How Life on Earth Could Have Started
Scientists redid anexperiment and found a new possibility of how life on Earth could have started.
In the 1931 movie“Frankenstein,” Dr Henry Frankenstein howled his triumph as massive bolts oflightning crackled and Frankenstein’s monster stirred on a laboratory table,its pieced-together corpse brought to life by the power of electricity.
Electrical energy mayhave also sparked the beginnings of life on Earth billions of years ago. Earthis around 4.5 billion years old, and the oldest direct fossil evidence ofancient life is stromatolites, microscopic organism preserved in layers known asmicrobial mats. These are about 3.5 billion years old. However, some scientistssuspect life originated even earlier, emerging from accumulated organicmolecules in bodies of water, a mixture sometimes referred to as primordialsoup.
But where did thatorganic material come from? Decades ago, researchers proposed that lightningcaused chemical reactions in the oceans, and spontaneously produced organicmolecules.
New research suggeststhat fizzes of barely visible “microlightning,” generated between chargeddroplets of water mist, could have cooked up amino acids from inorganicmaterials. Amino acids are life’s most basic building blocks and would havebeen the first step forward in the evolution of life.
For amino acids toform, they needed nitrogen atoms that could bond with carbon. Freeing up atomsfrom nitrogen gas requires severing powerful molecular bonds and takes anenormous amount of energy. Even microlightning has enough energy to breakmolecular bonds.
In 1953, chemistsStanley Miller and Harold Urey combined ammonia, methane, hydrogen and waterinside a glass sphere to mimic the atmosphere of ancient Earth. They thenjolted that atmosphere with electricity, producing simple amino acids. Thisexperiment supported the theory that life could emerge from nonlivingmolecules.
Scientists revisitedthe 1953 experiment but directed their attention toward electrical activity ona smaller scale. They looked at electricity exchanged between water dropletsmeasuring between 1 micron and 20 microns in diameter. (The width of a human hairis 100 microns.) The big droplets were positively charged. The little dropletswere negatively charged. When oppositely charged droplets are close together,electrons can jump from the negative charge to the positively charged.
The researchers mixedammonia, carbon dioxide, methane and nitrogen in a glass bulb, then sprayed thegases with water mist. A high-speed camera captured faint flashes ofmicrolightning in the vapor. When they examined the bulb’s contents, they foundorganic molecules, including the amino acid glycine and uracil, a nucleotidebase in RNA.
For the first time,scientists have seen that little droplets of water emit light and a spark. Andthat spark causes all types of chemical transformations.
Lightning is a dramaticdisplay of electrical power, but it sporadic and unpredictable. Lightning mayhave been too infrequent to produce amino acids in quantities sufficient forlife. Water spray, however, would have been more common than lightning. It ismore likely that mist-generated microlightning constantly zapped amino acidsinto existence from pools and puddles, where the molecules could accumulate andform more complex molecules.
However, questionsremain about life’s origins. An alternative abiogenesis hypothesis proposesthat Earth’s first amino acids were cooked up around hydrothermal vents on theseafloor. Yet another hypothesis suggests that organic molecules didn’toriginate on Earth at all. Rather, they formed in space and were carried hereby comets or fragments of asteroids, a process known as panspermia.
What do you think is alikely explanation?
