Life on Other Worlds Could Well Look VERY Different

Imagine if Earth had two Suns in its sky, similar to the otherworldly scenes we recall from movies like Star Wars. What would our gardens look like as we whirled around in a binary star system?

According to Jack O’Malley, a scientist at the University of St. Andrews in Scotland, it’s very possible that our gardens would NOT be the colorful delights we know today. They might very well be teeming with plants that are distinctly black or grey. He presented his ideas to the National Astronomy meeting of the Royal Astronomical Society this week.

How could strange darkened plants happen?  To understand the idea behind these science-fiction type blackish-grey plants that could flourish under the light of binary stars, we have to look at the process that makes green plants here on Earth: photosynthesis.  It provides the main energy source for plants, and of course for the animals that eat them. Photosynthesis is what a plant does to convert sunlight into energy.  On Earth, our plants are attuned to sunlight for their photosynthetic activities — and in particular, the color of the light streaming from our nearest star.

However, if those plants had evolved on an Earth with TWO Suns, they’d have twice as many light sources to choose from.  It’s entirely possible that they could use the light from both stars, or, perhaps some plants might evolve with a preference for the light from only one of the stars, particularly if they are exposed mostly to one of the stars for longer periods of time.

Think about this:  the temperature of a star determines its color, which is the color that photosynthesis relies on to do its job.  The star colors could then also affect the colors of the plants that are using photosythesis for their energy sources.  So, star color, availability of light, and the chance to utilize multiple star sources are big factors in the colors of the plants that could evolve on worlds blessed with more than one star.

This is an interesting thought experiment — and one that O’Malley and his PhD supervisors — are doing to figure out the potential for finding photosynthetic life on planets around other stars.  In particular, they are looking at the factors for such life in multi-star systems with different combinations of Sun-like stars and red dwarfs. Sun-like stars are known to host exoplanets and red dwarfs are the most common type of star in the Milky Way Galaxy. They are often found in multi-star systems, and are old and stable enough for life to have evolved.

O’Malley and his team are running simulations that consider Earth-like planets orbiting two stars close together or maybe are in orbit around one of two widely separated stars. Their simulations seem to show that planets in multi-star systems may host exotic forms of the more familiar plants we see on Earth.  If this is true, then they would look much different from what we grow here.

For example, explorers collecting plants growing in the light of dim red dwarf suns would find black-looking leaves and strange-colored flowers. Those plants would be absorbing light from across the entire visible wavelength range.  They’d have to use as much of the available light as possible in order to keep the photosynthesis process going.

It’s also possible that they could use infrared or ultraviolet radiation to drive photosynthesis. For planets orbiting two stars that are like our own, harmful radiation from intense stellar flares could lead to plants that develop their own ultraviolet-blocking sun-screens, or photosynthesizing microorganisms that could move in response to a sudden flare.

Someday, astronomers will find the chemical signatures of plants in the atmospheres of distant planets.  From the light output of their stars and the chemistry lesson we get from those worlds, perhaps we’ll finally be able to “see”  what gardens on the surfaces of faraway worlds will be like.  Maybe we’ll find out that the worlds we imagine in our science fiction movies are not even half as “weird” and different as the real worlds that lie out there around nearby stars.