Bursts of methane may have warmed early Mars

Related Articles

Related Articles

The presence of water on ancient Mars is a paradox. There’s plenty of geographical evidence that rivers periodically flowed across the planet’s surface. Yet in the time period when these waters are supposed to have run — three to four billion years ago — Mars should have been too cold to support liquid water.

So how did it stay so warm?

Researchers from the Harvard John A. Paulson School of Engineering and Applied Science (SEAS) suggest that early Mars may have been warmed intermittently by a powerful greenhouse effect. In a paper published in Geophysical Research Letters, researchers found that interactions between methane, carbon dioxide and hydrogen in the early Martian atmosphere may have created warm periods when the planet could support liquid water on the surface.

 

“Early Mars is unique in the sense that it’s the one planetary environment, outside Earth, where we can say with confidence that there were at least episodic periods where life could have flourished,” said Robin Wordsworth, assistant professor of environmental science and engineering at SEAS, and first author of the paper. “If we understand how early Mars operated, it could tell us something about the potential for finding life on other planets outside the solar system.”

Four billion years ago, the Sun was about 30 percent fainter than today and significantly less solar radiation — a.k.a. heat — reached the Martian surface. The scant radiation that did reach the planet was trapped by the atmosphere, resulting in warm, wet periods. For decades, researchers have struggled to model exactly how the planet was insulated.

The obvious culprit is CO2. Carbon dioxide makes up 95 percent of today’s Martian atmosphere and is the most well-known and abundant greenhouse gas on Earth.

But CO2 alone does not account for Mars’ early temperatures.

“You can do climate calculations where you add CO2 and build up to hundreds of times the present day atmospheric pressure on Mars and you still never get to temperatures that are even close to the melting point,” said Wordsworth.

There must have been something else in Mars’ atmosphere that contributed to a greenhouse effect.

The atmospheres of rocky planets lose lighter gases, such as hydrogen, to space over time. (In fact, the oxidation that gives Mars its distinctive hue is a direct result of the loss of hydrogen.)

Wordsworth and his collaborators looked to these long-lost gases — known as reducing gases — to provide a possible explanation for Mars’ early climate. In particular, the team looked at methane, which today is not abundant in the Martian atmosphere. Billions of years ago, however, geological processes could have been releasing significantly more methane into the atmosphere. This methane would have been slowly converted to hydrogen and other gases, in a process similar to that occurring today on Saturn’s moon, Titan.

To understand how this early Martian atmosphere may have behaved, the team needed to understand the fundamental properties of these molecules.

“When you’re looking at exotic atmospheres, you can’t compare them to Earth’s atmosphere,” said Wordsworth. “You have to start from first principles. So we looked at what happens when methane, hydrogen and carbon dioxide collide and how they interact with photons. We found that this combination results in very strong absorption of radiation.”

Carl Sagan first speculated that hydrogen warming could have been important on early Mars back in 1977, but this is the first time scientists have been able to calculate its greenhouse effect accurately. It is also the first time that methane has been shown to be an effective greenhouse gas on early Mars.

“This research shows that the warming effects of both methane and hydrogen have been underestimated by a significant amount,” said Wordsworth. “We discovered that methane and hydrogen, and their interaction with carbon dioxide, were much better at warming early Mars than had previously been believed.”

The researchers hope that future missions to Mars will shed light on the geological processes that produced methane billions of years ago.

“One of the reasons early Mars is so fascinating is that life needs complex chemistry to emerge,” said Wordsworth. “These episodes of reducing gas emission followed by planetary oxidation could have created favorable conditions for life on Mars.”

HARVARD JOHN A. PAULSON SCHOOL OF ENGINEERING AND APPLIED SCIENCES

Download the HeritageDaily mobile application on iOS and Android

More on this topic

LATEST NEWS

Camulodunum – The First Capital of Britannia

Camulodunum was a Roman city and the first capital of the Roman province of Britannia, in what is now the present-day city of Colchester in Essex, England.

African Crocodiles Lived in Spain Six Million Years Ago

Millions of years ago, several species of crocodiles of different genera and characteristics inhabited Europe and sometimes even coexisted.

Bat-Winged Dinosaurs That Could Glide

Despite having bat-like wings, two small dinosaurs, Yi and Ambopteryx, struggled to fly, only managing to glide clumsily between the trees where they lived, according to a new study led by an international team of researchers, including McGill University Professor Hans Larsson.

Ancient Maya Built Sophisticated Water Filters

Ancient Maya in the once-bustling city of Tikal built sophisticated water filters using natural materials they imported from miles away, according to the University of Cincinnati.

New Clues Revealed About Clovis People

There is much debate surrounding the age of the Clovis - a prehistoric culture named for stone tools found near Clovis, New Mexico in the early 1930s - who once occupied North America during the end of the last Ice Age.

Cognitive Elements of Language Have Existed for 40 Million Years

Humans are not the only beings that can identify rules in complex language-like constructions - monkeys and great apes can do so, too, a study at the University of Zurich has shown.

Bronze Age Herders Were Less Mobile Than Previously Thought

Bronze Age pastoralists in what is now southern Russia apparently covered shorter distances than previously thought.

Legio IX Hispana – The Lost Roman Legion

One of the most debated mysteries from the Roman period involves the disappearance of the Legio IX Hispana, a legion of the Imperial Roman Army that supposedly vanished sometime after AD 120.

Popular stories

Legio IX Hispana – The Lost Roman Legion

One of the most debated mysteries from the Roman period involves the disappearance of the Legio IX Hispana, a legion of the Imperial Roman Army that supposedly vanished sometime after AD 120.

The Secret Hellfire Club and the Hellfire Caves

The Hellfire Club was an exclusive membership-based organisation for high-society rakes, that was first founded in London in 1718, by Philip, Duke of Wharton, and several of society's elites.

Port Royal – The Sodom of the New World

Port Royal, originally named Cagway was an English harbour town and base of operations for buccaneers and privateers (pirates) until the great earthquake of 1692.

Matthew Hopkins – The Real Witch-Hunter

Matthew Hopkins was an infamous witch-hunter during the 17th century, who published “The Discovery of Witches” in 1647, and whose witch-hunting methods were applied during the notorious Salem Witch Trials in colonial Massachusetts.