Looking for life in all the wrong places

Feb 03, 2014 by Matt Terry
Alpha Centauri, the closest star system to the Solar System. Astrophysicist René Heller of McMaster’s Origins Institute says our planet may not be the most ideal place for life and scientists need to consider non-Earth-like, so-called “superhabitable” planets. Credit: European Southern Observatory

(Phys.org) —Scientists have long focused their search for extraterrestrial life on Earth-like planets – but that may be a mistake, according to a McMaster researcher.

Astrophysicist René Heller of McMaster's Origins Institute says our planet may not be the most ideal place for life and scientists need to consider non-Earth-like, so-called "superhabitable" .

These planets would probably be two or three times more massive and much less mountainous than Earth. They would probably be older, too.

"The Earth just scrapes the inner edge of the solar system's – the area in which temperatures allow Earth-like planets to have liquid surface water," says Heller. "So from this perspective, Earth is only marginally habitable. That led us to ask: could there be more hospitable environments for life on ?"

Heller and co-author John Armstrong of Weber State University describe superhabitable planets in a paper published in the journal Astrobiology early in January.

In it, they outline some of the characteristics such planets might have. They include many, shallower bodies of water (rather than a few large oceans), a more reliable global "thermostat" that impedes ice ages, and a magnetic shield, to protect the planet from cosmic radiation.

Heller says the theory means astronomers should be aiming their telescopes at planets that have so far not garnered much attention in the search for .

"We propose a shift in focus," he says. "We want to prioritize future searches for inhabited planets. We're saying 'Don't just focus on the most Earth-like planets if you really want to find life.'"

But is the discussion about which planets to look at even worth having? How likely are we ever to find on another planet?

"Statistically speaking, I would say it's very unlikely that there is nothing out there," says Heller. "For the first time in history, we have the ability – both technical and intellectual – to find and classify potentially inhabited planets. It's just a matter of how we spend our observation time."

Heller expects the paper to serve as a launching point for a debate about superhabitability. He says it may take some time for the scientific community to come around to the theory.

"When you follow a certain pattern for decades, it can be hard to change your mind."

Explore further: Looking for a 'superhabitable' world? Try Alpha Centauri B, paper says

More information: Read the complete paper here: arxiv.org/ftp/arxiv/papers/1401/1401.2392.pdf

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vlaaing peerd
3.8 / 5 (6) Feb 03, 2014
Sounds very logical, why would we expect earth's situation is the most ideal for life to exist?
Osteta
Feb 03, 2014
This comment has been removed by a moderator.
Osteta
Feb 03, 2014
This comment has been removed by a moderator.
Sinister1812
5 / 5 (7) Feb 03, 2014
Sounds very logical, why would we expect earth's situation is the most ideal for life to exist?

Because it's the only place we know that has life. I think they're jumping the gun a bit here. Earth-like still sounds reasonable.
TechnoCreed
3.8 / 5 (5) Feb 03, 2014
Sounds very logical, why would we expect earth's situation is the most ideal for life to exist?

Neither irony or sarcasm is argument.(Samuel Butler 1835-1902)
Sinister1812
5 / 5 (4) Feb 03, 2014
"Don't just focus on Earth-like planets". I agree with that point, actually. Life could exist anywhere. Even on planets that aren't like Earth. I wouldn't be surprised.
Modernmystic
5 / 5 (5) Feb 03, 2014
Sounds very logical, why would we expect earth's situation is the most ideal for life to exist?


For a very good reason, it's our only data point atm.

As far as "superhabitable" goes...well there may be a damn good reason complex life only develops on planets as massive as Earth, as mountainous as Earth, AND scraping the edge of the habitable zone. We simply don't have enough information to say one way or the other.

Sure there MIGHT be all kinds of different life out there, and there might be grumpkins in your cellar too....
GSwift7
5 / 5 (6) Feb 03, 2014
For a very good reason, it's our only data point atm


Yes, but that leads into a discussion I think is kinda interesting: There are several different ways to frame the discussion, such as "why does Earth have life?" or perhaps "how did life form on Earth?".

We are assuming that Earth is a good template for life because we know it has life, but we don't know how, why or when. I'm sure we will eventually find thousands of planets similar to Earth in physical traits. However, there will always be small differences, and we don't know which differences are important in the question of life. For example, the mass could be a little more, or there may not be a moon, or there could be no oceans. We don't know how those things would affect life because we don't have a clear idea of how or why life formed here.
GSwift7
5 / 5 (7) Feb 03, 2014
The article suggests that a planet with a bunch of smaller bodies of water might be better than large oceans. I wonder what basis they have for making that suggestion? As my previous post says, we really don't know which would be better.

They also mention that the planet should have a reliable thermostat, but our oceans seem to act as a very good thermostat. I wonder what they think would make a better thermostat than massive bodies of circulating water on the surface? Without our oceans distributing heat and helping to regulate the seasons, our climate should be much more variable. Not to mention the fact that oceans are very good at absorbing solar radiation, converting it into heat and storing it.
scottfos
5 / 5 (5) Feb 03, 2014
none of this is new, theoretically. a) we have 1 data point for life, b) said life is carbon based, c) needs water to be available in all 3 states, so d) we look for planets in habitable zones. historically folks have suggested Si based life instead of C based life. further investigation into Si has shown its very, very unlikely. so only a few sci-fi fans still talk about that. still, it was thinking outside the box (in the 30's or whenever it was popular). well, this is just a paper suggesting other places than a planet in the habitable zone. good food for thought, and folks *should* be thinking outside the box.
javjav
5 / 5 (7) Feb 03, 2014
sharks are pretty well adopted to their environment, but their body architecture is rather primitive, because they're living at the bottom of oceans all the time, so that they're not forced to evolve into high complexity
Sharks do not live "at the bottom of ocenas" but mainly in shallow waters, where they typically hunt. And they share their habitat with Dolphins, considered one of the most evolved creatures. Sharks don't need to evolve just because they are phenomenal as they are. And they are not unique, there are several fish and bird species that are even older and are sharing environment with the most evolved species.
Torbjorn_Larsson_OM
5 / 5 (3) Feb 03, 2014
There are good reasons why people do a perturbation analysis around the known cases of habitable environments. (Earth, Mars, Europa, ...) But of course we want to identify all relevant environments.
Torbjorn_Larsson_OM
4 / 5 (4) Feb 03, 2014
@Osteta: Large moons were a part of the daft Rare Earth model. All posited factors are now known to be wrong. Moon modelers made mistakes, and replication show it is not a problem:

"The moon's strong gravitational pull has kept Earth in line, limiting the planet's axial tilt to between 22 degrees and 24.6 degrees from the vertical over time, Lissauer said. This has minimized dramatic climate swings,".

"They found greater obliquity shifts than Earth experiences with its abnormally large moon (which helps stabilize the planet against the various gravitational tugs of other solar system bodies). But these variations were nowhere near as dramatic as those predicted by previous work.

During 100-million-year simulation runs, for example, Earth's tilt never got up to 40 degrees or down to 10 degrees, Lissauer said." "The obliquity shifts, he added, would be even less pronounced if Earth had retrograde rotation".

[ http://www.space....rth.html ]
Torbjorn_Larsson_OM
4 / 5 (4) Feb 03, 2014
@GS: As for "how" and "why" I think Russell et al proposes a phylogeny (which is under test) with 6-7 traits that we share with Archean alkaline hydrothermal vents. That is the only theory that ties us with identified geochemistry with known evolutionary methods.*

As for "when", if we accept the two separate, tentative Isua trace fossils proposed last year, we have life well before 3.8 Ga bp.

If the phylogeny bears out, it would make most habitable terrestrials and ice moons inhabited.

*I just saw Sara Walker's NASA webinar on chemical evolution. She made a strong case that during the pregenetic lamarckian evolution phase there is a "near life" phase of independent evolution of function and later replication, which ends by many cases of genetic take over phase changes.

It reminds of the later communal melting pot before lineages resolves, where instead genetic sweeps would repeatedly make the early heritage convoluted.

Then this phylogeny may be the best we can do.
Torbjorn_Larsson_OM
4 / 5 (4) Feb 03, 2014
[ctd] As for oceans as thermostat, the recent putative resolution of the Archean faint sun problem indicates that it is water clouds, not the amount of land masses, that makes terrestrials sturdy against climate swings.

The cloud behavior at large ice/water borders dampens cold swings.

[I would give references, but I need to move on; it's googeable.]
Whydening Gyre
4 / 5 (2) Feb 03, 2014
Sounds very logical, why would we expect earth's situation is the most ideal for life to exist?


For a very good reason, it's our only data point atm.

As far as "superhabitable" goes...well there may be a damn good reason complex life only develops on planets as massive as Earth, as mountainous as Earth, AND scraping the edge of the habitable zone. We simply don't have enough information to say one way or the other.

Sure there MIGHT be all kinds of different life out there, and there might be grumpkins in your cellar too....

Change creates/drives change..
Noumenon
3.7 / 5 (3) Feb 03, 2014
Heller expects the paper to serve as a launching point for a debate about superhabitability.


I think they should focus instead on superduperhabitability.

Change creates/drives change..


I don't think your logic is circular enough.
Whydening Gyre
5 / 5 (2) Feb 04, 2014
Heller expects the paper to serve as a launching point for a debate about superhabitability.


I think they should focus instead on superduperhabitability.

Change creates/drives change..


I don't think your logic is circular enough.

C'mon Noum... :-) There IS no fight club, remember?
vlaaing peerd
3 / 5 (2) Feb 04, 2014
For example the presence of large Moon leads to inclination of Earth axis, which is believed to be important for formation of climatic periods and fast evolution of complex organisms adopted to it.


You are describing how the moon has affected our development on OUR planet, yet the claim that the caused climatic and tidal changes are required for complex life persé is at the least very disputable.

The life requires fast changes, but not quite periodic for being forced into adaptation to it. IMO otherwise perfect warm & wet planet full of yummy hydrocarbons will not lead into formation of complex living forms, until its conditions will be quite stable.


So what is it, stable to develop or fast-changing to develop? Your post seems contradictive on this point. I see that changes drive evolution and that stability allows for development, but none of both should be a hard requirement just because we know "it worked here".
Modernmystic
4.3 / 5 (3) Feb 04, 2014
arge moons were a part of the daft Rare Earth model. All posited factors are now known to be wrong.


Maybe like "Big Bang" models are "known" to be wrong to creationists. You can do tilt models all day long, but you can't ignore what the moon does for tide pools, internal heating, luminosity, and a hundred factors you or I or anyone else hasn't thought of that might be VERY important. To say a model that deals with how complex as how life evolves and is influenced by everything on this planet is "wrong" is, quite frankly the height of hubris. It may be wrong, but every new factor we add adds another hurtle to jump over. We've come a LONG way since the Drake equation...we know that there are hundreds of factors (and likely MANY MANY more) that influence how life evolves or if it evolves. Every one we find is another nail in the coffin mediocrity in this debate.

Modernmystic
5 / 5 (3) Feb 04, 2014
(cont)

As to how important "Earthlike" models of life are, well until we find another example they are all important. The reason for that is because no one has a model for non carbon based life that we know works...period. So if you want to talk about how life might work "somewhere else" I'd rather talk about angles because we know they're nice and fluffy and sometimes grant wishes...

Gswift:

I agree that the discussion about habitability is important, and we're likely to find more questions than answers until we start getting better observation, but they're questions that we might not have thought of if we don't have the discussion at all.
antialias_physorg
4.3 / 5 (3) Feb 04, 2014
"Shallower bodies of water" does not sound like a good argument. What you want is stable conditions. Stable conditions in the face of changing global factors (like solar radiation or chemical changes in the atmosphere) means you want large buffer systems.
Shallow bodies of water have much less resilience against chemical changes or freezing completely than deep oceans.

For really stable conditions we should actually look BELOW the surface (deeper in the planet's crust). While that is not something accessible to telescopes there is a temperature zone (depth) where liquid water can exist on most any planet that still has some molten material inside. And that even far outside the 'Goldilocks zone'
GSwift7
5 / 5 (3) Feb 04, 2014
to Torbjorn:

Yes, but those are still Earth specific anctedotals. We don't know how robust those processese are to variations in conditions. On an exoplanet, could it be possible to see life form through an entirely different pathway? We may be able to set some upper and lower bounds on some aspects, but then again, could there be exceptions?

Based on the percentage of stars we have found to harbor planets, and our current assumptions about what percentage of those planets will be terrestrial and near the habitable zone, I would say that probability should favor the existence of any scenario you can imagine. Somewhere, at some time, there's bound to be at least one planet with conditions x,y,z.

As you pointed out, unless genesis requires incredibly rare circumstances, then there should be countless inhabited worlds. Even one in a million would still be a lot of worlds. Finding them in that case would still be no easy task though.
GSwift7
5 / 5 (3) Feb 04, 2014
continued:

As an example of what we don't know, we could talk about moons, since someone already mentioned them. We have absolutely zero knowledge about exomoons. One of the comments here described our moon as exceptionally large, but we really don't know that. Perhaps collisions between terrestrial planets and planetessimals are common? Maybe there's one or two such large moons in nearly every system?

Or, how about a binary planet; Is that possible? Certainly not likely, but can you really say that it cannot happen? As I pointed out in my previous post, probability actually favors even the most absurd notion. Unless it is completely impossible, then it's probably happening somewhere out there.

Present attempts to guess probabilities of habitation could be wrong by multiple orders of magnitude in either direction. I don't think we have even scratched the surface in terms of how diverse an exoplanet can be, if so, all bets are off regarding probabilities.
GSwift7
5 / 5 (3) Feb 04, 2014
Antialias

"Shallower bodies of water" does not sound like a good argument. What you want is stable conditions. Stable conditions in the face of changing global factors (like solar radiation or chemical changes in the atmosphere) means you want large buffer systems


Ah, good point. I was thinking about thermal buffer, but I didn't even think of the chemical buffer that a deep ocean provides. Torbjorn mentioned that clouds might be the best thermal buffer, but I am skeptical that you would have stable water vapor and water clouds in the atmosphere without deep oceans to buffer the atmospheric humidity. Not to metion absorbtion of gasses like oxygen and carbon dioxide.

Anyway, I agree with you, and I'm sticking with my previous suggestion that deep oceans should be more favorable than shallow seas and lakes.

I'm also not ready to buy into ocean vent genesis 100% quite yet. It just seems like we don't know enough to rule out alternatives yet.
triplehelix
3.8 / 5 (4) Feb 05, 2014
Larger planets have larger gravitational attraction capability. Assuming the solar system with these super massive earths have asteroid belts, even if life were to evolve, it would be constantly wiped out by asteroid impacts and advanced life-forms unlikely due to being physically disrupted.

Bacteria can survive asteroid impacts, small generation times, and easier to mutate to survive to harsh conditions, multi-cecullar organisms size of mammals etc cannot.

The reason Earth life-forms have evolved over the last hundreds of millions of years is because Jupiter sucks up a lot of the asteroids, so we don't get as many collisions. Jupiter is a big asteroid sponge, and allows Earthen life the time to become more complex.

Also, with the higher gravity, life-form size will be limited.
Requiem
4.3 / 5 (3) Feb 08, 2014
Obviously we can go on and on about all of the ways we can or cannot imagine "life" to form around the cosmos, but we should probably stick to the type that we actually know how to detect if the goal is to detect signs of life...
Requiem
4 / 5 (2) Feb 08, 2014
Larger planets have larger gravitational attraction capability. Assuming the solar system with these super massive earths have asteroid belts, even if life were to evolve, it would be constantly wiped out by asteroid impacts and advanced life-forms unlikely due to being physically disrupted.

Bacteria can survive asteroid impacts, small generation times, and easier to mutate to survive to harsh conditions, multi-cecullar organisms size of mammals etc cannot.

The reason Earth life-forms have evolved over the last hundreds of millions of years is because Jupiter sucks up a lot of the asteroids, so we don't get as many collisions. Jupiter is a big asteroid sponge, and allows Earthen life the time to become more complex.

Also, with the higher gravity, life-form size will be limited.


Basically everything you have said here is either outright wrong or pure speculation, just so you know. I find it tiresome pointing out that just because you think something doesn't mean it's true.
russell_russell
5 / 5 (1) Feb 09, 2014
If new pathways of life are discovered acceptable to a consensus of what life is, then we can question further what we mean by 'habitable'. Our 'pathway' appears so narrow we take extraordinary measures to find 'pathways' similar in nature.
Sinister1812
not rated yet Feb 09, 2014
Basically everything you have said here is either outright wrong or pure speculation, just so you know. I find it tiresome pointing out that just because you think something doesn't mean it's true


I don't know man, to be fair he has a point. If it wasn't for Jupiter, Earth would probably be destroyed by now. lol
Requiem
5 / 5 (1) Feb 09, 2014
Basically everything you have said here is either outright wrong or pure speculation, just so you know. I find it tiresome pointing out that just because you think something doesn't mean it's true


I don't know man, to be fair he has a point. If it wasn't for Jupiter, Earth would probably be destroyed by now. lol


Aside from the fact that Earth made it through the late heavy bombardment, and since that time the vast majority of objects travelling through the inner solar system would still be outside the orbit of Pluto if not for Jupiter(the vast majority of which it did not intercept). And the main asteroid belt would likely be a planet.