[ad_1]
Four billion years ago our host star was much weaker and cooler than today. And without the heat and energy of the young star, the planets around the Sun were also very different.
On Mars, temperatures are said to have frozen over, and yet early geological indicators suggest there was liquid water at some point during its early days. The cosmic mystery of how Mars was able to keep water liquid despite the cold is known as the Little Solar Paradox.
New research may have the answer. In a study published Wednesday in the journal Scientific advances, scientists suggest that Mars may have had liquid water below the surface – and the ideal conditions for life.
A new hope – Scientists believe Mars was once a humid and hot world, and may even have harbored life forms at some point in its history. But over time, the atmosphere of Mars has been stripped because the planet does not have a magnetic field like that of Earth, making it seemingly inhospitable.
Studies suggest that Mars had abundant liquid water around 4.1 billion to 3.7 billion years ago. But temperatures on Mars today plunge below -81 degrees Fahrenheit, and would have been much colder at a time when the Sun didn’t emit as much heat early in the planet’s history.
“Even though greenhouse gases like carbon dioxide and water vapor are pumped into the early Martian atmosphere during computer simulations, climate models are still struggling to sustain a hot and humid Mars in the long run. “Lujendra Ojha, assistant professor in the Department of Earth and Planets Science at Rutgers University and lead author of the new study, said in a statement.
To understand how Mars was able to keep water liquid during this time, the scientists behind the new study looked at various Mars datasets to see if heat-producing elements like uranium, thorium and potassium could have generated heat on Mars by radioactive decay. Most of this data comes from NASA’s Mars InSight spacecraft, which landed on Mars in 2018. It has allowed scientists to reconstruct the geological history of the Red Planet in unprecedented detail.
If the elements were present on Mars, scientists then theorized that the bottom of the thick ice caps below the Martian surface would have melted – even if the Sun was weak. Today, this geothermal heating process results in the formation of subglacial lakes in areas of the West Antarctic, Greenland, and Canadian Arctic ice cap here on Earth.
From the data, the researchers discovered that the conditions for geothermal heating would have existed on Mars four billion years ago. As a result, liquid water may have been present at extreme depths below the surface of Mars. So, if life existed on the red planet, it should have evolved to live far below the surface.
“At such depths, life could have been supported by hydrothermal activity – heating – and rock-water reactions,” Ojha said. “So the basement may represent the oldest habitable environment on Mars.”
It’s possible that the basement continued to harbor Martian life long after the planet lost its protective atmosphere, the researchers suggest:
“If life had ever originated on Mars, then it might have followed the water table to progressively greater depths where stable liquid water could persist. Moreover, the deep basement would have kept the first life of the late heavy bombardment.
One of the tasks of Perseverance Rover, NASA’s latest mission to Mars, is to search for signs of life on the surface of the planet. Perhaps in future missions, scientists can dig a little deeper to search for relics from the Martian past.
Abstract: Explaining the abundant evidence for liquid water from the past, the debate over whether Mars was mostly hot and humid or cold and arid 4 billion years ago (Ga) has continued for decades. The Sun’s luminosity was ~ 30% lower 4 Ga ago; thus, most Martian climate models find it difficult to raise the mean surface temperature above the melting point of water. The basal melting of the ice caps may help resolve this paradox. We modeled the thermophysical evolution of ice and estimated the geothermal heat flow required to produce meltwater on a cold, arid Mars. We then analyzed the geophysical and geochemical data, showing that basal fusion would have been feasible on Mars 4 Ga ago. If Mars was hot and humid 4 Ga ago, then the geothermal flow would have even supported hydrothermal activity. Regardless of the actual nature of the ancient Martian climate, the subsoil would have been the most habitable region on Mars.
[ad_2]
Source link