https://arxiv.org/pdf/2007.00105

“Ancient Venus and Earth may have been similar in crucial ways for the development of life, such as liquid water oceans, land-ocean interfaces, the favorable chemical ingredients and energy pathways. If life ever developed on, or was transported to, early Venus from elsewhere, it might have thrived, expanded and survived the changes that have led an inhospitable surface on Venus today. Today the Venus cloud layer may provide a refugium for extant life. We introduce the Venus Life equation – a theory and evidence based approach to calculate the probability of extant life on Venus”.

A bit overoptimistic, I think. But fossils may not be out of the question.

“A quick calculation using reported particle concentrations yields a count of 5×10^24 potential organisms suspended in the atmosphere. Other suggestions that have been put forward for Venus include surface life adapted to use supercritical carbon dioxide as a solvent (Budisa and Schulze-Makuch, 2014), and subsurface microbes in refugia of highly pressurized water (Schulze-Makuch et al., 2005).”

Having supercritical carbon dioxide solvent is a possibility that had never occurred to me.

https://www.mdpi.com/2075-1729/4/3/331/pdf

“Supercritical fluids have different properties compared to regular fluids and could play a role as life-sustaining solvents on other worlds. Even on Earth, some bacterial species have been shown to be tolerant to supercritical fluids. The special properties of supercritical fluids have recently been recognized in biotechnology and used to catalyze reactions that do not occur in water. One suitable example is enzymes when they are exposed to supercritical fluids such as supercritical carbon dioxide: enzymes become even more stable, because they are conformationally rigid in the dehydrated state. Planetary environments with supercritical fluids, particularly supercritical carbon dioxide, exist, even on Earth (below the ocean floor), on Venus, and likely on Super-Earth type exoplanets. These planetary environments may present a possible habitat for exotic life.”

“The change in properties from subcritical fluid to supercritical state is especially noteworthy for the common compounds water and carbon dioxide. These include:
(1) high solubility of gases within supercritical mixtures,
(2) miscibility of gases such as O2 and H2 in supercritical fluids,
(3) high diffusion rates and variable density, and
(4) high dissolving power.
As a conclusion, Ikushima advanced the case for supercritical fluids as an appropriate medium for chemical and biochemical processes under certain conditions”.

“Kalibanov was among the first to realize that the water bound to the enzyme determines the catalytic activity rather than the total water content of the system. The protein structure may largely be retained. For example, supercritical CO2 may dissolve from 0.3% to 0.5% (w/w) water, depending on the pressure and temperature. … Supercritical CO2 is believed to increase the fluidity of the cell membrane, enhancing its permeability and facilitate extraction of membrane components such as phospholipids”.

I find it startling that a water-based life form may exist in a CO2 solvent. I was expecting a different chemical system entirely.

This opens up a possibility that I hadn’t thought of before.

I’ve always thought that life can’t exist at high temperatures because the chemical reactions proceed too fast. 400˚C is way too hot.
I’ve always thought that life can’t exist in non-polar solvents because the chemical reactions proceed too slowly.

It hadn’t occurred to me that there is a possibility that life could exist at high temperatures in non-polar solvents.
High pressures are needed as well for this, to stop liquids turning to gas.

Where, well, the moon Triton for starters. With pressurised liquid nitrogen as the solvent, if the core is hot enough.

DNA/RNA is destroyed at temperatures above 200 deg C, regardless of solvent or pressure.

dv said:

DNA/RNA is destroyed at temperatures above 200 deg C, regardless of solvent or pressure.

supposing you brought the temperature inside of the body, which you can do either through the skin or in some other way. And I think you said you’re going to test that too. Sounds interesting

mollwollfumble said:

https://arxiv.org/pdf/2007.00105

“Ancient Venus and Earth may have been similar in crucial ways for the development of life, such as liquid water oceans, land-ocean interfaces, the favorable chemical ingredients and energy pathways. If life ever developed on, or was transported to, early Venus from elsewhere, it might have thrived, expanded and survived the changes that have led an inhospitable surface on Venus today. Today the Venus cloud layer may provide a refugium for extant life. We introduce the Venus Life equation – a theory and evidence based approach to calculate the probability of extant life on Venus”.

A bit overoptimistic, I think. But fossils may not be out of the question.

“A quick calculation using reported particle concentrations yields a count of 5×10^24 potential organisms suspended in the atmosphere. Other suggestions that have been put forward for Venus include surface life adapted to use supercritical carbon dioxide as a solvent (Budisa and Schulze-Makuch, 2014), and subsurface microbes in refugia of highly pressurized water (Schulze-Makuch et al., 2005).”

Having supercritical carbon dioxide solvent is a possibility that had never occurred to me.

https://www.mdpi.com/2075-1729/4/3/331/pdf

“Supercritical fluids have different properties compared to regular fluids and could play a role as life-sustaining solvents on other worlds. Even on Earth, some bacterial species have been shown to be tolerant to supercritical fluids. The special properties of supercritical fluids have recently been recognized in biotechnology and used to catalyze reactions that do not occur in water. One suitable example is enzymes when they are exposed to supercritical fluids such as supercritical carbon dioxide: enzymes become even more stable, because they are conformationally rigid in the dehydrated state. Planetary environments with supercritical fluids, particularly supercritical carbon dioxide, exist, even on Earth (below the ocean floor), on Venus, and likely on Super-Earth type exoplanets. These planetary environments may present a possible habitat for exotic life.”

“The change in properties from subcritical fluid to supercritical state is especially noteworthy for the common compounds water and carbon dioxide. These include:
(1) high solubility of gases within supercritical mixtures,
(2) miscibility of gases such as O2 and H2 in supercritical fluids,
(3) high diffusion rates and variable density, and
(4) high dissolving power.
As a conclusion, Ikushima advanced the case for supercritical fluids as an appropriate medium for chemical and biochemical processes under certain conditions”.

“Kalibanov was among the first to realize that the water bound to the enzyme determines the catalytic activity rather than the total water content of the system. The protein structure may largely be retained. For example, supercritical CO2 may dissolve from 0.3% to 0.5% (w/w) water, depending on the pressure and temperature. … Supercritical CO2 is believed to increase the fluidity of the cell membrane, enhancing its permeability and facilitate extraction of membrane components such as phospholipids”.

I find it startling that a water-based life form may exist in a CO2 solvent. I was expecting a different chemical system entirely.

Pacman life might have a chance I reckon

dv said:

DNA/RNA is destroyed at temperatures above 200 deg C, regardless of solvent or pressure.

Do you have a reference for that? Please. This reference? https://pdfs.semanticscholar.org/…

DNA is usually found in aqueous solutions both in vivo
and in vitro. Since DNA is stable at temperatures below
100 deg C as evident in polymerase chain reactions (PCR), its degradation at
higher temperatures cannot be easily tested in aqueous solutions.
We therefore conducted our measurements both
under dry conditions, and in water, using a pressure system
that prevented evaporation of the water. We found that
under dry conditions, at gradual temperatures, DNA degradation
occurs in a linear manner, with complete degradation
at around 190 deg C.

Degradation of the DNA starts
already at 130 deg C, as seen by weakening of the band (Fig. 1a,
b), and the DNA is gradually degraded until complete degradation
around 190 deg C.

we decided to measure the degradation in water,
using a pressure system that prevented evaporation of the
water. In this case, DNA degradation occurs between 100 deg C
and 110 deg C, much lower than under dry conditions.
This observation is surprising, since degradation in this experiment
was observed at a lower temperature than the
boiling temperature of water, a temperature range in which
DNA does not degrade when pressure is not applied.

Interesting. Degradation in superheated water is expected as reaction with water will break the carbohydrate bonds, and presumably other bonds as well. What is the chemical mechanism for degradation in the dry condition? If it is reaction with atmospheric oxygen then having an oxygen-free solvent may help with higher temperatures.

There has to be a limiting maximum temperature. But perhaps with the right solvent it’s higher than 200 deg C.

mollwollfumble said:

dv said:

DNA/RNA is destroyed at temperatures above 200 deg C, regardless of solvent or pressure.

Do you have a reference for that? Please. This reference? https://pdfs.semanticscholar.org/…

DNA is usually found in aqueous solutions both in vivo
and in vitro. Since DNA is stable at temperatures below
100 deg C as evident in polymerase chain reactions (PCR), its degradation at
higher temperatures cannot be easily tested in aqueous solutions.
We therefore conducted our measurements both
under dry conditions, and in water, using a pressure system
that prevented evaporation of the water. We found that
under dry conditions, at gradual temperatures, DNA degradation
occurs in a linear manner, with complete degradation
at around 190 deg C.

Degradation of the DNA starts
already at 130 deg C, as seen by weakening of the band (Fig. 1a,
b), and the DNA is gradually degraded until complete degradation
around 190 deg C.

we decided to measure the degradation in water,
using a pressure system that prevented evaporation of the
water. In this case, DNA degradation occurs between 100 deg C
and 110 deg C, much lower than under dry conditions.
This observation is surprising, since degradation in this experiment
was observed at a lower temperature than the
boiling temperature of water, a temperature range in which
DNA does not degrade when pressure is not applied.

Interesting. Degradation in superheated water is expected as reaction with water will break the carbohydrate bonds, and presumably other bonds as well. What is the chemical mechanism for degradation in the dry condition? If it is reaction with atmospheric oxygen then having an oxygen-free solvent may help with higher temperatures.

There has to be a limiting maximum temperature. But perhaps with the right solvent it’s higher than 200 deg C.

The reason I think there is a limit is that at some point the kinetic energy is going to be higher than that needed to break the hydrogen bonding.

Of course, I suppose life doesn’t have to he based on DNA/RNA.

dv said:

mollwollfumble said:

dv said:

DNA/RNA is destroyed at temperatures above 200 deg C, regardless of solvent or pressure.

Do you have a reference for that? Please. This reference? https://pdfs.semanticscholar.org/…

DNA is usually found in aqueous solutions both in vivo
and in vitro. Since DNA is stable at temperatures below
100 deg C as evident in polymerase chain reactions (PCR), its degradation at
higher temperatures cannot be easily tested in aqueous solutions.
We therefore conducted our measurements both
under dry conditions, and in water, using a pressure system
that prevented evaporation of the water. We found that
under dry conditions, at gradual temperatures, DNA degradation
occurs in a linear manner, with complete degradation
at around 190 deg C.

Degradation of the DNA starts
already at 130 deg C, as seen by weakening of the band (Fig. 1a,
b), and the DNA is gradually degraded until complete degradation
around 190 deg C.

we decided to measure the degradation in water,
using a pressure system that prevented evaporation of the
water. In this case, DNA degradation occurs between 100 deg C
and 110 deg C, much lower than under dry conditions.
This observation is surprising, since degradation in this experiment
was observed at a lower temperature than the
boiling temperature of water, a temperature range in which
DNA does not degrade when pressure is not applied.

Interesting. Degradation in superheated water is expected as reaction with water will break the carbohydrate bonds, and presumably other bonds as well. What is the chemical mechanism for degradation in the dry condition? If it is reaction with atmospheric oxygen then having an oxygen-free solvent may help with higher temperatures.

There has to be a limiting maximum temperature. But perhaps with the right solvent it’s higher than 200 deg C.

The reason I think there is a limit is that at some point the kinetic energy is going to be higher than that needed to break the hydrogen bonding.

Of course, I suppose life doesn’t have to he based on DNA/RNA.

The hydrogen bonding gives up at a much lower temperature than this. We’re talking about the degradation of single stranded DNA here.

I don’t know about whether fluoridation would make things better or worse. Fluorine actually has a slightly smaller atomic radius than hydrogen.

It’d be fun to look at the degradation temperature of DNA/RNA in an inert gas atmosphere.