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7 Theories on the Origin of Life

Planets: Mars
March 21, 2019
Hackers
September 2, 2018

Molecules of life met on clay


Dinosaur-Killing Asteroid Triggered Mile-High Tsunami That Spread Through Earth's Oceans


The first molecules of life might have met on clay, according to an idea elaborated by organic chemist Alexander Graham Cairns-Smith at the University of Glasgow in Scotland. These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now. The main role of DNA is to store information on how other molecules should be arranged. Genetic sequences in DNA are essentially instructions on how amino acids should be arranged in proteins. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves. Or maybe life began at the bottom of the sea. Keep going to learn how.


Life began at deep-sea vents


The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems.


Life had a chilly start


Ice might have covered the oceans 3 billion years ago, as the sun was about a third less luminous than it is now, scientists say. This layer of ice, possibly hundreds of feet thick, might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, allowing key reactions to happen. [Related: The Ingredients of Life] Understanding life’s origin may involve unravelling the mystery of DNA's formation, as we explain next.


The answer lies in understanding DNA formation


Nowadays DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA, which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins. Later DNA and proteins succeeded this "RNA world," because they are more efficient.

RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. And while some scientists think the molecule could have spontaneously arisen on Earth, others say that was very unlikely to have happened. Other nucleic acids other than RNA have been suggested as well, such as the more esoteric PNA or TNA.A study in 2015 suggests the missing link in this RNA puzzle may have been found.We have two last ideas to throw at you . . .


had simple beginnings


Instead of developing from complex molecules such as RNA, life might have begun with smaller molecules interacting with each other in cycles of reactions. These might have been contained in simple capsules akin to cell membranes, and over time more complex molecules that performed these reactions better than the smaller ones could have evolved, scenarios dubbed "metabolism-first" models, as opposed to the "gene-first" model of the "RNA world" hypothesis.


Life was brought here from elsewhere in space


Perhaps life did not begin on Earth at all, but was brought here from elsewhere in space, a notion known as panspermia. For instance, rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally.

Other scientists have even suggested that life might have hitchhiked on comets from other star systems. However, even if this concept were true, the question of how life began on Earth would then only change to how life began elsewhere in space.


A Deadly, Fast-Spreading Form of Super-Ice Could Be Killing Off Alien Life-Forms


There's a new kind of ice. It forms at speeds of more than 1,000 mph (1,600 km/h), it lies deep beneath our feet, it could destroy hopes for alien life, and — finally — scientists understand how it works.

Back in March, researchers writing in the journal Science revealed that they have found the first evidence for this ice, called "Ice VII." Scientists had predicted its existence beforehand. Under the right conditions, it was believed, ice could form in a pool of water without a layer of heat at the leading edge of its growing surface. That — along with super-intense pressures and temperatures —

would allow the ice to form without most of the usual brakes that slow its growth, Science Alert reported. It would also have a different crystal structure, or arrangement of atoms. Now, scientists say they've found that elusive ice for the first time in the frozen-water cores of diamonds that bubbled up from deep inside the Earth.

The diamonds, which contained Ice VII, had come from a point inside the planet known as the mantle's "transition zone," between 255 miles and 410 miles (410 and 660 kilometers) deep. (The mantle is the rocky layer between Earth's crust and core). And they knew that it had a crystal structure very different from the sort of ice that forms in clouds or lakes or in your freezer. [9 Strange, Scientific Excuses for Why We Haven't Found Alien Life Yet]

But they didn't know precisely how it formed, or what caused it to form that way.

New research, published Oct. 10 in the journal Physical Review Letters, found that there are particular combinations of temperature and pressure at which Ice VII forms. The mysterious Ice VII begins to form at 20,700 times Earth's atmospheric pressure at sea level and 40.7 degrees Fahrenheit (4.9 degrees Celsius), and the pressure/temperature combinations get only more intense from there.

could pose problems for the hunt for alien life, Physics Central reported. Pressure spikes — say, from meteor impacts — could cause the explosive formation of Ice VII on watery planets otherwise suited to alien life. But the mass formation of this cubic ice at ripping speeds would likely prevent any such life from forming or surviving. On worlds where this happens, life could get snuffed out before it really began.


Dinosaur-Killing Asteroid Triggered Mile-High Tsunami That Spread Through Earth's Oceans


When the dinosaur-killing asteroid collided with Earth more than 65 million years ago, it did not go gently into that good night. Rather, it blasted a nearly mile-high tsunami through the Gulf of Mexico that caused chaos throughout the world's oceans, new research finds.

The 9-mile-across (14 kilometers) space rock, known as the Chicxulub asteroid, caused so much destruction, it's no wonder the asteroid ended the dinosaur age, leading to the so-called Cretaceous-Paleogene (K-Pg) extinction.

"The Chicxulub asteroid resulted in a huge global tsunami, the likes of which have not been seen in modern history," said lead researcher Molly Range, who did the research while getting her master's degree in the Department of Earth and Environmental Sciences at the University of Michigan. [Image Gallery: Ancient Monsters of the Sea]

Range and her colleagues presented the research, which has yet to be published in a peer-reviewed journal, at the American Geophysical Union's annual meeting on Dec. 14 in Washington, D.C. And the research, first reported by EOS, is novel. "As far as we know, we are the first to globally model the tsunami from impact to the end of wave propagation," Range told Live Science.

The idea for the project got started when Range's two advisors — Ted Moore and Brian Arbic, both in the Department of Earth and Environmental Sciences at the University of Michigan — realized there was a glaring gap in the Chicxulub research field. Mainly, no one had published a global simulation of the tsunami the asteroid created.

"It wasn’t until starting this project that I realized the actual scale of this tsunami, and it’s been a fun research story to share," Range said. Getting to work

The researchers knew that the asteroid hit shallow water in the Gulf of Mexico. But to correctly model its huge impact, they needed a model that could compute "the large scale deformation of the [Earth’s] crust that formed the crater, as well as the chaotic waves from the initial blast of water away from the impact site, and waves from ejecta falling back into the water," Range said. So, the group turned to Brandon Johnson, an assistant professor who studies impact cratering at Brown University in Rhode Island.

Johnson ran a model detailing what happened in the 10 minutes following the impact, when the crater was nearly a mile deep (1.5 kilometers) and the blast was so powerful, there wasn't any water in the crater yet. "At this point, some water was moving back toward the crater," Range said. According to the model, "this water will then rush into the crater and then back out, forming the 'collapse wave.'"

In a second model, the team studied how the tsunami propagated through oceans around the world. They did this by taking the results from the first model (particularly the crater shape) and the impact's waves with respect to resting sea level and water speeds, Range said. They then used data sets on the ancient terrain of the ocean, and used that to determine how the tsunami would have played out.

The results show the effects of the tsunami were felt all around the world. [In Pictures: Japan Earthquake & Tsunami]

"We found that this tsunami moved throughout the entire ocean, in every ocean basin," Range said. In the Gulf of Mexico, water moved as fast as 89 mph (143 km/h), she found. Within the first 24 hours, the effects of the tsunami's impact spread out of the Gulf of Mexico and into the Atlantic, as well as through the Central American seaway (which doesn't exist anymore, but used to connect the Gulf to the Pacific).

After the initial nearly mile-high (1.5 km) wave, other huge waves rocked the world's oceans. In the South Pacific and North Atlantic, waves reached a whopping maximum height of 46 feet (14 m). In the North Pacific, they reached 13 feet (4 m). Meanwhile, the Gulf of Mexico saw waves as high as 65 feet (20 meters) in some spots and 328 feet (100 m) in others

.

To put that in perspective, the largest modern wave ever recorded in the Southern Hemisphere was a "measly" 78 feet (23.8 m) tall, which struck near New Zealand in May 2018, Live Science previously reported.

Hard evidence

There's evidence that supports the models, Range said. According to the second model, fast-moving water from the impact likely caused erosion and sediment disruption in South Pacific, North Atlantic and Mediterranean ocean basins.In a separate study (which also has yet to be published), Moore examined sediment records across the ocean. His findings agree with the tsunami model, Range said.

It can be hard to imagine such a cataclysmic tsunami, so the researchers compared it to the 2004 Indian Ocean tsunami that killed at least 225,000 people. The two tsunamis were as different as night and day, they found. "Over the first 7 hours of both tsunamis, the [Chicxulub] impact tsunami was 2,500 to 29,000 times greater in energy than the 2004 Indian Ocean tsunami," Range said.

Of course, the giant tsunami wasn't the only event that did in the non-avian dinosaurs. The asteroid also triggered shock waves and sent a vast amount of hot rock and dust into the atmosphere, which rubbed together with so much friction that they started forest fires and cooked animals alive. These particles also hovered in the atmosphere and blocked the sun's rays for years, killing plants and the animals that ate them.


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