The high seas of Mars may never have existed, according to a new study that looks at two opposite climate scenarios of early Mars and suggests that a cold and icy planet billions of years ago better explains water drainage and erosion features seen on the planet today.
For decades, researchers have debated the climate history of Mars and how the planet’s early climate led to the many water-carved channels seen today.
The idea that 3 to 4 billion years ago Mars was once warm, wet and Earth-like with a northern sea — conditions that could have led to life — is generally more popular than that of a frigid, icy planet where water is locked in ice most of the time and life would be hard put to evolve.
To see which early Mars better explains the modern features of the planet, researcher Robin Wordsworth of the Harvard Paulson School of Engineering and Applied Sciences and his colleagues used a 3-dimensional atmospheric circulation model to compare a water cycle on Mars under different scenarios 3 to 4 billion years ago, during what’s called the late Noachian and early Hesperian periods.
One scenario looked at Mars as a warm and wet planet with an average global temperature of 10 degrees Celsius (50 degrees Fahrenheit) and the other as a cold and icy world with an average global temperature of minus 48 degrees Celsius (minus 54 degrees Fahrenheit).
The study’s authors found that the cold scenario was more likely to have occurred than the warm scenario, based on what is known about the history of the Sun and the tilt of Mars’s axis 3 to 4 billion years ago. The cold model also did a better job explaining the water erosion features that have been left behind on the Martian surface, and which have puzzled and intrigued scientists since they were first discovered by the Viking orbiters in the 1970s.
A paper presenting the results has been accepted for publication in AGU’s Journal of Geophysical Research – Planets.
The colder scenario was more straightforward to model, Wordsworth explained, because Mars only gets 43 percent of the solar energy of Earth, and early Mars was lit by a younger Sun believed to have been 25 percent dimmer than it is today. That makes it very likely early Mars was cold and icy, he said.
An extreme tilt of the Martian axis would have pointed the planet’s poles at the Sun and driven polar ice to the equator, where water drainage and erosion features are seen today. More importantly, under a thicker atmosphere that likely existed under the colder scenario, highland regions at the equator get colder and northern low-lying regions get warmer – the so-called ‘icy highlands effect’ that is responsible for making the peaks of mountains snow-covered on Earth today. Despite a number of warming factors – including a thicker atmosphere filled with climate-warming carbon dioxide — Mars still would have been quite cold, Wordsworth added.
Creating a warm/wet Mars took more work, Wordsworth said. Previous studies have shown that even when the effects of climate-warming clouds, dust and carbon dioxide are taken into account, climate models still don’t show early Mars developing any warm and wet periods, he said.
But the conditions on early Mars may have been different than scientists’ thought, Wordsworth said. The study’s authors added to their model different climate effects to force Mars into a warmer, wet state.
Even then, however, the warm/wet early Mars does not explain the patchwork of Martian water erosion features and valley networks observed on the planet today, and why these features tend to be concentrated near the planet’s equator, Wordsworth said.
Under the warm/wet model, rainfall rates varied a lot with longitude and latitude. The warm/wet model predicts that on early Mars rain was greatest in an area called Arabia and around the Hellas basin, including in the west and southeast areas of the basin, where few water drainage features are found today. At the same time, several regions with many water-carved valleys, such as Margaritifer Sinus, received one-tenth to one-twentieth as much rain as Arabia and the Hellas basin under the warm/wet scenario.
In the warm/wet scenario, mountains also created rain shadows, like those that wring water from clouds to create deserts on Earth. On Mars, the bulge of Tharsis would have caused more rain to fall on the windward western side of the volcanic plateau, where few water features are seen today. To the east, downwind of the bulge, drier air would flow over Margaritifer Sinus, causing less rain to fall there – a situation that doesn’t match the drainage features observed there.
The cold/icy scenario isn’t perfect , Wordsworth said. While this scenario accumulates frozen water closer to the drainage features observed today on Mars, something had to have melted the ice which carved the valleys, he said. In this scenario, the climate is cool most of the time, and short-lived events like meteor impacts and volcanic eruptions likely caused the necessary melting, he said.
“I’m still trying to keep an open mind about this,” said Wordsworth. “There is lots of work to be done. .”
Proving that a cold climate on early Mars led to the features seen on the planet today is a “big question”, said Bethany Ehlmann, a planetary scientist at California Institute of Technology and NASA’s Jet Propulsion Laboratory in Pasadena, California, who was not involved in the new study.
The new paper answers part of that question by showing that locations with snow accumulation in the cold and icy scenario roughly correspond to valley network locations seen today, she said. Further, the model of the cold and icy early Mars shows that some melting of ice would occur, she said.
“We know from rover- and orbiter-based data that there were lakes on ancient Mars,” she said. “Key questions are: how long did they persist? Were they episodic or persistent? And does the feeder valley network demand rain or is snow and ice melt sufficient?”
The 3-D climate modeling used in the new study begins to address these questions with a new level of sophistication by investigating how specific locations might have accumulated rain or snow, she said.
The American Geophysical Union is dedicated to advancing the Earth and space sciences for the benefit of humanity through its scholarly publications, conferences, and outreach programs. AGU is a not-for-profit, professional, scientific organization representing more than 60,000 members in 139 countries. Join the conversation on Facebook, Twitter, YouTube, and our other social media channels.
Notes for Journalists
Journalists and public information officers (PIOs) of educational and scientific institutions who have registered with AGU can download a PDF copy of the article by clicking on this link: http://onlinelibrary.wiley.com/doi/10.1002/2015JE004787/abstract?campaign=wlytk-41855.5282060185
Or, you may order a copy of the final paper by emailing your request to Nanci Bompey at firstname.lastname@example.org. Please provide your name, the name of your publication, and your phone number.
Neither the papers nor this press release is under embargo.
“Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3D climate model”
Robin D. Wordsworth, School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA;
Laura Kerber, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA;
Raymond T. Pierrehumbert, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA;
Francois Forget, Laboratoire de Meterologie Dynamique, Institut Pierre Simon Laplace, Paris, France;
James W. Head, Department of Geological Sciences, Brown University, Providence, Rhode Island, USA.
Contact Information for the Authors:
Robin Wordsworth: email@example.com, +1 (617) 496-1270
+1 (202) 777-7524
Harvard Paulson School of Engineering and Applied Sciences Contact:
+1 (617) 496-0450
Nanci Bompey | American Geophysical Union
NASA examines Peru's deadly rainfall
24.03.2017 | NASA/Goddard Space Flight Center
Steep rise of the Bernese Alps
24.03.2017 | Universität Bern
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy