21 Apr. 2011

 

The colour of extraterrestrial plants

 

Attempting to predict what might be the dominant colour of plants, if they exist, on planets in other planetary systems is something that researchers sometimes try. This time, a possible scenario has been put forward by Jack O'Malley-James of the University of St Andrews, who has investigated double and triple stellar systems containing solar-type stars and red dwarfs.
Such systems are not rare, given that the two stellar classes are amongst the most common, and that, respectively, 25% and 50% of these stars belong to multiple systems.
The aim of O'Malley-James' research was to understand how the presence of different stellar types might affect the colour of vegetation, assuming, of course, that such vegetation is based on photosynthesis, converting light energy into chemical energy (sugars).
The simulations used considered both Earth-sized planets in orbit around very close pairs of stars, and planets in orbit around one star in a multiple system, where the separation between the stars is rather large, as well as mixed scenarios.
The results obtained, presented at the National Astronomy Meeting of the RAS (that ends today in Llandudno, Wales) highlights the importance of the surface temperature of the star that illuminates the hypothetical vegetation. This is not because it effects the amount of energy received (the planet/star distance also affects this) but rather because it controls the colour of the star, and therefore the colour of the light.
For example, if a red dwarf were to dominate the sky, and the plant's life cycle were synchronized with this, then in order to absorb as much light as possible, perhaps also including the infrared, the plants may be black, or very dark. In the opposite case, perhaps with two solar-type stars, terrestrial style vegetation might protect itself from the excess radiation by developing "filters", capable of blocking ultraviolet light.

 

by Michele Ferrara & Marcel Clemens

credit: J O'Malley-James, University of St Andrews