Celestia Forums

http://www.sciam.com/article.cfm?id=the ... her-worlds

Interesting article. I wonder what the color of plants would be on a world orbiting the double stars Delta Triangulii?

I take it these people have never come across red algae or photosynthetic purple bacteria?

I don't believe this news is really all that new. I've heard this specific story before.

ajtribick wrote:I take it these people have never come across red algae or photosynthetic purple bacteria?

Or red-leaved shrubs and bushes.

The original (good) papers are:

http://pubs.giss.nasa.gov/docs/2007/200 ... etal_1.pdf
http://pubs.giss.nasa.gov/docs/2007/200 ... etal_2.pdf

The first looks at all kinds of photosynthesis on Earth, including purple bacteria and other weird creatures (algae living off near infrared light?!) Lots of curious evolutionary adaptations such as coloured antenna pigments, the need for antioxidants and how to deal with UV. The second then applies this to alien worlds.

One should never judge a paper by its popularizations.

Does anybody know the UV balance on worlds orbiting hot F stars? On one hand they get a lot more UV energy, but they would orbit further out and if hit with lots of UV would also have more ozone. It is the M stars that might give real UV surprises when they flare.

Not all plants on this planet are green. We have many that are Red, gray, and some are vary dark burgundy in color almost a dark purple. So we have examples right here on Earth if we just open our eyes and look around a little.

Don. Edwars

Most of the plants which use different coloured photosynthetic pigments and antenna pigments live underwater, where the wavelengths and the intensity of the available light is quite different.

Note that in that paper the authors note that good protection from UV light can be obtained by living at certain depth under water. On some worlds land life might have real difficulties due to UV levels, assuming biochemistry similar to Earth life.

In the case of planets orbiting M dwarfes, if there's a big earth-like moon orbiting near a massive gas giant, such moon would receive lots of radiation from the planet that would hit the atmosphere, forming ozone layer. But such moon must have magnetic field to protect itself from higher radiations coming from the big flares of the star and to prevent atmospheric loss.

In the case of planets orbiting M dwarfes, if there's a big earth-like moon orbiting near a massive gas giant, such moon would receive lots of radiation from the planet that would hit the atmosphere, forming ozone layer. But such moon must have magnetic field to protect itself from higher radiations coming from the big flares of the star and to avoid atmospheric loss.