<p>In a nutshell, we are asked whether we are aware that the linked paper was <strong>peered reviewed</strong> (« complex review »), and if yes, what is the <strong>scientific consensus</strong> (« opinion of most scientists&quot;) on the conclusions of said paper. From this interpretation of the question, I would say that it is a valid one (not falling into the « opinion-based » category) for a SE community.</p>
<p>What is unclear – and I hope the OP will clarify – is whether the crux of the question is the scientific consensus on one of the possible consequences of the conclusions of Lewis Scott et.al., which then leads us to the debate on the Rare Earth Hypothesis mentionned in @David Hammen’s answer. It it is not the case, in other words, if the question is mainly on the validity of the scientific approach and scientific arguments of the paper, then I am afraid it is « off-topic » for Astronomy SE (as well), and I would concur then with @uhoh that it is rather a topic for Earth Science (which is the expertise of the paper’s authors, by the way).</p>
<p>Hence, I have assumed that the crux of the question is on the Rare Earth Hypothesis. It is self-evident that the authors of the paper believe that their results can contribute towards disqualifying this theory. But we should note that they have formulated their opinions in a professional way. Their abstract states :</p>
<blockquote>
<p>Biological or tectonic revolutions have been proposed to explain each of these stepwise increases in oxygen, but the principal driver of each event remains unclear. Here we show, using a theoretical model, that the observed oxygenation steps are a simple consequence of internal feedbacks within the long term biogeochemical cycles of carbon, oxygen and phosphorus, and there is no requirement for a specific ‘stepwise’ external forcing to explain the course of Earth surface oxygenation.</p>
</blockquote>
<p>Loosely paraphrasing, they stated that there is an alternative theoretical model that can equally, or even better, explain the observed history of Earth atmosphere oxygenation (the stepped increases) and this model is based on some &quot;simple&quot; feedback mechanisms. In this model, as soon as Life invented photosynthesis, the curve of Earth’s atmosphere oxygenation can be modelled accurately, including the stepped discontinuities. There is no doubt that this scientific result has implication on the Rare Earth Hypothesis debate. But I don’t think the profesionnalism of the authors is disputable, nor do I interpret that they concluded &quot;Now we know&quot;.</p>

CC BY-SA 4.0
2021-10-15T04:44:34.510Z
1/3 Question is clearly written in OP. Was this study already peered reviewed and did majority of scientists believe authors claim that stepwise Earth oxygenation is an inherent property of global biogeochemical cycling and once the Earth had the right microbes and plate tectonics (which were both established 3 billion years ago) it was only a matter of time before it reached the oxygen level it has now. Without any lucky external inputs (like massive volcanic eruptions) being necessary. I repeated this also JMP in comment section.
David Cage
CC BY-SA 4.0
2021-10-15T04:47:28.073Z
2/3 It can be also ask this way. What is chance that planet like early Earth with primitive photosynthetic organisms like Cyanobacteria evolve into planet with oxygen rich breathable atmosphere. Is it inherent process or most planets stay the way they are, without rising oxygen levels. I am not asking what is chance that primitive single cell life evolve on planet like Earth, but if early Earth-like planets should mostly stay way they are (with primitive S+M cell life and primitive form of photosynthesis) or inherently evolve into planets with oxygen rich breathable atmosphere.
David Cage
CC BY-SA 4.0
2021-10-15T04:49:37.970Z
3/3 Based on this everyone can make up his own opinion about how many planets with oxygen rich breathable atmospheres could exist in this galaxy. I asked this on Astronomy SE, because on Space exploration SE you suggest that this is more suitable forum. There is no planetary science SE and I will not ask this again on Earth science SE, because someone will again start arguing that it doesn't belong there. If someone want to answer this here OK, if not everyone can read citations list and made his own opinion.
David Cage
CC BY-SA 4.0
2021-10-15T08:37:26.207Z
@David Cage, thanks for clarifying. If asked, I would skip (but I now concur with those in favor of closure). It is rather off-topic here (although less so than Space SE). In Space SE, you said you couldn't find an answer in an extensive review of [a list of journals](https://space.stackexchange.com/questions/55266/list-of-thorough-space-journals). This showed you didn't know where to search, neither where to ask. You can't ask about consensus in pears to experts in apples. In your (3/3), you explained your aim which seems to be what SE consider as "opinion-based" talks, to be discouraged.
Ng Ph
CC BY-SA 4.0
2021-10-15T08:52:46.650Z
@David Cage, the paper appears to have been peered reviewed as it is now published in Science (paywalled). As others have noted, it was referred to by several papers, in the same field. If you don't have specific points for why you doubt the correctness of an approach, it is not appropriate to question the conclusion. If you do, you can edit your question (although, I have my doubt that you have experts in this field, on this site).
Ng Ph
CC BY-SA 4.0
2021-10-15T09:04:36.507Z
In which scientific journals should this review be published ? Here https://www.omicsonline.org/science-journals.php under category of Geology & Earth Science Journals List ?
David Cage
CC BY-SA 4.0
2021-10-15T12:06:24.730Z
@David Cage, sorry, you are asking the wrong person, possibly on the wrong SE too. W/o offense, if you have published scientific papers, you should be familiar that the referee's opinions are not public. You may try editing your question in the following direction: Does anybody know of a recent review paper that deals with the subject of Earth oxygenization theory and its impact on habitable planets? (If such a general review doesn't mention the U. of Leeds theory, you may draw some conclusion on its scientific impact).
Ng Ph
CC BY-SA 4.0
2021-10-14T14:38:13.373Z
2021-10-14T14:38:13.373Z
Ng Ph
<p>This question has been given a vote to close because it is opinion-based. I think that the best way to describe questions such as this is that scholarly opinion varies widely, ranging from the <a href="https://en.wikipedia.org/wiki/Rare_Earth_hypothesis" rel="nofollow noreferrer">rare Earth hypothesis</a>, which says that life (and in particular, intelligent life) is extremely rare, to its opposing hypothesis, which says that life is very common (e.g., the article cited in the question). What we do know is that we don't know, but some people, including scientists, like to post their opinions, one way or the other.</p>

CC BY-SA 4.0
2021-10-14T06:27:54.660Z
Not sure how you define opinion-based question. I asked if there were already some complex reviews about this important study is some scientific journals, because I couldn't find any. I also asked if majority of planetary scientists agree with this study or not. For example 95 % from all climate scientists believe that man made activity is cause of global warming. If someone ask if most climate scientists believe that human activity is cause of global warming, it is question about summarizing opinions in scientific community, not question about each individual climate scientist opinion.
David Cage
CC BY-SA 4.0
2021-10-14T08:42:49.463Z
Galileo didn't just post an opinion, he published a full [book](https://en.wikipedia.org/wiki/Dialogue_Concerning_the_Two_Chief_World_Systems). Although the publication was authorized by Pope Urban VIII, it was later banned because the Church suspected that Galileo was smearing the Pope ("opinion-based"?).
Ng Ph
CC BY-SA 4.0
2021-10-14T10:21:49.593Z
@DavidCage An opinion-based question is a question on which opinions vary. Most StackExchange sites do not like opinion-based questions. Whether life is very widespread or extremely rare is, at least for now, a matter of opinion. That is for example why the Mars rovers are looking for signs of past life on Mars. What science knows right now is that it doesn't know the answer to the question of the universality of life.
David Hammen
CC BY-SA 4.0
2021-10-14T10:26:48.870Z
What is known is that very simple life appears to have originated on Earth rather shortly (within less than a billion years) after the Earth formed. Also known: It took about four billion years for complex life to appear on Earth. Also known: The Earth has about another billion years before it becomes inhospitable to life. Maybe the Earth hit the one out of a trillion jackpot regarding life / intelligent life. Or maybe life is so universally abundant that life originating on Earth is not surprising at all. Asking which of those is the case is the quintessential opinion-based question.
David Hammen
CC BY-SA 4.0
2021-10-15T05:53:50.477Z
1/3 As I wrote in comments to Ng Ph answer this question is only about authors claim that " stepwise Earth oxygenation is an inherent property of global biogeochemical cycling and based on this model, once the Earth had the right microbes and plate tectonics, which were both established 3 billion years ago, it was only a matter of time before it reached the oxygen level it has now, regardless of volcanic activity and land-based plants."
David Cage
CC BY-SA 4.0
2021-10-15T05:56:35.173Z
2/3 If you look at timeline of O2 build-up in the Earth's atmosphere https://en.wikipedia.org/wiki/Great_Oxygenation_Event it doesn't look like inherent process, but their claim is that " the observed oxygenation steps are a simple consequence of internal feedbacks within the long term biogeochemical cycles of carbon, oxygen and phosphorus, and there is no requirement for a specific ‘stepwise’ external forcing to explain the course of Earth surface oxygenation. "
David Cage
CC BY-SA 4.0
2021-10-15T05:58:37.090Z
3/3 Based on this everyone can make up his own mind about how common can be exoplanets with oxygen rich breathable atmosphere in this galaxy.
David Cage
CC BY-SA 4.0
2021-10-14T04:11:46.117Z
2021-10-14T04:11:46.117Z
David Hammen
<p>I remember <a href="https://www.universetoday.com/144402/science-fiction-might-be-right-after-all-there-might-be-breathable-atmospheres-across-the-universe/" rel="nofollow noreferrer">this two year old article from Universe Today</a> about <a href="https://core.ac.uk/download/pdf/237067780.pdf" rel="nofollow noreferrer">this study</a>, &quot;Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling&quot;, by Lewis J. Alcott, Benjamin J. W. Mills, Simon W. Poulton of the School of Earth and Environment, University of Leeds, in the UK.</p>
<p>In summary, widely accepted the three-step model of Earth’s oxygenation outlines three major shifts in Earth’s history, with each one substantially altering the Earth’s atmosphere by adding more oxygen. The history of Earth’s oxygenation is complicated, it wasn’t a linear progression and a certain level of luck is required to create an oxygen-rich world. Based on this, exoplanets with oxygen rich breathable atmosphere should be extremely rare.</p>
<p>The authors of this study created different model where stepwise Earth oxygenation is an inherent property of global biogeochemical cycling and based on this model, once the Earth had the right microbes and plate tectonics, which were both established 3 billion years ago, it was only a matter of time before it reached the oxygen level it has now, regardless of volcanic activity and land-based plants. That means that exoplanets with oxygen rich breathable atmospheres could be much more common than was previously thought.</p>
<p>What are the opinions of the majority of planetary scientists on this study ? Do most of them still believe in three-step model of Earth’s oxygenation or this new model where Earth’s oxygenation was inherent process and matter of time since evolution of early photosynthetic organisms ? Was this study already peered reviewed in scientific journals ? Despite that it is almost 2 years old and on very important topic, I could not find any reviews in scientific journals that I read.</p>

CC BY-SA 4.0
2021-10-13T14:59:18.693Z
Reviews come out only every few years. Particularly with papers claiming grand things like this, it can take a while to properly digest those claims and their foundations inside of the scientific community. I wouldn't expect this process to be complete only 2 years after publication.
AtmosphericPrisonEscape
CC BY-SA 4.0
2021-10-13T15:05:57.563Z
The study already has 22 citations. You could go through all 22 articles and see what they say when citing the study: acceptance ("following Alcott et al., we blablabla..."), refutation ("contrary to Alcott et al., we think that..."), or something in between ("according to Alcott et al., it could be...").
Jean-Marie Prival
CC BY-SA 4.0
2021-10-13T15:39:38.430Z
@Jean-Marie Prival Where can I find (how to google) list of all 22 articles with citations from this study. I found only bunch of articles in science magazines where author summarized presented claims, without offering opinions from other planetary scientists. Did most planetary scientists still believe in three-step model of Earth’s oxygenation or this new model where Earth’s oxygenation was inherent property of global biogeochemical cycling and once Earth had the right microbes and plate tectonics, no lucky external inputs (like massive volcanic eruptions) were necessary.
David Cage
CC BY-SA 4.0
2021-10-13T16:38:54.723Z
@DavidCage https://ui.adsabs.harvard.edu/search/q=Lewis%20J.%20Alcott1*%2C%20Benjamin%20J.%20W.%20Mills&sort=date%20desc%2C%20bibcode%20desc&p_=0 or more specifically https://ui.adsabs.harvard.edu/abs/2019Sci...366.1333A/citations (but I only see there 13)
planetmaker
CC BY-SA 4.0
2021-10-13T17:11:17.857Z
@planetmaker Thanks, great tool, maybe there is more in sites of different universities.
David Cage
CC BY-SA 4.0
2021-10-13T17:51:29.183Z
Ads is hosted and operated there but not specific to Harvard. It's one of the major abstract servers in the science community, especially in physical sciences
planetmaker
CC BY-SA 4.0
2021-10-13T18:00:13.013Z
The 31 citations come from https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=Lewis+J.+Alcott%2C+Benjamin+J.+W.+Mills&btnG=  - you can click on citations and it will list all with a link there, too
planetmaker
CC BY-SA 4.0
2021-10-13T20:05:49.400Z
Mine were from the article at Science: https://doi.org/10.1126/science.aax6459 There is a metrics button, then a citations tab.
Jean-Marie Prival
CC BY-SA 4.0
2021-10-13T22:52:00.423Z
@DavidCage In Stack Exchange cross-posting the same question in multiple sites (i.e. "I [ask this also in Astronomy SE](https://space.stackexchange.com/q/55355/12102)") is strongly discouraged. You should probably delete one copy before someone starts downvoting both for cross-posting. I agree that solar system formation is much more on-topic in Astronomy SE than Space SE. There aren't really space exploration aspects to this, we can't send a rocket to check this out. However I wonder if [Earth Science SE](https://earthscience.stackexchange.com/) isn't actually the best site for this?
uhoh
CC BY-SA 4.0
2021-10-14T04:02:12.007Z
@uhoh I've disagreed elsewhere with regard to your comment. Earth Science.SE is for asking questions about the Earth. This site is the best match for questions about astrobiology.
David Hammen
CC BY-SA 4.0
2021-10-14T04:59:38.797Z
@DavidHammen in addition to "Earth" being mentioned six times, the question is asking about the study titled "Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling" by folks from the "School of Earth and Environment" so this question seems to me to be spot-on for Earth Science SE.
uhoh
CC BY-SA 4.0
2021-10-14T05:00:58.450Z
@uhoh I strongly disagree that this is on-topic at Earth Sciences.SE. All caps STRONGLY. This is the correct home for this question.
David Hammen
CC BY-SA 4.0
2021-10-14T05:04:08.173Z
@DavidHammen I acknowledge your all caps
uhoh
CC BY-SA 4.0
2021-10-14T10:06:16.393Z
@DavidCage If you are asking about the Earth rather than other planets in the solar system or exoplanets elsewhere in the universe, then uhoh's suggestion to ask your question at Earth Science.SE is correct. If on the other hand you are asking about Earth-like life elsewhere in the universe (which is what it appears you are asking), this site is a better match.
David Hammen
<earth><exoplanet><astrobiology>
What are opinions of most planetary scientists on this study (link below), were there already some complex reviews in scientific journals?
David Cage
# What are opinions of most planetary scientists on this study (link below), were there already some complex reviews in scientific journals?

(Asked by: username_0 on 2021-10-13)

I remember [this two year old article from Universe Today](https://www.universetoday.com/144402/science-fiction-might-be-right-after-all-there-might-be-breathable-atmospheres-across-the-universe/) about [this study](https://core.ac.uk/download/pdf/237067780.pdf), "Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling", by Lewis J. Alcott, Benjamin J. W. Mills, Simon W. Poulton of the School of Earth and Environment, University of Leeds, in the UK.

In summary, widely accepted the three-step model of Earth’s oxygenation outlines three major shifts in Earth’s history, with each one substantially altering the Earth’s atmosphere by adding more oxygen. The history of Earth’s oxygenation is complicated, it wasn’t a linear progression and a certain level of luck is required to create an oxygen-rich world. Based on this, exoplanets with oxygen rich breathable atmosphere should be extremely rare.

The authors of this study created different model where stepwise Earth oxygenation is an inherent property of global biogeochemical cycling and based on this model, once the Earth had the right microbes and plate tectonics, which were both established 3 billion years ago, it was only a matter of time before it reached the oxygen level it has now, regardless of volcanic activity and land-based plants. That means that exoplanets with oxygen rich breathable atmospheres could be much more common than was previously thought.

What are the opinions of the majority of planetary scientists on this study ? Do most of them still believe in three-step model of Earth’s oxygenation or this new model where Earth’s oxygenation was inherent process and matter of time since evolution of early photosynthetic organisms ? Was this study already peered reviewed in scientific journals ? Despite that it is almost 2 years old and on very important topic, I could not find any reviews in scientific journals that I read.

**Tags:** earth, exoplanet, astrobiology

> **Comments:**
> **username_1**: Reviews come out only every few years. Particularly with papers claiming grand things like this, it can take a while to properly digest those claims and their foundations inside of the scientific community. I wouldn't expect this process to be complete only 2 years after publication.  
> **username_2**: The study already has 22 citations. You could go through all 22 articles and see what they say when citing the study: acceptance ("following Alcott et al., we blablabla..."), refutation ("contrary to Alcott et al., we think that..."), or something in between ("according to Alcott et al., it could be...").  
> **username_0**: @username_2 Where can I find (how to google) list of all 22 articles with citations from this study. I found only bunch of articles in science magazines where author summarized presented claims, without offering opinions from other planetary scientists. Did most planetary scientists still believe in three-step model of Earth’s oxygenation or this new model where Earth’s oxygenation was inherent property of global biogeochemical cycling and once Earth had the right microbes and plate tectonics, no lucky external inputs (like massive volcanic eruptions) were necessary.  
> **username_3**: @username_0 https://ui.adsabs.harvard.edu/search/q=Lewis%20J.%20Alcott1*%2C%20Benjamin%20J.%20W.%20Mills&sort=date%20desc%2C%20bibcode%20desc&p_=0 or more specifically https://ui.adsabs.harvard.edu/abs/2019Sci...366.1333A/citations (but I only see there 13)  
> **username_0**: @username_3 Thanks, great tool, maybe there is more in sites of different universities.  
> **username_3**: Ads is hosted and operated there but not specific to Harvard. It's one of the major abstract servers in the science community, especially in physical sciences  
> **username_3**: The 31 citations come from https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=Lewis+J.+Alcott%2C+Benjamin+J.+W.+Mills&btnG=  - you can click on citations and it will list all with a link there, too  
> **username_2**: Mine were from the article at Science: https://doi.org/10.1126/science.aax6459 There is a metrics button, then a citations tab.  
> **username_4**: @username_0 In Stack Exchange cross-posting the same question in multiple sites (i.e. "I [ask this also in Astronomy SE](https://space.stackexchange.com/q/55355/12102)") is strongly discouraged. You should probably delete one copy before someone starts downvoting both for cross-posting. I agree that solar system formation is much more on-topic in Astronomy SE than Space SE. There aren't really space exploration aspects to this, we can't send a rocket to check this out. However I wonder if [Earth Science SE](https://earthscience.stackexchange.com/) isn't actually the best site for this?  
> **username_5**: @username_4 I've disagreed elsewhere with regard to your comment. Earth Science.SE is for asking questions about the Earth. This site is the best match for questions about astrobiology.  
> **username_4**: @username_5 in addition to "Earth" being mentioned six times, the question is asking about the study titled "Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling" by folks from the "School of Earth and Environment" so this question seems to me to be spot-on for Earth Science SE.  
> **username_5**: @username_4 I strongly disagree that this is on-topic at Earth Sciences.SE. All caps STRONGLY. This is the correct home for this question.  
> **username_4**: @username_5 I acknowledge your all caps  
> **username_5**: @username_0 If you are asking about the Earth rather than other planets in the solar system or exoplanets elsewhere in the universe, then username_4's suggestion to ask your question at Earth Science.SE is correct. If on the other hand you are asking about Earth-like life elsewhere in the universe (which is what it appears you are asking), this site is a better match.  

---

## 2 answers

### Answer by username_6 on 2021-10-14. Score: 1

In a nutshell, we are asked whether we are aware that the linked paper was **peered reviewed** (« complex review »), and if yes, what is the **scientific consensus** (« opinion of most scientists") on the conclusions of said paper. From this interpretation of the question, I would say that it is a valid one (not falling into the « opinion-based » category) for a SE community.

What is unclear – and I hope the OP will clarify – is whether the crux of the question is the scientific consensus on one of the possible consequences of the conclusions of Lewis Scott et.al., which then leads us to the debate on the Rare Earth Hypothesis mentionned in @username_5’s answer. It it is not the case, in other words, if the question is mainly on the validity of the scientific approach and scientific arguments of the paper, then I am afraid it is « off-topic » for Astronomy SE (as well), and I would concur then with @username_4 that it is rather a topic for Earth Science (which is the expertise of the paper’s authors, by the way).

Hence, I have assumed that the crux of the question is on the Rare Earth Hypothesis. It is self-evident that the authors of the paper believe that their results can contribute towards disqualifying this theory. But we should note that they have formulated their opinions in a professional way. Their abstract states :

> Biological or tectonic revolutions have been proposed to explain each of these stepwise increases in oxygen, but the principal driver of each event remains unclear. Here we show, using a theoretical model, that the observed oxygenation steps are a simple consequence of internal feedbacks within the long term biogeochemical cycles of carbon, oxygen and phosphorus, and there is no requirement for a specific ‘stepwise’ external forcing to explain the course of Earth surface oxygenation.

Loosely paraphrasing, they stated that there is an alternative theoretical model that can equally, or even better, explain the observed history of Earth atmosphere oxygenation (the stepped increases) and this model is based on some "simple" feedback mechanisms. In this model, as soon as Life invented photosynthesis, the curve of Earth’s atmosphere oxygenation can be modelled accurately, including the stepped discontinuities. There is no doubt that this scientific result has implication on the Rare Earth Hypothesis debate. But I don’t think the profesionnalism of the authors is disputable, nor do I interpret that they concluded "Now we know".

> **Comments:**
> **username_0**: 1/3 Question is clearly written in OP. Was this study already peered reviewed and did majority of scientists believe authors claim that stepwise Earth oxygenation is an inherent property of global biogeochemical cycling and once the Earth had the right microbes and plate tectonics (which were both established 3 billion years ago) it was only a matter of time before it reached the oxygen level it has now. Without any lucky external inputs (like massive volcanic eruptions) being necessary. I repeated this also JMP in comment section.  
> **username_0**: 2/3 It can be also ask this way. What is chance that planet like early Earth with primitive photosynthetic organisms like Cyanobacteria evolve into planet with oxygen rich breathable atmosphere. Is it inherent process or most planets stay the way they are, without rising oxygen levels. I am not asking what is chance that primitive single cell life evolve on planet like Earth, but if early Earth-like planets should mostly stay way they are (with primitive S+M cell life and primitive form of photosynthesis) or inherently evolve into planets with oxygen rich breathable atmosphere.  
> **username_0**: 3/3 Based on this everyone can make up his own opinion about how many planets with oxygen rich breathable atmospheres could exist in this galaxy. I asked this on Astronomy SE, because on Space exploration SE you suggest that this is more suitable forum. There is no planetary science SE and I will not ask this again on Earth science SE, because someone will again start arguing that it doesn't belong there. If someone want to answer this here OK, if not everyone can read citations list and made his own opinion.  
> **username_6**: @username_0, thanks for clarifying. If asked, I would skip (but I now concur with those in favor of closure). It is rather off-topic here (although less so than Space SE). In Space SE, you said you couldn't find an answer in an extensive review of [a list of journals](https://space.stackexchange.com/questions/55266/list-of-thorough-space-journals). This showed you didn't know where to search, neither where to ask. You can't ask about consensus in pears to experts in apples. In your (3/3), you explained your aim which seems to be what SE consider as "opinion-based" talks, to be discouraged.  
> **username_6**: @username_0, the paper appears to have been peered reviewed as it is now published in Science (paywalled). As others have noted, it was referred to by several papers, in the same field. If you don't have specific points for why you doubt the correctness of an approach, it is not appropriate to question the conclusion. If you do, you can edit your question (although, I have my doubt that you have experts in this field, on this site).  
> **username_0**: In which scientific journals should this review be published ? Here https://www.omicsonline.org/science-journals.php under category of Geology & Earth Science Journals List ?  
> **username_6**: @username_0, sorry, you are asking the wrong person, possibly on the wrong SE too. W/o offense, if you have published scientific papers, you should be familiar that the referee's opinions are not public. You may try editing your question in the following direction: Does anybody know of a recent review paper that deals with the subject of Earth oxygenization theory and its impact on habitable planets? (If such a general review doesn't mention the U. of Leeds theory, you may draw some conclusion on its scientific impact).  

---

### Answer by username_5 on 2021-10-14. Score: 0

This question has been given a vote to close because it is opinion-based. I think that the best way to describe questions such as this is that scholarly opinion varies widely, ranging from the [rare Earth hypothesis](https://en.wikipedia.org/wiki/Rare_Earth_hypothesis), which says that life (and in particular, intelligent life) is extremely rare, to its opposing hypothesis, which says that life is very common (e.g., the article cited in the question). What we do know is that we don't know, but some people, including scientists, like to post their opinions, one way or the other.

> **Comments:**
> **username_0**: Not sure how you define opinion-based question. I asked if there were already some complex reviews about this important study is some scientific journals, because I couldn't find any. I also asked if majority of planetary scientists agree with this study or not. For example 95 % from all climate scientists believe that man made activity is cause of global warming. If someone ask if most climate scientists believe that human activity is cause of global warming, it is question about summarizing opinions in scientific community, not question about each individual climate scientist opinion.  
> **username_6**: Galileo didn't just post an opinion, he published a full [book](https://en.wikipedia.org/wiki/Dialogue_Concerning_the_Two_Chief_World_Systems). Although the publication was authorized by Pope Urban VIII, it was later banned because the Church suspected that Galileo was smearing the Pope ("opinion-based"?).  
> **username_5**: @username_0 An opinion-based question is a question on which opinions vary. Most StackExchange sites do not like opinion-based questions. Whether life is very widespread or extremely rare is, at least for now, a matter of opinion. That is for example why the Mars rovers are looking for signs of past life on Mars. What science knows right now is that it doesn't know the answer to the question of the universality of life.  
> **username_5**: What is known is that very simple life appears to have originated on Earth rather shortly (within less than a billion years) after the Earth formed. Also known: It took about four billion years for complex life to appear on Earth. Also known: The Earth has about another billion years before it becomes inhospitable to life. Maybe the Earth hit the one out of a trillion jackpot regarding life / intelligent life. Or maybe life is so universally abundant that life originating on Earth is not surprising at all. Asking which of those is the case is the quintessential opinion-based question.  
> **username_0**: 1/3 As I wrote in comments to username_6 answer this question is only about authors claim that " stepwise Earth oxygenation is an inherent property of global biogeochemical cycling and based on this model, once the Earth had the right microbes and plate tectonics, which were both established 3 billion years ago, it was only a matter of time before it reached the oxygen level it has now, regardless of volcanic activity and land-based plants."  
> **username_0**: 2/3 If you look at timeline of O2 build-up in the Earth's atmosphere https://en.wikipedia.org/wiki/Great_Oxygenation_Event it doesn't look like inherent process, but their claim is that " the observed oxygenation steps are a simple consequence of internal feedbacks within the long term biogeochemical cycles of carbon, oxygen and phosphorus, and there is no requirement for a specific ‘stepwise’ external forcing to explain the course of Earth surface oxygenation. "  
> **username_0**: 3/3 Based on this everyone can make up his own mind about how common can be exoplanets with oxygen rich breathable atmosphere in this galaxy.  

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