Tag Archives: early Earth

Illustration of early Earth. Credit: Harvard University.

Meteorites impacting ancient Earth could have formed the basic ingredients for life

Artistic depiction of the Hadean.

If you’d travel back in time four billion years ago, you would surely be shocked by what you’d see around you — through the visor of a life-support suit you’d need to survive.

Instead of peaceful blue skies and an oxygen-rich atmosphere, the Earth is covered in a haze of noxious fumes, seas of lava, and a never-ending onslaught of asteroid and meteorite impacts. Welcome to the Hadean Earth!

Fittingly, this geological era was named after Hades, the Greek god of the underworld, and also the Hebrew word for hell. Perhaps the most chilling realization is that there are no lifeforms to speak of, not even the tiny microscopic bacteria.

Is this truly hell?

Well, almost. In a puddle of bubbling liquid nearby, inconspicuous amino acids are assembling into proteins, which will eventually give rise to the first single-celled organisms. But where did these amino acids come from?

The origin of life is perhaps the most debated existential question out there, known for giving scientists and philosophers angst and headaches for centuries. Today, the consensus seems to be that the emergence of amino acids can be pinned down to either endogenous formation or extraterrestrial delivery via meteorites.

It this latter scenario that Japanese researchers at Tohoku University, National Institute for Materials Science (NIMS), the Center for High Pressure Science & Technology Advanced Research (HPSTAR), and Osaka University have explored by simulating the chemical reactions involved when a meteorite crashes into the ocean.

Single stage propellant gun used for the simulation of impact-induced reactions. Credit: Yoshihiro Furukawa.

Using a complex experimental setup that employed more carbon dioxide and nitrogen in order to mimic the Hadean atmosphere, the researchers fired a single stage propellant gun to simulate the impact of an iron-rich meteorite.

Strikingly, these environmental conditions and the force of impact triggered chemical reactions that led to the formation of amino acids such as glycine and alanine, the main building blocks of proteins.

 “Making organic molecules form reduced compounds like methane and ammonia are not difficult, but they are regarded as minor components in the atmosphere at that time,” Yoshihiro Furukawa, a researcher at Tohoku University and the corresponding author of the new study, said in a statement.

“The finding of amino acid formation from carbon dioxide and molecular nitrogen demonstrates the importance in making life’s building blocks from these ubiquitous compounds,” he added.

It’s quite likely that carbon dioxide and nitrogen were also major constituent gases of Mars’ ancient atmosphere. Up until two billion years ago, Mars hosted oceans of liquid water and may have been very much Earth-like. If Mars ever harbored life, the same essential building blocks may have been seeded similarly to how it may have happened on Earth — at the very least, the new study shows that such a scenario is plausible.

Previously, other studies found that phosphates, essential ingredients for DNA-based life forms, may have originated from space. NASA scientists also found that hydrothermal vents are plausible hotspots that can enable the spontanous generation of molecules required for life.

The findings appeared in the journal Scientific Reports.

Credit: American Chemical Society.

Scientists uncover new insights into the origin of life

New research investigated whether early Earth could have supported some of the conditions required for the building blocks of life — as proposed by a famous experiment. Turns out it did.

Credit: American Chemical Society.

Credit: American Chemical Society.

How did we get here? That’s one of the big questions that has been vexing humans probably since we first became conscious. Thanks to the theory of evolution by natural selection, scientists are confident that our species evolved from a common ancestor that we share with other apes alive today. However, Homo sapiens represents a single twig on a branch of the evolutionary tree that reaches back some seven million years. If you follow these branches all the way to the stem, you’ll eventually reach ground zero: the very first lifeform out of which all other life evolved.

Although the Earth is thought to be 4.5 billion years old, the oldest rocks on the record are about 4 billion years old. Not long after this period, tantalizing evidence of life emerges, including 3.7-billion-year-old stromatolites(layered structures created by bacteria) found in Greenland and 4-billion-year-old stromatolites found in the Labrador Peninsula in Canada.

In 1953, chemists Harold Urey and Stanley Miller conducted one of the most famous experiments of the past century, commonly known as the primordial soup experiment. In order to find out how the first signs of life on Earth surfaced, the scientists exposed a mix of gases to a lightning-like electrical discharge to create amino acids. Amino acids are very important because they form proteins, which, in turn, form cellular structures and control reactions in living things. Remarkably, when water, methane, ammonia, and hydrogen — all chemicals present on early Earth — were hit by the simulated lightning, they reacted to form hydrogen cyanide, formaldehyde, and other intermediate molecules that reacted further to generate amino acids, along with other biomolecules.

But some scientists think that this experiment relies on too many things coming together. Early Earth — whose conditions are still rather poorly understood — was wrapped in a hazy atmosphere which would have made it very difficult for lightning and ultraviolet light to reach the planet’s surface.

However, that doesn’t mean that there weren’t other alternative forms of energy that could have jump-started these primordial reactions. Indian researchers at the CSIR-National Chemical Laboratory led by Kumar Vanka wondered if heat from ocean waters — which 4 billion years ago were nearly boiling — might have been one such driving force.

In their experiment, Vanka and colleagues used an ab initio nanoreactor that simulates how mixtures of molecules collide and react, forming new molecules. Their results suggest that ancient ocean heat was enough for hydrogen cyanide and water to mix and form the molecules required to produce the amino acid glycine, as well as the precursors of RNA.

Writing in the journal ACS Central Science, the authors conclude that these reactions are both thermodynamically and kinetically feasible, meaning they do not require a catalyst or a lot of energy.

We might never find out exactly how life first emerged on Earth but the fact that there are multiple pathways that could have given rise to it offers some exciting possibilities. It suggests that maybe the conditions necessary for life to form aren’t all that singular, so perhaps many other planets elsewhere in the galaxy and beyond are blessed with this rare gift.