Category Archives: extrasolar planets

Gardening on Worlds with Two Suns

Life on Other Worlds Could Well Look VERY Different

Black plants on a world with two Suns. Courtesy Jack O' Malley, University of St. Andrews.

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.

In M star radiation habitats, vegetation may have more photosynthetic pigments in order to make use of a fuller range of wavelengths, giving them a ‘black’ appearance. These are terrestrial examples of a dark plants (and flowers).

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.

Arsenic-Eating Life and New Planets

Scientists Study Places Where Life Thrives…

and where it May Someday Exist

Judging by the uproar over the past few days in the blog-o-sphere and comment-o-sphere, you’d think that NASA was announcing that life had been discovered on Mars or Titan or any number of other unlikely places.  What I’ve seen in idle speculation and comments on blogs, FaceBook, and even on some news sites,  leads me to wonder if there’s any intelligent life left on the Web. I mean, come on.  There’s been some pretty irresponsible commentary by all kinds of people (including journalists, bloggers, and some scientists) and it’s really taking away from the wonderfulness of the actual discoveries.  Well, let’s take a look at the REAL stories and see what all the fuss is about.

Arsenic-processing bacteria like those growing in Mono Lake, California. Courtesy NASA.

The first, being talked about today, is the finding that some bacteria that live in Mono Lake in California appear to eat and apparently thrive on arsenic — a chemical that is usually toxic to life.  This finding is based on laboratory studies of these bacteria. In such a setting, not only can these buggers eat the stuff, but they appear to have evolved enough to be able to chemically alter it and incorporate it into their DNA. The lead researcher, Dr. Felisa Wolfe-Simon at the U.S. Geological Survey, put it pretty well: “”We know that some microbes can breathe arsenic, but what we’ve found is a microbe doing something new — building parts of itself out of arsenic,” she said. “If something here on Earth can do something so unexpected, what else can life do that we haven’t seen yet?”

Bugs eating arsenic?  That result is going to have a huge impact on other areas of research into life and its processes, including the study of Earth’s evolution, organic chemistry, biogeochemical cycles, disease mitigation and Earth system research.  To put it simply, this has implications for understanding the chemical environments that life can exist and thrive in.  Essentially, this NASA-funded research is changing our very basic knowledge about what kinds of life forms we have on this planet, and where they can exist and thrive.

Now, this is a far cry from breathless claims that NASA was going to announce life on Mars and all the other shouting that we’ve been seeing on the Web and in the press the past couple of days. Those are the usual claims, and I find them wearisome when they come without any proof or understanding of the actual science being reported.

On the other hand, this report is REAL science being shared by real scientists who have been out the field doing what science does best: examining, studying, and understanding what’s right in front of us. It’s exciting. It’s different. And, it’s going to spur other scientists to study the results and extend them into other areas.  But it’s not little green life forms holding up their middle fingers and saying, “Take me to your arsenic.” Quite the opposite: the little life forms seem to have found their arsenic and said, “We’re happy here, thank you very much.”

You can also read more about this fascinating biological discovery at Science’s web site, the journal that is publishing the story of the arsenic-loving critters.

Artist's conception of the super-Earth planet GJ 1214b. Courtesy ESO.

The second discovery this week that has implications for life is the revelation by astronomers using the Very Large Telescope in Chile of a super-Earth exoplanet (i.e. a semi-Earthlike planet bigger than Earth) that has what appears to be a water-rich atmosphere.   This water could be in the form of steam, or wet clouds or hazes.  GJ 1214b has a radius of about 2.6 times that of the Earth and is about 6.5 times as massive. Its host star is a small faint star about 40 light-years from Earth in the constellation of Ophiuchus. You can read more details here.

Of course, as soon as news of this discovery came out, I began to see speculation about life being discovered on that planet.  Not just in news sites, but all around the web-o-sphere and by commentators who should have known better.  I hate to be a wet blanket (so to speak), but the presence of water does NOT equal the presence of life. It DOES mean, however, that the environment on that planet could be conducive to the formation of life that depends on water.  And, that’s pretty darned cool.  Still, no actual discovery of life has happened there… yet.

I think that this tells us, more than ever, that the conditions for life do exist “out there” and that the formation of planets where life could form and exist is not limited to our own solar system.  It’s not surprising to find these planets — eventually we were bound to. Coupled with the astrobiology discovery announced today, it tells ME that this universe is complex, fascinating, and always ready to hand us a surprise or two!