Our chances of finding life on other planets has just skyrocketed
The odds for life existing on other planets has just skyrocketed after a NASA rover unearthed new evidence on Mars.
The odds for life existing on other planets just skyrocketed.
NASA’s stoic Perseverance rover has scraped up potential evidence of ancient microbes on Mars.
The James Webb Telescope has found what may be the first signs of an atmosphere around a rocky, Earth-sized planet.
They’re just baby steps in the search for life beyond our pale blue dot. It’s encouraging progress.
But the extraterrestrial hunt has thrown up nothing but false positives and wild goose chases since it began in the 1960s. And odds are not evidence.
They’re just … odd. Therefore exciting.
Evidence of an atmosphere on a rocky planet would be big – if true.
As would the discovery of even fossilised – if not live – alien microbes.
It hasn’t happened yet. But we’re much closer.
And how we’re getting there is amazing.
Spectral fingerprints
The TRAPPIST-1 solar system generated a storm of excitement when it was examined in 2017.
Observers found seven rocky planets. All are similar in size to Earth. And up to four of them sit within the “Goldilocks Zone” – the distance from their small Red Dwarf star that provides enough heat to support liquid water.
The system is about 40 light-years away. And that puts it on the edge of the James Webb Space Telescope’s ability to pull enough pixels out of a pinprick of light to point to an atmosphere around an Earth-sized planet.
That’s what it has done.
A study published in The Astrophysical Journal Letters.
It’s the best positioned in the star’s life-support zone. But scientists are unsure whether the unusual orbital mechanics of a Red Dwarf make stable atmospheres possible.
The planets are tidally locked. That means they circle their star like the Moon orbits the Earth – with one face permanently turned towards it.
One side would be in permanent light, and therefore hot. The other is in perpetual darkness and therefore frozen.
Its neighbour had already been found to be dead.
A similar scan of TRAPPIST-1d produced no discernible sign of an atmosphere. But that in itself has helped astronomers narrow down the range of conditions in which they will conduct future searches.
The spectrum of light extracted from TRAPIST-1e is much more lively.
The Red Dwarf’s light changes as it passes by the planet.
“Each molecule has a spectral fingerprint. You can compare your observations with those fingerprints to suss out which molecules may be present,” says lead researcher Ana Glidden.
So far, the atmosphere is unlike anything seen before.
It does not appear to have much hydrogen. Or carbon dioxide. But it could contain nitrogen.
The researchers say this may point to a liquid ocean, ice sheets – or a volcanic blanket of greenhouse gases spreading the star’s warmth around the planet.
“However, we stress that the evidence neither warrants the detection of an atmosphere nor rules one out,” the study warns.
“Stellar activity strongly interferes with the planetary interpretation of the data because we can only observe a potential atmosphere through starlight,” Glidden explains. “It is challenging to separate out which signals come from the star versus from the planet itself.”
Red herrings
It may be “only” 225 million kilometres from Earth. But five decades of satellite surveys and probing rovers haven’t been enough to crack the mystery of Mars.
It’s provided its moments, though.
Early images of its surface convinced many onlookers that it was covered in ruins. Canals. Pyramids. An enormous sculpted “face”.
It all turned out to be pareidolia (wishful thinking). The mind’s eye was seeing what it expected to see amid the blurry and pixelated scenes.
The 1976 Viking landers caused excitement. One experiment produced a chemical impact on soil that could be created by microbes. Other tests carried by the first-generation robots did not.
Then there are the tiny, wiggly shapes found in Martian rocks blasted off its surface by asteroid impacts and sent spinning on their way to Earth. But experiments have shown these are not necessarily fossilised microbes. Such deposits can also be produced by geological processes.
But the Perseverance Rover has been poking about the 3.7 billion-year-old Jezero Crater since 2021. Orbital surveys found an ancient river valley there. It is an ideal spot for sediments to have fossilised any telltale signs.
Now, several of its sample collections have sent hopes soaring.
The Rover’s sensors had already found trace samples of iron and phosphorus. That’s a good – but inconclusive – sign of ancient microbial poo.
Now it has sifted out strange-looking seed and pollen-like shapes from the sand.
“This is the kind of signature that we would see that was made by something biological,” NASA associate administrator Nick Fox said this week.
But looks can be deceptive. And science demands certainty.
“That’s part of the reason why we can’t go so far as to say, ‘A-ha, this is proof positive of life,” explains researcher Joel Hurowitz. “All we can say is one of the possible explanations is microbial life, but there could be other ways to make this set of features that we see.”
The sample has been bundled and stored. One of Perseverance’s jobs is to create caches of interesting finds for a future lander to collect and return to Earth.
That $US11 billion project is yet to be funded.
Hope, or hype?
We’ve been here before.
The Viking landers weren’t even the first to throw up false positives. The detection of regular interstellar radio pulses sparked excitement in the 1960s. But, since then, astronomers have found them to be a natural phenomenon – pulsars.
More recently, a 2023 study of James Webb Space Telescope data found the molecule dimethyl sulphide (DMS) in the atmosphere of K2-18b, a planet orbiting a Red Dwarf star some 120 light-years away.
The announcement made worldwide headlines. But science, by nature, is sceptical.
The data was re-examined. The numbers crunched again. And no statistically reliable result has been reproduced.
“Science hype, the raising of expectations around the prospects of success of a field, can be a positive force by attracting the attention and inviting the contribution of the public and a plurality of societal actors to help shape the future direction of research,” a group of Japanese researchers report in PLOS ONE.
“On the downside, failure of expectations can be damaging to the credibility of institutions associated with them.”
As a result, international efforts are underway to create a Confidence of Life Detection (CoLD) scale. This numerical checklist is intended to score research results. The resulting mark will be an indicator of the strength of the evidence.
“The current state of scientific knowledge about the prevalence of life in the universe is still highly uncertain,” the researchers write. “We don’t know if life exists elsewhere in the universe, and we don’t know if we are ever going to reach a definite answer to the main question.”
But the thrill of the hunt remains.
“It’s incredible to measure the details of starlight around Earth-sized planets 40 light-years away and learn what it might be like there, if life could be possible there,” says Glidden.
“We are seeing two possible explanations for what’s going on at Trappist-1e,” study co-authors Hannah Wakeford and Ryan MacDonald write in The Conversation. “The most exciting possibility is that the planet has a so-called secondary atmosphere containing heavy molecules such as nitrogen and methane. But the four observations we obtained aren’t yet precise enough to rule out the alternative explanation of the planet being a bare rock with no atmosphere.”
Jamie Seidel is a freelance writer | @jamieseidel.bsky.social
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Originally published as Our chances of finding life on other planets has just skyrocketed
