Could Cyanobacteria Help to Terraform Mars?

Billions of years ago, Earth’s atmosphere was much different than it is today. Whereas our current atmosphere is a delicate balance of nitrogen gas, oxygen and trace gases, the primordial atmosphere was the result of volcanic outgassing – composed primarily of carbon dioxide, methane, ammonia, and other harsh chemicals. In this respect, our planet’s ancient atmosphere has something in common with Mars’ current atmosphere.

For this reason, some researchers think that introducing photosynthetic bacteria, which helped covert Earth’s atmosphere to what it is today, could be used to terraform Mars someday. According to a new study by an international team of scientists, it appears that cyanobacteria can conduct photosynthesis in low-light conditions. The results of this study could have drastic implications for Mars, where low-light conditions are common.

The study, titled “Photochemistry beyond the red limit in chlorophyll f–containing photosystems“, appeared in the the journal Science. The study was led by Dennis J. Nürnberg of the Department of Life Sciences at Imperial College, London, and included members from the Research School of Chemistry, ANU, the Consiglio Nazionale delle Ricerche, Queen Mary University of London, and the Institut de Biologie Intégrative de la Cellule.

Cyanobacteria Spirulina Credit:

Cyanobacteria are some of the most ancient organisms on Earth, with fossil evidence indicating that they existed as early as the Archean Era (c.a 3.5 billion years ago). During this time, they played a vital role in converting the abundant CO² in the atmosphere into oxygen gas, which eventually gave rise to ozone (O³) that helped protect the planet from harmful solar radiation.

The photochemistry used by these microbes is similar to what plants and trees – which subsequently evolved – rely on today. The process comes down to red light, which plants absorb, while reflecting green lights thanks to their chlorophyll content. The darker the environment, the less energy plants are able to adsorb, and thus convert into chemical energy.

For the sake of their study, the team led by Nürnberg sought to investigate just how dark an environment can become before photosynthesis becomes impossible. Using a species of bacteria known as Chroococcidiopsis thermalis (C. thermalis), they exposed samples of cyanobacteria to low light to find out what the lowest wavelengths that they could absorb were.

Previous research has suggested that the lower limit for photochemistry to occur was a light wavelength of 700 nanometers – known as the “red limit”. However, the team found that C. thermalis continued to conduct photosynthesis at wavelengths of up to 750 nanometers. The key, according to the team, lies in the presence of previously undetected long-wavelength chlorophylls, which the researchers traced back to the C. thermalis genome.

The researchers traced the origin of these chlorophylls to the C. thermalis genome, which they located in a specific gene cluster that is common in many species of cyanobacteria. This suggests that the ability to surpass the red limit is actually quite common, which has numerous implications. For one, the findings indicate that the limits of photosynthesis are greater than previously thought.

On the other hand, these findings indicate that certain organisms can function using less fuel, which the researchers refer to as an “unprecedented low-energy photosystem”. To Krausz and his colleagues, this photosystem could be the first wave in an effort to terraform Mars. Along with efforts to thicken the atmosphere and warm the environment, the introduction of C. thermalis and terrestrial plants could slowly make Mars suitable for human habitation.

As Krausz explained in a recent interview with Cosmos:

“This might sound like science fiction, but space agencies and private companies around the world are actively trying to turn this aspiration into reality in the not-too-distant future. Photosynthesis could theoretically be harnessed with these types of organisms to create air for humans to breathe on Mars. Low-light adapted organisms, such as the cyanobacteria we’ve been studying, can grow under rocks and potentially survive the harsh conditions on the red planet.”

Artist’s concept of a Martian astronaut standing outside the Mars One habitat. Credit: Bryan Versteeg/Mars One

In this respect, Krausz and his colleagues are joined by groups like the CyanoKnights – a team of students and volunteer scientists from the University of Applied Science and the Technical University in Darmstadt, Germany. Much like Krausz’s team, the CyanoKnights that want to seed Mars with cyanobacteria in order to trigger an ecological transformation, thus paving the way for colonization.

This idea was submitted as part of the Mars One University Competition, which took place in the summer of 2014. What’s more, there have been recent research findings that indicate that organisms similar to cyanobacteria may already exist on other planets. If this most recent study is correct, it means that such organisms could survive in low-light conditions, which means astronomers could expand their search for potential life to other locations in the Universe.

From offering humans the means to conduct terraforming under more restrictive conditions to assisting in the search for extra-terrestrial life, this research could have some drastic implications for our understanding of life in the Universe, and how to expand our place in it.

Further Reading: Cosmos, Science

About 2.3 Billion Years Ago, a Firehose of Oxygen was Released Into the Atmosphere

Billions of years ago, Earth’s environment was very different from the one we know today. Basically, our planet’s primordial atmosphere was toxic to life as we know it, consisting of carbon dioxide, nitrogen and other gases. However, by the Paleoproterozoic Era (2.5–1.6 billion years ago), a dramatic change occurred where oxygen began to be introduced to the atmosphere – known as the Great Oxidation Event (GOE).

Until recently, scientists were not sure if this event – which was the result of photosynthetic bacteria altering the atmosphere – occurred rapidly or not. However, according to a recent study by a team of international scientists, this event was much more rapid than previously thought. Based on newly-discovered geological evidence, the team concluded that the introduction of oxygen to our atmosphere was “more like a fire hose” than a trickle.

The study, titled “Two-billion-year-old evaporites capture Earth’s great oxidation“, recently appeared in the journal Science. Led by Clara Blättler, a postdoctoral research fellow in the Department of Geosciences at Princeton, the team also included members from the Blue Marble Space Institute of Science, the Karelian Science Center, the British Geological Survey, the Geological Survey of Norway, and multiple universities.

Roughly 2.5 billion years ago, towards the end of the Archaean Era, oxidation of our atmosphere began. Credit:

In short, the Great Oxygenation Event took began roughly 2.45 billion years ago at the beginning of the Proterozoic eon. This process is believed to have been the result of cyanobacteria slowly metabolizing the carbon dioxide (CO2) and producing oxygen gas, which now makes up about 20% of our atmosphere. However, until recently, scientists were unable to place much in the way of constraints on this period.

Luckily, a team of geologists from the Geological Survey of Norway – in collaboration with the Karelian Research Center in Petrozavodsk, Russia – recently recovered samples of preserved crystallized salts in Russia that are dated to this period. They were extracted from a 1.9 km-deep (1.2 mi) hole in Karelia in northwest Russia, from the the Onega Parametric Hole (OPH) drilling site on the western shores of Lake Onega.

These salt crystals, which are roughly 2 billion years ago, were the result of ancient seawater evaporating. Using these samples, Blättler and her team were able to learn things about the composition of the oceans and the atmosphere that existed on Earth around the time of the GOE. For starters, the team determined that they contained a surprisingly large amount of sulfate, which is the result of seawater reacting with oxygen.

As Aivo Lepland – a researcher at the Geological Survey of Norway, a geology specialist at Tallinn University of Technology, and senior author on the study – explained in recent Princeton press release:

“This is the strongest ever evidence that the ancient seawater from which those minerals precipitated had high sulfate concentrations reaching at least 30 percent of present-day oceanic sulfate as our estimations indicate. This is much higher than previously thought and will require considerable rethinking of the magnitude of oxygenation of Earth’s 2-billion year old atmosphere-ocean system.”

New evidence indicates that The Great Oxygenation Event (GOE) may have been much more rapid than previously thought. Credit: MIT

Prior to this, scientists were unsure how long it took for our atmosphere to reach its current balance of nitrogen and oxygen, which is essential for life as we know it. Basically, opinion was divided between it being something that happened rapidly, or occurred over the course of millions of years. Much of this stems from the fact that the oldest rock salts discovered were dated to a billion years ago.

“It has been hard to test these ideas because we didn’t have evidence from that era to tell us about the composition of the atmosphere,” said Blättler. However, by discovering rock salts that are roughly 2 billion years old, scientists now have the evidence they need to place constraint on the GOE. The find was also very fortunate, given that such rock salts samples are rather fragile.

The samples used for this study contained halite (which is chemically identical to table salt or sodium chloride) as well as other salts of calcium, magnesium and potassium – which dissolve easily over time. However, the sample obtained in this case was exceptionally-well preserved deep within the Earth. As such, they are able to provide scientists with invaluable clues as to what happened around the time of the GOE.

Looking ahead, this latest study is likely to lead to new models that explain what occurred after the GOE to cause oxygen gas to accumulate in our atmosphere. As John Higgins, an assistant professor of geosciences at Princeton who provided interpretation of the geochemical analysis, explained:

“This is a pretty special class of geologic deposits. There has been a lot of debate as to whether the Great Oxidation Event, which is tied to increase and decrease in various chemical signals, represents a big change in oxygen production, or just a threshold that was crossed. The bottom line is that this paper provides evidence that the oxygenation of the Earth across this time period involved a lot of oxygen production… There may have been important changes in feedback cycles on land or in the oceans, or a large increase in oxygen production by microbes, but either way it was much more dramatic than we had an understanding of before.”

These models are also likely to help in the hunt for life beyond our Solar System. By understanding what took place on our own planet billions of years ago to make it suitable for life, we will be able to spot these same conditions and processes on other planets.

Further Reading: Princeton University, Science