Venus: Secrets of Our Strange Sister Planet

 

Clouds of Venus

 

Will New NASA and ESA Missions Show Early Venus Had Oceans and Life? ESA and NASA have decided this year to send no less than three space exploration missions over the next decade to our sister planet, the second closest planet to the Sun, described by Stephen Hawking as Earth’s “kissing cousin.” Venus is like Earth in so many ways,” explained Hawking. “She’s almost the same size as Earth, a touch closer to the Sun. And, she has an atmosphere that could crush a submarine.”

“The three recently selected space missions to Venus– VERITAS  DAVINCI and ESA’s EnVision — will embark scientific instruments to test the existence of ancient oceans on Venus. The main strategy so far is to observe some of the best preserved terrains — named the “tesserae” — to look for spectroscopic or morphological signatures left by the early oceans,” astronomer Martin Turbet at the University of Geneva told The Daily Galaxy. Turbet’s research focuses on the interface between astrophysics, climate sciences and geophysics, specifically, on exoplanets potentially similar to the Earth, but which have evolved in a way very different from Earth’s currently human-driven epoch.

Life-Bearing Clouds of Venus? -Its Upper Atmosphere is the Most Earth-like Location in the Solar System

NASA’s VERITAS mission scheduled for 2028 will help create the first global high-resolution topographic and radar images of Venus. DaVinci (image at top of page), launching in 2029, will be the first U.S. mission to enter Venus’ atmosphere in over 40 years to determine if it was habitable, and to understand how it ended up as hellish nightmare it did.  ESA’s EnVision launching in 2031– will embark scientific instruments to test the existence of ancient oceans on Venus.

 

“We simulated the climate of the Earth and Venus at the very beginning of their evolution, more than four billion years ago, when the surface of the planets was still molten”, explains Martin Turbet. “The associated high temperatures meant that any water would have been present in the form of steam, as in a gigantic pressure cooker.” Using sophisticated three-dimensional models of the atmosphere, similar to those scientists use to simulate the Earth’s current climate and future evolution, the team studied how the atmospheres of the two planets would evolve over time and whether oceans could form in the process.

Oceans of Venus Nixed?

“Thanks to our simulations, we were able to show that the climatic conditions did not allow water vapor to condense in the atmosphere of Venus”, says Martin Turbet lead author of the 2021 study led by the UNIGE and the NCCR PlanetS to investigate the past of Venus to find out whether Earth’s sister planet once had oceans.

This means that the temperatures never got low enough for the water in its atmosphere to form raindrops that could fall on its surface. Instead, water remained as a gas in the atmosphere and oceans never formed. “One of the main reasons for this is the clouds that form preferentially on the night side of the planet. These clouds cause a very powerful greenhouse effect that prevented Venus from cooling as quickly as previously thought”, continues the Geneva researcher.

Earth Could Easily Have Suffered the Same Fate as Venus

Surprisingly, reports the University of Geneva study, the astrophysicists’ simulations also reveal that the Earth could easily have suffered the same fate as Venus. If the Earth had been just a little closer to the Sun, or if the Sun had shone as brightly in its ‘youth’ as it does nowadays, our home planet would look very different today. It is likely the relatively weak radiation of the young Sun that allowed the Earth to cool down enough to condense the water that forms our oceans. 

Reversal of the ‘Faint Young Sun Paradox’

For Emeline Bolmont, professor at UNIGE, member of PlaneS and co-author of the study, “this is a complete reversal in the way we look at what has long been called the ‘Faint Young Sun paradox’. It has always been considered as a major obstacle to the appearance of life on Earth!” The argument was that if the Sun’s radiation was much weaker than today, it would have turned the Earth into a ball of ice hostile to life. “But it turns out that for the young, very hot Earth, this weak Sun may have in fact been an unhoped-for opportunity”, continues the researcher.

Existence of a Gas Associated with Life Where There is No Oxygen?

Recent research has revealed that Venus might have looked like Earth for three billion years, with vast oceans that could have been friendly to life leading to recent speculation that it may have been the first life-bearing planet. A conjecture spurred by the announcement in September of 2020 by an international group of researchers reported in the journal Nature Astronomy, that there may be a whiff of life in the famously inhospitable planet’s atmosphere in the form of traces of phosphine, a gas that is associated with life where there is no oxygen.

 

 

First Habitable Planet? –”Plenty of Time for Evolution to Kick In”

“That’ s what sets my imagination on fire,” says Darby Dyar, a planetary scientist at Mount Holyoke College with NASA’s Solar System Exploration team, about the 2020 announcement, which led her to surmise: “If that’s the case, there was plenty of time for evolution to kick into action,” and conclude that Venus may have been the first habitable planet in the Solar System — “a place where life was just as likely to arise as it was on Earth.” On Earth, says Dyar, phosphine is found “in sewage facilities and in the guts of living animals.”

“The problem,” observed Dyar, “is that we haven’t thought too much about whether phosphine can be created abiotically on Venus, in part because we know so little about the planet and its chemistry.”

Spectral signatures of almost 1000 atmospheric molecules

Fast forward to 2021 research released by an international team, led by scientists at the University of New South Wales (UNSW) in Sydney, Australia , who have made a key contribution to this and any future searches for life on other planets by demonstrating how an initial detection of a potential biosignature must be followed by searches for related molecules, revealing the spectral signatures of almost 1000 atmospheric molecules that may be involved in the production or consumption of phosphine.

“The only way we’re going to be able to look at exoplanets and see whether there’s life there is to use spectral data collected by telescopes – that is our one and only tool,” says quantum chemist and molecular physicist, Dr. Laura McKemmish at the University of New South Wales, referring to the upcoming launch of the infrared James Webb Space Telescope (JWST). The JWST will be able to identify the spectral signatures of atmospheric molecules that may be involved in the production or consumption of phosphine that may indicate evidence of life if found in the atmospheres of small rocky planets like our own, where it is produced by the biological activity of bacteria.

“To identify life on a planet, we need spectral data,” says McKemmish about the new crossroads in the search for life beyond Earth with the ability to point a telescope at a planet and with the right spectral data determine what molecules are in the planet’s atmosphere such as phosphorus, an essential element for life. “Up until now,” she says, “astronomers could only look for one polyatomic phosphorus-containing molecule, phosphine.” 

 

When an international team of scientists last year claimed to have detected phosphine— a chemical compound made of one phosphorous atom surrounded by three hydrogen atoms (PH3)– in the atmosphere of Venus, it raised the prospect of the first evidence of life on another planet – albeit the primitive, single-celled variety. Some scientists however questioned whether the phosphine in Venus’s atmosphere was really produced by biological activity, or whether phosphine was detected at all.

“Unusual Chemistry or Little Green Men?”

In a paper published in the journal Frontiers in Astronomy and Space Sciences, they described how the team used computer algorithms to produce a database of approximate infrared spectral barcodes for 958 molecular species containing phosphorous. 

“Phosphine is a very promising biosignature because it is only produced in tiny concentrations by natural processes. However, if we can’t trace how it is produced or consumed, we can’t answer the question of whether it is unusual chemistry or little green men who are producing phosphine on a planet,” says McKemmish, who brought together a large interdisciplinary team to understand how phosphorus behaves chemically, biologically and geologically and ask how this can be investigated remotely through atmospheric molecules alone.

“What was great about this study is that it brought together scientists from disparate fields – chemistry, biology, geology – to address these fundamental questions around the search for life elsewhere that one field alone could not answer,” says astrobiologist and co-author on the study, Associate Professor Brendan Burns.

P-molecules

“At the start, we looked for which phosphorous-bearing molecules – what we called P-molecules – are most important in atmospheres but it turns out very little is known,” says McKemmish. “So we decided to look at a large number of P-molecules that could be found in the gas-phase which would otherwise go undetected by telescopes sensitive to infrared light.”

Barcode data for new molecular species are normally produced for one molecule at a time, McKemmish says, a process that often takes years. But the team involved in this research used what she calls “high-throughput computational quantum chemistry” to predict the spectra of 958 molecules within only a couple of weeks.

“Though this new dataset doesn’t yet have the accuracy to enable new detections, it can help prevent misassignments by highlighting the potential for multiple molecular species having similar spectral barcodes – for example, at low resolution with some telescopes, water and alcohol could be indistinguishable.

 

“The data can also be used to rank how easy a molecule is to detect. For example, counter-intuitively, alien astronomers looking at Earth would find it much easier to detect 0.04% CO2 in our atmosphere than the 20% O2. This is because CO2 absorbs light much more strongly than O2 – this is actually what causes the greenhouse effect on Earth.”

Extending the technique to the radio wavelengths 

“Our paper provides a novel scientific approach to following up the detection of potential biosignatures and has relevance to the study of astrochemistry within and outside the Solar System,” says McKemmish. “Further studies will rapidly improve the accuracy of the data and expand the range of molecules considered, paving the way for its use in future detections and identifications of molecules.”

Fellow co-author and Commonwealth Scientific and Industrial Research Organization (CSIRO) astronomer Dr Chenoa Tremblay says the team’s contribution will be beneficial as more powerful telescopes come online in the near future. She says although the team’s work was focused on the vibrational motions of molecules detected with telescopes sensitive to infrared light, they are currently working to extend the technique to the radio wavelengths as well, which will be important for current and new telescopes like the upcoming Square Kilometer Array to be built in Western Australia.

Fragments of Early Venus on the Moon?

In 2019, Yale astronomers suggested that our Moon may harbor impact fragments from Venus revealing that may may have had an Earth-like environment with water and a thin atmosphere billions of years ago. Their findings follow recent studies suggesting that our sister planet may have been the solar system’s first habitable planet.

Ancient fragments of Venus on the Moon “will certainly be interesting once we find them, especially since the surface of Venus is so hard to study with landed vehicles, due to the high temperature and pressure,” Fred Taylor, Halley Professor of Physics Emeritus at the University of Oxford told The Daily Galaxy.

Avi Shporer, Research Scientist, MIT Kavli Institute for Astrophysics and Space Research via Martin Turbet, Nature, UNSW and University of Geneva

Image credit: Shutterstock License, thick clouds over Venus. 3D illustration by Jurik Peter

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