04. Beginning of Life

The Beginning of Life on Earth
2021-03-09. Ancient Earth was a water world. By Paul Voosen, Science Magazine. Excerpt: ...sea levels have risen and fallen with temperatures—but Earth’s total surface water was always assumed to be constant. Now, evidence is mounting that some 3 billion to 4 billion years ago, the planet’s oceans held nearly twice as much water—enough to submerge today’s continents above the peak of Mount Everest. The flood could have primed the engine of plate tectonics and made it more difficult for life to start on land. Rocks in today’s mantle, the thick layer of rock beneath the crust, are thought to sequester an ocean’s worth of water or more in their mineral structures. But early in Earth’s history, the mantle, warmed by radioactivity, was four times hotter. Recent work using hydraulic presses has shown that many minerals would be unable to hold as much hydrogen and oxygen at mantle temperatures and pressures. “That suggests the water must have been somewhere else,” says Junjie Dong, a graduate student in mineral physics at Harvard University who led a model, based on those lab experiments, that was published today in AGU Advances. “And the most likely reservoir is the surface.”...“There’s pretty clear geological evidence,” too, says Benjamin Johnson, a geochemist at Iowa State University. Titanium concentrations in 4-billion-year-old zircon crystals from Western Australia suggest they formed underwater. And some of the oldest known rocks on Earth, 3-billion-year-old formations in Australia and Greenland, are pillow basalts, bulbous rocks that only form as magma cools underwater…. [https://www.sciencemag.org/news/2021/03/ancient-earth-was-water-world

2020-12-21.  Habitability and the Evolution of Life Under Our Magnetic Shield. By Manasvi Lingam, Eos/AGU. Excerpt: ...The existence of a global magnetic field raises questions about how it affects habitability and life. This is a question wide in scope, and the discussion here is limited to only a couple of salient effects. It is commonly thought that magnetic fields are necessary to protect planetary atmospheres from erosion by the solar wind, which hastens the acceleration and escape of atmospheric particles through electromagnetic interactions. But how valid is this premise? ...There is promising evidence that Earth’s geodynamo initiated as early as 4.2 billion years ago and that the crystallization of Earth’s inner core, which paved the way for the geodynamo of today, occurred more than half a billion years ago. Although the changes in Earth’s magnetic field wrought by these transitions were likely profound, the concomitant effects on our planet’s biosphere are much less clear. Earth’s organisms must have been affected to some degree, but fathoming the magnitude and nature of these repercussions necessitates further research synthesizing knowledge from geology, astronomy, plasma physics, microbiology, evolutionary biology, and other disciplines. By resolving the riddle of whether Earth’s magnetic field played a significant role in modulating the evolution of life, we will be better positioned to consider the related question of whether a magnetic field is necessary for a planet to be habitable in the first place.... [https://eos.org/science-updates/habitability-and-the-evolution-of-life-under-our-magnetic-shield]  See also The Herky-Jerky Weirdness of Earth’s Magnetic Field  and A Field Guide to the Magnetic Solar System 

2020-01-15. This Strange Microbe May Mark One of Life’s Great Leaps. By Carl Zimmer, The New York Times. [https://www.nytimes.com/2020/01/15/science/cells-eukaryotes-archaea.html] Excerpt: An organism living in ocean muck offers clues to the origins of the complex cells of all animals and plants. ...A bizarre tentacled microbe discovered on the floor of the Pacific Ocean may help explain the origins of complex life on this planet and solve one of the deepest mysteries in biology, scientists reported on Wednesday. Two billion years ago, simple cells gave rise to far more complex cells. Biologists have struggled for decades to learn how it happened. ...The new species, called Prometheoarchaeum, turns out to be just such a transitional form, helping to explain the origins of all animals, plants, fungi — and, of course, humans. The research was reported in the journal Nature....  

2019-01-10. How an ancient cataclysm may have jump-started life on Earth. By Robert F. Service, Science Magazine. 

2018-09-17. How Did Life Learn to Breathe? By Lucas Joel, Eos/AGU. 


2010 August 5. National Science Foundation Press Release 10-136: The Secret Life May Be As Simple As What Happens Between the Sheets--Mica Sheets. Excerpt: …The so-called "life between the sheets" mica hypothesis was developed by Helen Hansma of the University of California, Santa Barbara, with funding from the National Science Foundation (NSF). …According to the hypothesis, structured compartments that commonly form between layers of mica--a common mineral that cleaves into smooth sheets--may have sheltered molecules that were the progenitors to cells. Provided with the right physical and chemical environment in the structured compartments to survive and evolve, the molecules eventually reorganized into cells, while still sheltered between mica sheets.

…Because mica surfaces are hospitable to living cells and to all the major classes of large biological molecules, including proteins, nucleic acids, carbohydrates and fats, the "between the sheets" mica hypothesis is consistent with other well-known hypotheses that propose that life originated as RNA, fatty vesicles or primitive metabolisms
…Some micas are estimated to be over 4 billion years old. And micas such as biotite have been found in regions containing evidence of the earliest life-forms, which are believed to have existed about 3.8 million years ago.
… Hansma says that recent advancements in imaging techniques, including the AFM [atomic force microscopy], made possible her recent research...

2010 May 19. Calcium from new supernova 'could unlock secrets to life on Earth'. By Andrew Hough. Telegraph.co.uk. Excerpt: …Astronomers believe they have found a cosmic link to how calcium is formed in people's bones.
…They say a new type of supernova, called SN2005E, may be the chief source of calcium in the universe and on Earth.
…Scientists say the mineral provides vital strength to bones, which could show how humans have an ability to stand upright, the Nature journal …reported.
…So much calcium was present that it accounted for half the material thrown out by the explosion.

2010 May 17. A Marine Chemist Studies How Life Began. By Claudia Dreifus. The NY Times. Excerpt:

...Q. DO WE KNOW HOW THEY BECAME LIFE?
A. We are closing in on that question. The Earth had to cool down enough for water to appear. Water allows molecules to dissolve and interact, which is why it is essential to life. We do know that we went from simple molecules to more complex molecules and eventually to RNA, which evolved into DNA. This took about a billion years.
...Q. SO WE’RE PROBABLY NOT ALONE?
A. I don’t want to say “we” because people immediately think of something like a human being. But life as we know it — a self-replicating system — is probably not unique to the Earth. Under the right conditions, with the right chemistry, it can happen. There may be simple chemistry happening on Titan, a moon of Saturn. Some people think it could be happening on the satellites of Jupiter. There are compelling reasons to think that Mars was wet when it was young and that the raw materials for life could have been there. We don’t know how far it progressed.

2009 August 19. NASA RELEASE: 09-192. NASA Research Reveals Major Insight Into Evolution Of Life On Earth. Excerpt: MOFFETT FIELD, Calif. -- Humans might not be walking on Earth today if not for the ancient fusing of two microscopic, single-celled organisms called prokaryotes, NASA-funded research has found.
By comparing proteins present in more than 3000 different prokaryotes - a type of single-celled organism without a nucleus - molecular biologist James A. Lake from the University of California at Los Angeles' Center for Astrobiology showed that two major classes of relatively simple microbes fused together more than 2.5 billion years ago. Lake's research reveals a new pathway for the evolution of life on Earth....
This endosymbiosis, or merging of two cells, enabled the evolution of a highly stable and successful organism with the capacity to use energy from sunlight via photosynthesis. Further evolution led to photosynthetic organisms producing oxygen as a byproduct. The resulting oxygenation of Earth's atmosphere profoundly affected the evolution of life, leading to more complex organisms that consumed oxygen, which were the ancestors of modern oxygen-breathing creatures including humans.
"Higher life would not have happened without this event," Lake said. "These are very important organisms. At the time these two early prokaryotes were evolving, there was no oxygen in the Earth's atmosphere. Humans could not live. No oxygen-breathing organisms could live."...

2009 June 15. New Glimpses of Life’s Puzzling Origins. By Nicholas Wade, The NY Times. Excerpt: Some 3.9 billion years ago, a shift in the orbit of the Sun’s outer planets sent a surge of large comets and asteroids careening into the inner solar system....
Yet rocks that formed on Earth 3.8 billion years ago, almost as soon as the bombardment had stopped, contain possible evidence of biological processes. If life can arise from inorganic matter so quickly and easily, why is it not abundant in the solar system and beyond? If biology is an inherent property of matter, why have chemists so far been unable to reconstruct life, or anything close to it, in the laboratory?
The origins of life on Earth bristle with puzzle and paradox. Which came first, the proteins of living cells or the genetic information that makes them? How could the metabolism of living things get started without an enclosing membrane to keep all the necessary chemicals together? But if life started inside a cell membrane, how did the necessary nutrients get in?
The questions may seem moot, since life did start somehow. But for the small group of researchers who insist on learning exactly how it started, frustration has abounded. Many once-promising leads have led only to years of wasted effort....
In the last few years, however, four surprising advances have renewed confidence that a terrestrial explanation for life’s origins will eventually emerge....

2009 May 20. NASA STUDY SHOWS ASTEROIDS MAY HAVE ACCELERATED LIFE ON EARTH. NASA RELEASE: 09-11. Excerpt: WASHINGTON -- A NASA-funded study indicates that an intense asteroid bombardment nearly 4 billion years ago may not have sterilized the early Earth as completely as previously thought. The asteroids, some the size of Kansas, possibly even provided a boost for early life. The study focused on a particularly cataclysmic occurrence known as the Late Heavy Bombardment, or LHB. This event occurred approximately 3.9 billion years ago and lasted 20 to 200 million years. ... while the Late Heavy Bombardment might have generated enough heat to sterilize Earth's surface, microbial life in subsurface and underwater environments almost certainly would have survived. "Exactly when life originated on Earth is a hotly debated topic," said Michael H. New, the astrobiology discipline scientist and manager of the Exobiology and Evolutionary Biology Program at NASA Headquarters in Washington. "These findings are significant because they indicate that if life had begun before the LHB or some time prior to 4 billion years ago, it could have survived in limited refuges and then expanded to fill our world."
"Our new results point to the possibility life could have emerged about the same time that evidence for our planet's oceans first appears," said Mojzsis, principal investigator of the project.
A growing scientific consensus is that during our solar system's formation, planetary bodies were pummeled by debris throughout the Late Heavy Bombardment. ...Surface habitats for microbial life on early Earth would have been destroyed repeatedly by the bombardment. However, at the same time, impacts could have created subsurface habitats for life, such as extensive networks of cracks or even hydrothermal vents. Any existing microbial life on Earth could have found refuge in these habitats.


2008 December 8. Meteor impacts may have sparked life on Earth. By Emma Young, New Scientist. Excerpt: While space rocks hurtling in from space threaten to deal modern life a mortal blow, meteorite impacts during Earth's early history may have played a pivotal role in kick-starting life on the planet.
Exactly how and when organic molecules appeared in abundance on the young Earth, leading to the origin of life about 4 billion years ago, has been unclear. But new research suggests that meteor impacts could have created amino acids, the building blocks of life.
Yoshihiro Furukawa at Tohoku University in Sendai, Japan, and colleagues used a high-velocity propellant gun to simulate the impacts of ordinary carbon-containing chondrite meteorites - the most common type of meteorite - into the early ocean. Afterwards, they recovered a variety of organic molecules, including fatty acids, amines, and an amino acid.
Oceans began to form about 4.3 billion years ago, when meteorites were hitting Earth about 1000 times more frequently than they do today, says Furukawa. "This study is the first to show that an amino acid can be synthesised by a naturally possible mechanism on the early Earth," he says....


2008 October 16. Volcanoes May Have Provided Sparks and Chemistry for First Life. NASA Earth Observatory. Excerpt: Lightning and gases from volcanic eruptions could have given rise to the first life on Earth, according to a new analysis of samples from a classic origin-of-life experiment by NASA and university researchers....
...From 1953 to 1954, Professor Stanley Miller, then at the University of Chicago, performed a series of experiments with a system of closed flasks containing water and a gas of simple molecules. At the time, the molecules used in the experiment (hydrogen, methane, and ammonia) were thought to be common in Earth's ancient atmosphere.
The gas was zapped with an electric spark. After running the experiment for a few weeks, the water turned brown. When Miller analyzed the water, he found it contained amino acids, which are the building blocks of proteins -- life's toolkit... The spark provided the energy for the molecules to recombine into amino acids, which rained out into the water....
...Professor Jeffrey Bada, a co-author of the paper, was [Miller's] graduate student in chemistry between 1965 and 1968....
"...When Adam and I found the samples from the original experiments, it was a great opportunity to reanalyze these historic samples using modern methods," said Bada. The team wanted to see if modern equipment could discover chemicals that could not be detected with the techniques of the 1950s. They analyzed the samples and turned to Daniel Glavin and Jason Dworkin of NASA's Goddard Space Flight Center in Greenbelt, Md....
..."We discovered 22 amino acids, 10 of which have never been found in any other experiment like this," said Glavin. This is significant because thinking on the composition of Earth's early atmosphere has changed. Instead of being heavily laden with hydrogen, methane, and ammonia, many scientists now believe Earth's ancient atmosphere was mostly carbon dioxide, carbon monoxide, and nitrogen....


2006 June 6. STUDY SHOWS OUR ANCESTORS SURVIVED 'SNOWBALL EARTH' - Earth Observatory. Excerpt: It has been 2.3 billion years since Earth's atmosphere became infused with enough oxygen to support life as we know it. About the same time, the planet became encased in ice that some scientists speculate was more than a half-mile deep. That raises questions about whether complex life could have existed before "Snowball Earth" and survived, or if it first evolved when the snowball began to melt. New research shows organisms called eukaryotes -- organisms of one or more complex cells that engage in sexual reproduction and are ancestors of the animal and plant species present today -- existed 50 million to 100 million years before that ice age and somehow did survive. The work also shows that the cyanobacteria, or blue-green bacteria, that put the oxygen in the atmosphere in the first place, apparently were pumping out oxygen for millions of years before that, and also survived Earth's glaciation. The findings call into question the direst models of just how deep the deep freeze was, said University of Washington astrobiologist Roger Buick, a professor of Earth and space sciences. While the ice likely was widespread, it probably was not consistently as thick as a half-mile, he said. "That kind of ice coverage chokes off photosynthesis, so there's no food for anything, particularly eukaryotes. They just couldn't survive," he said. "But this research shows they did survive."

8 January 2004. NASA RELEASE : 04-016, Borax Minerals May Have Been Key To Start Of Life On Earth. Astrobiologists, supported by NASA, have announced a major advance in understanding how life may have originated on Earth billions of years ago. A team of scientists report in the January 9 issue of Science that ribose and other simple sugars that are among life's building blocks could have accumulated in the early Earth's oceans if simple minerals, such as borax, were present.

SATELLITE DATA TO PREDICT PLANKTON BLOOMS BY ANALYZING OCEAN COLOR -- Scientists analyzing satellite data on ocean color are gaining new insights into ocean productivity and climate. A green ocean is a productive ocean; the light from the sun fuels the "bloom" of phytoplankton, tiny ocean plants that turn the sea's surface a light green each spring. This production in turn drives ocean food webs. New research, published in the journal Science on April 26, assesses the color of the ocean and finds that it may yield clues about the relation between marine ecosystems and the climate system. The research was funded by the National Science Foundation (NSF) and NASA

 

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