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’.
Traces of phosphine gas detected in the clouds above Venus, seen here in an image taken by NASA’s Mariner 10 spacecraft — could be an indication that the planet supports microbial life
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.
‘If no known chemical process can explain phosphine within the upper atmosphere of Venus, then it must be produced by a process not previously considered plausible for Venusian conditions,’ they added.
‘This could be unknown photochemistry or geochemistry — or possibly life.’
‘Even if confirmed, we emphasise that the detection of phosphine is not robust evidence for life, only for anomalous and unexplained chemistry.’
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, pictured
The researchers detected a so-called spectral signature (pictured) that is unique to phosphine — furthermore were able to estimated that the gas is present in Venus’ clouds in an abundance of around 20 parts-per-billion. However, they were unable to determine the exactly source of the detected trace quantities of the gas
‘There are substantial conceptual problems for the idea of life in Venus’s clouds — the environment is extremely dehydrating as well as hyperacidic.
‘However, we have ruled out many chemical routes to phosphine, with the most likely ones falling short by four to eight orders of magnitude.’
‘To further discriminate between unknown photochemical and/or geological processes as the source of Venusian phosphine, or to determine whether there is life in the clouds of Venus, substantial modelling and experimentation will be important.’
‘Ultimately, a solution could come from revisiting Venus for in situ measurements or aerosol return.’
The second-closest planet to the Sun, Venus is inhospitable — with temperatures on its surface (pictured, as imaged by the Magellan spacecraft) of around 867°F (464°C) and pressures 92 times that of on the Earth. However, its upper cloud deck — 33–38 miles above the surface — is a more temperate 120°F (50°C), with a pressure equal to that at Earth sea level
‘This is one of the most exciting signs of the possible presence of life beyond Earth I have ever seen — and certainly from the most surprising location I could imagine,’ said astronomer Alan Duffy, who was not involved in the present study.
‘Our twin planet Venus is a hellish world,’ added the expert from the Swinburne University of Technology in Melbourne, Australia.
‘While the surface is hot enough to melt lead, the temperature drops as you go higher into the clouds, becoming Earth-like in both temperature and pressure by an altitude of 50 kilometres [31 miles], exactly where the phosphine was found.’
‘While the temperature is benign, the clouds contain sulphuric acid which should break down the phosphine,’ he continued.
This, he explained, means that ‘something is forming it anew — and as phosphine is associated with life on Earth, it is tempting to think it could be life on Venus.’
‘But before we can become more confident about that we have to rule out all possible other non-biological means of producing it.’
The full findings of the study were published in the journal Nature Astronomy.
KEY DISCOVERIES IN HUMANITY’S SEARCH FOR ALIEN LIFE
Discovery of pulsars
British astronomer Dame Jocelyn Bell Burnell was the first person to discover a pulsar in 1967 when she spotted a radio pulsar.
Since then other types of pulsars that emit x-rays and gamma rays have also been spotted.
Pulsars are essentially rotating, highly magnatised neutron stars but when they were first discovered it was believed they could come from aliens.
‘Wow!’ radio signal
In 1977, an astronomer looking for alien life in the nigh sky above Ohio spotted a powerful radio signal so strong that he excitedly wrote ‘Wow!’ next to his data.
In 1977, an astronomer looking for alien life in the nigh sky above Ohio spotted a powerful radio signal so strong that he excitedly wrote ‘Wow!’ next to his data
The 72-second blast, spotted by Dr Jerry Ehman through a radio telescope, came from Sagittarius but matched no known celestial object.
Conspiracy theorists have since claimed that the ‘Wow! signal’, which was 30 times stronger than background radiation, was a message from intelligent extraterrestrials.
Fossilised martian microbes
In 1996 Nasa and the White House made the explosive announcement that the rock contained traces of Martian bugs.
The meteorite, catalogued as Allen Hills (ALH) 84001, crashed onto the frozen wastes of Antarctica 13,000 years ago and was recovered in 1984.
Photographs were released showing elongated segmented objects that appeared strikingly lifelike.
Photographs were released showing elongated segmented objects that appeared strikingly lifelike (pictured)
However, the excitement did not last long. Other scientists questioned whether the meteorite samples were contaminated.
They also argued that heat generated when the rock was blasted into space may have created mineral structures that could be mistaken for microfossils.
Behaviour of Tabby’s Star in 2005
The star, otherwise known as KIC 8462852, is located 1,400 light years away and has baffled astonomers since being discovered in 2015.
It dims at a much faster rate than other stars, which some experts have suggested is a sign of aliens harnessing the energy of a star.
The star, otherwise known as KIC 8462852, is located 1,400 light years away and has baffled astonomers since being discovered in 2015 (artist’s impression)
Recent studies have ‘eliminated the possibility of an alien megastructure’, and instead, suggests that a ring of dust could be causing the strange signals.
Exoplanets in the Goldilocks zone in 2015
In February this year astronomers announced they had spotted a star system with planets that could support life just 39 light years away.
Seven Earth-like planets were discovered orbiting nearby dwarf star ‘Trappist-1’, and all of them could have water at their surface, one of the key components of life.
Three of the planets have such good conditions, that scientists say life may have already evolved on them.
Researchers claim that they will know whether or not there is life on any of the planets within a decade, and said ‘this is just the beginning.’