In a quest to unravel the mysteries of the origin of life, recently a team of researchers have come up with a model which suggests how life came into existence on Earth.

In a paper published in the journal Proceedings of the Royal Society , the authors stated how “bouncing” comets are likely to have distributed the raw ingredients for life, which are known as prebiotic molecules, across the star systems which are similar to our system. Throughout the study, the team emphasised simulating rocky exoplanets which orbit around sun-size stars.

As per scientists, there are two theories regarding how life came on Earth – one suggests that the ingredients for life came from a primordial soup on the planet and the other states that the molecules required for life, were brought from elsewhere, and were “seeded” on the Earth by the cosmos.

A team of scientists, while keeping the second theory in mind, came up with a model which explains how the ingredients of life may have been delivered on the Earth and how it is likely to happen on other planets outside our solar system.

Life seeded by comets or meteors

Although the exact process by which life formed on Earth is not well understood, the origin of life requires the presence of carbon-based molecules, liquid water and an energy source. Because some Near-Earth Objects contain carbon-based molecules and water ice, collisions of these object with Earth have significant agents of biologic as well as geologic change.

For the first billion years of Earth’s existence, the formation of life was prevented by a fusillade of comet and asteroid impacts that rendered the Earth’s surface too hot to allow the existence of sufficient quantities of water and carbon-based molecules. Life on Earth began at the end of this period called the late heavy bombardment, some 3.8 billion years ago.

The earliest known fossils on Earth date from 3.5 billion years ago and there is evidence that biological activity took place even earlier – just at the end of the period of late heavy bombardment. So the window when life began was very short. As soon as life could have formed on our planet, it did.

But if life formed so quickly on Earth and there was little in the way of water and carbon-based molecules on the Earth’s surface, then how were these building blocks of life delivered to the Earth’s surface so quickly? The answer may involve the collision of comets and asteroids with the Earth, since these objects contain abundant supplies of both water and carbon-based molecules.

Once the early rain of comets and asteroids upon the Earth subsided somewhat, subsequent impacts may well have delivered the water and carbon-based molecules to the Earth’s surface – thus providing the building blocks of life itself.

It seems possible that the origin of life on the Earth’s surface could have been first prevented by an enormous flux of impacting comets and asteroids, then a much less intense rain of comets may have deposited the very materials that allowed life to form some 3.5 – 3.8 billion years ago.

Comets have this peculiar duality whereby they first brought the building blocks of life to Earth some 3.8 billion years ago and subsequent cometary collisions may have wiped out many of the developing life forms, allowing only the most adaptable species to evolve further.

Where did life on Earth begin?

Two possibilities are in volcanically active hydrothermal environments on land and at sea.

Some microorganisms thrive in the scalding, highly acidic hot springs environments like those found today in Iceland, Norway and Yellowstone National Park.

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.

Organic molecules may also have formed in certain types of clay minerals that could have offered favorable conditions for protection and preservation. This could have happened on Earth during its early history, or on comets and asteroids that later brought them to Earth in collisions. This would suggest that the same process could have seeded life on planets elsewhere in the universe.