A single molecule is not sufficient to prove the existence of extraterrestrial life
DrThe discovery of extraterrestrial life, even if in microbiological form, would be a triumph for science. Every mysterious proposition rests on open ears – as was the last case in September 2020 with the supposed discovery of monophosphorous gas in Venus’ atmosphere. This could indicate the existence of life, as was said at the time. The discovery report published by Jane Graves of Cardiff University quickly sparked criticism: Experts even questioned whether Graves and her colleagues had even measured phosphorous gas. Instead, it would have been sulfur dioxide, as has been speculated.
In November, the researchers admitted that they had overestimated the phosphorous concentration due to a data error in the Alma telescope’s network, but the gas was present. This means that some processes on our neighboring planet must provide for regeneration, otherwise the gas will long ago disappear. In their work, Graves and colleagues assessed that this could be biological as unlikely, but it was not excluded. This was enough for this account, promoted by responsible press offices, to elicit a media response that few scientific publications receive.
This is what the Extremely Large Telescope (ELT) will look like when completed
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Bild: This
We will soon know whether or not Venus’ atmosphere contains phosphine: After a pandemic-related fracture, Alma resumed operations in March. So what if the discovery is confirmed? Do the microorganisms that produce phosphine as a metabolic product live in the clouds of Venus, or does the gas come from “unexplained chemistry,” as the researchers vaguely described it?
Find fingerprints from life
Questions like these will arise frequently in the future. The US James Webb Space Telescope, scheduled to be launched in the fall of 2021, or the European Very Large Telescope currently under construction in Chile, will soon also be able to examine the atmosphere of Earth-like planets around the Sun in one form or another. The stars are the fingerprints of life. It won’t be easy, not even with more obvious biomarkers like oxygen.
This occurs on Earth during photosynthesis in plants, and from an evolutionary point of view, it is reasonable to assume that plants on other planets could also use the light of their stars to generate energy. However, the signal of oxygen in the atmosphere of an exoplanet would not be a clear sign of life, as Joshua Chrisensen Toton of the University of California, Santa Cruz and several colleagues are now doing. In the magazine “AGU Advances”.
Their computer models of Earth-like planets show that planets with a much larger or smaller proportion of water than Earth can reach the oxygen-containing atmosphere without the interference of living things, for example by splitting water molecules into hydrogen and oxygen by a star. UV. “There has been a lot of debate in the past about whether discovering oxygen as evidence for life is ‘sufficient’,” says co-author Jonathan Fortney.
The James Webb telescope is scheduled to enter service in the fall of 2021.
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Photo: dpa
“Our work shows that you must know the context: What other molecules are there and which ones aren’t? What do they tell us about the evolution of the planet?” In addition to the full spectral coverage of the atmosphere, the nature of the planet’s surface will be important: Is it covered in water or like a desert? Is there volcanic activity? Even with the latest telescopes, it wouldn’t be easy to see.
On the phosphine puzzle trail with simulations
Monophosphine, a chemical compound made of one phosphorous and three hydrogen atoms, is on astrophysicists’ wish lists far below oxygen, but its potential discovery on Venus spurred their interest in the substance. But the same thing applies here: the molecule has yet to be discovered, such as a team led by Juan Trujillo of the University of New South Wales in Australia. In the journal “Frontiers in Astronomy and Space Sciences” Indicated. “Phosphorous is a promising biomarker because it is produced in very small quantities in other natural processes,” says co-author Laura McKemmish.
“As long as we do not know exactly how they are produced and destroyed, we cannot say with certainty whether they are caused by unusual chemical processes or by little green men.” To find out, it is necessary to track down other phosphorous molecules that play a role in the production and destruction of monophosphorous. To this end, the researchers simulated the spectra of nearly 1,000 phosphorous-containing molecules on a computer. Not all of them can be detected with telescopes today. But the sheer scale shows the investigative work that astrobiology can expect in the coming years.
There is still a long way to go before there is clear evidence, beyond doubt, of life on another planet, even if only indirectly through biomarkers in its atmosphere. It is best for observers of the scientific community to bear this fact in mind: alleged erotic reports such as the recent ones in the case of Venus will definitely be more frequent in the future.
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