how life started on earth?(200-500) words
Answers
Explanation:
ATLANTA—A cataclysm may have jump-started life on Earth. A new scenario suggests that some 4.47 billion years ago—a mere 60 million years after Earth took shape and 40 million years after the moon formed—a moon-size object sideswiped Earth and exploded into an orbiting cloud of molten iron and other debris.
The metallic hailstorm that ensued likely lasted years, if not centuries, ripping oxygen atoms from water molecules and leaving hydrogen behind. The oxygens were then free to link with iron, creating vast rust-colored deposits of iron oxide across our planet's surface. The hydrogen formed a dense atmosphere that likely lasted 200 million years as it ever so slowly dissipated into space.
After things cooled down, simple organic molecules began to form under the blanket of hydrogen. Those molecules, some scientists think, eventually linked up to form RNA, a molecular player long credited as essential for life's dawn. In short, the stage for life's emergence was set almost as soon as our planet was born.
That scenario captivated participants at an October 2018 conference here, where geologists, planetary scientists, chemists, and biologists compared notes on the latest thinking on how life got its start. No rocks or other direct evidence remain from the supposed cataclysm. Its starring role is inferred because it would solve a bevy of mysteries, says Steven Benner, an origin of life researcher at the Foundation for Applied Molecular Evolution in Alachua, Florida, who organized the Origins of Life Workshop.
The metal-laden rain accounts for the distribution of metals across our planet's surface today. The hydrogen atmosphere would have favored the emergence of the simple organic molecules that later formed more complex molecules such as RNA. And the planetary crash pushes back the likely birthdate for RNA, and possibly life's emergence, by hundreds of millions of years, which better aligns with recent geological evidence suggesting an early emergence of life.
Answer:
The origin of life is one of the great mysteries in the Universe. To determine the origin of life, scientists are investigating the problem in several different ways. Some scientists are studying life on our own planet. Some scientists are seeking out life or fossil life on other planets or moons in our solar system. And other scientists are trying to detect life in other solar systems, either by measuring life's effects on the atmospheres of distant planets or by measuring artificial radiation like radio signals that may be produced by advanced life.
Thus far, the most fruitful approach has been to examine life on our own planet. However, even in our own backyard, it is difficult to determine life's origins because it began at least 3.5 billion years ago. We know that life began at least 3.5 billion years ago, because that is the age of the oldest rocks with fossil evidence of life on earth. These rocks are rare because subsequent geologic processes have reshaped the surface of our planet, often destroying older rocks while making new ones. Nonetheless, 3.5 billion year old rocks with fossils can be found in Africa and Australia. They are usually a mix of solidified volcanic lavas and sedimentary cherts. The fossils occur in sedimentary cherts.
Above) 3.5 billion year old lava. Above Right) 3.5 billion year old sedimentary chert.
Chemical traces of life have also been detected in slightly older rocks. In Greenland, a series of ancient metamorphosed sediments have been found. Analyses indicate the sediments were deposited about 3.8 billion years ago. They also revealed carbon isotope signatures that appear to have been produced by organisms that lived when the sediments were deposited.
In all cases, life as we understand it must have water. This general rule is true on Earth and is thought to be true elsewhere in the solar system. Currently, life is being sought on Mars where water may have once flowed on the surface and Europa where a subterranean sea of water may exist beneath its icy surface.
If one analyzes the genetic information in a variety of modern organisms living on Earth, one can begin to group and separate organisms based on their common (or disparate) properties. This type of analyses is intuitive at some levels. For example, most people recognize that mule deer and white tail deer are more closely related than mule deer and grizzly bears. Consequently, in a tree of life, mule deer would appear closer to white tail deer than grizzly bears. This same process can be applied to all organisms and has led to three large domains of life: Bacteria, Archaea, and Eukarya. Humans, as well as other complex mammals, are part of the Eukarya group. If one traces the genetic information in organisms in all three groups, it appears they have a common ancestor or at least ancestors that share a common set of traits. In either case, it appears the earlist form of life in the tree of life were thermophilic or hyperthermophilic organism, which means they lived in systems composed of hot water.