Bottom line: New evidence from Harvard suggests that – a few billion years ago – Earth was a true water world, completely covered by a global ocean, with little if any visible land.
Currently, the most favored explanation for where the Earth got its water is that it acquired it from water-rich objects (planetesimals) that made up a few percent of its building blocks. These water-rich planetesimals would have been either comets or asteroids.
In Earth's Beginning
At its beginning, Earth was unrecognizable from its modern form. At first, it was extremely hot, to the point that the planet likely consisted almost entirely of molten magma. Over the course of a few hundred million years, the planet began to cool and oceans of liquid water formed.
Scientists have found evidence that Earth was covered by a global ocean that turned the planet into a “water world” more than 3bn years ago. Telltale chemical signatures were spotted in an ancient chunk of ocean crust which point to a planet once devoid of continents, the largest landmasses on Earth.
Life is believed to have originated in sea water (also known as earth's primordial soup) because sea water contained all the essential elements that were required for the origin of first life. Secondly, at the time of origin of life, the ozone layer was not formed, so terrestrial origin of life was not feasible.
Evidence shows that life probably began in the ocean at least 3.5 billion years ago. Photosynthesis began more than 2.5 billion years ago—the Great Oxidation Event. But it took hundreds of millions of years for enough oxygen to build up in the atmosphere and ocean to support complex life.
New research suggests ancient Earth was a water world, with little to no land in sight. And that could have major implications for the origin and evolution of life. While modern Earth's surface is about 70 percent water-covered, the new research indicates that our planet was a true ocean world some 3 billion years ago.
It suggests that most of Earth's water was on the surface at that time, during the Archean Eon between 2.5 and 4 billion years ago, with much less in the mantle. The planet's surface may have been virtually completely covered by water, with no land masses at all.
Nearly 4 billion years ago, during the Late Heavy Bombardment, countless meteors rained down on the Earth and the Moon. Over time, these icy asteroids and comets delivered oceans to Earth, depositing the water directly to the surface.
As much as half of all the water on Earth may have come from that interstellar gas according to astrophysicists' calculations. That means the same liquid we drink and that fills the oceans may be millions of years older than the solar system itself.
Washington, DC—Our planet's water could have originated from interactions between the hydrogen-rich atmospheres and magma oceans of the planetary embryos that comprised Earth's formative years, according to new work from Carnegie Science's Anat Shahar and UCLA's Edward Young and Hilke Schlichting.
The same goes for deep-sea hydrothermal vents. These chimney-like vents form where seawater comes into contact with magma on the ocean floor, resulting in streams of superheated plumes. The microorganisms that live near such plumes have led some scientists to suggest them as the birthplaces of Earth's first life forms.
Adam is the name given in Genesis 1-5 to the first human. Beyond its use as the name of the first man, adam is also used in the Bible as a pronoun, individually as "a human" and in a collective sense as "mankind".
There was no life on Earth for the first billion years because the atmosphere was not suitable for life. Earth's first atmosphere had lots of water vapor but had almost no oxygen. Later, frequent volcanic eruptions put several different gases into the air (Figure 12.13).
Now, evidence is mounting that some 3 billion to 4 billion years ago, the planet's oceans held nearly twice as much water—enough to submerge today's continents above the peak of Mount Everest. The flood could have primed the engine of plate tectonics and made it more difficult for life to start on land.
Water may not be lost from the earth's atmosphere; however, an apparent loss does exist from the “free” water in the atmosphere. It has been absorbed by the increase in living beings (people an animals) and therefore not available in abundant quantities as in previous generations.
Water, water everywhere—and not a drop to drink. In 1972, scientists were astonished to see pictures from NASA's Mariner 9 mission as it circled Mars from orbit. The photos revealed a landscape full of riverbeds—evidence that the planet once had plenty of liquid water, even though it's dry as a bone today.
The planets of our solar system were created around 4.6 billion years ago from clumps of rocks spinning around the Sun. Earth was moulded from rocks that came from the inner solar system where the fierce heat of the Sun would have boiled away any water. So, according to the textbooks, water must have come later.
The whole world will never be underwater. But our coastlines would be very different. If all the ice covering Antarctica , Greenland, and in mountain glaciers around the world were to melt, sea level would rise about 70 meters (230 feet). The ocean would cover all the coastal cities.
Earth was formed approximately 4.6 billion years ago, likely as the result of a supernova (star explosion). The debris from this explosion began to collapse in on itself due to gravity, forming the sun.
The tectonic plates of the oceans are being subducted under the continental plates, or under other oceanic plates. Examples include the Pacific Ocean moving under Japan, and subductions within the Mediterranean region.
Over millions of years, much of this water is recycled between the inner Earth, the oceans and rivers, and the atmosphere. This cycling process means that freshwater is constantly made available to Earth's surface where we all live.
What's Under the Sea. While you might be picturing smooth, sandy floors, The Atlantic points out that the seabed is actually “a jagged and dynamic landscape” with as much variation as we see on land. Under the depths of the ocean, there are mountains, canyons, hot springs, lakes and hillsides.
Researchers have identified traces of what they believe is the earliest known prehistoric ancestor of humans – a microscopic, bag-like sea creature, which lived about 540 million years ago.