Thread: Green Planet?

In the long history of the Earth, was there ever a time when our planet appeared as a predominantly green orb if viewed from outer space? Today, for the most part, the oceans, rivers and lakes appear blue from that same vantage point. Was there a time when algae and the vegetation that took over the continent(s) allowed the Earth to take on a green hue? It seems as if vegetation is always trying to cover something left unattended.

Just like to add another dumb question: If a life sustaining planet is either predominantly blue or green then will it be possible to someday narrow the search for planets that could harbor life by simply figuring out what color they are?

http://exoplanets.jpl.nasa.gov/CES_F...net_Poster.pdf
It would seem that yellow/green is the most abundant light frequency that reaches the Earth's surface from solar emissions. Hence the color of terrestrial flora.
Exoplanets might have flora of different color depending on atmospheric conditions and emission spectra of the star's they orbit.

There was a recent article that suggest it might also be possible to detect the spectral pattern of tall trees and the deep shadows they might cast on other planets.

http://www.universetoday.com/81605/f...solar-planets/

Originally Posted by GiantEvil

Exoplanets might have flora of different color depending on atmospheric conditions and emission spectra of the star's they orbit.

Doesn't the technology already exist that can determine either or both? If so then could an educated guess be made as to what color might be expected?

Still would like to know if the Earth ever appeared green from outer space?

Most Exoplanets aren't being detected by direct observation.

Originally Posted by Lynx_Fox

Most Exoplanets aren't being detected by direct observation.

I realize that. I understand they look for gravitational wobbles and they have a way of detecting minute decreases in light as a planet transits its star. Can we get a read on said planet's atmospheric conditions through spectral analysis of the starlight or by some other means?

Originally Posted by zinjanthropos

Was there a time when algae and the vegetation that took over the continent(s) allowed the Earth to take on a green hue?

There may well have been a giant algal bloom at the end of snowball Earth episodes.

Originally Posted by zinjanthropos

Originally Posted by Lynx_Fox

Most Exoplanets aren't being detected by direct observation.

I realize that. I understand they look for gravitational wobbles and they have a way of detecting minute decreases in light as a planet transits its star. Can we get a read on said planet's atmospheric conditions through spectral analysis of the starlight or by some other means?

Tinetti (2006? 2007?) argues that a single pixel of starlight through an exoplanet's atmosphere could provide evidence of life, but that still requires direct imaging of the planet.

We currently cannot do that.

As for the Earth being green, highly unlikely given that the surface of the Earth has been dominated by oceans and a variable atmospheric composition that would probably not tend toward green.