Posted on Apr 8, 2018
Researchers may have solved a key puzzle about how objects from space could have kindled life on Earth. While it is generally accepted that some important ingredients for life came from meteorites bombarding the early Earth, scientists have not been able to explain how that inanimate rock transformed into the building blocks of life.
A 2013 study showed how a chemical, similar to one now found in all living cells and vital for generating the energy that makes something alive, could have been created when meteorites containing phosphorus minerals landed in hot, acidic pools of liquids around volcanoes, which were likely to have been common across the early Earth.
"Chemical life would have been the intermediary step between inorganic rock and the very first living biological cell. You could think of chemical life as a machine –a robot, for example, is capable of moving and reacting to surroundings, but it is not alive. With the aid of these primitive batteries, chemicals became organised in such a way as to be capable of more complex behavior and would have eventually developed into the living biological structures we see today," said Terry Kee at the University of Leeds.
While it is generally accepted that some important ingredients for life came from meteorites bombarding the early Earth, scientists have not been able to explain how that inanimate rock transformed into the building blocks of life. A past study from reseachers at the University of Leeds shows how a chemical, similar to one now found in all living cells and vital for generating the energy that makes something alive, could have been created when meteorites containing phosphorus minerals landed in hot, acidic pools of liquids around volcanoes, which were likely to have been common across the early Earth.
All life on Earth is powered by a process called chemiosmosis, where the chemical adenosine triphosphate (ATP), the rechargeable chemical 'battery' for life, is both broken down and re-formed during respiration to release energy used to drive the reactions of life, or metabolism. The complex enzymes required for both the creation and break down of ATP are unlikely to have existed on the Earth during the period when life first developed. This led scientists to look for a more basic chemical with similar properties to ATP, but that does not require enzymes to transfer energy.
Phosphorus is the key element in ATP, and other fundamental building blocks of life like DNA, but the form it commonly takes on Earth, phosphorus (V), is largely insoluble in water and has a low chemical reactivity. The early Earth, however, was regularly bombarded by meteorites and interstellar dust rich in exotic minerals, including the far more reactive form of phosphorus, the iron-nickel-phosphorus mineral schreibersite.
"The mystery of how living organisms sprung out of lifeless rock has long puzzled scientists, but we think that the unusual phosphorus chemicals we found could be a precursor to the batteries that now power all life on Earth. But the fact that it developed simply, in conditions similar to the early Earth, suggests this could be the missing link between geology and biology," said Kee.
Phosphorus is an essential element for life — but that there was enough of it for life to start on Earth might just have been a matter of luck, new research suggest.
Most of the universe's phosphorus was created during the last gasps of dying massive stars or during a supernova. According to new observations of the Crab Nebula (below) — the leftovers from a supernova called Cassiopeia A (image at top of page) first seen by Chinese astronomers in 1054 — presented on April 5 at the European Week of Astronomy and Space Science in Liverpool, England, the abundance and distribution of phosphorus in the Milky Way galaxy may be more random than scientists previously thought
Researchers found up to 100 times more phosphorus in the Crab Nebula powered by its pulsar than what's observed in the rest of the Milky Way. Which means that some places in the galaxy may not have enough phosphorus to support life, even if they are exoplanets in the habitable zone.
Recently, astronomers Jane Greaves and Phil Cigan of Cardiff University in the U.K. pointed the William Herschel Telescope in the Canary Islands toward the Crab Nebula, located about 6,500 light-years away. Preliminary data, analyzed just two weeks ago, shows an amount of phosphorus more similar to the values found in the interstellar gas and dust of the Milky Way — a pittance compared with the abundance in Cassiopeia A.
"It's not a guaranteed thing to have phosphorus abundant everywhere, ripe for the picking," Cigan told Live Science. "It seems to look like luck plays a bigger role in this."
If the production of phosphorus varies widely across the galaxy, so might the likelihood of life on other planets. Even if a planet had every other condition required for habitability, it might still be bereft of life because it formed where there was a dearth of phosphorus, the researchers said.
But the observations are still preliminary; the astronomers were only able to measure parts of the nebula before clouds and a snowstorm spoiled the rest of their observing run. Still, Cigan said, the data they do have show significantly less phosphorus in the Crab Nebula than in Cassiopeia A.
Ultimately, astronomers will need to measure phosphorus in other supernova remnants across the cosmos, Cigan said. "We really want to look at how it's spreading out from supernova remnants and falling back into the interstellar medium — that's the key."
The Daily Galaxy via University of Leeds and Live Science
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