(ORDO NEWS) — According to all our measurements, the surface of Mars is currently an inhospitable wasteland. Only dusty devils roam the arid surface; the only water is ice. However, evidence that water once flowed and accumulated on the planet’s surface continues to grow.
The presence of liquid water means Mars could have sustained life as we know it … but one burning question remains: How warm was Mars in the early days of the solar system, when the young Sun was colder and weaker?
New research has found the answer: geothermal heat could have risen from deep within the planet – in this case the best place to live – deep below the surface.
“Even if greenhouse gases such as carbon dioxide and water vapor are pumped into the atmosphere of early Mars in computer simulations, climate models still have a hard time keeping Mars warm and humid,” said planetary scientist Lujendra Oja of Rutgers University in New Brunswick.
“My coauthors and I propose that the faint young Sun paradox could be solved, at least in part, if Mars had strong geothermal heat in the past.”
The Weak Young Sun Paradox is the contradiction between the presence of liquid water in the early solar system and the weakness of the sun. According to our understanding of stellar evolution, a billion or so years after its formation 4.6 billion years ago, solar heat and light accounted for only about 70 percent of its current production.
Even today, Mars is a cool place. It only receives about 43 percent of the solar flux that the Earth receives. Consequently, the average temperature is much lower than Earth’s -63 degrees Celsius (-81 degrees Fahrenheit). Of course, this is just an average; the temperature does rise above the melting point of water, up to about 30 degrees Celsius (although due to the low atmospheric pressure on Mars, ice is currently sublimated rather than melted).
Between 4.1 and 3.7 billion years ago, water is believed to be abundant on the planet’s surface, but climate models struggle to reach average temperatures above -0.15 degrees Celsius.
The possibility that the planet is warming up internally, maintaining liquid groundwater for a long time, is not new. Hydrothermal minerals mined deep underground by comet impacts and evidence of groundwater diagenesis at a number of sites support internal heating patterns.
Here on Earth, we see the effects of geothermal heating beneath ice sheets at high latitudes. The radioactive decay of elements such as uranium, potassium, and thorium in the earth’s crust produces heat that spreads to the surface; Not much, but when there is a thick layer of ice preventing heat from escaping, enough heat can be trapped to melt some of that ice, creating subglacial lakes.
So Oja and his team have modeled the thermophysical evolution of ice and estimated how much heat would be required to form melt water and subglacial lakes on cold and frozen Mars.
They then compared this to various datasets of Mars to determine if it was possible on Mars 4 billion years ago. And they found that the conditions for melting groundwater were ubiquitous at the time, and volcanism and meteorite impacts may have provided additional heat.
It is still possible that the surface of Mars was warm and humid for a while, but this climate, according to the researchers, will not be stable in the long term. Mars lost its magnetic field quite early in its history.
According to the researcher, only at great depths, maintained in a liquid state by geothermal heating, the water could remain stable for a long time. If there were life on the surface, it could follow the water inward.
“So, the bowels may represent the longest lived habitable environment on Mars.”
Another study using sonar suggests liquid water is still present underground on Mars today. Scientists believe that Mars’ underground lakes can be extremely saline as salinity lowers the freezing point of water.
Scientists have found evidence of mud volcanism on Mars, where underground, wet deposits are pushed upward by pressure. The water will of course sublimate when it reaches the surface.
In July of this year, three new missions to Mars were launched, which are due to arrive in February 2021. We may be very close to getting many more answers.
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