[ad_1]
Life, as we understand it on Earth, requires some basic ingredients. Water is one of them. And for years, NASA’s succession of robotic missions have “followed the water” to Mars to learn more about the planet’s history, including whether it ever sustained life.
While many scientists believe Mars was hot and humid billions of years ago before becoming the frozen desert it is today, others point to the feeble paradox of the young sun.
Four billion years ago, our sun was much weaker, about 30% weaker. It got warmer and brighter over time. If so, ancient Mars would have been too cold and dry for the water or life on its surface.
Today Mars receives only about 43% of the concentrated sunlight that the Earth receives from the sun. This means that temperatures on ancient Mars would have struggled to exceed the melting point of water ice.
But the geological features on Mars show evidence of hydrated minerals and ancient river and lake beds. This evidence points to the fact that Mars likely had an abundance of liquid water during the Noachian era, or between 3.7 and 4.1 billion years ago.
This contradiction between climate models and the geological record of Mars is the feeble paradox of the young sun.
The rocky planets of our solar system – Earth, Venus, Mercury, and Mars – contain elements that create heat through radioactive decay. These elements include uranium, potassium and thorium.
This type of heating would suffice to melt the bottom of thick ice sheets to create liquid water, even with a faint sun. On Earth, this type of warming, called geothermal heat, can be seen in subglacial lakes that form in parts of the West Antarctic ice sheet, the Canadian Arctic, and Greenland.
The phenomenon of geothermal heat also explains liquid water on a freezing Mars 4 billion years ago.
Understanding ancient Mars
The researchers used a variety of datasets to test their theory of geothermal warming on Mars billions of years ago. These data included the thickness of ice deposits in the southern Martian highlands and estimates of the planet’s annual surface temperature and internal-to-surface heat flux 4 billion years ago.
Through modeling, the scientists found that underground melting of thick ice sheets would lead to an abundance of groundwater on Mars.
“Even though greenhouse gases such as carbon dioxide and water vapor are pumped into the early Martian atmosphere in computer simulations, climate models still struggle to support a long-term hot and humid Mars,” said the author. study principal Lujendra Ojha, an assistant professor in the department of earth and planetary sciences at the Rutgers University-New Brunswick School of Arts and Sciences, in a statement. “My co-authors and I propose that the feeble young sun paradox can be reconciled, at least in part, if Mars previously had high geothermal heat.”
Although they don’t know what happened to make Mars so inhospitable, even though it once sustained a hot and humid climate, over time the red planet lost its magnetic field, deprived itself of much of its atmosphere, and experienced a decline in its global temperature.
This means that in order for liquid water to have a stable presence on Mars, it would have to be below the surface.
“Regardless of the actual nature of the ancient Martian climate, the subsoil would have been the most habitable region on Mars,” the authors wrote in the study.
As the water penetrated deeper into Mars, the researchers suggested, any existing life may have followed it miles below the surface.
“At such depths, life could have been sustained by hydrothermal (warming) activity and water-rock reactions,” Ojha said. “So, the subsoil could represent the longest lived habitable environment on Mars.”
It may have been so on early Earth as well.
“Much of the Earth’s microbial biomass resides in its crust, where water is readily available,” the authors wrote in the study. “Substantial biological diversity exists throughout the enormous volume of underground habitable environments, which can reach a depth (greater than 5 kilometers). Therefore, the subsoil could have been the most vital habitat for simple ancient life forms on the early Earth and maybe on Mars “.
Currently, NASA’s Mars InSight lander is studying the interior of Mars after landing in 2018 (InSight is short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport). The data collected by the lander can help researchers learn more about how geothermal warming can. impacted the habitability of Mars billions of years ago, the researchers said.
And any evidence of a potential past life on Mars, such as biomarkers, could be hidden beneath the surface where they have been shielded from radiation.
.
[ad_2]
Source link
