Take the 2-minute tour ×
Astronomy Stack Exchange is a question and answer site for astronomers and astrophysicists. It's 100% free, no registration required.

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...

share|improve this question

1 Answer 1

up vote 4 down vote accepted

Twelve plus Mars are considered as potentially habitable (as of February 10, 2014).

share|improve this answer
    
Mars? Seriously? With artificial live support almost any (even the moon) can be. –  Magno C Feb 11 at 22:45
    
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. (phl.upr.edu/projects/earth-similarity-index-esi) –  Gerald Feb 11 at 23:35
    
Extremophiles exist on Mars? –  Magno C Feb 17 at 13:16
1  
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 Feb 18 at 22:11
    
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 Feb 18 at 22:15

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.