A couple of Astrobotanical stories have caught my eye in the past week.

I renewed my subscription to SciAm Digital today and read the story Black Plants and Twilight Zones. It’s subscription only, but if you read the first bit and then I tell you that Nancy Kiang of the NASA Goddard Institute for Space Studies speculates that plants on the new discovered exoplanet Gliese 581g could be black, allowing them to absorb as much starlight as possible.

There are some problems. One, as the story notes, is that Gliese 581g seems to have disappeared. It cannot be confirmed as any other astronomical group so far, so it’s possible that it’s an artefact in the data. I’m a puzzled by the idea that plants would be black. If more is better, wouldn’t black also be the normal colour of leaves on Earth? Clearly I need to read her article The color of plants on other worlds [PDF] where she describes her reasoning in more detail. Her bibliography has more papers on photosynthesis and Astrobiology.

Another problem is due to the pedant in me. If plant-like life is found on an exoplanet then sooner or later someone will point out that, in evolutionary terms, we have more in common with plants than the new lifeforms. Whether stationary photosynthesizing lifeforms are plants or not could be a “Pluto moment” for Botany.

You could also question if plant-like life is unique to earth, but there may soon be a way of finding out. A paper Detecting Tree-like Multicellular Life on Extrasolar Planets” in Astrobiology. The authors, Doughty and Wolf, propose that the presence of life should be revealed by the way light is reflected from a planet surface. There is a simpler explanation of the process at Universe Today. If they are right, then positive results may start appearing within the next couple of decades as new NASA and ESA observatories are launched.