Goldilocks planets ‘with a tilt’ may develop more complex life


Research News


Planets which are tilted on their axis, like Earth, are more capable of evolving complex life. This finding will help scientists refine the search for more advanced life on exoplanets. This NASA-funded research is presented at the Goldschmidt Geochemistry Conference.

Since the first discovery of exoplanets (planets orbiting distant stars) in 1992, scientists have been looking for worlds which might support life. It is believed that to sustain even basic life, exoplanets need to be at just the right distance from their stars to allow liquid water to exist; the so-called ‘Goldilocks zone’. However, for more advanced life, other factors are also important, particularly atmospheric oxygen.

Oxygen plays a critical role in respiration, the chemical process which drives the metabolisms of most complex living things. Some basic life forms produce oxygen in small quantities, but for more complex life forms, such as plants and animals, oxygen is critical. Early Earth had little oxygen even though basic life forms existed.

The scientists produced a sophisticated model of the conditions required for life on Earth to be able to produce oxygen. The model allowed them to input different parameters, to show how changing conditions on a planet might change the amount of oxygen produced by photosynthetic life.

Lead researcher Stephanie Olson (Purdue University) said “The model allows us to change things such as day length, the amount of atmosphere, or the distribution of land to see how marine environments and the oxygen-producing life in the oceans respond.”

The researchers found that increasing day length, higher surface pressure, and the emergence of continents all influence ocean circulation patterns and associated nutrient transport in ways that may increase oxygen production. They believe that these relationships may have contributed to Earth’s oxygenation by favouring oxygen transfer to the atmosphere as Earth’s rotation has slowed, its continents have grown, and surface pressure has increased through time.

“The most interesting result came when we modelled ‘orbital obliquity’ – in other words how the planet tilts as it circles around its star,” explained Megan Barnett, a University of Chicago graduate student involved with the study. She continued “Greater tilting increased photosynthetic oxygen production in the ocean in our model, in part by increasing the efficiency with which biological ingredients are recycled. The effect was similar to doubling the amount of nutrients that sustain life.”

Earth’s sphere tilts on its axis at an angle of 23.5 degrees. This gives us our seasons, with parts of the Earth receiving more direct sunlight in summer than in winter. However, not all planets in our Solar System are tilted like the Earth: Uranus is tilted at 98 degrees, whereas Mercury is not tilted at all. “For comparison, the Leaning Tower of Pisa tilts at around 4 degrees, so planetary tilts can be quite substantial”, said Barnett.

Dr Olson continued “There are several factors to consider in looking for life on another planet. The planet needs to be the right distance from its star to allow liquid water and have the chemical ingredients for the origin of life. But not all oceans will be great hosts for life as we know it, and an even smaller subset will have suitable habitats for life to progress towards animal-grade complexity. Small tilts or extreme seasonality on planets with Uranus-like tilts may limit the proliferation of life, but modest tilt of a planet on its axis may increase the likelihood that it develops oxygenated atmospheres that could serve as beacons of microbial life and fuel the metabolisms of large organisms. The bottom line is that worlds that are modestly tilted on their axes may be more likely to evolve complex life. This helps us narrow the search for complex, perhaps even intelligent life in the Universe”.

Timothy Lyons, Distinguished Professor of Biogeochemistry in the Department of Earth and Planetary Sciences at the University of California, Riverside commented:

“The first biological production of oxygen on Earth and its first appreciable accumulation in the atmosphere and oceans are milestones in the history of life on Earth. Studies of Earth teach us that oxygen may be one of our most important biosignatures in the search for life on distant exoplanets. By building from the lessons learned from Earth via numerical simulations, Olson and colleagues have explored a critical range of planetary possibilities wider than those observed over Earth history. Importantly, this work reveals how key factors, including a planet’s seasonality, could increase or decrease the possibility of finding oxygen derived from life outside our solar system. These results are certain to help guide our searches for that life”.

Professor Lyons was not involved in this work, this is an independent comment


From EurekAlert!

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Robert Heath
July 11, 2021 2:05 am

Isn’t this bloody obvious.

Reply to  Robert Heath
July 11, 2021 4:14 am

I don’t think so. If the planet doesn’t have a tilt, it won’t have seasons.

On the Earth, near the equator, the seasons are less pronounced and life abounds. Given that, the reason why complex life evolves better on planets with seasons is not at all obvious.

Tom in Florida
Reply to  commieBob
July 11, 2021 5:59 am

A couple of things I did not see mentioned. The atmospheric circulation cells and tides. The circulation cells are directly attributed to the axial tilt so their is probably a Goldilocks zone of optimum obliquity. But it is the Moon caused tides that allowed sea water containing plant life to be deposited on land which then was exposed to sunlight causing the start of massive photosynthesis around the Earth. Thus began the huge increase of oxygen in our atmosphere changing it into one that could support larger life forms.

Pat Frank
Reply to  Tom in Florida
July 11, 2021 10:19 am

Photosynthesis began in the oceans. Probably as cyanobacteria. The earliest photosynthesis (Photosystem I) didn’t evolve oxygen (O2).

The later evolution of Photosystem II produced oxygen as a waste product; the first serious pollution crisis that chased anaerobic life into hiding.

That huge advance led to 2 billion years of heaving green sludge and shore-side stromatolites, modest in deportment but promising much as it turned out.

Reply to  commieBob
July 11, 2021 7:38 am

But CommieBob they have a real world sample size of 1 …. oh wait 🙂

Rich Davis
Reply to  LdB
July 11, 2021 10:15 am

Oh come on, LdB. Didn’t you see the NASA photograph of the tilted exoplanet? Oh wait, it’s an artist’s impression. That’s odd. I wonder why they didn’t use one of their actual photographs.

The YouReekAlot! article says:

This finding will help scientists refine the search for more advanced life on exoplanets.

So they definitely would need to be able to get a high resolution picture to detect the axial tilt, right? They must have that, otherwise Stephanie and Megan have a wee gap in their thesis, no?

Pat Frank
Reply to  commieBob
July 11, 2021 10:04 am

Anything emergent from a model is built into the model. Anything critical to physical reality left out of a model is invisible to the model and makes no appearance in the output.

These folks are modeling emergence of life with no physical theory in hand of the emergence of life. Their results are an interesting commentary on the behavior of the model.

But the relevance of the results to the physically real emergence of life and of photosynthesis is unknown.

Matthew Schilling
Reply to  commieBob
July 13, 2021 5:36 am

Wouldn’t the tilt be of benefit to the equatorial zone (vs. no tilt)? Aren’t I right in thinking a 23 degree tilt greatly reduces the amount of time the sun is directly overhead at the equator? Doesn’t the earth’s tilt expand the equatorial zone and spread out the area bombarded by a directly overhead sun? When the sun is directly over the Tropic of Cancer then it isn’t directly over the equator.

I would think the earth’s tilt has a homogenizing effect, allowing more of the planet to experience the benefit of strong sunlight, while sparing a small area too much of a good thing. It seems there is a real net benefit to a set of longer days, even if it means a set of longer nights follows.

I can light a dry leaf on fire by pointing a magnifying glass at a single spot, concentrating sunlight there. But how successful am I likely to be if I slowly and smoothly move the glass back and forth, spreading out the area struck by the concentrated light over a quarter of the length of the leaf?

Reply to  Robert Heath
July 11, 2021 4:35 am

Life in general – no, intelligent life – yes. You need enhanced climate variability to enforce more versatile adaptability. Humans originated near equator but progressed up the scale only after moving further north.

Reply to  Vuk
July 11, 2021 4:55 am

So it sounds like you’re saying that the humans that migrated out of Africa weren’t intelligent.

Anyway, the story isn’t about the development of civilization, it’s about the evolution of complex life forms.

I’m not actually disagreeing with the researchers’ thesis, I’m just replying to Robert that I don’t think it’s at all obvious.

Last edited 1 year ago by commieBob
Reply to  commieBob
July 11, 2021 5:16 am

….achieving the pinnacle of intelligence when they reached Canada.
Freedom of thought is absolute, freedom of expression not so.

Richard (the cynical one)
Reply to  Vuk
July 11, 2021 6:12 am

Not so sure about pinnacle. We have some pretty regressive life forms here in Canada, most of them migrated to Ottawa.

Reply to  Richard (the cynical one)
July 11, 2021 10:09 am

From Quebec. And we won the war of the Plains of Abraham Sept 13th, 1759 against France, and yet they rule Canada for much of the time. Time for a referendum by the rest of Canada to see if we want Quebec in the confederation.

After all, it is the last great discrimination of a people yearning to be free from the yoke of their conquering masters. Let Quebec be free, free of Canada. They are a distinct society, and deserve independence.

Pat Frank
Reply to  Richard (the cynical one)
July 11, 2021 10:20 am

And the worst of them running the country. In the US, too.

Rich Davis
Reply to  Richard (the cynical one)
July 11, 2021 10:37 am

Ouch! You’re not taking that lying down are you cb?

Let’s you and Richard fight!

Rich Davis
Reply to  Rich Davis
July 11, 2021 10:39 am

Oops I misread that, I thought he said Ontario.

I guess we call the whole thing off and I’ll need to rouse rabble elsewhere.

Rich Davis
Reply to  commieBob
July 11, 2021 10:31 am

How could you disagree with their thesis? It’s based on a model that must have been validated by looking at growth rates of oxygen-producing life forms as a function of axial tilt.

I’m not that familiar with exoplanets that we’ve visited to measure that, but it must have been done. Otherwise the model’s surprising result might just be, um wrong.

And as further proof, the result is consistent with there being intelligent life on earth, which has an oblique axis of rotation. qed

Gary Pearse
Reply to  commieBob
July 11, 2021 11:29 am

cb: Hippos migrated out of Africa as far as the Thames R.

Rich Davis
Reply to  Gary Pearse
July 11, 2021 1:21 pm

Those were the smart hippos

Reply to  Vuk
July 11, 2021 7:40 am

According to Griff Intelligent life exists only in countries that use HVDC power and who have grids powered by the wind … these are Griff facts.

Rich Davis
Reply to  LdB
July 11, 2021 10:43 am

Hmm “griff facts”. That is easier to say and write than the polysyllabic “phantasmagorical fallacies”. Let’s go with that.

Gary Pearse
Reply to  Vuk
July 11, 2021 11:27 am

But, but if you had no variability, life would adapt that!

Reply to  Robert Heath
July 11, 2021 9:16 am

Yes it is bloody obvious. It is basic high school biology. If this is the level of research that NASA is funding then the American tax payer is getting ripped off.

Gary Pearse
Reply to  Marty
July 11, 2021 11:34 am

Here’s my model: all planets in our solar system have axial tilts except for Mercury. Planets with a tilt are the rule!

Reply to  Gary Pearse
July 12, 2021 8:27 am

Yes…what are the odds of all these exoplanets ‘standing’ straight up relative to their plane of their ecliptic of their orbit about their star? The odds must be that the majority of exoplanets have some axial tilt based upon the accretion of their solar disc formation, and all the ruckus that goes on for the first few hundred million years with things smashing about before settling down.

Derek Wood
July 11, 2021 2:14 am

I quickly lost track of the “May, might, could, and possibly” count. Modelling eh? What’s not to like? “Species evolves into intelligent life-form, and concludes that planets such as its own are more likely to evolve intelligent life”. That’s settled then.

Reply to  Derek Wood
July 11, 2021 5:21 am

Easy as leaning Tower of Pisa pie. One example of anything and a model explaining it can prove whatever you want.

Reply to  Derek Wood
July 11, 2021 7:41 am

Well they had a sample of one to build the model on 🙂

a happy little debunker
July 11, 2021 2:21 am

I;s also speculate that the likelihood if life developing also depends on having a moon, resulting in a regular tidal movement.
Always assuming that carbon-based life forms are a pre-requisite…

Richard (the cynical one)
Reply to  a happy little debunker
July 11, 2021 6:16 am

Those are very narrow minded models, I mean model programmers, to exclude all non-oxygen processing organisms as life forms. Very carbonist.

Pat Frank
Reply to  Richard (the cynical one)
July 11, 2021 10:27 am

Molecular oxygen is the only strong oxidant that has a significant barrier to reaction with reductants. Emergence of complex life will require oxygen.

Carbon is the only element that forms large stable concatenated molecules. Phosphazines are stable, but more complex and less readily accessible and so don’t seem likely.

Reply to  Pat Frank
July 12, 2021 12:24 am

Silicon is not able to crate large stable concatenated molecules? Thinking about that always I’m using my Silicone putty or gaskets.

Reply to  Pat Frank
July 13, 2021 9:46 am

You forgot about the silicon-based Horta from Janus VI.

Brian R Catt
July 11, 2021 3:35 am

It’s a model. And therefore= wrong. Where are the experiments? I see no deterministic science with observational proof of the assertions made in testying these presumptions. They could have tested plants in this way, by varying the presumed effects one by one between control and normal. Why didn’t they? Did I miss the bit where scientific method was applied to the science fiction of modellers virtual reality? If you have no other test, fine. When you do, why not?

Reply to  Brian R Catt
July 11, 2021 12:22 pm

You must love drugery. I suppose you still put your cereal in a bowl and wash the bowl afterwards instead of utilizing the oh so more reasonable modern method of buying serial in little boxes from which it can be eaten directly, then the box discarded.

James Donald Bailey
July 11, 2021 4:11 am

supposedly, our day was very short and the moon very close shortly after it formed. over time tidal forces lengthened the day and caused the moon to move away.

it makes sense that the moon started out close since they think it formed from debris from a collision. and it makes sense that tidal forces will slow down earth’s rotation, lengthening the day.

so, does ‘increasing day length’ mean that a longer day is helpful, or does it mean a lengthening day was helpful?

the latter requires moon and ocean.

James Donald Bailey
July 11, 2021 4:42 am

have they actually observed things like tilt, oceans, moons and atmospheres of planets orbiting distant stars yet? What about day length?

do they expect to measure these things, or something that can infer them soon?

such simulation results could be useful if we can measure the inputs they varied. not sure how the connection to life can be really tested without visiting planets.

I can’t imagine us ever conducting a space probe that takes generations to reach the target. even a robotic probe. imagine trying to regain contact by sending a reboot command to a probe 10 light years away. half a career will pass before you learn if it worked.

July 11, 2021 4:46 am

“This helps us narrow the search for complex, perhaps even intelligent life in the Universe”

Why are they looking for “intelligent life in the Universe” ??
it’s a big enough job finding intelligent life on earth, the little there was is being wiped out by a pandemic of tick-toc & twit-face.

Last edited 1 year ago by 1saveenergy
Reply to  saveenergy
July 11, 2021 5:32 am

So as not to overwhelm the hospitals, another planet with intelligent life must be found. In the meantime, nurses will work on new dance routines and parades to honor first responders will take place as Australia remains shut down to prepare for double Greek letter variants.

July 11, 2021 5:22 am

But of course it must be right. Look at all the Class M planets they discovered in Star Trek. We observe that, no matter where the planet is in the galaxy, there is somewhere on earth that looks just like it! Who can doubt this is the way it must be? After all, that is the way it is in Exhibit A, er, E. So it must be that way everywhere.

They also speak English on those planets, and understand each other perfectly with just a few minutes ear training.

Remember, the operative word in “Science Fiction” is – fiction.

Thomas Gasloli
July 11, 2021 5:43 am

And this “sophisticated model” was compared to what real data to demonstrate its accuracy?

Jimmy Walter
July 11, 2021 5:43 am

The moon is much more important. How many will have a moon the size of ours relative to earth?×1.html

Nick Schroeder
July 11, 2021 5:47 am

“The principle of science, the definition, almost, is the following: The test of all knowledge is experiment. Experiment is the sole judge of scientific “truth.””
Richard P. Feynman, “Six Easy Pieces”

The non-radiative heat transfer processes of the contiguous participating atmospheric molecules prevent the surface from upwelling LWIR as a BB and supplying the “extra” energy need by the GHGs to warm as advertised.

A Modest Experiment 063018 R2.jpg
Reply to  Nick Schroeder
July 11, 2021 6:35 am

you are basically saying that everyone is ignoring convection and evaporation plus lumping that heat into a black body calculation with an emissivity of 1.0…so you are at the “see Spot run” level of literature study…..there is no 333 watts “extra”….the atmosphere is warmer than outer space and the 333 is the downwelling IR at surface from the “sky” versus the 396 IR upwelling for a net of 63, of which 40 goes directly to outer space through the IR window. This is annual “average”…nighttime, daytime, different latitudes, cloudy….are all different and varying hourly….

Nick Schroeder
Reply to  DMacKenzie,
July 11, 2021 12:54 pm

You appear to be referencing the ubiquitous K-T diagram.
160 W/m^2 reach the surface. No more than 160 W/m^2 can leave.
17 sensible + 80 latent + 63 LWIR = 160.
The balance is closed.
The leftover 333 is a result of an assumption that the 16 C surface radiates as a BB, i.e. 396, and in fact

Averaging is stupid since it does not slightly resemble how the earth actually heats and cools.

K-T Handout.jpg
Reply to  Nick Schroeder
July 12, 2021 12:27 am

Actually more than 160W/m^2 is leaving Earth. You need simply add geothermal radioactive decay heat.
Earth is source of radiation too.

Curious George
Reply to  Peter
July 12, 2021 5:50 pm

That would make it 160.09.

Don Bennett
July 11, 2021 6:22 am

Earth’s obliquity varies between 22.1° and 24.5° and is stabilized by the Moon. If the Earth didn’t have the Moon then it’s obliquity might change from 0° to 90° much like Mars’ does.

Tom in Florida
Reply to  Don Bennett
July 11, 2021 7:12 am

Mars historic obliquity is not really known other than it currently being at 23 degrees. However 90 is too much so please give us a reference on that.

Joe Chang
July 11, 2021 6:44 am

the moon stabilizes earths tilt, but must have causes massive earth quakes in the early periods. Someone said that one difference between Earth and Venus is that Venus does not have plate tectonics? Venus has one complete shell?

Pat Frank
Reply to  Joe Chang
July 11, 2021 10:34 am

It does. So do Mars and Mercury.

The collision that blew most of Earth’s crust into space and formed the moon is the jackpot that allowed life to form on Earth.

Ocean basins, tectonics, and the resulting ability to precipitate 60 bars of CO2 into carbonate.

Crustal monoplates are probably the default of planetary formation. Earth is very likely an outlier in this regard in our galaxy. I suspect complex life will be rare or absent elsewhere.

Rich Davis
Reply to  Pat Frank
July 11, 2021 11:15 am

Yes, so many unique circumstances line up to give us this amazing spaceship Earth, and after decades of seti no evidence at all.

Joao Martins
July 11, 2021 6:55 am

The SUPER-KEYWORD occurs in the title:


It seems we are not living our lives, instead we are “existing” in what MAY HAPPEN in our lives…

July 11, 2021 6:56 am

I am amazed that so many believe that simply having all the necessary conditions for life automatically means life should exist. WOW The information encoded in DNA simply encodes itself and life appears. Where is the science? How does information create itself?

Pat Frank
Reply to  Jim
July 11, 2021 10:36 am

How does information create itself?” Chemical self-organization. Manfred Eigen described the process in the 1970’s

Peta of Newark
July 11, 2021 7:06 am

We’re getting (a bit, notta lot) close(r) with this….
Quote:”part by increasing the efficiency with which biological ingredients are recycled. The effect was similar to doubling the amount of nutrients that sustain life

Yes OK, lovely..
But, you have to generate those nutriments first and THEN, either ‘recycle’ them or keep pulling more out of the hat.

To to that, you need Plate Tectonics.
You need volcanoes, subduction and mountain building.

Without those things, life may flower but only briefly – exactly as per Planet Mars.

So, do tilted planets have tectonics, or tectonics similar to Earth?
Otherwise you’re wasting your time.

Yes, that IS = Soil Erosion – an inevitable process if CO2 and liquid water are present. To keep life going you need, as they say, ‘recycling’

Last edited 1 year ago by Peta of Newark
H. D. Hoese
July 11, 2021 7:15 am

Current issue of American Scientist–“Also Featured:
Human history has shown that interactions between distinct cultures are often disruptive, challenging, and even violent—and interactions with aliens could be similarly dangerous. Cultural anthropologist and professor of religious studies John W. Traphagan exemplifies how any efforts at extraterrestrial communication force us to confront cultural assumptions—in “Who Should Speak for the Earth?””

Reply to  H. D. Hoese
July 11, 2021 7:45 am

Greta elected herself to speak for Earth the UN was busy at lunch like always.

Last edited 1 year ago by LdB
Tim Spence
July 11, 2021 7:35 am

They should have a few bears at least !

Reply to  Tim Spence
July 11, 2021 7:46 am

And a Northern Icecap, if they don’t have those then they are doomed.

Last edited 1 year ago by LdB
July 11, 2021 7:53 am

Are they claiming to have modeled how plants and animals evolve?

July 11, 2021 8:21 am

Pure speculation. It’s not science until we can actually observe what planets actually have life and which do not. I’d argue that making such models is a waste of time and effort.

Dave Fair
Reply to  Jim Whelan
July 11, 2021 12:02 pm

The Federal government needs excuses to spend its borrowed money.

July 11, 2021 9:10 am

This is news? My sources have known for decades about the necessity of a tilt.

Reply to  Art
July 13, 2021 9:17 am

That’s what I thought. It’s included in a list I started over a decade ago of the many characteristics a planet requires for intelligent life to evolve.

Bruce Cobb
July 11, 2021 11:05 am

So, imagine you’re the first single-celled organism. All alone. You’d be like: Hello? Anyone there? Helloooooo!!! I need a hug. I know, I’ll divide in two. Divides in two. Then, he is beside himself with joy. Biology, amiright?

Gary Pearse
July 11, 2021 11:22 am

“Planets which are tilted on their axis, like Earth, are more capable of evolving complex life. ”

Surely, at least one astrophysicist stood up and said axial tilts of planets are the default situation! In our solar system only Mercury has no tilt and half the planets have a tilt similar to that of earth. Sheesh!

Reply to  Gary Pearse
July 13, 2021 9:19 am

More useful would be for them to come up with the ideal angle of tilt. Requirement of a tilt is really old news.

July 11, 2021 12:11 pm

Ptolemy had a model too. It worked, and predicted the future positions of the planets as observed. Ptolemy’s model was the accepted science for 1500 years. If you disagreed with his model, the authorites would come and kill you.

Not much has changed to today. Models are fun until they become religious icons.

bill Johnston
July 11, 2021 12:45 pm

This paper says water an oxygen are necessary for life on other planets. Why? Isn’t this projecting our form of existence elsewhere? Might it just be possible that other life forms exist on other basics of life other than water and oxygen?

Reply to  bill Johnston
July 13, 2021 9:24 am

It’s pretty basic chemistry. Other than in science fiction, our knowledge of chemistry precludes other complex life forms that do not require water/oxygen. Life starts and ends with chemical reactions.

Joel O'Bryan
July 11, 2021 1:09 pm

Models do nothing more than the assumptions of the programmers who made it. That is not evidence.

Gary Pearse
Reply to  Joel O'Bryan
July 11, 2021 5:14 pm

The reason models tend to work in physics and engineering is the abundance of high quality data already accumulated by researchers. Climate science is almost all assumptions. Practitioners know it’s all backdrop to a new world totalitarian order. So there has been no new ideas in 40yrs.

July 11, 2021 3:12 pm

So apparently they say that life only requires some good water based chemistry on a planet with a bit of a tilt.
Maybe so but why does so much of life on this planet have biological cycles that are linked to our rather overlarge, moon?
Such lunar cycles may not be required for life to start, but can life go on and evolve fast enough without that Lunar tidal rhythm which happens constantly? Lunar affects that pulls oceans about bringing tides that run up and down shorelines regularly, lunar effects that affect the atmosphere and it’s movements and thus affects the weather.

Reply to  tom0mason
July 12, 2021 6:16 am

The moon affects life?
How does the Moon affect life on Earth? By Kerry Lotzof
“From weeping trees to teeth stronger than Kevlar, senior curator Dr Tom White sheds some light on a few of the fascinating, unnoticed ways the Moon shapes the course of life on Earth.
‘The Moon has been up there as long as evolution has been taking place, and lunar rhythms are embedded in the life cycles of many organisms,’ Tom says.’The challenge is working out when the Moon truly is a factor and what is merely myth and legend.'”

“Does the Lunar Cycle Affect Reef Fish Catch Rates?…
The lunar effect in the bottom longline fishery differed between species, with increased CPUE consistently predicted to occur near the new moon for Red Grouper and to take place proximal to the full moon for Tilefish. Red Grouper captured with vertical line gear had two CPUE increases predicted around the waxing and waning lunar phases. Inconsistencies in lunar effect between gear types for Red Grouper were present, possibly due to different mechanisms affecting CPUE.”

“The responses to the lunar cycle can not be generalized across taxonomic group, but instead are highly species specific and relate directly to the species’ ecology. The primary reasons for changes in amphibian behavior in response to the lunar cycle appear to be temporal synchronization of breeding and predator avoidance. Responses to changes in prey availability, facilitation of visual signalling and use of lunar cues in navigation and homing are less prevalent but merit further investigation.”

Lunar cycles in diel prey migrations exert a stronger effect on the diving of juveniles than adult Galapagos fur seals. By M Horning and Fritz Trillmich.

Marine Animal Behaviour In Relation To Lunar Phase by E. Naylor

Human Responses to the Geophysical Daily, Annual and Lunar Cycles by Russell G.Foster Till Roenneberg

There are quite a few more.

July 11, 2021 4:36 pm

If you want to find another habitable planet read the books “Rare Earth” and “the Privileged Planet”. The latter tells you exactly what to look for to find a planet capable of housing metazoans. But that isn’t sufficient for life. Life is more than just add water and give it a place to grow. Only if you wrongly assume that nature put life here would you think that just finding the right planet solves the problem.

Michael in Dublin
July 11, 2021 4:52 pm

Is there even a single shred of evidence that complex life is to be found on any planet other than our earth? This is not science but science fiction.

Reply to  Michael in Dublin
July 12, 2021 7:09 am

Roswell, 1947. Or do you really think that intelligence officers confused a weather balloon for a space craft?

John in Oz
July 11, 2021 6:00 pm

All swans are white…………until they’re not

Walter Sobchak
July 11, 2021 8:02 pm

Models. They found nothing. They played video games all night.

Steve Z
July 12, 2021 9:12 am

It’s not clear why a planet whose axis of rotation is tilted relative to the axis of revolution around its star would be more favorable to the development of life, or oxygen in its atmosphere. It is true that, for the Earth with its size and distance from the sun, that the 23.5-degree tilt enables life to exist farther from the Equator than would ordinarily be possible with a non-tilted axis (an earth without seasons). In temperate regions (about 35 to 60 degrees latitude), the current tilt enables the favored (spring/summer) hemisphere to receive enough sunlight to prevent water from freezing for several consecutive months, providing a frost-free and ice-free growing season which would not occur at those latitudes on a season-less earth.

But what about a hypothetical planet with an Earth-like chemical composition which was slightly closer to its star than Earth (or the same distance from a stronger star)? For such a planet, water could remain liquid farther from its equator even without a tilted axis, and life in its equatorial regions could be better adapted to warm water, while life in its middle latitudes to cooler water.

For a hypothetical Earth-like planet slightly farther from its star than Earth (or with a weaker star than the sun), liquid water would be limited to a narrow band around its equator, and any tilt in its axis would make its “tropics” colder on average, and possibly unable to support life.

An extreme tilt such that of Uranus would be extremely unfavorable to the development of life, regardless of distance to the star. For example, an axis tilt of exactly 90 degrees would result in polar regions with the star nearly at the zenith part of the year, and total darkness another part of the year, while equatorial regions would receive very strong insolation twice a year (when the equator faced the star), and very weak insolation twice a year (with the equator perpendicular to the line from the planet to the star). This extreme variability of climate with seasons would probably make most regions either too hot or too cold for life at various times all over the planet.

In the search for life on other planets outside our solar system, the main factors to consider are the intensity of radiation from the star, distance of the planet from the star, gravity of the planet (which affects its ability to hold an atmosphere), and presence of oxygen in its atmosphere and liquid water on the surface. The tilt of the axis of rotation relative to the plane of revolution (ecliptic) is a relatively minor factor.

Cliff Hiilton
July 12, 2021 5:42 pm

There will never be additional “intelligent” life discovered. We only know of angels and man. All intelligent life is right here. I know this without hesitation. Its as plain as the nose on your face.

Intelligent life did not evolve from un-intelligent.

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