New study dramatically narrows the search for advanced life in the universe

New study dramatically narrows the search for advanced life in the universe
Three planets orbiting TRAPPIST-1 fall within that star’s habitable zone. Credit: R. Hurt/ NASA/JPL-Caltech

Scientists may need to rethink their estimates for how many planets outside our solar system could host a rich diversity of life.

In a new study, a UC Riverside–led team discovered that a buildup of toxic gases in the atmospheres of most makes them unfit for as we know it.

Traditionally, much of the search for has focused on what scientists call the "," defined as the range of distances from a star warm enough that liquid water could exist on a planet's surface. That description works for basic, single-celled microbes—but not for complex creatures like animals, which include everything from simple sponges to humans.

The team's work, published today in The Astrophysical Journal, shows that accounting for predicted levels of certain toxic gases narrows the safe zone for complex by at least half—and in some instances eliminates it altogether.

"This is the first time the physiological limits of life on Earth have been considered to predict the distribution of complex life elsewhere in the universe," said Timothy Lyons, one of the study's co-authors, a distinguished professor of biogeochemistry in UCR's Department of Earth and Planetary Sciences, and director of the Alternative Earths Astrobiology Center, which sponsored the project.

"Imagine a 'habitable zone for complex life' defined as a safe zone where it would be plausible to support rich ecosystems like we find on Earth today," Lyons explained. "Our results indicate that complex ecosystems like ours cannot exist in most regions of the habitable zone as traditionally defined."

Using computer models to study atmospheric climate and photochemistry on a variety of planets, the team first considered dioxide. Any scuba diver knows that too much of this gas in the body can be deadly. But planets too far from their require carbon dioxide—a potent greenhouse gas—to maintain temperatures above freezing. Earth included.

"To sustain liquid water at the outer edge of the conventional habitable zone, a planet would need tens of thousands of times more carbon dioxide than Earth has today," said Edward Schwieterman, the study's lead author and a NASA Postdoctoral Program fellow working with Lyons. "That's far beyond the levels known to be toxic to human and on Earth."

New study dramatically narrows the search for advanced life in the universe
Credit: University of California - Riverside

The new study concludes that carbon dioxide toxicity alone restricts simple animal life to no more than half of the traditional habitable zone. For humans and other higher order animals, which are more sensitive, the safe zone shrinks to less than one third of that area.

What is more, no safe zone at all exists for certain stars, including two of the sun's nearest neighbors, Proxima Centauri and TRAPPIST-1. The type and intensity of ultraviolet radiation that these cooler, dimmer stars emit can lead to high concentrations of carbon monoxide, another deadly gas. Carbon monoxide binds to hemoglobin in animal blood—the compound that transports oxygen through the body. Even small amounts of it can cause the death of body cells due to lack of oxygen.

Carbon monoxide cannot accumulate on Earth because our hotter, brighter sun drives chemical reactions in the atmosphere that destroy it quickly. Although the team concluded recently that microbial biospheres may be able to thrive on a planet with abundant carbon monoxide, Schwieterman emphasized that "these would certainly not be good places for human or animal life as we know it on Earth."

Scientists have confirmed nearly 4,000 planets orbiting stars other than the sun, but none of them will be possible to visit in person. They are simply too far away. Closest is Proxima Centauri b, which would take 54,400 years for current spacecraft to reach. Using telescopes to detect abundances of certain gases in their atmospheres is one of the only ways to study these so-called exoplanets.

"Our discoveries provide one way to decide which of these myriad planets we should observe in more detail," said Christopher Reinhard, a former UCR graduate student now an assistant professor at the Georgia Institute of Technology, co-author of this study, and co-leader of the Alternative Earths team. "We could identify otherwise habitable planets with or carbon monoxide levels that are likely too high to support complex life."

Findings from the team's previous work is already informing next-generation space missions such as NASA's proposed Habitable Exoplanet Observatory. For example, because oxygen is essential to complex life on Earth and can be detected remotely, the team has been studying how common it may be in different planets' atmospheres.

Other than Earth, no planet in our solar system hosts life that can be characterized from a distance. If life exists elsewhere in the solar system, Schwieterman explained, it is deep below a rocky or icy surface. So, exoplanets may be our best hope for finding habitable worlds more like our own.

"I think showing how rare and special our planet is only enhances the case for protecting it," Schwieterman said. "As far as we know, Earth is the only planet in the universe that can sustain human life."


Explore further

Carbon monoxide detectors could warn of extraterrestrial life

More information: Edward W. Schwieterman et al. A Limited Habitable Zone for Complex Life, The Astrophysical Journal (2019). DOI: 10.3847/1538-4357/ab1d52
Journal information: Astrophysical Journal

Citation: New study dramatically narrows the search for advanced life in the universe (2019, June 10) retrieved 24 August 2019 from https://phys.org/news/2019-06-narrows-advanced-life-universe.html
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Jun 10, 2019
Considering that Oxygen is highly reactive and a toxin for many organisms, yet life here has managed to make use of it. So I think it likely that life will use whatever materials are there for it to come about, of course Earth Life may not come about because of what does or does not survive at any point in time along the range where life starts to form an ecosystem that is self-sustaining.

It may be that other planets use Sulfur Dioxide as we use Oxygen, perhaps hydrogen or Methane instead, but it seems to be a series of self-replicating chemical reactions can be found in a number of different habitat niches and since nearly every niche we look in here, from the Cold Antarctica to the Atacama deserts there is life in forms that go beyond our present full understanding.

From what we see here on Earth, life should be ubiquitous, even if it lives at different timescales to our own, different chemistry, gravity and temperatures all sweet spots where life should be able to form, with time

Jun 10, 2019
We still only have one example. Until we've got another one, we won't really know what constraints there actually are. Then again, if another example fails to turn up after an enormous amount of searching, we might well wonder whether life as we know it on Earth is not some kind of incredible fluke, and so rare that there might be just one example in the galaxy at this time: us.

Jun 10, 2019
I confess I do not really see the utility of this study. For one thing, only considering the possibility of life to those places whose temperature permit liquid water at the surface seems overly limiting. It appears that even Pluto may have a liquid subsurface ocean.

Secondly, refusing to consider the possibility of water based life (advanced or not) because of levels of CO2, CO, HS, etc. that are toxic to earth based organisms also seems quite limiting. There are examples even here on earth of organisms thriving in environments that are quite toxic to most other organisms.

Jun 10, 2019
Fascinating, but... There is an obvious error that stands out from the diagram above, figure 5 in the published paper. The position of Gliese 581 d and g are shown the wrong way around. Gliese 581 d is not the one closer to the inner edge of the habitable zone. Although it has a letter earlier in the alphabet this only describes Gliese 581d relative order of discovery in relation to the other planets in that star system, and not its relative distance from the star. It's a bit of a moot point because GJ 581 g likely doesn't exist but still what an amateurish mistake for them to make. Lol!

Jun 10, 2019
Comments seem to be on the same page on this curious study, which is unusual for fizz·org. There must be more to the thing. It seems to be an egregiously chauvinistic point of view to see chemical and biological evolution through our own particular solution to the various challenges.

They have narrowed the habitable zone because of the toxic levels of CO2 needed to retain heat at the perimeter, as though carbon dioxide were the only GHG. How about (abiotic) methane?

Edit: they did consider Methane:
"CH4 and/or H2—are strongly reducing and thus chemically incompatible at high concentrations with the levels of O2 required for the energy-intensive metabolisms of large, complex organisms (Catling et al. 2005)."

Jun 10, 2019
Fascinating, but... There is an obvious error that stands out from the diagram above, figure 5 in the published paper. The position of Gliese 581 d and g are shown the wrong way around. Gliese 581 d is not the one closer to the inner edge of the habitable zone.
What they've done is swap the two positions in the diagram in the study they cited (Habitable Zones around Main-Sequence Stars: New Estimates, Ravi Kumar Kopparapu et al. 2013)

Jun 10, 2019
So intelligent life can't arise in oceans?

Ridiculous.

This presupposes that intelligent undersea life with, say, opposable thumbs, couldn't build spaceships. Given that we have ballistic missile submarines, that assumption seems much too restrictive.

Jun 10, 2019
Anyhow, the easiest way to find advanced life capable of interstellar travel is to go to the one unique place in the Galaxy that all intelligent life will want to investigate and study: the central supermassive black hole at Sagittarius A*.

Given that all intelligent life will make the same conclusion, it is the logical place for all embassies as well.

If we had a good enough telescope facing the vicinity of Sagittarius A*, we might be able to see all the embassy parties.

Jun 10, 2019
The scientists will be the last to know.
https://billymeie...ejarens/
Ptaah:
In this respect I can give you our data, and these state that your galaxy, the Milky Way, according to our calculations, has about 156,000,000,000 stars and 431,000,000,000 planets with solid matter....The principal normal stars, which are comparable to SOL, must be calculated to be about 21,000,000,000, and only in their sphere of influence are many forms of higher life possible...Of these 156,000,000,000 stars about 7,000,000 are smaller and larger solar systems, which have planets and planet-planets upon which higher life is supported. Some of the smaller and larger solar systems have several planets and planet-planets upon which higher life exists, whereby the number of life supporting planets and planet-planets greatly increases....
Billy:
Quetzal said that there are 2,630,000 highly developed civilizations and 1,040,000 low-developed civ...

Jun 10, 2019
The scientists will be the last to know.
https billymeier·wordpress·com/2014/08/31/here-is-your-disclosure-from-the-plejarens
Here is the disclosure from Billy's ex-wife:
"In 1997, Meier's ex-wife, Kalliope, told interviewers that his photos were of spaceship models he crafted with items like trash can lids, carpet tacks and other household objects, and that the stories he told of his adventures with the aliens were similarly fictitious. She also said that photos of purported extraterrestrial women "Asket" and "Nera" were really photos of Michelle DellaFave and Susan Lund, members of the singing and dancing troupe The Golddiggers. It was later confirmed that the women in the photographs were members of The Golddiggers performing on The Dean Martin Show." Wikipedia

Jun 10, 2019
You are standing on a promontory overlooking a beach with waves breaking onto the soft black sands. Overhead, the Sun shines softly on your face as you look up at the scattered white clouds interspersed with clear blue sky. And you think to yourself, "What a beautiful day this is here on this Earth."
You wonder as you look up to the heavens and try to imagine yourself on another planet so similar to Earth and what might you be in appearance and what kind of air you would breathe if you were not where you are.
Across the Universe, a lone intelligent life form stands on a promontory overlooking the ocean waters breaking on a sandy beach where little creatures scurry about searching for food that the breakers may have brought in. He looks up at the Star that shines on his many faces as his hundred eyes stare up at the purple clouds interspersed by a green sky and thinks to himself, "What a beautiful day" and then wonders, "What if I lived on another planet far away..."

Jun 10, 2019
Hey DanR- Thanks you know nothing armchair researcher/ regurgitator
http://www.future...pe_Meier
Please explain her signed witness statements of various events including eye witnessing Ptaah in her living room.
His ex-wife, who was mentally unstable and only bad mouthed him after suddenly receiving a large sum of money .
A former Air Force OSI top case manager Joe Tysk has authenticated the case, so if you don't have a higher qualification than Office of Special Investigations for the USAF, STFU.
But I'm sure you've been to Hinterschmidruti and have spoken to several eye witnesses, am I right?

Jun 10, 2019
DanR- I'm sure you know that the then head of the NASA JPL photo lab analyzed and authenticated the photos? Yeah, I'm sure you must know that.
http://www.future...Evidence

Robert Post: JPL photo laboratory for 22 years, was the head of that lab in 1979, and oversaw the developing and printing of every photograph that came out of JPL at the time: "From a photography standpoint, you couldn't see anything that was fake about the Meier photos. That's what struck me. They looked like legitimate photographs. I thought, 'God, if this is real, this is going to be really something."

Hey Phys.org- you can shut your site down now, because danR knows everything already. Maybe change the name to danR.org?

Jun 10, 2019
you can want it
you can wish it
you can hope for it
you can pray for it

but until you come hovering over my house in broad day light?
toss me the keys?
& let me pilot your flying saucer around the county?

i'm calling you a liar!

i want a hands-on machine i can test.
all your nonsense fabulisms are vaporware made of paper-mache unobtanium.
that will either be delivered
yesterday?
or
tomorrow?
but NEVER today!

or you are full of steamy crap!

our own Solar System,
with all it's failed, dead worlds?
is plenty of proof of how many losing bets there are against the existence of Living Worlds.

even with the best odds for success.

& then there are even worse odds to sustain life over billions of years.
long-enough for the evolution of macro-organisms.

- cont'd -

Jun 10, 2019
Hey DanR- Thanks you know nothing armchair researcher/ regurgitator
Please explain her signed witness statements of various events including eye witnessing Ptaah in her living room.
His ex-wife, who was mentally unstable and only bad mouthed him after suddenly receiving a large sum of money .
A former Air Force OSI top case manager Joe Tysk has authenticated the case, so if you don't have a higher qualification than Office of Special Investigations for the USAF, STFU
You're going about this all wrong. You only have to go to Wikipedia, sign in, enter the excellent material you've found and provide linked citations. Then everyone can see for themselves. Clearly you owe it to world, to humanity, to truth, to posterity. I don't know if I have a qualification higher than any office of the USAF, STFU, btw. I've never even   h e a r d   of STFU. Is that a special function of the DoD?

Jun 10, 2019
- cont'd -

octopus had several hundred million years of varying opportunity to put their brain nodes to work with their versatile tentacles.
& their greatest achievement is being delicious calamari.

for more than hundreds of millions of years seagoing reptiles & dinosaurs, even with hands?
failed to grasp the opportunity.

Many of today's intelligent mamals are seagoing.
a few with hands.
the rest trapped in the evolutionary dead-end of the 'whale dream'.

as for the hypothesized Living Ocean Worlds?
a minor downer, ancestors of all seagoing, air-breathing lifeforms?
originally left the oceans to adapt to survival on land.

they grew legs BEFORE returning to the Oceans.
reptiles & dinosaurs, avians & mammals. many fabulous mutations & adaptations.

& none of them will survive a ravenous;y destructive human genius programmed with monkey instincts.

Jun 10, 2019
Isaac Asimov's "Rare Earth Hypothesis" - i make a summary of Isaac Asimov's "Extraterrestrial Civilizations" which is the original "Rare Earth hypothesis." I also include latest findings that already double up on the rarity of Intelligent life.

https://wwwscient...03338026

Jun 11, 2019
They really should say "human-habitable", to make it clear. Our habitable environment is extremely narrowly defined compared to what's out there.

As for underwater intelligence, as someone suggested, it may be difficult to develop technology familiar to us, much less getting into space, without fire. Maybe hot magma would work as a substitute where we use fire, but their development would likely be very different from ours.

Jun 11, 2019
Admittedly, "habitable zone" may be a sloppy use of words. It's really just the "liquid water on rocky planets with atmosphere zone." That of course, leaves much to be said. Are we looking for life, advanced life, life like ourselves, or are we looking for a second home for humans? Do we care if it contains indigenous life? How hostile is too hostile? With each of these questions the complexity grows and the potential candidates dwindle. One possibility not considered in this article is that life in the universe may be incredibly common, while at the same time a suitable second Earth could be unfathomably rare.

Jun 11, 2019
"But planets too far from their host star require carbon dioxide—a potent greenhouse gas—to maintain temperatures above freezing. Earth included."

That needs to be repeated to all the "trace gas" conspiracy nuts.

Jun 11, 2019
A planet which does not contain indigenous life is, by definition, not habitable by humans. No life means no oxygen in the air to breathe, unless someone can come up with a non-life mechanism to provide it.

A planet with indigenous life is probably also not habitable by humans; wrong air pressure range, wrong temperature, too much gravity, too much carbon dioxide (we're evolved for a tiny amount), too little oxygen (we need a lot). Plus, lots of organic molecules in the air or water which we will almost certainly become allergic to, assuming it's not outright poisonous to us.

Jun 11, 2019
So much for Frank Drake's 1960ś formula for extraterrestrial life. 80% of all stars are bad behaving red dwarfs. No life there for a plethora of reasons. We are here because Earth had an encounter with Theia, which came to us from the outer solar system. Theia brought carbon, water,
gave us our moon, 23 1/2 degree axial tilt, 24 hour day, nitrogen, and the many minerals that make life possible here. Earth was sterile before this encounter. Earth before Theia burned away the things that make life of any form possible.

Jun 11, 2019
It is an important work of course, the surface habitable zone is just a coarse filter to narrow down astrobiologically interesting planets (while leaving out ice moons and other possible habitats). And keeping with the carbon life, oxygen complex life known example there are obvious tensions between oxygen and carbon dioxide. First, carbon dioxide controls climate and erosion. Second, oxygenating photosynthesis will convert between the two, at the same time as enzymes that handle one molecule often handle the other.

That said, our biosphere evolved under a lot less carbon dioxide than could be the general case. Instead of having key enzymes that handle both molecules (carbon fixating RuBisCO, that is poisoned by oxygen; oxygen and carbon dioxide transporting hemoglobin), one can envision evolving separate ones.

- tbctd -

Jun 11, 2019
- ctd -

The paper use the transporter idiosyncrasy, as well as the slight acidification that CO2 contribute, to observe animal "severe physiological stress", but also note that the work is "a useful starting point".

One cannot but agree. And an effective search will likely use these narrowed zones when it comes to budgeting telescope time in early days. Later extensions to wider zones will certainly be exciting too!

Jun 11, 2019
So much for Frank Drake's 1960ś formula for extraterrestrial life.


It works well with any HZ you care to define.

We are here because Earth had an encounter with Theia, which came to us from the outer solar system. Theia brought carbon, water, gave us our moon, 23 1/2 degree axial tilt, 24 hour day, nitrogen, and the many minerals that make life possible here. Earth was sterile before this encounter. Earth before Theia burned away the things that make life of any form possible.

It is open questions where Theia came from and how much volatiles it delivered. Raw numbers means Tellus, the protoplanet, had 90 % of current volatiles and had time to evolve life. (It likely did not however since Theia seems to have hit a global lava ocean for some reason.)

Axial tilt varies in all planets, and Moon has likely hindered more than helped keep volatiles, it is not considered important today. And models say most Earth analogs see 0-3 Theia type late impactors.

Jun 11, 2019
theta was not only important to founding the modern Earth/Luna pairing.

an additiomal, subtle outcome from the Theta Event was the non-event that is key to how our Venus developed.

if Theta had missed the Earth? i speculate what if it had hit Venus instead?

Both Earth w/no moon & Venus with a Moon?
would have developed quite different than what we see today.
Perhaps our speculated no-moon-Earth would still be capable of supporting a biosphere?
a lot dryer of course but still at least seas & polar icecaps.

Our Venus we actually have is a result of sabotage by the Earth/Luna combined gravitational attraction hogging the majority of infalling icebergs, carbonaceous amalgamates & nickle-iron-phosphates rocks.

Depriving our moonless Venus of billions of years of replenishment of those vital resources.

Earth w/no Moon would miss out on what bypasses that orbit & gets captured by Venus w/Moon.
both planets would be deprived but possibly still become Living Worlds?

Jun 12, 2019
Hey DanR- Thanks you know nothing armchair researcher/ regurgitator
http://www.future...pe_Meier
Please explain her signed witness statements of various events including eye witnessing Ptaah in her living room.
says doogsnova

Many years ago in the 1960s there was a science fiction paperback book, the author of it I cannot recall nor the title of the book. But I do recall that one of the characters was an extraterrestrial named Ptaah or Ptaaah. The story took place on another planet where this Ptaah lived and where humans had arrived. The gist of it is that the extraterrestrial, Ptaah and the gorgeous human female fall in love. But there are a few things that are in their way. I don't recall the rest and what happens. But your mentioning Ptaah jogged my memory of that paperback scifi character.
Not certain if it was Asimov, Heinlein, Poul Anderson or Arthur C. Clarke. They were great authors but I think that they all have passed on, sadly.

Jun 12, 2019
Using, Human life as a ruler in determining whether other planets could support complex life is basically the definition of Anthropocentrism. Are these papers peer reviewed? Who let them publish this balogna?

...You're going about this all wrong. You only have to go to Wikipedia, sign in, enter the excellent material you've found and provide linked citations. Then everyone can see for themselves. Clearly you owe it to world, to humanity, to truth, to posterity. I don't know if I have a qualification higher than any office of the USAF, STFU, btw. I've never even   h e a r d   of STFU. Is that a special function of the DoD?...

That is the theory. I invite you to read the version history for the Billy Meier article https://en.wikipe...ly_Meier on Wikipedia. You will be amazed with what verve the dominating figures have erased more unbiased descriptions and lists of sources because they did not fit with their belief system for our world. That while thousands of stories about Christian phantasies and absurdities pass without any problem on that "objective" platform.

you can want it
you can wish it
you can hope for it
you can pray for it

but until you come hovering over my house in broad day light?
toss me the keys?
& let me pilot your flying saucer around the county?

i'm calling you a liar!


Do you also leave the thinking to others to do on your behalf? If not, then go ahead and create the proof for yourself:
https://www.amazo...30050456

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