from
https://www.bbc.com/news/science-environment-66950930

It is best to go to the citation to see graphics and read better.

Alien life in Universe: Scientists say finding it is 'only a matter of time'
Published
14 hours ago

Share
Photograph of Jupiter moon Europe
IMAGE SOURCE,ESA
Image caption,
Europa, one of Jupiter's icy moons is the most likely place in our solar
system to be home to alien life
By Pallab Ghosh
Science correspondent
Many astronomers are no longer asking whether there is life elsewhere in
the Universe.

The question on their minds is instead: when will we find it?

Many are optimistic of detecting life signs on a faraway world within
our lifetimes - possibly in the next few years.

And one scientist, leading a mission to Jupiter, goes as far as saying
it would be "surprising" if there was no life on one of the planet's icy
moons.

Nasa's James Webb Space Telescope (JWST) recently detected tantalising
hints at life on a planet outside our Solar System - and it has many
more worlds in its sights.

Numerous missions that are either under way or about to begin mark a new
space race for the biggest scientific discovery of all time.

"We live in an infinite Universe, with infinite stars and planets. And
it's been obvious to many of us that we can't be the only intelligent
life out there," says Prof Catherine Heymans, Scotland's Astronomer Royal.

"We now have the technology and the capability to answer the question of
whether we are alone in the cosmos."

The 'Goldilocks zone'
Telescopes can now analyse the atmospheres of planets orbiting distant
stars, looking for chemicals that - on Earth at least - can be produced
only by living organisms.

The first flicker of such a discovery came earlier this month. The
possible sign of a gas that, on Earth, is produced by simple marine
organisms was detected in the atmosphere of a planet named K2-18b, which
is 120 light years away.

The planet is in what astronomers call ''the Goldilocks zone' - the
right distance away from its star for the surface temperature to be
neither too hot nor too cold, but just right for there to be liquid
water, which is essential to support life.

K2-18 b orbits the cool dwarf star K2-18 just far enough away from it
for the temperature to support life.
IMAGE SOURCE,NASA
Image caption,
Artwork: K2-18 b orbits a cool dwarf star shown in red just far enough
away for its temperature to support life.
The team expects to know in a year's time whether the tantalising hints
are confirmed or have gone away.

Prof Nikku Madhusudhan of the Institute of Astronomy at Cambridge
University, who led the study, told me that if the hints are confirmed
"it would radically change the way we think about the search for life".

"If we find signs of life on the very first planet we study, it will
raise the possibility that life is common in the Universe."

He predicts that within five years there will be "a major
transformation" in our understanding of life in the Universe.

The amazing images taken by the $10bn telescope
Tantalising sign of possible life on faraway world
If his team don't find life signs on K2-18b, they have 10 more
Goldilocks planets on their list to study - and possibly many more after
that. Even finding nothing would "provide important insights into the
possibility of life on such planets", he says.

His project is just one of many that are under way or planned for the
coming years searching for signs of life in the Universe. Some search on
the planets in our Solar System - others look much further, into deep space.

chart showing different projects searching for life in space.
As powerful as Nasa's JWST is, it has its limits. Earth's size and
proximity to the Sun enable it to support life. But JWST wouldn't be
able to detect faraway planets as small as Earth (K2-18b is eight times
bigger) or as close to their parent stars, because of the glare.

So, Nasa is planning the Habitable Worlds Observatory (HWO), scheduled
for the 2030s. Using what is effectively a high-tech sunshield, it
minimises light from the star which a planet orbits. That means it will
be able to spot and sample the atmospheres of planets similar to our own.

Also coming online later this decade is the Extremely Large Telescope
(ELT), which will be on the ground, looking up at the crystal-clear
skies of the Chilean desert. It has the largest mirror of any instrument
built, 39-metres in diameter, and so can see vastly more detail at
planetary atmospheres than its predecessors.

All three of these atmosphere-analysing telescopes make use of a
technique, used by chemists for hundreds of years, to discern the
chemicals inside materials from the light they give off.

They are so incredibly powerful that they can do this from the tiny pin
prick of light from the atmosphere of a planet orbiting a star, hundreds
of light years away.

Graphic showing how light can be split into different wavelengths and
that if it has passed through an atmosphere some wavelengths will be
missing - depending on what was in the atmosphere - which scientists can
then interpret
Searching close to home
While some look to distant planets, others are restricting their search
to our own backyard, to the planets of our own Solar System.

The most likely home for life is one of the icy moons of Jupiter,
Europa. It is a beautiful world with cracks on its surface that look
like tiger stripes. Europa has an ocean below its icy surface, from
which plumes of water vapour spew out into space.

Nasa's Clipper and the European Space Agency (ESA)'s Jupiter Icy Moons
Explorer (Juice) missions will both arrive there in the early 2030s.

Tiger stripes in brown and green on surface of Europa
IMAGE SOURCE,NASA
Image caption,
Europa's tiger stripes are caused by cracks on its icy surface
Shortly after the Juice mission was approved in 2012, I asked Prof
Michelle Dougherty, who is the lead scientist of the European mission,
if she thought there was a chance of finding life. She replied: "It
would be surprising if there wasn't life on one of the icy moons of
Jupiter."

Nasa is also sending a spacecraft called Dragonfly to land on one of the
moons of Saturn, Titan. It is an exotic world with lakes and clouds made
from carbon-rich chemicals which give the planet an eerie orange haze.
Along with water these chemicals are thought to be a necessary
ingredient for life.

Titan plumes
IMAGE SOURCE,ESA
Image caption,
A view of Titan taken by ESA’s Huygens lander as it descended to its surface
Mars is currently too inhospitable for living organisms, but
astrobiologists believe that the planet was once lush, with a thick
atmosphere and oceans and able to support life.

Nasa's Perseverance rover is currently collecting samples from a crater
thought once to have been an ancient river delta. A separate mission in
the 2030s will bring those rocks to Earth to analyse them for potential
microfossils of simple life forms that are now long gone.

Could aliens be trying to contact us?
Some scientists consider this question the realm of science fiction and
a long shot, but the search for radio signals from alien worlds has gone
on for decades, not least by the Search for Extra Terrestrial
Intelligence (Seti) institute.

All of space is a large place to look, so their searches have been
random to date. But the ability of telescopes, such as JWST, to identify
the most likely places for alien civilisations to exist means that Seti
can focus its search.

That has injected fresh impetus, according to Dr Nathalie Cabrol,
director of Seti's Carl Sagan Center for the study of life in the
Universe. The institute has modernised its telescope array and is now
using instruments to look for communications from powerful laser pulses
from distant planets.

As a highly qualified astrobiologist, Dr Cabrol understands why some
scientists are sceptical of Seti's search for a signal.

But chemical signatures from faraway atmospheres, interesting readings
from moon flybys and even microfossils from Mars are all open to
interpretation, Dr Cabrol argues.

Looking for a signal "might seem the most far-fetched of all the various
approaches to find signs of life. But it would also be the most
unambiguous and it could happen at any time".

"Imagine we have a signal that we can actually understand," says Dr Cabrol.

Thirty years ago, we had no evidence of planets orbiting other stars.
Now more than 5,000 have been discovered, which astronomers and
astrobiologists can study in unprecedented detail.

All the elements are in place for a discovery that will be more than
just an incredible scientific breakthrough, according to Dr Subhajit
Sarker of Cardiff University, who is a member of the team studying K2-18b.

"If we find signs of life, it will be a revolution in science and it is
also going to be a massive change in the way humanity looks at itself
and its place in the Universe."

"a425couple" wrote in message news:trqSM.33637$NkG.29483@fx41.iad...

The 'Goldilocks zone'
Telescopes can now analyse the atmospheres of planets orbiting distant
stars, looking for chemicals that - on Earth at least - can be produced
only by living organisms.

---------------------------------

https://www.liebertpub.com/doi/10.1089/ast.2019.2139

"Interestingly, the sulfur-containing molecules detected on Mars include
thiophene and some of its derivatives (2-methylthiophene, 3-methylthiophene,
and presumably benzothiophene) as well as smaller fragments (methanethiol,
dimethyl sulfide, carbonyl sulfide, carbon disulfide, hydrogen sulfide, and
sulfur dioxide) .."

" Finally, this study provides suggestions for future investigations on Mars
and in Earth-based laboratories to answer the question whether the martian
thiophenes are of biological origin."

We can't rule out a non biotic origin of dimethyl sulfide.

"Jim Wilkins" wrote in message news:uffhkj$35pno$1@dont-email.me...

This article asserts that dimethyl sulfide was present on Earth before life
began:
https://www.nature.com/articles/s41467-023-39917-0

"Here we show that this abiotic mechanism occurs also outside living cells
and might have contributed to CH4 levels before life emerged. All needed
components: (i) methylated S- and N-compounds, (ii) Fe2+ and (iii) ROS are
found under early-earth conditions. (i) In a prebiotic world, methylated
S-compounds like methanethiol, dimethyl sulfide (DMS) or dimethyl sulfoxide
(DMSO) were formed abiotically under the reducing conditions of hydrothermal
vents or transported to Earth by carbonaceous meteorites during early Earth
meteorite bombardment."