Again there were suddenly ‘signs of alien life’ in the news. In April, a research team from the University of Cambridge reported that chemical traces of life were seen in the atmosphere of K2-18B, a planet at 124 light-year distance from the earth. With the help of the James WebB spacecraft, Dimethylsulfide would have been discovered in the atmosphere, a gas that is only produced on earth by microorganisms such as Plankton.
Immediately other scientists expressed severe criticism of the research and the way in which author Nikku Madhusadhan visited the spotlights, with a press conference and a press release in which it was about “an ocean that is teeming with life”.
“This is exactly how it should be: in such a way you ask a lot of attention for something that is not nearly certain, which you should first discuss within the scientific community,” says Inge Loes ten Kate. Ten Kate is astrobiologist at the Faculty of Geosciences at Utrecht University. She is interested in the origin of life on earth, and the related question of whether there is an alien life somewhere.
And indeed: Studies soon appeared where the Dimethylsulfide measurements are explained with fabrics that have also been found on the (insofar as we know) lifeless planets Jupiter, Saturn and on Saturnus Maan Titan. Madhusudhan holds Foot: “We see those signals – that is the core of the matter,” he said Last week against the trade magazine Science.
“You have seen how it is possible,” says Ten Kate. A few weeks before the K2-18B message, she had invited me to look together at the live stream of a presentation during the 56th Lunar and Planetary Science Conference in Texas, in which scientists also announce the discovery of possible signs of alien life, but then in a very different way, facts separately. Only the website of Nature written About it.
Intriguing rock
There was, however, a striking description: ‘poppy seeds’ and ‘leopard spots’. The peculiar speckles reminded those Mars researchers Joel Hurowitz of the Stony Brook-University in New York on a stone in an old river bed on Mars. The most suitable explanation appears to be the earlier presence of microorganisms, arguing Hurowitz and ninety fellow researchers in a short article that visitors could already read before the congress. A peer reviewed – commented by expert colleagues – article in the trade journal Nature Communications is in preparation.
Vinder of the intriguing rock is NASA’s Robotkar Perseverance, which landed on 18 February 2021 at the Jezero crater, an impact crater on Mars. Before Mars 3.8 billion years ago, atmosphere was largely lost and turned into an ice -cold, bone -dry desert, this crater was full of water. That had been streamed in by a breach in the crater wall. On the bottom of the riverbed that formed there, Persverance found a rock with a strange spot pattern in July 2024.
On the reddish rock – the color is caused by rust -colored oxidized iron -containing minerals – can be seen sharply -marked dark dots, about a tenth millimeter wide, calling the researchers ‘poppy seeds’. In between you can see slightly larger circles, between 0.2 and 1 millimeter, who are reminiscent of the spots of a leopard with some imagination. Inside the leopard spots, the reddish rock is bleached.
Persverance took measurements on the rock with Pixl, a device that measures X -rays and Sherloc, a so -called ramanspectrometer Who analyzes the spectrum of batching ultraviolet light. “With the help of the Ramansprum we see organic material,” says Hurowitz, or material with lots of carbon-carbon bonds, “and that signal is the strongest in the most faded spots in the middle of the leopard stains.”
Wet mud
A possible interpretation is that once, when the rock was still wet mud, there was colonies of microorganisms in Huisden. “They have been dead themselves now, but they have been traced,” says Ten Kate, “it’s a bit similar to” the weather. ” Those are the dark, indelhable speckles that appear in the upholstery of sails or garden benches if they have been wet for too long. “Even if you were those at 90 degrees, you can’t get those stains out of it. They are organic remains that are not soluble.”
The find of organic molecules also matches that story, although it is certainly not evidence in itself. “We now know that countless complex organic molecules have been formed in the outer regions of the solar system,” says Ten Kate. For example, around sixteen thousand different carbon and nitrogen-containing molecules were found in a sample of the asteroid Bennu.
One theory about the origin of life means that such substances, fell to earth in meteorites, have been a kind of starter kit for life. “But that also means that you cannot say at the find of complex organic molecules: you see, life!”, Ten Kate says.
Another indication of the local showing inside the leopard spots, so exactly where the organic material is. This points to reduction, the opposite of oxidation, of the IJzeratomas in the stone. That process only takes place on earth under the influence of microorganisms. But what applies on earth does not have to apply to Mars: perhaps there is an ‘abiotic’ reduction process, a process that does not involve life forms.
There is no scream, not shouting yourself. I like that very well
Another indication is the sharp contours of the poppy seeds and the leopard spots. If there are already abiotic chemical processes that can cause reduction, it is difficult to imagine why they do not take place in one place, and a tenth millimeter away. Ten Kate: “That also indicates a microbial form of life that can form small colonies.”
Yet after the presentation, Ten Kate is not yet convinced, “that it is one Potential Biosignature I agree with that. It is interesting enough to keep digging and to keep thinking: how is this possible? But evidence, that’s not nearly. And so it is not presented: there is no scream, not shouting yourself. I really like that. ”
The discovery of extraterrestrial life, even if it would only be microorganisms, would be a discovery of the outside category. It would have consequences for our ideas about the origin of life, how often that happens, how easily it spreads, and ultimately even for the question of whether we are only in the universe as an intelligent species.
But perhaps the biggest problem in the search is that we have no idea what alien life should look like. Does it also use DNA, water, proteins and other well -known biomolecules? Is it at all based on carbon compounds? Or does it lean on a completely different type of chemistry or other patterns? Because in the latter case there are hardly any meaningful starting points, astrobiologists often assume carbon chemistry.
Difficult to explain
A common reasoning is that living processes leave traces or biosignures: phenomena that are difficult to explain without life. Such as Dimethylsulfide, or, for example, the chemically reactive oxygen in our own atmosphere, three billion years ago produced by blue algae. The problem is that for many biosignatures, abiotic processes are often conceivable, such as volcanic or other geochemical processes. You have to exclude them all.
A practical complication is that it is very difficult to take measurements on millions of kilometers away-in the case of Mars-or even hundreds of light years, such as with the planet K2-18B. Persverance has a number of high -tech measuring instruments on board, but compared to what is possible in earthly laboratories, they are limited. “You would like to measure the compositions of those stains much more precisely with all kinds of techniques,” says Ten Kate. “That is why we really want to retrieve the monsters.”
And that was also the plan. Where earlier Marssondes had to do everything themselves, Persverance collects 38 interesting rock monsters, in order to be able to pick them up later for analysis on earth. A monster is also stored in a titanium tube of the poppy seeds and leopard spots.
But whether that tube will ever come home? The planned space mission of NASA and the European space organization ESA, working title Mars Sample-Return (MSR), is in heavy weather. In September 2024 it turned out that the costs of the mission, now in the draft stage, had already risen from 7 billion to 11 billion dollars. In the last proposals of the American White House for the NASA budget, MSR is simply deleted in favor of manned trips to Mars. Some people prefer to bring life to Mars than to pick it up.
AlienWhere have we heard that before?
Alleged traces of life Outside the earth appealed to the imagination. But on closer inspection, little remained. Four famous cases.
Channels on Mars
In 1877 the Italian astronomer Giovanni Schiaparelli described Canali On Mars, apparently straight lines that looked like earthy waterways. The British astronomer Percival Lowell interpreted this as a word ‘channels’, and assumed that they were dug by Mars dwellers. Schiaparelli’s Canali were probably optical illusions, encouraged by imperfections in telescopic lenses.
Little Green Men
In November 1967, astronomer Jocelyn Bell Burnell made the recordings with the new radio telescope of her university in Cambridge. She discovered a radio pulses that came back very precisely every 1,337 seconds. Radio stirrers, she and her supervisor first thought, but the pulses clearly came from one direction in the sky. When a second pulsating source was discovered, astronomers called the signal half-joking LGM-1, after ‘Little Green Men’ or ‘small green males’.
The pulses were found from rapidly circular neutron stars that were baptized ‘Pulsars’. “We did not really believe that we had picked up signals from another civilization, but of course the idea had come up with us,” Bell wrote about it later.
Nanoknolletjes in Marsmeteorite
In 1996, researchers found in the 1.93 kilos of Meteorite ALH84001, originating from Mars, miniscule ball structures. They interpreted these nanocnars of around 20 to 100 nanometers as fossilized ‘nanobacteria’, hypothetical bacteria smaller than all existing microorganisms.
The discovery of possible alien life became world news. Even US President Bill Clinton made a statement about it, for the greater honor and glory of the scientists and NASA’s space program.
But skeptics found other explanations for the creation of the nanocnolljes, which also seem too small to function as cells. In the meantime there are very few scientists who believe they have ever lived. They have created the astrobiology field
Phosphine on Venus
Phosphine, or pH3is a smelly, toxic, and chemically unstable gas produced on earth by some bacteria. The surprise was great when a team of researchers announced in 2020 that with the radio telescope Alma in Chile in Chile, they had detected traces of phosphine high in the atmosphere of Venus.
Venus, our neighboring planet, does not seem very suitable for life at first sight. On the surface it is around 450 degrees Celsius, and high above it drives a dense cloud cover of sulfuric acid, among other things. No environment where phosphine can occur or can exist for a long time.
That made the discovery to possible biosignature, said Sara Seager, one of the authors of an article in Nature Astronomyagainst CNN. “Something completely unexpected and very intriguing is happening on Venus, which produces the unexpected presence of small amounts of phosphine gas.”
She did not explicitly claim that they had discovered life on Venus, although many media themselves did draw that conclusion. But the measurements were not very robust, and five years later few researchers accept the find of phosphine on Venus, and the interpretation as a trail of possible life.