[ad_1]
The Martian subsoil may have been habitable billions of years ago, even though the planet’s surface was a dry, icy wasteland.
March likely produced enough geothermal heat in the ancient past to melt the bases of thick ice caps, generating large amounts of potentially life-saving groundwater, a new study suggests.
The findings could help scientists better understand a decades-old mystery known as the weak young paradox of the sun. Four billion years ago, the sun was about 30% weaker than it is today – too weak, apparently, to support a continually hot and humid Mars. Yet evidence of liquid water at this time abounds; From NASA Curiosity of the rover on Mars, for example, has spent the past eight years exploring an ancient system of lakes and streams. Hence the paradox.
Water on Mars: Exploration and evidence
“Even though greenhouse gases like carbon dioxide and water vapor are pumped out Martian atmosphere in computer simulations, climate models still struggle to sustain a hot and humid Mars in the long term, ”said lead study author Lujendra Ojha, assistant professor at Rutgers University-New Brunswick in the New Jersey, in a statement.
“My co-authors and I propose that the weak young sun paradox can be reconciled, at least in part, if Mars had high geothermal heat in its past,” Ojha said.
He and his colleagues investigated whether the required internal heat – generated by the radioactive decay of elements such as thorium, potassium, and uranium – actually sank during the Noachian era of Mars, which lasted there. is about 4.1 billion to 3.7 billion years old. Researchers focused their attention on the southern Martian highlands, an area that likely hosted large ice caps at the time.
The team modeled the thickness, behavior and evolution of these ice sheets using various datasets, including observations from NASA. Mars Odyssey Orbiter, which has been studying the Red Planet since 2001. Odyssey is equipped with a gamma spectrometer, which has enabled scientists to map the abundance of thorium and potassium in the Martian crust.
The researchers determined that the heat from the Martian mantle and crust would likely have been sufficient to melt the lower layers of thick ice caps long ago, creating potentially habitable environments underground, regardless of surface conditions. of the planet.
What the Noachian surface looked like – mostly hot and humid or mostly cold and dry, with intermittent fusion jets – remains a subject of considerable debate. But it’s widely believed that Mars changed dramatically shortly after this era. The planet has lost its global magnetic field, leaving its once thick atmosphere vulnerable to solar wind stripping. Such stripping left the Martian surface cold, dry, blasted by radiation and seemingly uninhabitable, at least for Earth-like life.
But pockets of groundwater likely persisted, although they likely retreated to deeper and deeper depths as the surface dried out. Some of them Martian aquifers may even have survived to the present day.
“At such depths, life could have been sustained by hydrothermal activity and rock-water reactions,” Ojha said in the same statement. “So the basement may represent the oldest habitable environment on Mars.”
The new study, which was published online today (December 2) in the journal Scientific advances, could have applications beyond the red planet. For example, the weak young sun paradox complicates our understanding of the emergence of life on early Earth, Ojha noted. X-ray heat may have played an important role in building our habitable planet a long time ago, he said.
A similar reasoning could also apply to exoplanets. For example, some alien worlds that appear to orbit too far from their host star to support life may in fact be habitable “on their own merit, by their own generation of radioactive heat,” Ojha told Space.com.
The new findings do not completely resolve the weak young sun paradox: “This is a partial solution at best,” Ojha said. He also pointed out that the numbers of heat fluxes he and his team achieved are somewhat uncertain, given that they come from elemental abundances. Researchers would like to extrapolate backwards from actual measurements of Martian underground heat flow, he said, but no such data is available.
NASA’s InSight Mars lander, which landed in November 2018, carries an instrument capable of collecting such information – a digging heat probe dubbed “the mole,” designed to reach at least 10 feet underground. So far, however, Martian soil has blocked the efforts of the mole, keeping the small shovel glued to the surface or just below.
Mike Wall is the author of “Over there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book on the search for extraterrestrial life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
[ad_2]
Source link