Bigger Goldilocks zone increases chance of finding life in space

Nov 14, 2011 By Adele Rackley
Bigger Goldilocks zone increases chance of finding life in space
Artist's impression of a planet orbiting red dwarf GJ1214.

New research suggests the habitable zone around some stars – the so-called Goldilocks zone – could be up to 30 per cent bigger than previously thought.

This makes it much more likely that life-supporting planets exist elsewhere in our galaxy.

The study looked at the relationship between the radiation from red dwarf stars and the reflective quality – or albedo – of snow and ice cover on orbiting planets.

Red dwarfs are cooler than G-type stars like our Sun and give off energy at longer wavelengths. More of this energy is absorbed by snow and ice than reflected back into space. This warms the planet's surface, melting some of the ice to produce liquid water – a fundamental requirement for life.

"We knew that red dwarfs emit energy at a different wavelength, and we wanted to find out exactly what that might mean for the albedo of planets orbiting these stars," explained Dr. Manoj Joshi from the National Center for Atmospheric Science, who carried out the research in collaboration with Robert Haberle from the NASA Ames Research Center.

Red dwarfs, or M-stars, make up 80 per cent of the stars in our galaxy, and are thought to be very long-lived, so identifying their habitable zones is an important goal.

The albedo effect of snow and ice is important for climate because it is part of what's known as a positive feedback loop. An increase in ice cover reflects more radiation, further cooling the planet and leading to the formation of more ice. Conversely, a loss of ice cover means less radiation is reflected and more is absorbed, which means the planet gets warmer and more ice is lost.

So anything that lowers average albedo will have implications for the climates of ice-covered planets – much more than it would for planets like Earth, which has relatively little ice cover.

Though our ability to see further into space is improving all the time, so far we can only speculate about what planets outside our solar system might be like – how much ocean or land, ice or snow they might have, for example. But scientists have identified actual planets around red dwarfs.

The researchers used the radiation from two red dwarfs, Gliese 436 and GJ 1214, to calculate the effect of longer wavelengths on the albedo of ice and snow for a planet with a surface temperature of 200o Kelvin. This is the temperature at which 1 bar of CO2 condenses, often used as an indicator, or proxy, for the outer edge of the habitable zone – anything below this temperature and a planet would simply be too cold to sustain life.

They found that planets with significant snow and ice cover will have higher surface temperatures under longer wavelength radiation when the effect on the albedo of snow and ice is taken into account. In fact it makes such a difference that the researchers calculate the outer edge of the habitable zone around M-stars may be 10 to 30 per cent further away from the parent star than previously thought.

"Previous studies haven't included such detailed calculations of the different albedo effects of ice and snow,' explains Joshi. 'But we were a little surprised how big the effect was."


This story is republished courtesy of Planet Earth online, a free, companion website to the award-winning magazine Planet Earth published and funded by the Natural Environment Research Council (NERC).

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More information: Manoj M Joshi & R Haberle. Suppression of the water, ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone. Forthcoming in Astrobiology, 2011.

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antialias_physorg
4.6 / 5 (11) Nov 14, 2011
Since energy can come from other sources (e.g. warmth from the molten core of planets, radioisotopes, tidal interaction of nearby massive bodies like those of a gas giant upon its moons, etc.) we shouldn't be too stuck to the idea that only the power of a sun can be the source for energy that could sustain life.

We have found archaeobacteria kilometers down in rock on Earth (and we currently don't know whether those migrated down from the surface or if they are the precursors of the types up here)

We're way too stuck on the idea that life must be surface dwelling or somehow atmosphere-dependent. If we drop this view, as I feel we should, then the term 'Goldilocks zone' needs to be reevaluated or dropped altogether.

Where there is energy - and a relatively stable environment - life can probably develop.
javjav
not rated yet Nov 14, 2011
Less light is reflected. Habitable zone is extended in the far side, but is it not equally reduced in the near-star side? Planets in this side can not reflect excesive heat...
Isaacsname
1 / 5 (1) Nov 14, 2011
Would planets found by Red dwarfs lack sufficient net radiation pressure thrust to provide a diurnal effect ? Would any of them rotate ?
antialias_physorg
5 / 5 (3) Nov 14, 2011
Why shouldn't they rotate?

Rotation is not primarily a function of radiation pressure (otherwise we wouldn't have stuff like Venus, which rotates opposite to the rest of the planets in the solar system or the rotation of Pluto which is nearly sideways)
MorituriMax
3 / 5 (2) Nov 14, 2011
I wonder if our universe was created (via the big bang) with a bias towards life?

@antialias_physorg,
"we shouldn't be too stuck to the idea that only the power of a sun can be the source for energy that could sustain life."

Well, don't we technically have to have the Sun as the intitial source that creates those other local energy-rich conditions?
[ nitpicking off, 8 ) ]
antialias_physorg
5 / 5 (2) Nov 14, 2011
Well, don't we technically have to have the Sun as the intitial source that creates those other local energy-rich conditions?


Tidal forces can be of any two massive bodies. Not only solar systems form from dust clouds (it is entirely thinkable that not one object in a particular collapsing dustcloud gathers up enough mass to start continuous fusion. You might get something like a gas giant with some orbiting moons - but no sun)

Radioisotopes need to have been created by a previous sun, though (e.g. a supernova that seeded some dustcloud which then collapses without having a sun itself)...but that still leaves no 'Goldilocks zone'. However, life may still originate there.
Isaacsname
not rated yet Nov 14, 2011
Why shouldn't they rotate?

Rotation is not primarily a function of radiation pressure (otherwise we wouldn't have stuff like Venus, which rotates opposite to the rest of the planets in the solar system or the rotation of Pluto which is nearly sideways)


I don't know, but I do know that some, like Gliese 581 g for example, do not rotate.

jsa09
5 / 5 (3) Nov 14, 2011
A few points I never see mentioned in calculating goldilocks zones is atmospheric pressure.

Higher atmospheric pressures increases ground based temperature and thus increases outward any goldilocks zone.

Since pressure is pretty important I think the goldilocks zones need to be color co-ordinated with color representing atmospheric pressure.

A very low atmospheric pressure such as top of mount everest will have a very narrow band of life forming ability whereas a a high pressure, such as at the bottom of the sea may have a very wide band of life forming ability.
Deesky
5 / 5 (6) Nov 14, 2011
I wonder if our universe was created (via the big bang) with a bias towards life?

Well, yes, it was, otherwise there wouldn't be individuals like you and I talking about it. The mix of physical laws present in the universe clearly allow for the formation of life.

However, I wouldn't call it a 'bias' nor would I use the word 'created' when it comes to the universe - those terms are way too loaded and could easily be jumped on by the cretinists.
MorituriMax
4.2 / 5 (5) Nov 14, 2011
Deesky, what I meant was not whether there is a bias towards life on one planet in the whole universe, but whether there is a bias in general towards life everywhere in the universe.

So far, the only place we !definately! know there is life is on Earth. Keeping my fingers crossed that we aren't a fluke.

That's also why when I said created, I qualified it with "via the big bang." I'm not going to bend over backwards to be PC and let the creationists own the word "created."
Deesky
5 / 5 (3) Nov 14, 2011
Deesky, what I meant was not whether there is a bias towards life on one planet in the whole universe, but whether there is a bias in general towards life everywhere in the universe.

Yes, I know, that's how I took it.

So far, the only place we !definately! know there is life is on Earth. Keeping my fingers crossed that we aren't a fluke.

If we accept that the laws of physics are the same everywhere (cosmological principle), then there is absolutely no reason why life could not arise many times elsewhere, where conditions are favorable. The same laws of physics apply.

That's also why when I said created, I qualified it with "via the big bang." I'm not going to bend over backwards to be PC and let the creationists own the word "created."

I take your point, but unfortunately, given the world we live in, I prefer to be as precise as possible when expressing myself so as not to give anything to the woo crowd.
Decimatus
4 / 5 (4) Nov 14, 2011
I wonder if our universe was created (via the big bang) with a bias towards life?


It's all just a big computer simulation anyway. The reason we don't understand quantum mechanics is because we don't know how the source code for the program is written or ordered. We don't even know what kind of "hardware" our simulation could even be running on.
Deesky
5 / 5 (3) Nov 14, 2011
It's all just a big computer simulation anyway.

What's your evidence? Perhaps it's an abacus simulation. :)
Decimatus
5 / 5 (1) Nov 14, 2011
It's all just a big computer simulation anyway.

What's your evidence? Perhaps it's an abacus simulation. :)


The AI god programmed me to inherently know this as truth.
MorituriMax
3.7 / 5 (3) Nov 14, 2011
Deesky, maybe it's a universal drinking game. 100 omygazillion bottles of beer on the wall, 100 omygazillion bottles of BEER! You take one down, PASS IT AROUND, 1 LESS BOTTLES OF BEER ON THE WALL!!!!!! OKAY, REPEAT CHORUS!!!
bluehigh
1 / 5 (1) Nov 14, 2011
Okay Deesky a 5 to you for interesting and 'cretinists' is amusing.

The mix of physical laws present in the universe clearly allow for the formation of life.


Are the current 'physical laws' then optimum for life? What realistic changes to the 'physical laws' may be less favorable to life? Can the 'physical laws' be any different for our 'reality', in the sense that these 'laws' might be 'compulsory' for life?

Just shooting the breeze, so to speak.

bluehigh
1 / 5 (1) Nov 14, 2011
Chorus: 99 omygazillion bottles of beer on the wall, 99 omygazillion bottles of BEER! You take one down, PASS IT AROUND, 1 LESS BOTTLE OF BEER ON THE WALL!
Deesky
5 / 5 (3) Nov 14, 2011
Are the current 'physical laws' then optimum for life?

Who can say? You'd have to examine all possible variations and measure the outcomes. Not likely.

What realistic changes to the 'physical laws' may be less favorable to life? Can the 'physical laws' be any different for our 'reality', in the sense that these 'laws' might be 'compulsory' for life?

A change to a 'magical' constant would have profound effects on the nature of the universe. The constant is Alpha or the fine-structure constant (actually a composite of several other constants). If it were just a few percent bigger or smaller than it is, stars would not be able to sustain nuclear reactions that synthesize carbon, oxygen & other atoms, vital for life (as we know it).

Other changes would preclude any stars at all from forming, or even atoms. Of course, other forms of life may be possible, but since we can't know what they are, it's hard to speculate if under other very different laws, life could arise.
RealScience
5 / 5 (2) Nov 15, 2011
antialias - power output of stars decreases much faster than mass, so the habitable zone around red dwarfs is so close to the star that planets are expected to be tidally locked.

However tidally locked may not mean lifeless, and large moons of those planets could be very good places to look (although we don't yet know whether small stars have planets with large moons).

javjav - this particular finding wouldn't affect the inside edge of the habitable zone because at the inside edge there is no ice/snow cover.
Isaacsname
5 / 5 (3) Nov 15, 2011
Thanks realscience, that's what I was getting at. I'm curious how circadian rhythms would develop for life on a non-rotating body, or whether they would at all. Aren't we pretty much evolutionarily shaped by chronobiological functioning ?

I guess the real question I have is: Without zeitgebers, is surface life possible ?
antialias_physorg
5 / 5 (2) Nov 15, 2011
I don't know, but I do know that some, like Gliese 581 g for example, do not rotate.

The Moon also does not rotate (as seen from the Earth-Moon system).

Tidal locking can occur if one of the bodies in question has an uneven mass distribution.
(I was going to say that Mercury is gravitationaly locked, but just looked it up and found out that that is not true)
power output of stars decreases much faster than mass, so the habitable zone around red dwarfs is so close to the star that planets are expected to be tidally locked.

Power output of stars has no effect on the distance of the planets. And as noted: a definition of habitable zones based solely on solar radiation is a very dubious concept at best.
Planets can be very hot or cold - further away or closer in (e.g. Venus is very hot - and this has very little to do with it being closer to the sun)
antialias_physorg
5 / 5 (2) Nov 15, 2011
I'm curious how circadian rhythms would develop for life on a non-rotating body, or whether they would at all.

Obviously they wouldn't. (Small exception: If the main axis does have a small angel of precssion and life is limited to the terminator zones then you could, conceivably get a faux cicardian seasonal rythm.)

I guess the real question I have is: Without zeitgebers, is surface life possible ?

Why not? Subterranean/Subaquatic life seems to do very well without them. No reason to suspect that a species couldn't adapt to life on land starting from such predecessors (as they probably did here on Earth).
Isaacsname
5 / 5 (1) Nov 15, 2011
Hmm,.. zeitgebers are not just light vs dark though, circadian rhythms are found in almost all subterranean/subaquatic forms of life, afaik from some cursory reading, and are also persistent in organisms regardless of whether the stimulus is present or not. Not that they are set in stone, that's been known for quite some time.

I'd be curious exactly what a " faux cicardian seasonal rhythm " is ? I'm having a little trouble grasping that..
RealScience
5 / 5 (1) Nov 15, 2011
Isaacsname - if life did indeed have geochemical origins (best theory seems to be 'white smokers', which have good chemical gradients for a sulphide-based metabolism and form bacterial-cell-sized pores that concentrate larger molecules, with mica and clays also being reasonable candidate substrates), then life formed without a circadian rhythm.

You have raised an excellent question - do hydrothermal vent creatures have some rhythm (cellular or whole organism) that performs a similar function to the circadian rhythm (e.g. triggering cell repair)? I don't recall seeing research on this (the PAS domain involved in the circadian rhythm is present but has broader uses). It would make a good topic for a doctoral dissertation.
MorituriMax
3 / 5 (2) Nov 15, 2011
I would think that better conditions for life in a given universe would be those that allowed life to be based on some much stronger material that could absorb pretty much anything as food. Like... black holes! My God, this universe is tuned in favor of black holes!
CHollman82
2 / 5 (8) Nov 16, 2011
I very much enjoyed reading most of these comments.