Robin Wordsworth Studies the Climates of Mars
By Rosalyn Brady
January 21, 2023
UPDATED 12:00 PM EST
[Photo Credit: Getty Images]
Martian river valleys and erosion features deliver strong evidence that water once flowed on Mars, but its ancient climate has remained unknown until recently. A study conducted by Robin Wordsworth, planetary scientist, Gordon McKay Professor of Environmental Science and Engineering, and Professor of Earth and Planetary Science at Harvard University’s John A. Paulson School of Engineering and Applied Sciences, helped to decipher the climate of early Mars by recreating two possible scenarios for what the Martian climate could have been.
Wordsworth and his colleagues constructed a three-dimensional model of Mars’ atmosphere, complete with clouds and carbon dioxide and using randomized greenhouse gas injections and oxidization caused by hydrogen escape to demonstrate the climate conditions, in order to compare two different Martian climate scenarios that could have occurred during the late Noachian and early Hesperian periods, three to four billion years ago. One of these scenarios investigated Mars as warm and wet with an average temperature of 10 degrees Celsius, while the other investigated Mars as a much colder planet with an average temperature of negative 48 degrees Celsius.
The warm and wet model of Mars’s climate showed wide variation in rainfall with longitude and latitude, with most rainfall taking place in an area in the north of Mars called ‘Arabia Terra’, and in the Hellas Planitia basin in the south of Mars. Little evidence of water is seen there, though it may have appeared briefly. Additionally, regions such as Margaritifer Sinus in the northwest, where much evidence of water is seen, were shown as having little to no rainfall at all. It also established that some mountains would block rainfall, thus creating drier areas known as ‘rain shadows’ in Margaritifer Sinus - which has ample evidence of water - and that the area west of the Thassis volcanic plateau would have had a large amount of rainfall, despite its lack of abundance of water features.
Wordsworth’s study found that the warm, wet climate model did not match the locations of most Martian water features, and that the cold, icy climate was more straightforward to model and was more likely to have occurred. Due to Mars’s distance from Earth, it only gets 43 percent of the solar energy Earth gets, and three to four billion years ago, the Sun was believed to have been 25 percent dimmer than it is today, making it extremely likely that ancient Mars was a frigid planet. Additionally, the extreme tilt the Martian axis had been on at the time would have pointed the poles towards the Sun, which would melt polar ice and drain it towards the equator, where the telltale signs of water such as erosion or interconnecting water drainage channels similar to interconnected rivers on Earth - several smaller rivers which all flow into a larger one - are seen.
However, the presence of water in such a climate is unaccounted for. It is predicted that shorter events such as meteor impacts or volcanic eruptions melted the ice, or that it could have happened if high atmospheric carbon dioxide levels coincided with peak release rates of certain atmospheric compounds called ‘reducing’ gases. Although the ‘cold, icy Mars’ theory is not perfect, it may lead us closer to an understanding of the Red Planet, even though we still have a long way to go before anything is established as certain.
O’Hanlon, Larry. “Unveiling the Ancient Climate of Mars.” Seas.harvard.edu, seas.harvard.edu/news/2015/06/unveiling-ancient-climate-mars. Accessed 12 Dec. 2022.
Ogasa, Nikk. “Robin Wordsworth Re-Creates the Atmosphere of Ancient Mars.” Sciencenews.org, 29 Sept. 2022, www.sciencenews.org/article/robin-wordsworth-mars-sn-10-scientists-to-watch#:~:text=Wordsworth. Accessed 12 Dec. 2022.
“Study Shows Mars’ Early Climate Was Intermittently Warm |.” SBU News, 8 Mar. 2021, news.stonybrook.edu/homespotlight/study-shows-mars-early-climate-was-intermittently-warm/. Accessed 12 Dec. 2022.