August 01, 2018
With every new exoplanet discovered, the same question arises: Could this world host Life?
Life Needs Sunlight — and That Could Change Where We Look for Aliens
The default way scientists first approach that question is to check if the planet lies in the so-called habitable zone, the range of distances from a star in which a planet can hold liquid water on its surface. But water alone doesn't make life, so in a new paper, a team of scientists looked at another aspect of habitability: whether a planet receives enough ultraviolet radiation to create life's building blocks.
"The thing that you know best about any exoplanet system is the star," Paul Rimmer, lead author on the new study and an astrochemist at the University of Cambridge in the United Kingdom, told Space.com. "So, that seemed like a natural thing to start with."
Most scientists think that life began with ribonucleic acid (RNA). Like DNA, this molecule can transmit information, but unlike DNA, it can also help other molecules react with each other, potentially allowing RNA to replicate itself. But getting that RNA in the first place is tricky. This feat is so tricky, in fact, that the problem of creating RNA has haunted chemists interested in the origins of life for almost half a century, Sukrit Ranjan, a planetary scientist at the Massachusetts Institute of Technology, told Space.com. Ranjan has collaborated with the researchers in the recent study but was not involved in the new work.
He said that scientists know how to create each of the three building blocks that make up a molecule of RNA. In previous work, chemists have also figured out how to piece those building blocks together into two of the four flavors of RNA by focusing on a specific tricky chemical bond first. "The thing that jumped out to planetary scientists was that this mechanism requires UV [ultraviolet] light to function," Ranjan said.
So, Rimmer asked questions like what type of lights the chemists were using in their experiments and how closely those setups mimic the light produced by stars. For the new paper, Rimmer and his colleagues watched that mechanism work on two different chemical mixes meant to imitate a sulfur-rich young world and under a range of ultraviolet conditions. Those experiments let them calculate a minimum amount of ultraviolet light required for RNA formation.
This was Rimmer's first time doing formal chemistry lab research, and he said he appreciated taking the new approach. "I really enjoyed that aspect, because I think that experimentation is really the way that you can ground yourself in reality," he said. "It's like observation. It's something that you can very much see."
Others may not be so convinced by the new experiments: Frances Westall, an astrobiologist at the National Center for Scientific Research in France who was not involved with the study, called the paper more of an "interesting thought experiment" in an email to Space.com. She said she's particularly concerned that one of the two initial sulfur mixes the team used didn't create RNA under Earth-like conditions — and, after all, we're positive life started here somehow.
"One of my problems with many prebiotic chemistry experiments run by chemists is that they do not consider what the early Earth really was like," she wrote, mentioning that the team used what she considers an outdated recipe of gases to represent our planet's early atmosphere. "[Chemists] use spurious concepts simply because they can get good results under certain physicochemical conditions," Westall wrote.
Once Rimmer and his colleagues had that minimum requirement for ultraviolet light, they pored over exoplanets, selecting which worlds to include in their analysis. The researchers wanted planets that scientists are confident are rocky and so focused on planets less than 1.4 Earth radiuses in size. The scientists also wanted planets that previous studies had shown were the right distances from their sun to be able to hold liquid water on their surfaces.
Those criteria narrowed the study's focus down to a dozen exoplanets, a list that includes some of the most astrobiologically intriguing worlds we know of, like TRAPPIST-1e, f and g Kepler-452b; and LHS 1140b. (The team eliminated another popular contender, Proxima b, because astronomers don't have a firm enough measure of that world's size.)
Then, they turned to ultraviolet radiation, calculating how much light these planets receive from their stars today. That left just one firm contender, Kepler-452b, which was discovered in 2015 and which NASA billed at the time as "the first near-Earth-size planet [identified] in the 'habitable zone' around a sun-like star."
Similar calculations for yet-to-be discovered planets could help scientists prioritize where they look for life, Rimmer said. That could be particularly helpful given how expensive the necessary observations of these planets' atmospheres will be — once such work is even technologically possible. These measures will happen via instruments like the long-delayed James Webb Space Telescope. "You want to make sure you're looking at the places where you have the best chances," he said.
That said, the team's ultraviolet radiation calculations are not the last word on habitability. Their analyses leave out two key factors: the impact of solar flares, which can cause dramatic fluctuations in the ultraviolet radiation the star releases, and the changes a star undergoes as it ages, becoming calmer and less active.
The second factor could be particularly important, Rimmer said. That's because, right now, astronomers' best bet for finding exoplanets where they can identify life is to search around small, faint M dwarf stars — which currently produce much less light than they did when they were younger. That means that while these stars may not currently foster the conditions RNA needs to form, they may have done so long ago. And life that arose in the past could still be hiding out on the surface of planets surrounding these stars.
Rimmer already has plans to build on the new research: He said he wants to use xenon lamps, which more closely mimic the ultraviolet light coming from stars, providing better estimates of where RNA formation can occur.
The research is described in a paper published today (Aug. 1) in the journal Science Advances.
Latest News
Top news around the world
Russo-Ukrainian War

The Russo-Ukrainian War has been ongoing between Russia and Ukraine since February 2014.

Russia's war in Ukraine has proven almost every assumption wrong, with Europe now wondering what left is safe to assume.

Around the World

Celebrity News

> Latest News in Media

Watch It
Madonna’s most bizarre TikTok and Instagram videos of 2022 | Page Six Celebrity News
December 30, 2022
Ggk_RlohXuI
Teresa Giudice and Luis Ruelas stand by sex multiple times a day: It’s ‘normal’ | Page Six
December 30, 2022
AljKbtgRGnc
Lisa Hochstein shared video confronting Lenny Hochstein & girlfriend at Miami club #shorts | PageSix
December 30, 2022
j_JVk60r6EI
'Channel 5' Creator Andrew Callaghan Talks BTS of 'This Place Rules' Documentary Feature
December 30, 2022
dJit_YG5fjg
#brendanfraser on getting jacked to play 'George of the Jungle' after 'Airheads" with #adamsandler
December 30, 2022
bkwreE4eMRQ
Selena Gomez, Ryan Gosling and Julia Fox Top the List Of Variety's Best Red Carpet Moments Of 2022
December 29, 2022
pv2A-331cLg
Wiz Khalifa Joins Neek Bucks For Upcoming 'Shot Caller' Video | TMZ
December 26, 2022
TxkRr1jj-gk
Andrew Zimmern Says TikTok Recipes Need to Stop This Holiday Season | TMZ
December 26, 2022
DdlO88KfJoY
Top 7 WTF Moments of 2022 | TMZ
December 26, 2022
3JA-5abr6A4
Most HIGHLY ANTICIPATED Movies of 2023 | E! News
January 01, 2023
3-1K1VSRjys
22 Pop Culture Moments That Defined 2022: Link in Comments! #shorts | E! News
December 31, 2022
MNnChuudoSA
Suspect Charged With Murder in Idaho College Killings | E! News
December 31, 2022
aeonRlI5xL0
TV Schedule
Late Night Show
Watch the latest shows of U.S. top comedians

Sports

Latest sport results, news, videos, interviews and comments
Latest Events
01
Jan
ENGLAND: Premier League
Tottenham Hotspur - Aston Villa
01
Jan
ENGLAND: Premier League
Nottingham Forest - Chelsea
01
Jan
ENGLAND: Championship
Coventry - Bristol City
01
Jan
ENGLAND: Championship
Blackburn - Cardiff City
01
Jan
ENGLAND: Championship
Huddersfield - Luton
01
Jan
ENGLAND: Championship
Millwall - Rotherham
01
Jan
ENGLAND: Championship
Blackpool - Sunderland
31
Dec
ENGLAND: Premier League
Manchester City - Everton
31
Dec
ENGLAND: Premier League
Wolves - Manchester United
31
Dec
ENGLAND: Premier League
Brighton - Arsenal
31
Dec
SPAIN: La Liga
Barcelona - Espanyol
31
Dec
SPAIN: La Liga
Real Sociedad - Osasuna
31
Dec
ENGLAND: Premier League
Bournemouth - Crystal Palace
31
Dec
ENGLAND: Premier League
Newcastle United - Leeds
31
Dec
ENGLAND: Premier League
Fulham - Southampton
31
Dec
SPAIN: La Liga
Villarreal - Valencia
30
Dec
SPAIN: La Liga
Real Valladolid - Real Madrid
30
Dec
ENGLAND: Premier League
Liverpool - Leicester City
30
Dec
ENGLAND: Championship
Birmingham - Hull City
30
Dec
ENGLAND: Championship
Stoke City - Burnley
30
Dec
ENGLAND: Championship
Norwich City - Reading
30
Dec
ENGLAND: Premier League
West Ham United - Brentford
30
Dec
ENGLAND: Championship
Swansea City - Watford
30
Dec
SPAIN: La Liga
Celta Vigo - Sevilla
30
Dec
SPAIN: La Liga
Cadiz - Almeria
30
Dec
SPAIN: La Liga
Getafe - Mallorca
29
Dec
SPAIN: La Liga
Atletico Madrid - Elche
29
Dec
ENGLAND: Championship
West Bromwich Albion - Preston NE
29
Dec
ENGLAND: Championship
Blackpool - Sheffield United
28
Dec
ENGLAND: Premier League
Leeds - Manchester City
27
Dec
ENGLAND: Premier League
Manchester United - Nottingham Forest
27
Dec
ENGLAND: Premier League
Chelsea - Bournemouth
26
Dec
ENGLAND: Premier League
Arsenal - West Ham United
26
Dec
ENGLAND: Premier League
Brentford - Tottenham Hotspur
26
Dec
ENGLAND: Premier League
Aston Villa - Liverpool
Find us on Instagram
at @feedimo to stay up to date with the latest.
Featured Video You Might Like
zWJ3MxW_HWA L1eLanNeZKg i1XRgbyUtOo -g9Qziqbif8 0vmRhiLHE2U JFCZUoa6MYE UfN5PCF5EUo 2PV55f3-UAg W3y9zuI_F64 -7qCxIccihU pQ9gcOoH9R8 g5MRDEXRk4k
Copyright © 2020 Feedimo. All Rights Reserved.