When the Earth Was Purple

Ollabelle writes "It's always been a bit of a mystery why plants absorb red and blue light, reflecting green, when the sun emits the peak energy of the visible spectrum in the green. A new theory offers one possible answer: that the first chlorophyll-utilizing microbes evolved to exploit the red-and-blue light that older green-absorbing microbes didn't use, eventually out-competing them through greater efficiency and the rise of oxygen."

Comments

Re:Plants on other planets

[timmarhy]

your just poo pooing other peoples assumptions while making your own in the same breath.

Re:Plants on other planets

[owlnation]

I can't understand people who think that to find life on other planets we have to look for conditions similar to Earth.

I guess the simple reason is that people's imaginations have been constrained by TV budgets. Earthlike is cheaper to produce and design, being the reason why the aliens in ST TOS all kind of looked a bit Middle Eastern, and in ST TNG they all had funny foreheads.

Still fighting old battles

[Flying pig]

I belive that one reason is that scientists are still trying to defeat, with evidence and reason, the religious fundamentalists who believe we are the only "intelligent" life in the Universe, and on the only planet that supports life. On this argument, which I personally doubt, conclusive evidence that life existed elsewhere in the universe and could make itself known would cause the collapse of fundamentalist religions, to the enormous benefit of the rest of us.

I don't buy into it because (a) these people aren't rational and (b) taking away their religion could make them worse - they could easily be converted into Stalinists or extreme nationalists. But I am sure that this, as well as the desire to get budget for exploration, is one of the factors in the search for life on Mars, and in SETI.

Finally, looking for water is not irrelevant. Any practical life form is going to need a solvent and carrier for the various chemicals it needs to get from place to place internally. Water is unique because its strong hydrogen bonding gives it a wide liquid temperature range. Other small molecules which are good solvents also tend to have very low boiling points, meaning that the range of reactions that can take place in them is much more limited. Water has very unusual properties, in fact, that make it more probable that life would evolve on a planet with lots of liquid water than, say, one covered in methane or liquid carbon dioxide.

Re:Plants on other planets

[Rob Kaper]

I can't understand people who think that to find life on other planets we have to look for conditions similar to Earth. All of the hubbub over liquid water seems so silly to me.

It would be silly to exclude conditions not similar to Earth alltogether, but it is definitely reasonable to focus on conditions that are similar. Other conditions could qualify but that's pure speculation, for the conditions we live in we actually have a proof of concept. I'll take the refined "it works here, so why not elsewhere" over "anything could work" any day.

Your idea of looking for non-natural patterns is interesting but note that it would very much limit search results to life so intelligent that like ourselves we would consider it above natural. You wouldn't find any microbes on Europe because in our frame of reference they too would be very natural.

Re:Plants on other planets

[ResidntGeek]

Looking for liquid water isn't just human arrogance. Water is an effective and stable polar solvent, and there aren't many chemical processes as widely applicable as hydrolysis. In addition, the presence of liquid water indicates temperatures cool enough to allow organic molecules to stay stable, but warm enough to undergo the reactions necessary for life. These things are true throughout the universe, not just here.

Re:How about

[daniel23]

Your argument, put another way, reads: since plants use chlorophyll and that specific molecule requires energy levels corresponding to red & blue light, things are required to be like they are. This is almost tautologic. The more interesting question would be, why something like chlorophyll evolved to power plants, instead of reactions with a potentially higher gain

Re:Plants on other planets

[MobyDisk]

I believe that it is inevitable that computers/robots will gain intelligence. If I am right, then there will be a non-carbon based intelligent life form on this planet. So perhaps we should be looking for steel, aluminum, and silicon instead of water and carbon.