An unexplained chemical has turned up in the upper atmosphere of Venus. Scientists are tentatively suggesting it could be a sign of life.
The unknown chemical is phosphine gas (PH3), a substance that on Earth mostly comes from anaerobic (non-oxygen-breathing) bacteria or "anthropogenic activity" — stuff humans are doing. It exists in the atmospheres of gas giant planets, due to chemical processes that occur deep in their pressurized depths to bind together three hydrogen atoms and a phosphorus atom. But scientists don't have any explanation for how it could appear on Venus; no known chemical processes would generate phosphine there. And yet, it seems to be there, and no one knows of anything that could make phosphine on Venus except for living organisms.
This discovery, published today (Sept. 14) in the journal Nature Astronomy, caught everyone by surprise — including the team that found it.
Back in June of 2017, that team pointed the James Clerk Maxwell Telescope in Hawaii at Venus and tuned it to look for signatures of phosphine. "The aim was a benchmark for future developments," they wrote in the journal article.
In other words, they were checking what the phosphine signatures might look like as a baseline, on a planet assumed to have no natural way of producing the substance.
"But unexpectedly," the researchers wrote in the study, "our initial observations suggested a detectable amount of Venusian PH3 was present."
They confirmed what they were seeing using the Atacama Large Millimetre/submillimetre Array in Chile. Variations in the light coming from Venus' upper atmosphere showed a substantial amount of phosphine there.
But phosphine on Venus doesn't necessarily mean life on Venus, the authors wrote. They raised the possibility of life because bacteria are the only known way of making phosphine on a planet without a gas giant's super-high atmospheric pressures. But it's just as possible that some previously-unknown chemical process is producing the gas.
"This could be unknown photochemistry [chemical reactions that require light] or geochemistry, or possibly life," they wrote. "Information is lacking — as an example, the photochemistry of Venusian cloud droplets is almost completely unknown."
That means that no one really knows how the chemicals in Venus' upper clouds react to sunlight.
Venus has not previously been considered a likely site for life in this solar system, so scientists had yet to explore such questions with the same level of resources devoted to hunting for signs of life on Mars. The hot, almost Earth-size planet with its toxic atmospheric chemistry destroys even the hardiest robots within minutes. How would life survive on Venus?
In the past, the authors of the new paper pointed out, some researchers have suggested the possibility of life in the planet's uppermost cloud layer. Unlike the surface, which averages 867 degrees Fahrenheit (464 degrees Celsius), Venus' higher clouds are relatively cool, reaching 85 F (30 C) in the layer where phosphine was detected, and could more plausibly offer a habitat for some sort of floating life.
Figuring out whether that really is the source of Venusian phosphine, or whether it came from some other source, will take more data and better modeling of the planet's behavior, the researchers wrote.
Originally published on Live Science.
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The problem is more than speculative evidence for some anaerobic microbe producing a phosphine signature. The problem goes back to where that microbe came from. The evolution of proteins and nucleic acids has to come first. How likely is that in clouds above Venus, or above anywhere...leading to a LUCA-type microbe living in the clouds?Reply
To understand the evolution of proteins and nucleic acids, one needs to understand the planet history... although it may seem impossible to have this kind of process today, it is possible that in the past (1M of years ago) it was possible... who knows?!Broadlands said:The problem is more than speculative evidence for some anaerobic microbe producing a phosphine signature. The problem goes back to where that microbe came from. The evolution of proteins and nucleic acids has to come first. How likely is that in clouds above Venus, or above anywhere...leading to a LUCA-type microbe living in the clouds?
It is not necessary to know anything more about the history of a planet other than it is in the so-called Goldilocks zone. A location where water is available but so is dry land with the Star's energy not too hot and not too cold. The initial peptide bonds for assembling the amino acids into chains need the input of energy and the removal of water. Not likely in clouds.Reply
Broadlands said:Not likely in clouds.
The nature of living organisms as we know them, and likely elsewhere, requires the presence of large amounts of liquid water, to evolve and to exist. It is always essential since liquid water drives the formation of membranes, and the folding of proteins, and the diffusion of metabolites and waste products into and out of cells, to name just a few issues. Entire books have been devoted to the subject of water and chemicals regarding life. They usually have the word "biochemistry" in their titles.
You need large amounts of liquid water to support life anywhere. It is highly unlikely to survive, much less evolve, in the clouds of any planet.
Large amounts of water are not needed to get life started. Indeed the reverse. Once the first cells had evolved is quite different. Richard Dickerson made the situation clear when he wrote (back in 1978):Reply
"The central problem in understanding how the polymers were formed on the primitive earth is understanding how reactions requiring both the input of energy and the removal of water could take place in the ocean."
Or in clouds?
Broadlands said:Large amounts of water are not needed to get life started.
One would have to question the meaning of "large amounts of water."
Whatever the case, in order for life to arise from "scratch", a substantial aqueous milieu would be required containing a vast assortment of chemicals in a stable thermal environment. Such conditions would be required in order to provide such a variety of chemicals in sufficient volume and dilution, and a stable, moderate temperature to allow for the vast assortment of complex chemical interactions required.
Life would never arise in a near chemical grid-lock of concentrated components. Such conditions would not allow for the rapid interplay of thousands of various chemicals required to kick-start life. The chemical kinetics of abiogenesis would be rather exacting, one should think. Only relatively dilute mixtures in considerable volumes of water, which are constantly mixed and replenished by thermal vents, are likely involved in such complex processes.
The nutrients and thermal stability are provided in the oceans of earth. Since photosynthesis did not arise until later, the nutrient source likely was from reduced compounds expelled from thermal vents, which also would provide for long term thermal stability (locally to the vents) within large, oceanic bodies.
It has been suggested that abiogenesis required a million years or more to develop into the most primitive replicating organism. It seems likely that such an environment would require a substantial body of water to hold all of the chemicals, as well as providing a very stable thermal condition for extended periods. Small bodies of water are also subject to more rapid changes in temperature, which would be detrimental to abiogenesis.
Large amounts of chemicals in large volumes of thermally stable water is the most likely scenario for abiogenesis anywhere.
As a side note : thermal extremophiles almost certainly arose from preexisting life forms which evolved under relatively mild temperature.
"Large amounts of chemicals in large volumes of thermally stable water is the most likely scenario for abiogenesis anywhere."Reply
The problem remains for the formation of the initial bonds in any body of water that may have accumulated primordial amino acids. Heating and cooling with wetting and drying must take place....with added water (rain) to keep the locations from total dehydration. A difficult scenario, but so are all others.
The extremophiles at the base of the tree of life (LUCA) are not just thermophiles, they are also microaerophiles... Aquifex. Small amounts of free oxygen are needed.
Broadlands said:Heating and cooling with wetting and drying must take place
The most likely theories of abiogenesis require a continuous aqueous milieu at a stable, moderate temperature. Fluctuations in heating/cooling and drying would be random and/or relatively extreme events unsuitable for any complex organization of macromolecules to assemble into the first living cell. It cannot be ruled out that some of the chemicals used in abiogenesis underwent various processes before their incorporation, where "extremes" may have played a role. But the assembly and origin almost certainly occurred in a thermally stable solution of substantial volume.
Solid phases are believed to have played a major role, silicates being the most likely as they have surfaces with variable chemistries which can bind a variety of chemical species - ionized, polar and non-polar. Any chemical organization of such complexity on a solid surface could only occur when exposed to a fully liquid environment - the continuous capacity for diffusion of all the primary chemicals in water would be a major requirement for abiogenesis.
"The most likely theories of abiogenesis require a continuous aqueous milieu at a stable, moderate temperature."Reply
All laboratory experiments are made under so-called "prebiotic conditions". The most likely theories and experiments are done indoors. They do not even require protection from intense solar UV. Nor do they require protection from oxidation by the ambient free molecular oxygen. The more successful ones (David Usher) have been done under heating/cooling, wetting/drying conditions. All needed for initial peptide or nucleotide bond formation. Solid phases (clay minerals) only add to the many complexities. Maybe the most likely answer (for the Earth) is Panspermia?
Broadlands said:The most likely theories and experiments are done indoors. They do not even require protection from intense solar UV.
Life arising in the oceans precludes any need for UV shielding.
Broadlands said:The more successful ones (David Usher) have been done under heating/cooling, wetting/drying conditions. All needed for initial peptide or nucleotide bond formation.
Proteins are widely believed to have been a secondary development due to an initial RNA-based life form. Self-assembly of proteins and polynucleotides in liquids is documented.
Broadlands said:Solid phases (clay minerals) only add to the many complexities.
The complexities involved are clearly not well established, and adding solid phases is just another element of complexity. That would hardly rule it out. Occam's razor is no where to be seen in this topic.