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Is there life on Venus? Scientists detect traces of phosphine gas that could be coming from MICROBES in clouds swirling high in the planet’s atmosphere

Written by on 15/09/2020

  • Phosphine is a colourless gas that smells somewhat like garlic, or decaying fish
  • On Earth, it is produced naturally by bacteria or the decay of organic matter
  • Experts led from the UK have found traces of the gas in the clouds above Venus
  • Unlike on the planet’s surface, conditions in the upper cloud layer are Earth-like
  • However, experts have warned that there could be other sources for the gas

Traces of phosphine gas detected in the clouds above Venus could be an indication that the planet supports microbial life, a study has concluded.

On Earth, phosphine — a colourless gas that smells like garlic, or decaying fish — is naturally produced mainly by certain microorganisms in the absence of oxygen.

It can also be released in small amounts from the breakdown of organic matter, or industrially synthesised in chemical plants.

Experts from the UK, however, found signs of phosphine in Venus’ atmosphere — suggesting the planet must support unknown chemical processes, or even life.

The second-closest planet to the Sun, Venus is inhospitable — with a surface temperature around 867°F (464°C) and pressure 92 times that of on the Earth.

However, its upper cloud deck — 33–38 miles (53–62 kilometres) above the surface — is a more temperate 120°F (50°C), with a pressure equal to that at Earth sea level.

The clouds are also highly acidic — meaning that the phosphine would be broken down very quickly and must therefore be being continually replenished.

The researchers have cautioned, however, that life is only one possible explanation for the source of the phosphine — with further investigation needed.

NASA is presently considering two missions to Venus that propose to study the planet’s atmosphere and geochemistry — dubbed ‘DAVINCI’ and ‘VERITAS’.

In their study, astronomer Jane Greaves of Wales’ Cardiff University and colleagues observed Venus using both the James Clerk Maxwell Telescope at Hawaii’s Mauna Kea Observatory and the Atacama Large Millimeter/submillimeter Array in Chile.

They detected a so-called spectral signature that is unique to phosphine — and furthermore were able to estimated that the gas is present in Venus’ clouds in an abundance of around 20 parts-per-billion.

The team explored assorted ways that the gas could have been produced in this setting — including from sources on the surface of the planet, micrometeorites, lightning, or chemical processes happening within the clouds themselves.

However, they were unable to determine exactly what is the source of the detected trace quantities of the gas.

The researchers have cautioned that the detection of phosphine is not itself robust evidence for alien microbial life — and only indicates that potentially unknown geological or chemical processes are occurring on the planet.

Further observations and modelling will be needed, they added, to better explore the origin of the gas in the planet’s atmosphere.

‘Phosphine could originate from unknown photochemistry or geochemistry — or, by analogy with biological production of phosphine on Earth, from the presence of life,’ the research team wrote in their paper.

VENUS: THE BASICS 

Venus, the second planet from the sun, is a rocky planet about the same size and mass of the Earth.

However, its atmosphere is radically different to ours — being 96 per cent carbon dioxide and having a surface temperature of 867°F (464°C) and pressure 92 times that of on the Earth.

The inhospitable planet is swaddled in clouds of sulphuric acid that make the surface impossible to glimpse via the visible light spectrum.

In the past, Venus likely had oceans similar to Earth’s — but these would have vaporised as it underwent a runaway greenhouse effect.

The surface of Venus is a dry desertscape, which is periodically changed by volcanic activity.

The planet has no moons and orbits the Sun every 224.7 Earth days. 


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