<p>The question was whether there were any "Earth-like" planets, not whether any were habitable. I believe the answer is currently, not very many.</p>

<p>Of the 31 (as of 6th Aug 2015) confirmed <a href="http://phl.upr.edu/projects/habitable-exoplanets-catalog" rel="nofollow">potentially habitable planets</a> most orbit K and M-dwarfs and are much closer to their Sun than we are; all are probably bigger and more massive than the Earth. There are 3 that orbit G-type stars: tau Cet e, Kepler 22b and Kepler 452b, all are thought to be at least 50% bigger than Earth.</p>

<p>So it depends how far you are prepared to stretch your definition of "Earth-like", but I would say there are about 3. Kepler 452b is the only one with an orbital "year" greater than 300 days.</p>

CC BY-SA 3.0
2014-12-13T21:41:07.713Z
2015-08-06T20:47:54.630Z
2015-08-06T20:47:54.630Z
ProfRob
<p><a href="http://phl.upr.edu/projects/habitable-exoplanets-catalog">Twelve plus Mars are considered as potentially habitable</a> (as of February 10, 2014).</p>

CC BY-SA 3.0
2014-02-11T22:45:52.757Z
Mars? Seriously? With artificial live support almost any (even the moon) can be.
Magno C
CC BY-SA 3.0
2014-02-11T23:35:00.277Z
That's according to the current assessment. The definition of "potentially habitable" has been chosen rather wide with the discovery of extremophiles. Only two of the twelve have an Earth Similarity Index of above 0.8. (http://phl.upr.edu/projects/earth-similarity-index-esi)
Gerald
CC BY-SA 3.0
2014-02-17T13:16:17.090Z
Extremophiles exist on Mars?
Magno C
CC BY-SA 3.0
2014-02-18T22:11:40.133Z
There is no evidence for extant or extinct life on Mars yet. But we know by now almost for shure, that Mars has been habitable for microorganisms about 4 billion years ago. On Earth some microorganisms live above 100 centigrade, others can survive temperatures close to absolute zero. Only for some period they need liquid water. Some extremophiles can be transported from Earth to Mars as spores and survive there for a while. This is called forward contamination; missions to Mars always need to take care to avoid this, to avoid false positive life detection in future missions.
Gerald
CC BY-SA 3.0
2014-02-18T22:15:57.727Z
ESA ExoMars is designed to look for extant and extinct life on Mars. Hence these options are taken into account. At the moment, it's not ruled out, that extant life could exist underground on Mars.
Gerald
CC BY-SA 3.0
2014-02-10T18:09:25.850Z
2014-02-10T18:09:25.850Z
Gerald
<p>Well, the title says everything...
How many earth-like planets have we discovered out there?
Discard too big (made of gas), too cold, too hot, etc.
Consider earth-like sun distance, size, temperature, the rocky ones...</p>

<exoplanet>
How many earth-like planets do we know at this moment?
Magno C
# How many earth-like planets do we know at this moment?

(Asked by: username_0 on 2014-02-10)

Well, the title says everything...
How many earth-like planets have we discovered out there?
Discard too big (made of gas), too cold, too hot, etc.
Consider earth-like sun distance, size, temperature, the rocky ones...

**Tags:** exoplanet


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## 2 answers

### Answer by username_2 on 2014-02-10. Score: 7 | Accepted answer

[Twelve plus Mars are considered as potentially habitable](http://phl.upr.edu/projects/habitable-exoplanets-catalog) (as of February 10, 2014).

> **Comments:**
> **username_0**: Mars? Seriously? With artificial live support almost any (even the moon) can be.  
> **username_2**: That's according to the current assessment. The definition of "potentially habitable" has been chosen rather wide with the discovery of extremophiles. Only two of the twelve have an Earth Similarity Index of above 0.8. (http://phl.upr.edu/projects/earth-similarity-index-esi)  
> **username_0**: Extremophiles exist on Mars?  
> **username_2**: There is no evidence for extant or extinct life on Mars yet. But we know by now almost for shure, that Mars has been habitable for microorganisms about 4 billion years ago. On Earth some microorganisms live above 100 centigrade, others can survive temperatures close to absolute zero. Only for some period they need liquid water. Some extremophiles can be transported from Earth to Mars as spores and survive there for a while. This is called forward contamination; missions to Mars always need to take care to avoid this, to avoid false positive life detection in future missions.  
> **username_2**: ESA ExoMars is designed to look for extant and extinct life on Mars. Hence these options are taken into account. At the moment, it's not ruled out, that extant life could exist underground on Mars.  

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### Answer by username_1 on 2014-12-13. Score: 5

The question was whether there were any "Earth-like" planets, not whether any were habitable. I believe the answer is currently, not very many.

Of the 31 (as of 6th Aug 2015) confirmed [potentially habitable planets](http://phl.upr.edu/projects/habitable-exoplanets-catalog) most orbit K and M-dwarfs and are much closer to their Sun than we are; all are probably bigger and more massive than the Earth. There are 3 that orbit G-type stars: tau Cet e, Kepler 22b and Kepler 452b, all are thought to be at least 50% bigger than Earth.

So it depends how far you are prepared to stretch your definition of "Earth-like", but I would say there are about 3. Kepler 452b is the only one with an orbital "year" greater than 300 days.


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