherited it.
Consequently, some fraction of the water in our Solar System predates the Sun," Cleeves explained in the September 25, 2014 University of Michigan Press Release.
All of the life that evolved on our planet depends on water.
Understanding where it came from and when can help astronomers to calculate how common water might be throughout our entire Milky Way Galaxy.
"The implications of these findings are pretty exciting.
If water formation had been a local process that occurs in individual stellar systems, the amount of water and other important chemical ingredients necessary for the formation of life might vary from system to system.
But because some of the chemically rich ices from the molecular cloud are directly inherited, young planetary systems have access to these important ingredients," Cleeves added.
Dr.
Bergin explained in the same Press Release that "Based on our simulations and our growing astronomical understanding, the formation of water from hydrogen and oxygen atoms is a ubiquitous component of the early stages of stellar birth.
It is this water which we know from astronomical observation forms at only 10 degrees above absolute zero before the birth of the star, this is provided to nascent stellar systems everywhere.
" "Our findings show that a significant fraction of the Solar System's water, the most fundamental ingredient in fostering life, is older than the Sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems," Dr.
Alexander commented in the September 25, 2014 Carnegie Institution Press Release.
Identifying the original source of Earth's water is central to our scientific understanding of how life-sustaining environments emerge and how likely they are to be discovered elsewhere.
In the September 25, 2014 issue of the journal Science, a team of astronomers announced their new findings suggesting the possibility that half of the water on Earth is older than the Solar System itself--perhaps originating in the very ancient, frigid, dark molecular cloud that gave rise to our Sun and its surrounding, nourishing planet-birthing disk composed of gas and dust.
Water can be found throughout our entire Solar System--not just on our own planet.
It also exists on the multitude of frozen comets that dwell in our Solar System's outer limits, as well as on the icy moons of the four giant gaseous planets of the outer Solar System--Jupiter, Saturn, Uranus, and Neptune.
Water has even been found secreted in the shadowed basins of Mercury, which is the closest planet to our Sun.
Indeed, water has been detected in mineral samples from meteorites, and on Earth's Moon and Mars.
Primitive objects like comets and asteroids are precious "time capsules" that tell of the long-vanished conditions that existed during the most ancient eras of our Solar System's existence.
Their tattle-tale ices can reveal to scientists information about the ice that surrounded our Star after its birth about 4.
56 billion years ago--the origin of which was an unanswered question, until now! When our Sun was a bouncy, sparkling young Star, it was surrounded by a solar nebula, from which the planets were born.
However, it was previously unclear to astronomers whether the ice in this primordial disk originated from the Sun's own parental interstellar molecular cloud, from which it was formed, or whether this interstellar water had been destroyed and was re-formed by the chemical reactions occurring in the solar nebula.
"Why is this important? If water in the early Solar System was primarily inherited as ice from interstellar space, then it is likely that similar ices, along with the prebiotic organic matter that they contain, are abundant in most or all protoplanetary disks around forming stars.
But if our early Solar System's water was largely the result of local chemical processing during the Sun's birth, then it is possible that the abundance of water varies considerably in forming planetary systems, which would obviously have implications for the potential for the emergence of life elsewhere," explained Dr.
Conel Alexander in a September 25, 2014 Carnegie Institution of WashingtonPress Release.
Dr.
Alexander, a member of the research team, is of the Carnegie Institution which is located in Washington D.
C.
By reconstructing the mysterious conditions that existed in this primordial protoplanetary disk--composed of gas and dust--from which our Solar System was born, the astronomers have concluded that our planet, as well as other bodies that circle our Sun, must have received a large quantity of their water from the ancient cloud of gas from which our Star was born--instead of forming later.
The astronomers believe that such interstellar water would also be included in the formation of most other stellar systems, and perhaps of other Earth-like exoplanets dwelling in the distant families of stars beyond our Sun.
These very dense molecular clouds of gas and dust haunt our Milky Way Galaxy in huge numbers--floating like enormous, billowing dark ghosts through the space between stars.
These ghostly clouds also harbor abundant quantities of water, in the form of ice.
When a baby star first ignites, it heats up the cloud around it with its furious searing-hot fires, and it also floods it with radiation--thus vaporizing the ice and shattering some of the water molecules into their component oxygen and hydrogen atoms.
A Star Is Born Protostars form surrounded by a nourishing disk of gas and dust, termed the solar nebula or the protoplanetary accretion disk.
This dusty gaseous ring encircling the baby star harbors the material from which planets are born.
Planetary systems, such as our own Solar System, form when a relatively small, very dense blob, embedded within one of the many gigantic, dark, and frigid molecular clouds billowing ghost-like throughout interstellar space, collapses under its own heavy weight.
Most of the collapsing blob congregates at the center, eventually catching fire as a result of the process of nuclear fusion, thus giving birth to the protostar.
The leftover gas and dust becomes the accretion disk, from which planets, moons, and an assortment of smaller planetary system objects, may form.
These very thick, swirling disks are both extremely hot and very massive, and they can circle their stars for as long as 10 million years.
However, by the time the baby star has reached what is termed the T Tauri stage of its development, the thick encircling protoplanetary disk has cooled off quite a bit and thinned out dramatically.
A T Tauri is a youthful, variable Sun-like star, of the tender age of 10 million years--or less--that is also extremely active.
These stellar toddlers carry a mass that is about the same as that of our Sun, but they show diameters that are several times larger.
However, T Tauris are still in the process of shrinking.
Baby stars that are like our Sun shrink as they grow older.
By the time the stellar toddler has reached this active stage, less volatile materials have started to condense close to the center of its swirling, surrounding disk, producing a multitude of naturally sticky and very fine grains of dust.
The delicate, fragile dust motes carry crystalline silicates.
The very fine dust particles bump into each other and then stick together in the very dense disk environment.
Gradually, the merging dust motes create ever larger and larger objects--from pebble-size, to boulder-size, to mountain-size, to planet-size.
The dust particles "glue" themselves to one another to create objects that can reach several centimeters in size, and these objects gradually grow into what are termed planetesimals--which are the building blocks of major planets.
Planetesimals can attain sizes of 1 kilometer across--or even larger--and they are a very plentiful population within the disk environment.
Some planetesimals can even linger long enough to still be around literally billions of years after a mature planetary system has formed.
In our own Solar System, the asteroids and comets are remnant planetesimals--the leftovers of the ancient era of planet-building.
Water Most Ancient For a long time, astronomers have been uncertain about how much of the "old" disk water would be able to survive the turbulent process of planetary system formation.
If most of the "old", original water molecules had been broken up into hydrogen and oxygen, water would have had to reform in our ancient Solar System.
However, the environment that made this possible could be specific to our Solar System, in which case there may well be a large number of other, very distant stellar systems that were left dry--bereft of life-sustaining water, according to Ilsedore Cleeves, a doctoral student in astrochemistry at the University of Michigan's College of Literature, Science, and the Arts in Ann Arbor.
According to Cleeves, who led the new study, if some of the "old" water was able to survive the turbulent star-birthing process, and if our Solar System's example is typical of what occurs in other systems, it means that water is readily available as a universal ingredient at the time of planet-building.
Between 30 and 50 percent of the water originated in the very ancient billowing, cold, dark molecular cloud that gave birth to our Solar System, according to the new study, Cleeves went on to explain.
In order to arrive at that particular estimate, Cleeves and Dr.
Edwin Bergin, a professor of astronomy at the University of Michigan, simulated the chemistry that went on as our Solar System formed.
The two colleagues focused on the ratio of two slightly different varieties of water--the common kind and a more exotic heavier version.
In our Solar System today, comets and Earth's churning oceans contain particular ratios of heavy water--higher ratios than the Sun contains.
"Chemistry tells us that Earth received a contribution of water from some source that was very cold--only tens of degrees above absolute zero, while our Sun being substantially hotter had erased this deuterium, or heavy water, fingerprint," Dr.
Bergin explained in a September 25, 2014 University of Michigan Press Release.
To begin their Solar System supercomputer simulation, the astronomers went far back in time to zero in on heavy water.
They proceeded with their simulation, and then waited to see if eons of Solar System formation could lead to the ratios they were seeing today on our planet and in comets.
"We let the chemistry evolve for a million years--the typical lifetime of a planet-forming disk--and we found that chemical processes in the disk were inefficient at making heavy water throughout the Solar System.
What this implies is the planetary disk didn't make the water, it inherited it.
Consequently, some fraction of the water in our Solar System predates the Sun," Cleeves explained in the September 25, 2014 University of Michigan Press Release.
All of the life that evolved on our planet depends on water.
Understanding where it came from and when can help astronomers to calculate how common water might be throughout our entire Milky Way Galaxy.
"The implications of these findings are pretty exciting.
If water formation had been a local process that occurs in individual stellar systems, the amount of water and other important chemical ingredients necessary for the formation of life might vary from system to system.
But because some of the chemically rich ices from the molecular cloud are directly inherited, young planetary systems have access to these important ingredients," Cleeves added.
Dr.
Bergin explained in the same Press Release that "Based on our simulations and our growing astronomical understanding, the formation of water from hydrogen and oxygen atoms is a ubiquitous component of the early stages of stellar birth.
It is this water which we know from astronomical observation forms at only 10 degrees above absolute zero before the birth of the star, this is provided to nascent stellar systems everywhere.
" "Our findings show that a significant fraction of the Solar System's water, the most fundamental ingredient in fostering life, is older than the Sun, which indicates that abundant, organic-rich interstellar ices should probably be found in all young planetary systems," Dr.
Alexander commented in the September 25, 2014 Carnegie Institution Press Release.
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