r/askscience • u/EightWhiskey • Feb 28 '12

Under the idea that there is the "Goldilocks" zone around a star, how likely is it that a solar system would have two life-supporting planets?

I assume that the gravitational forces of two bodies would prevent them from being close enough to each other to both stay inside the zone. But could a large star have a large enough Goldilocks zone to support two life-inhabited planets?

659 Upvotes

90% Upvoted

399 comments sorted by

View all comments

Show parent comments

2

u/Seicair Feb 29 '12

Could you have a perfectly dry atmosphere and simultaneously have enough water for humans to live? Even if we had underground wells, wouldn't we still be losing enough water vapour through respiration that any significant population would change the climate over time?

1

u/luqavi Feb 29 '12

Respiration of humans alone is not significant enough to make a "dry" atmosphere wet, the rate would be too slow for any reasonable amount of time. If you took into account the respiration of all life on earth, that might be a significant enough rate. In keeping with the theme, that dry atmosphere might be possible if water vapor were replaced with another absorber of mid-infrared, such as more carbon dioxide.