Where Did All Our Oceans Come From?

Scientists have many theories about the origin of our oceans and one of the prevailing theories is that ice comets struck Earth long ago.

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Each week on TestTubePlus, we pick one topic and cover it from multiple angles. This week, we're delving deep into everything you've ever wondered or been curious about in regards to the Ocean. So far, Trace has talked about why its so hard to track how much life is in the world's oceans, how scientists are just now mapping the ocean floor, and how human life is still completely dependent on oceans. Today, we find out where the Earth's oceans came from.

The truth is, scientists aren't even 100 percent sure how the Earth go all its water. Until recently, the prevailing theory is that early Earth was bombarded by icy comets which melted and became today's oceans. However, a study conducted in 2014 by the Woods Hole Oceanographic Institution (WHOI) says that while comets may have added water later, the Earth formed 4.6 billion years ago with water on the surface. This theory is supported by an alternative study found a huge reservoir of water between the upper and lower mantle, somewhere between 250 to 410 miles (400 to 660 km) below the Earth's crust.

Water is something that astronomers as busy looking for on other planets because, based on our understanding of life, it would likely be a prerequisite for extraterrestrial life. Alien life would need a solvent (like water) and an element like carbon for its function and structure. The most common elements in the universe are (in order): hydrogen, helium, oxygen, neon, nitrogen, carbon, silicon, magnesium, iron and sulfur. Keeping this in mind, liquid water (H2O), is the most abundant candidate for a solvent to support the complex biochemistry required for life to emerge.

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Why Do We Look For Water When Searching For Life (io9)
"... Given the chemical possibilities available from the most abundant elements in the universe, even an alien scientist with a different biochemistry would probably agree that a water-solvent-based biochemistry is quite likely to occur elsewhere in the universe."

How do we use marine resources? (Hermoine.net)
"Fisheries: For food - fish, such as orange roughy, blue ling, grenadier and redfish, and shellfish (e.g., oysters, mussels, crabs and lobsters) are in high demand by communities all over the world. Oil: Fuel, plastics, man-made fibres, chemicals (e.g., pain-killers), rubber, fertilsers...the list is endless! Gas:Central heating, cooking, plastic and chemical production (e.g. antifreeze!), food-processing, some transportation."

Big data maps world's ocean floor (University of Sydney)
"It is the first time the composition of the seafloor, covering 70 percent of the Earth's surface, has been mapped in 40 years; the most recent map was hand drawn in the 1970s."

Ocean (Encyclopedia of Earth)
"Oceans cover approximately 65.7% or 335 million square kilometers (129 million square miles) of Earth's surface with a volume of about 1,370 million cubic kilometers (329 million cubic miles). The average depth of these extensive bodies of seawater is about 3.8 kilometers (2.4 miles). Maximum depths can exceed 10 kilometers (6.2 miles) in a number of areas known as ocean trenches."

Why Are Oceans Salty? (Live Science)
"Ocean water contains lots of different mineral salts: sodium, chloride, sulfate, magnesium, calcium, potassium, bicarbonate and bromide. These salts enter the ocean through rivers, which pass over rocks and soil, picking up salt along the way."