DEKALB, Ill. - The National Science Foundation has awarded a prestigious Faculty Early Career Development Program…
DeKALB, Ill. — Wesley Swingley has spent his career studying organisms that are too small to be seen with the naked eye, yet exist all around us. But the assorted Lego spacecraft on his office shelves betray his other keen interest, which sometimes has him gazing toward distant stars.
A new $340,000 grant from NASA will allow the Northern Illinois University microbiology professor to pursue both passions.
Over the next two years, Swingley will lead a team of scientists on work that could help assess which distant planets observed by future space telescopes might exhibit signs of life. The research team is interested in what life might look like on “exoplanets” that orbit stars outside our solar system.
The new study will derive critical clues from microorganisms that are plentiful on our own planet—blue-green bacterial algae known as cyanobacteria.
While liquid water is considered the key prerequisite ingredient for life, cyanobacteria play a starring role in the evolution of life on our planet.
These bacteria employ oxygen-producing photosynthesis, essentially harnessing light to convert water into oxygen for our atmosphere. The same process occurs in the chloroplasts found in plants, which descended from early cyanobacteria.
“At some point more than 2.5 billion years ago, these organisms figured out how to capture light, take water and produce oxygen from it—a tricky reaction that requires a lot of energy,” said Swingley, who studies the early origins of life on Earth. “Then cyanobacteria started pumping oxygen into the atmosphere, and they managed, over time, to oxygenate the atmosphere to near modern levels.”
The new study will help determine whether similar processes could evolve on exoplanets that receive much less light energy than Earth.
The project team includes Niki Parenteau of the NASA Ames Research Center in California, Nancy Kiang of the NASA Goddard Institute for Space Studies in New York City, Robert Blankenship of Washington University in St. Louis and Min Chen of the University of Sydney in Australia. Two NIU graduate students and several undergrads will also be involved in the research.
The team aims to gain a better understanding of the photosynthetic mechanisms that cyanobacteria use to convert water into oxygen and pin down the light energy limits needed to power this reaction.
As next-generation telescopes come online, scientists from NASA’s Virtual Planetary Laboratory team hope to explore detectable exoplanet atmospheres. Information from Swingley’s study will be useful in evaluating atmospheric “biosignatures,” or signals of potential biological activity.
Those biosignatures include the presence of atmospheric oxygen and something known as the “vegetation red edge”—the leftover infrared light that is not absorbed by algae and vegetation, and is potentially detectable through a planet’s spectral analysis. On our planet, both of these biosignatures originated from oxygen-producing photosynthesis in ancient cyanobacteria.
Swingley’s study focuses on the cyanobacterium Acaryochloris, which can convert water to oxygen using near-infrared light. This type of light exists on many exoplanets. The majority of stars in the Milky Way are red dwarfs, which are cooler than our sun and produce light mostly in the far-red and infrared range, which has lower energy per photon than the visible light used by most photosynthetic organisms on Earth.
“If we find oxygen in the atmosphere of an exoplanet, one assumption scientists could make is that oxygen was somehow produced by life using light from its star,” Swingley said. “But oxygen could also be produced through a variety of chemical processes that have nothing to do with life, so we want to set the physical limits on the type and amount of light energy that life needs to convert water to oxygen.”
To better understand the mechanisms of far-red/infrared photosynthesis, Swingley’s team will analyze the genomes of Acaryochloris and several of its relatives. The scientists will also grow the cyanobacteria under different light regimes that will include the solar spectra of other stars.
“We’ll be analyzing oxygen production at the furthest limits of red light,” Swingley said. “Ultimately, we hope this will establish realistic constraints for oxygen production by exoplanet life.”
Media Contact: Tom Parisi
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